FIELD

[0001] This disclosure relates to a method and system for separating components in a used oil and, in particular, using selectively permeable membranes to separate lubricant-range hydrocarbons from lower boiling components and higher boiling components in a used oil during pretreatment.

BACKGROUND OF THE INVENTION

[0002] Lubricant products, unlike fuels, are not consumed as a result of their use; instead, they lose their effectiveness over time due to degradation and contamination, and must be replaced. A representative used oil contains approximately 70-75% lubricant-range hydrocarbons, with the balance comprising both lower boiling (water, entrained fuels, cracked molecules) and higher-boiling molecules (spent additives, sludge). Used oil generation is generally in the range of 50-60% of total lubricant demand in each market.

[0003] There is significant interest in re-refining used lubricant oils into new fuels or lubricant products, in order to generate value and improve sustainability. Used oil re-refining consists of two major steps: pretreatment to recover the lubricant-range hydrocarbons, followed by upgrading via solvent extraction or hydroprocessing to produce base stocks.

[0004] Conventional thermal separations, particularly vacuum distillation, are typically used today for used oil pretreatment; however, this approach has multiple downsides. First, the presence of additives causes used lubricant oil to degrade at a lower temperature than crude oil, which limits the recovery of the vacuum gas oil (VGO)-range hydrocarbons via vacuum distillation. To counteract this, a thin film evaporator is commonly used at the bottom of the primary vacuum distillation tower to improve hydrocarbon recovery from the heavy tail. Second, used oil re-refineries are generally small (1-5 kbd capacity) and have run lengths of less than a year due to fouling and other issues. Third, the carbon footprint of conventional rerefining is substantial due to the need to vaporize -80% of the used oil during vacuum distillation, which offsets some of the sustainability benefits of re-refining.

[0005] There is a need for a method, instead of a vacuum distillation method, to recover the valuable hydrocarbon molecules from used lubricant oils during pretreatment. There is a need for a method that can provide an economic advantage due to more linear cost scaling with throughput and elimination of the vacuum system and the thin film evaporator. Additionally, there is a need for a method that can enhance the sustainability impact of used oil re-refining by decreasing the energy consumption of the pretreatment step.

SUMMARY OF THE INVENTION

[0006] This disclosure relates to a method and system that utilize membranes instead of vacuum distillation to recover the valuable hydrocarbon molecules from used lubricant oils during pretreatment. The use of membranes can provide an economic advantage due to their more linear cost scaling with throughput and elimination of the vacuum system and the thin film evaporator. Additionally, the use of membranes can enhance the sustainability impact of used oil re-refining by decreasing the energy consumption of the pretreatment step.

[0007] This disclosure relates in part to a method for separating components in a used oil. The method comprises providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane, in which the selectively permeable membrane has a first surface and a second surface opposite to the first surface; passing the stream of used oil to the filtration unit to remove solids; passing the stream having removed solids to the flash distillation column to remove water and light ends; and contacting the stream having removed water and light ends with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface. The feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C. The oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[0008] This disclosure also relates in part to a system for separating components in a used oil. The system comprises a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; at least one filtration unit; at least one flash distillation column; and at least one selectively permeable membrane, in which the selectively permeable membrane has a first surface and a second surface opposite to the first surface. In the system, the used oil is passed to the filtration unit to remove solids; the stream having removed solids is passed to the flash distillation column to remove water and light ends; and the stream having removed water and light ends is contacted with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface. The feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C. The oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[0009] This disclosure further relates in part to a composition comprising a wide-cut vacuum gas oil (VGO) product. The composition is produced by a process comprising providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane, in which the selectively permeable membrane has a first surface and a second surface opposite to the first surface; passing the stream of used oil to the filtration unit to remove solids; passing the stream having removed solids to the flash distillation column to remove water and light ends; and contacting the stream having removed water and light ends with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface. The feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C. The oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate. [0010] It has been surprisingly found that, in accordance with this disclosure, selectively permeable membranes (e.g., nanofiltration and ultrafiltration membranes), instead of vacuum distillation, can be used to recover valuable lubricant-range hydrocarbon molecules from used lubricant oils during pretreatment. The defuel tower used in conventional used oil pretreatment can be eliminated, and the vacuum distillation + thin film evaporator used in conventional used oil pretreatment can be replaced with a selective permeable membrane, to provide a membranebased used oil pretreatment having operational and economic advantages over conventional used oil pretreatment.

[0011] Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWING

[0012] Fig. 1 shows a conventional used oil pretreatment process using vacuum distillation + thin film evaporator.

[0013] Fig. 2 shows a used oil pretreatment process using one membrane stage in accordance with this disclosure.

[0014] Fig. 3 graphically shows membrane flux as a function of stage cut for batch experiments of raw used oil with different membranes, in accordance with the Examples.

[0015] Fig. 4 graphically shows boiling point distribution of raw used oil feed and permeates from various membranes, in accordance with the Examples.

[0016] Fig. 5 lists heteroatom content of raw used oil feed and permeates from various membranes, in accordance with the Examples.

[0017] Fig. 6 shows representative photos of samples of raw used oil and the membrane permeate and retentate products, in accordance with the Examples.

[0018] Fig. 7 graphically shows membrane flux as a function of stage cut from batch membrane experiments with dewatered used oil feed at three temperatures with a membrane, in accordance with the Examples.

[0019] Fig. 8 graphically shows viscosity data for permeates of batch experiments at different feed temperatures, in accordance with the Examples.

[0020] Fig. 9 lists heteroatom content of raw used oil feed and permeates of batch experiments at different feed temperatures, in accordance with the Examples. [0021] Fig. 10 graphically shows impact of feed pressure on flux versus stage cut, in accordance with the Examples.

[0022] Fig. 11 graphically shows viscosity data for permeates of batch experiments at different pressures, in accordance with the Examples.

[0023] Fig. 12 lists heteroatom content of raw used oil feed and permeates of batch experiments at different feed pressures, in accordance with the Examples.

[0024] Fig. 13 graphically shows flux versus stage cut for a high stage cut batch experiment, in accordance with the Examples.

[0025] Fig. 14 graphically shows boiling point distribution of feed and various permeate samples from high stage cut batch experiment, in accordance with the Examples.

[0026] Fig. 15 graphically shows the difference in flux versus stage cut for raw and dewatered used oil, in accordance with the Examples.

[0027] Fig. 16 shows a used oil pretreatment process using single-stage membrane and defuel tower.

[0028] Fig. 17 shows a used oil pretreatment process using two membrane stages.

[0029] Fig. 18 graphically shows modeling results for proposed two-stage membrane pretreatment process, in accordance with the Examples.

[0030] Fig. 19 shows a used oil pretreatment process using two membrane stages in reverse order (i.e., removing the fuel molecules first).

[0031] Fig. 20 shows a used oil pretreatment process using two membrane stages and fractionation.

[0032] Fig. 21 shows a used oil pretreatment process using three membrane stages.

[0033] Fig. 22 graphically shows modeling results for three-stage membrane pretreatment process, in accordance with the Examples.

[0034] Fig. 23 lists parameters used in process modeling of used oil membrane pretreatment in Figs. 18 and 22, in accordance with the Examples.

[0035] Fig. 24 summarizes the product quality of a wide-cut VGO product produced by a membrane-based process, in accordance with the Examples.

DETAILED DESCRIPTION OF THE INVENTION

[0036] In various aspects, systems and methods are provided for the pretreatment of used oils using selectively permeable membranes (e.g., polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic) nanofiltration and ultrafiltration membranes). This disclosure utilizes selectively permeable membranes instead of vacuum distillation to recover valuable hydrocarbon molecules from used lubricant oils during pretreatment.

[0037] As used herein, the term “used oil” refers to a petroleum-based oil selected from the group consisting of a natural oil, a mineral oil, and a synthetic oil.

[0038] As used herein, the term “selectively permeable membrane(s)” refers to any membranes that allow the passage of some molecules and inhibit the passage of other molecules. Selective permeable membranes include, for example, nanofiltration membranes, ultrafiltration membranes, and the like.

[0039] As used herein, the terms "nanofiltration” and “ultrafiltration” refer to a membrane modality in which slow permeating molecules (rejected molecules) can be on the same size order of magnitude as the pore of the membrane. The slow permeating molecule moves through molecular sieving and experiences a chemical potential gradient driving force which can be described as the difference between pressure gradient across the membrane and the osmotic pressure gradient across the membrane. The fast permeating molecules (permeate molecules) are much smaller than the pore and are driven through the membrane by hydraulic pressure. Accordingly, increasing transmembrane pressure can actually increase rejection in nanofiltration and ultrafiltration. In nanofiltration and ultrafiltration, fast permeating and slow permeating molecules generally do not differ in size by more than an order of magnitude.

[0040] The term "molecular weight cut-off or "MWCO" is a characterization method to describe the pore size distribution and retention capabilities of membranes. It is defined as the lowest molecular weight (in Daltons) at which greater than 90% of a solute with a known molecular weight is retained by the membrane. Dextran, polyethylene glycol, polystyrene and dye molecules of various molecular weights are commonly used to obtain the MWCO of membranes. For example, a membrane that can retain solutes with molecular weights of 2000+ Daltons has a molecular weight cut-off of 2000 Daltons.

[0041] In an embodiment, a membrane-based method for separating components in a used oil is provided. The method involves providing a used oil stream having lubricant-range hydrocarbon components, lower boiling components (e.g., entrained fuels, cracked molecules, and water), and higher boiling components (e.g., sludge and spent additives); providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane (e.g., a polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic) nanofiltration or ultrafiltration membrane), in which the selectively permeable membrane has a first surface and a second surface opposite to the first surface; passing the stream of used oil to the filtration unit to remove solids; passing the stream having removed solids to the flash distillation column to remove water and light ends; and contacting the stream having removed water and light ends with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface.

[0042] In the membrane-based method, the feed flow rate can range from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure can range from about 200 psig to about 1200 psig, and the feed temperature can range from about 50°C to about 250°C. The oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[0043] In the membrane-based method, the oil permeate is preferably a wide-cut vacuum gas oil (VGO) product. The membrane-based method can include additional membranes for separating fuel molecules from the VGO. This can facilitate additional heteroatom reductions, e.g., from additive molecules that are lighter than VGO or that were cracked during use as a result of thermal or shearing effects. Additionally, this can minimize impacts to the lubes fractionation unit by removing most of the fuel-range molecules in the pretreatment phase.

[0044] In an embodiment, the wide-cut vacuum gas oil (VGO) product can be treated via solvent extraction or hydroprocessing to produce a base stock. The base stock can be, for example, a Group I base stock, or a Group II base stock, or a Group III base stock.

[0045] In another embodiment, a membrane-based system for separating components in a used oil is provided. The membrane-based system includes a used oil stream having lubricantrange hydrocarbon components, lower boiling components (e.g., entrained fuels, cracked molecules, and water), and higher boiling components (e.g., sludge and spent additives); at least one filtration unit; at least one flash distillation column; and at least one selectively permeable membrane (e.g., a polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic) nanofiltration or ultrafiltration membrane), in which the selectively permeable membrane has a first surface and a second surface opposite to the first surface.

[0046] In the membrane-based system, the used oil is passed to the filtration unit to remove solids; the stream having removed solids is passed to the flash distillation column to remove water and light ends; and the stream having removed water and light ends is contacted with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface.

[0047] In the membrane-based system, the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C. The oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[0048] The oil permeate typically has a boiling point distribution from about 350°F to about 1050°F, or a boiling point distribution from about 450°F to about 1050°F, or a boiling point distribution from about 650°F to about 1050°F.

Selectively Permeable Membranes

[0049] Selectively permeable membranes useful in this disclosure include, for example, nanofiltration membranes, ultrafiltration membranes, and the like. The selectively permeable membranes include polymeric and ceramic membranes, and mixed polymeric/ceramic membranes or polymeric/inorganic membranes. In particular, the selectively permeable membranes useful in this disclosure include organic (e.g. polymeric) membranes, inorganic (e.g. metallic, silica, ceramic, carbon, graphene, zeolite, MOF, oxide or glass) membranes, hybrid or mixed-matrix membranes comprised of inorganic particles (e.g. a zeolite, carbon, metal, and/or metal oxide) as the dispersed phase and a polymer matrix as the continuous phase. [0050] The selectively permeable membranes may be formed from any polymeric or ceramic material which provides a separating layer capable of fractionating the lubricant-range hydrocarbon content or separating the desired lubricant-range hydrocarbon content from the lower boiling components and the higher boiling components present in the used oil.

[0051] For example, the selectively permeable membranes may be formed from or comprise a material chosen from any polymeric materials suitable for fabricating selectively permeable membranes, including for example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polysulfone, polyethersulfone, polyacrylonitrile, polyamide, polyimide, polyamideimide, polyetherimide, cellulose acetate, polyaniline, polypyrrole, polyetheretherketone (PEEK), polybenzimidazole, and mixtures thereof.

[0052] Illustrative polymer materials suitable for fabricating selectively permeable membranes include perfluoropolymers, cross-linked silicone, polyimides, cellulose acetate, polysulfones regenerated cellulose, cellulose triacetate, polyether sulfones, polyetherimide, polyvinylidenefluoride, aromatic polyamides, aliphatic polyamides, polyamide-imides, polyetherimides, polyetheresters, polysulfones, polybenzimidazoles, polybenzoxazoles, polyacrylonitrile, polyaromaticpolyamide imides, polyamide esters, polyesters, and combinations, copolymers, and substituted polymers thereof, nitrile rubber, neoprene, polydimethylsiloxane and related silicone polymers, chlorosulfonated polyethylene, polysilicone-carbonate copolymers, fluoroelastomers, plasticized polyvinylchloride, polyurethane, cis-polybutadiene, cis-polyisoprene, poly(butene-l), polystyrene-butadiene copolymers, polyamide-polyether block copolymers, styrene/butadiene/styrene block copolymers, styrene/ethylene/butylene block copolymers, and thermoplastic polyolefin elastomers.

[0053] Illustrative ceramics useful for fabricating the selectively permeable membranes include clays, titania, silica, alumina, cordierite, ferric oxide, boron nitride, zirconia, zeolitic materials, SiC, layered mineral structures, kaolinite, earthen ware materials, SO2/Fe2O3, composites, layered structures comprising a combination of materials, foamed structures comprising a combination of materials, honey-combed configurations comprising a combination of materials, silicon nitride, sol-gel materials, steatite, porcelain, perovskites, macroporous and mesoporous materials, carbons, mixed matrix materials, and combinations thereof. In an embodiment, the ceramics as used in the present disclosure are selected from materials comprised from clays, titania, silica, alumina, cordierite, ferric oxide, boron nitride, zirconia, zeolitic materials, glass, and SiC.

[0054] The selectively permeable membranes can be made by any technique known to the art, including sintering, stretching, track etching, template leaching, interfacial polymerization, or phase inversion. In an embodiment, the selectively permeable membranes may be crosslinked or treated so as to improve its stability in the reaction solvents. For example, by way of non-limiting example, the nanofiltration membranes described in U.S. Patent Nos. 10,934,501 and 11,084,985, the contents of which are incorporated herein by reference, may be used in this disclosure.

[0055] In an embodiment, the selectively permeable membrane is a crosslinked or noncrosslinked composite material comprising a support and a thin, selectively permeable layer. The thin, selectively permeable layer may, for example, be formed from or comprise a material chosen from modified poly siloxane based elastomers including polydimethyl siloxane (PDMS) based elastomers, ethylene-propylene diene (EPDM) based elastomers, polynorbomene based elastomers, polyoctenamer based elastomers, polyurethane based elastomers, butadiene and nitrile butadiene rubber based elastomers, natural rubber, butyl rubber based elastomers, polychloroprene (Neoprene) based elastomers, epichlorohydrin elastomers, polyacrylate elastomers, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF) based elastomers, polyetherblock amides (PEBAX), polyurethane elastomers, crosslinked polyether, polyamide, polyaniline, polypyrrole, and mixtures thereof [0056] In another embodiment, the selectively permeable membranes or selectively permeable composite membranes comprise a polyimide, particular preferred is a polyimide subject to post-formation crosslinking and impregnation with a low volatility compound. Illustrative polyimides are disclosed in GB 2437519 and Soroko et al. (Journal of Membrane Science, 381(1-2) (2011), 152-162) the contents of which are incorporated herein by reference. [0057] In another embodiment, the selectively permeable membrane is prepared from an inorganic material such as, for example, silicon carbide, silicon oxide, zirconium oxide, titanium oxide, and zeolites, using any technique known to those skilled in the art such as sintering, leaching, or sol-gel processing.

[0058] In a further embodiment, the selectively permeable membranes comprise a polymer membrane with dispersed organic or inorganic matrices in the form of powdered solids present at amounts up to 20 wt % of the polymer membrane. Carbon molecular sieve matrices can be prepared by pyrolysis of any suitable material as described in U.S. Patent No. 6,585,802.

[0059] Zeolites may also be used as an inorganic matrix. Illustrative useful zeolites are described in U.S. Patent No. 6,755,900. Metal oxides, for example, titanium dioxide, zinc oxide, and silicon dioxide may be used. Mixed metal oxides such as mixtures of cerium, zirconium, and magnesium may also be used. In an embodiment, the matrices will be particles less than 1.0 micron in diameter, for example less than 0.1 microns in diameter, such as less than 0.01 microns in diameter.

[0060] The selectively permeable membrane (e.g., nanofiltration membrane) can have an average pore size, for example, from about 0.1 nanometers (0.0001 microns) to about 20 nanometers (0.2 microns), or from about 0.2 nanometers (0.0002 microns) to about 10 nanometers (0.01 microns), or from about 0.5 nanometers (0.0005 microns) to about 5 nanometers (0.005 microns).

[0061] Nanofiltration and ultrafiltration membranes differ in pore size (e.g., nanofiltration membranes can preferably have a pore size from about 0.001 microns to about 0.01 microns, and ultrafiltration membranes can preferably have a pore size from about 0.002 microns to about 0.1 microns).

[0062] In an embodiment, the selectively permeable membrane allows organic molecules having a molecular weight of approximately 300 Daltons to 800 Daltons to pass through. Molecules having a molecular weight greater than 1000 Daltons are preferentially retained and trapped by the membrane. The selectively permeable membranes useful in this disclosure possess a molecular weight cut-off of between 200 Daltons and 100,000 Daltons, or between 200 Daltons and 50,000 Daltons, or between 400 Daltons and 20,000 Daltons, or between 600 Daltons and 10,000 Daltons.

[0063] In another embodiment, the selectively permeable membrane has a molecular weight cut-off ranging from about 150 Daltons to about 1,500 Daltons, or from about 200 Daltons to about 800 Daltons, or from about 200 Daltons to less than or equal to 600 Daltons. In an embodiment, the selectively permeable membranes useful in this disclosure possess a molecular weight cut-off of between 150 Daltons and 1500 Daltons, or between 200 Daltons and 800 Daltons, or between 200 Daltons and 600 Daltons.

[0064] Nanofiltration and ultrafiltration membranes differ in molecular weight cut-off (e.g., nanofiltration membranes can preferably have a MWCO from about 200 Daltons to about 1000 Daltons, and ultrafiltration membranes can preferably have a MWCO of about 2000 Daltons or greater, or about 5000 Daltons or greater, or about 10,000 Daltons or greater, or about 50,000 Daltons or greater.

[0065] In an embodiment, more than one membrane and more than one membrane separation step can be utilized in the process of the invention. For example, two different membranes having two different molecular weight cut-offs can be used, e.g., one membrane having a molecular weight cut off between 400 Daltons and 1500 Daltons, especially between 500 Daltons and 800 Daltons, and membrane with a different molecular weight cut-off between 150 Daltons and 600 Daltons, especially between 200 Daltons and 500 Daltons, can be used. That the ranges mentioned before overlap does not mean that the membranes are identical, in contrast, it has to be understood that a membrane having a molecular weight cut-off of 400 Daltons can be combined with a membrane having a molecular weight cut-off of 600 Daltons. [0066] To perform membrane separations on liquid hydrocarbons such as used oil, the selectively permeable membranes utilized are hydrocarbon resistant, meaning that they need to be able to maintain stability under severe operating conditions. Specifically, the selectively permeable membranes employed in this disclosure are chemically stable in the liquid hydrocarbon environment. Used oils, whole crudes and crude fractions contain solvent range molecules such as benzene, toluene, xylenes, pentane, hexane, heptane, and other common hydrocarbon solvent mixtures like kerosene, that can dissolve or embrittle non-hydrocarbon resistant membrane. Furthermore, used oils and whole crudes contain heavy molecules which oftentimes require elevated temperatures to ensure flowability of the feed. Thus, the selectively permeable membranes used in this disclosure have good thermal integrity.

[0067] The processes of this disclosure utilize elevated temperatures. The selectively permeable membranes employed in this disclosure are stable at elevated transmembrane temperatures from about 50-400°C, e.g., between about 100-300°C or 100-200°C.

[0068] The processes of this disclosure utilize elevated transmembrane pressures. The selectively permeable membranes used herein can withstand transmembrane pressures greater than from about ambient to about 2000 psig. For example, with nanofiltration the feed is pressurized typically between 100 psig to 1200 psig, with 2000 psig being a typical limit for a nanofiltration membrane module. In nanofiltration, the permeate side is typically between ambient pressure to about 100 psig.

[0069] The selectively permeable membranes useful in this disclosure exhibit high flux and selectivity at high yields for separation of the lubricant-range hydrocarbon components from the lower boiling components and the higher boiling components.

[0070] Selectively permeable membranes (e.g., nanofiltration and ultrafiltration membranes) useful in this disclosure are commercially available.

Operating Conditions

[0071] The selectively permeable membranes (e.g., nanofiltration membranes and ultrafiltration membranes) useful in this disclosure provide high flux, high selectivity, and enable high temperature and high pressure operation. High flux reduces capital costs, high selectivity results in very high removal of heteroatom-containing components, and high temperature and pressure operation enable processing of viscous feeds.

[0072] The feed stream is contacted with the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer across the membrane, to provide an oil permeate and an oil retentate.

[0073] In an embodiment, the feed flow rate can range from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, or from about 0.5 gal/min to about 2.5 gal/min per membrane leaf, or from about 1.0 gal/min to about 2.0 gal/min per membrane leaf.

[0074] In an embodiment, the feed pressure can range from about 200 psig to about 1200 psig, or from about 500 psig to about 1000 psig, or from about 700 psig to about 900 psig.

[0075] In an embodiment, the feed temperature can range from about 50°C to about 250°C, or from about 130°C to about 220°C, or from about 150°C to about 200°C.

[0076] In an embodiment, the permeate pressure can range from about 0 psig to about 50 psig, or about 0 psig to about 30 psig, or about 0 psig to about 15 psig.

[0077] In an embodiment, the permeate temperature can range from about 50°C to about 250°C, or from about 130°C to about 220°C, or from about 150°C to about 200°C.

[0078] In an embodiment, the permeate yield or stage cut can range from about 5 wt% to about 85 wt% of a whole used oil feed, or from about 5 wt% to about 80 wt% of a whole used oil feed, or from about 75 wt% to about 80 wt% of a whole used oil feed.

[0079] For membrane-based processes of this disclosure which utilize multiple membranes (e.g., 2 and 3 membranes as disclosed in Figs. 14 and 16-18), the operating conditions and average pore size of the additional membranes can vary, and differ from the initial membrane, so as to collect different fractions of each resulting permeate stream.

[0080] In an embodiment, the feed flow rate for the additional membrane(s) can range from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, or from about 0.5 gal/min to about 2.5 gal/min per membrane leaf, or from about 1.0 gal/min to about 2.0 gal/min per membrane leaf.

[0081] In an embodiment, the feed pressure for the additional membrane(s) can range from about 200 psig to about 1200 psig, or from about 500 psig to about 1000 psig, or from about 700 psig to about 900 psig.

[0082] In an embodiment, the feed temperature for the additional membrane(s) can range from about 30°C to about 200°C, or from about 50°C to about 170°C, or from about 100°C to about 150°C.

[0083] In an embodiment, the permeate pressure for the additional membrane(s) can range from about 0 psig to about 50 psig, or about 0 psig to about 30 psig, or about 0 psig to about 15 psig.

[0084] In an embodiment, the permeate temperature for the additional membrane(s) can range from about 50°C to about 250°C, or from about 130°C to about 220°C, or from about 150°C to about 200°C.

[0085] In an embodiment, the permeate yield or stage cut for the additional membrane(s) can range from about 5 wt% to about 80 wt% of a permeate feed, or from about 5 wt% to whole about 75 wt% of a permeate feed, or from about 75 wt% to about 80 wt% of a permeate feed.

[0086] For the additional membrane(s), different pore sizes are needed to collect the different fractions. Thus, the additional selectively permeable membrane(s) have an average pore size that can differ from the initial selectively permeable membrane. For example, the additional selectively permeable membrane(s) can have an average pore size from about 0.1 nanometers to about 5 nanometers, or from about 0.2 nanometers to about 2 nanometers, or from about 0.5 nanometers to about 1 nanometers.

[0087] The selectively permeable membranes useful in this disclosure can be regenerated to control fouling thereof. Illustrative regenerating methods include solvent backflushing. Conventional regeneration methods can be used.

[0088] In an embodiment, a guard bed can be provided to enable co-processing of the wide- cut vacuum gas oil (VGO) product into an existing refinery.

[0089] In an embodiment, membrane configurations useful in this disclosure can include, for example, multiple membranes of one material (e.g., polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic)), or multiple membranes of more than one material. The number of membranes and materials depends on the particular operation.

[0090] Also, the present techniques may be integrated into a various configurations, which may include a variety of compositions for the streams. Membrane separation processes and systems, as described above, are useful for development and production of lubricant-range hydrocarbons from used hydrocarbon streams. [0091] The selectively permeable membranes useful in this disclosure are solvent stable and can withstand operations under high temperature and high pressure. The separation range of the selectively permeable membranes of this disclosure is specific and tight in order to separate carbon deposits, wear metals, water, and spent additives from lubricant-range hydrocarbons in the used oil. The entire process requires minimal pumps to move the feed streams and permeate streams.

[0092] Herein listed are non-limiting embodiments of the disclosure as disclosed.

[0093] Embodiment 1. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; and e) contacting the stream having removed water and light ends from d) with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C; and wherein the oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[0094] Embodiment 2. The method of embodiment 1 wherein the oil permeate comprises a wide-cut vacuum gas oil (VGO) product.

[0095] Embodiment s. The method of embodiment 1 wherein the oil permeate comprises a wide-cut vacuum gas oil (VGO) product and fuel-range molecules. [0096] Embodiment 4. The method of embodiment 1 further comprising contacting the oil permeate with one or more selectively permeable membranes, one or more defuel distillation columns, one or more vacuum distillation columns, or combinations thereof, for removing fuel-range molecules from the oil permeate.

[0097] Embodiment 5. The method of embodiment 1 wherein low boiling components comprise entrained fuels, cracked molecules, and water.

[0098] Embodiment 6. The method of embodiment 1 wherein high boiling components comprise sludge and spent additives.

[0099] Embodiment 7. The method of embodiment 6 wherein the spent additives comprise detergents, antioxidants, dispersants, corrosion inhibitors, friction modifiers, and/or anti -wear agents.

[00100] Embodiment 8. The method of embodiment 1 wherein the oil retentate has a concentration of heteroatoms and metals greater than the oil permeate.

[00101] Embodiment 9. The method of embodiment 1 wherein the oil permeate has a boiling point distribution from about 350°F to about 1050°F.

[00102] Embodiment 10. The method of embodiment 1 wherein the oil permeate has a boiling point distribution from about 450°F to about 1050°F.

[00103] Embodiment 11. The method of embodiment 1 wherein the oil permeate has a boiling point distribution from about 650°F to about 1050°F.

[00104] Embodiment 12. The method of embodiment 1 wherein the feed flow rate is from about 0.5 gal/min to about 2.5 gal/min per membrane leaf.

[00105] Embodiment 13. The method of embodiment 1 wherein the feed flow rate is from about 1.0 gal/min to about 2.0 gal/min per membrane leaf.

[00106] Embodiment 14. The method of embodiment 1 wherein the feed pressure is from about 500 psig to about 1000 psig.

[00107] Embodiment 15. The method of embodiment 1 wherein the feed pressure is from about 700 psig to about 900 psig.

[00108] Embodiment 16. The method of embodiment 1 wherein the feed temperature is from about 130°C to about 220°C.

[00109] Embodiment 17. The method of embodiment 1 wherein the feed temperature is from about 150°C to about 200°C. [00110] Embodiment 18. The method of embodiment 1 having a permeate pressure from about 0 psig to about 50 psig.

[00111] Embodiment 19. The method of embodiment 1 having a permeate pressure from about 0 psig to about 30 psig.

[00112] Embodiment 20. The method of embodiment 1 having a permeate temperature from about 50°C to about 250°C.

[00113] Embodiment 21. The method of embodiment 1 having a permeate temperature from about 130°C to about 220°C.

[00114] Embodiment 22. The method of embodiment 1 having a permeate yield or stage cut from about 5 wt% to about 80 wt% of a whole used oil feed.

[00115] Embodiment 23. The method of embodiment 1 having a permeate yield or stage cut from about 5 wt% to about 75 wt% of a whole used oil feed.

[00116] Embodiment 24. The method of embodiment 1 having a permeate yield or stage cut from about 75 wt% to about 80 wt% of a whole used oil feed.

[00117] Embodiment 25. The method of embodiment 1 wherein the selectively permeable membrane comprises a material chosen from polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic).

[00118] Embodiment 26. The method of embodiment 1 wherein the selectively permeable membrane comprises a material selected from polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polysulfone, polyethersulfone, polyacrylonitrile, polyamide, polyimide, polyamideimide, polyetherimide, cellulose acetate, polyaniline, polypyrrole, polyetheretherketone (PEEK), polybenzimidazole, and mixtures thereof.

[00119] Embodiment 27. The method of embodiment 1 wherein the selectively permeable membrane comprises a polyimide.

[00120] Embodiment 28. The method of embodiment 1 wherein the selectively permeable membrane is a composite material comprising a support and a selectively permeable layer, wherein the selectively permeable layer comprises a material chosen from- polydimethylsiloxane (PDMS) based elastomers, ethylene-propylene diene (EPDM) based elastomers, polynorborene based elastomers, polyoctenamer based elastomers, polyurethane based elastomers, butadiene and nitrile butadiene rubber based elastomers, natural rubber, butyl rubber based elastomers, polychloroprene (Neoprene) based elastomers, epichlorohydrin elastomers, polyacrylate elastomers, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF) based elastomers, polyetherblock amides (PEBAX), polyurethane elastomers, crosslinked polyether, polyamide, polyaniline, polypyrrole, and mixtures thereof.

[00121] Embodiment 29. The method of embodiment 1 wherein the selectively permeable membrane comprises an inorganic material selected from silicon carbide, silicon oxide, zirconium oxide, titanium oxide, and zeolites.

[00122] Embodiment 30. The method of embodiment 1 wherein the selectively permeable membrane comprises a polymer membrane with dispersed organic or inorganic matrices in the form of powdered solids present in amounts up to about 20 wt % of the polymer membrane.

[00123] Embodiment 31. The method of embodiment 1 wherein the selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers.

[00124] Embodiment 32. The method of embodiment 1 wherein the selectively permeable membrane has an average pore size from about 0.2 nanometers to about 10 nanometers.

[00125] Embodiment 33. The method of embodiment 1 wherein the selectively permeable membrane has an average pore size from about 0.5 nanometers to about 5 nanometers.

[00126] Embodiment 34. The method of embodiment 1 wherein the selectively permeable membrane has a molecular weight cut-off of between 200 and 100,000 Daltons.

[00127] Embodiment 35. The method of embodiment 1 wherein the selectively permeable membrane has a molecular weight cut-off of between 400 and 10,000 Daltons.

[00128] Embodiment 36. The method of embodiment 1 wherein the used oil comprises a petroleum-based oil selected from the group consisting of a natural oil, a mineral oil, and a synthetic oil.

[00129] Embodiment 37. The method of embodiment 1 further comprising regenerating the selectively permeable membrane to control fouling thereof.

[00130] Embodiment 38. The method of embodiment 37 wherein the regenerating comprises solvent backflushing.

[00131] Embodiment 39. The method of embodiment 2 further comprising providing a guard bed to enable co-processing of the wide-cut vacuum gas oil (VGO) product into an existing refinery.

[00132] Embodiment 40. The method of embodiment 2 further comprising treating the wide-cut vacuum gas oil (VGO) product via solvent extraction or hydroprocessing to produce a base stock.

[00133] Embodiment 41. The method of embodiment 40 wherein the base stock is a Group I base stock, or a Group II base stock, or a Group III base stock.

[00134] Embodiment 42. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) contacting the stream having removed solids from c) with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; and e) passing the oil permeate from d) to the flash distillation column to remove water and light ends; wherein the selectively permeable membrane has a feed flow rate from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, a feed pressure from about 200 psig to about 1200 psig, and a feed temperature from about 50°C to about 250°C; and wherein the oil permeate from d) has a concentration of lubricant-range hydrocarbon components greater than the oil retentate from d), and the oil retentate from d) has a concentration of lower boiling components and higher boiling components greater than the oil permeate from d).

[00135] Embodiment 43. The method of embodiment 42 wherein the stream having removed water and light ends from e) comprises a wide-cut vacuum gas oil (VGO) product. [00136] Embodiment 44. The method of embodiment 42 wherein the stream having removed water and light ends from e) comprises a wide-cut vacuum gas oil (VGO) product and fuel-range molecules.

[00137] Embodiment 45. The method of embodiment 44 wherein the fuel-range molecules are separated downstream from the wide-cut vacuum gas oil (VGO) product .in a fluid catalytic cracking (FCC) main column or during lube fractionation.

[00138] Embodiment 46. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, at least one selectively permeable membrane, and at least one defuel distillation column; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; e) contacting the stream having removed water and light ends from d) with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; and f) passing the oil permeate from e) to the defuel distillation column to remove fuel components; wherein the selectively permeable membrane has a feed flow rate from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, a feed pressure is from about 200 psig to about 1200 psig, and a feed temperature is from about 50°C to about 250°C; and wherein the oil permeate from e) has a concentration of lubricant-range hydrocarbon components greater than the oil retentate from e), and the oil retentate from e) has a concentration of lower boiling components and higher boiling components greater than the oil permeate from e). [00139] Embodiment 47. The method of embodiment 46 wherein the defuel distillation column gives a wide-cut vacuum gas oil (VGO) product.

[00140] Embodiment 48. The method of embodiment 46 wherein the defuel distillation column gives a first stream comprising a wide-cut vacuum gas oil (VGO) product, and a second stream comprising fuel components.

[00141] Embodiment 49. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; e) contacting the stream having removed water and light ends from d) with the first surface of a first selectively permeable membrane at a first feed flow rate, a first feed pressure and a first feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a first oil permeate contacting the second surface and a first oil retentate contacting the first surface; and f) contacting the first oil permeate from e) with the first surface of a second selectively permeable membrane at a second feed flow rate, a second feed pressure and a second feed temperature, to separate fuel components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a second oil permeate contacting the second surface and a second oil retentate contacting the first surface; wherein the first feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the first feed pressure is from about 200 psig to about 1200 psig, and the first feed temperature is from about 50°C to about 250°C; wherein the second feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the second feed pressure is from about 200 psig to about 1200 psig, and the second feed temperature is from about 30°C to about 200°C; and wherein the second oil permeate has a concentration of lubricant-range hydrocarbon components greater than the second oil retentate, and the second oil retentate has a concentration of lower boiling components and higher boiling components greater than the second oil permeate.

[00142] Embodiment 50. The method of embodiment 49 wherein the first selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers, and the second selectively permeable membrane has an average pore size from about 0.1 nanometers to about 5 nanometers.

[00143] Embodiment 51. The method of embodiment 49 wherein the second oil permeate comprises a wide-cut vacuum gas oil (VGO) stream.

[00144] Embodiment 52. The method of embodiment 49 wherein the second selectively permeable membrane gives a first stream comprising a wide-cut vacuum gas oil (VGO) product, and a second stream comprising fuel components.

[00145] Embodiment 53. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; e) contacting the stream having removed water and light ends from d) with the first surface of a first selectively permeable membrane at a first feed flow rate, a first feed pressure and a first feed temperature, to separate fuel components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a first oil permeate contacting the second surface and a first oil retentate contacting the first surface; and f) contacting the first oil permeate from e) with the first surface of a second selectively permeable membrane at a second feed flow rate, a second feed pressure and a second feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a second oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the first feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the first feed pressure is from about 200 psig to about 1200 psig, and the first feed temperature is from about 50°C to about 250°C; wherein the second feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the second feed pressure is from about 200 psig to about 1200 psig, and the second feed temperature is from about 30°C to about 200°C; and wherein the second oil permeate has a concentration of lubricant-range hydrocarbon components greater than the second oil retentate, and the second oil retentate has a concentration of lower boiling components and higher boiling components greater than the second oil permeate.

[00146] Embodiment 54. The method of embodiment 53 wherein the first selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers, and the second selectively permeable membrane has an average pore size from about 0.1 nanometers to about 5 nanometers.

[00147] Embodiment 55. The method of embodiment 53 wherein the second oil permeate comprises a wide-cut vacuum gas oil (VGO) product.

[00148] Embodiment 56. The method of embodiment 53 wherein the first selectively permeable membrane gives a first stream comprising a wide-cut vacuum gas oil (VGO) product, and a second stream comprising fuel components.

[00149] Embodiment 57. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, at least one selectively permeable membrane, and at least one vacuum distillation column; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; e) contacting the stream having removed water and light ends from d) with the first surface of a first selectively permeable membrane at a first feed flow rate, a first feed pressure and a first feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a first oil permeate contacting the second surface and an oil retentate contacting the first surface; f) contacting the first oil permeate from e) with the first surface of a second selectively permeable membrane at a second feed flow rate, a second feed pressure and a second feed temperature, to separate fuel components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a second oil permeate contacting the second surface and an oil retentate contacting the first surface; and g) passing the second oil permeate from f) to the vacuum distillation column for fractionation; wherein the first feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the first feed pressure is from about 200 psig to about 1200 psig, and the first feed temperature is from about 50°C to about 250°C; wherein the second feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the second feed pressure is from about 200 psig to about 1200 psig, and the second feed temperature is from about 30°C to about 200°C; and wherein the second oil permeate has a concentration of lubricant-range hydrocarbon components greater than the second oil retentate, and the second oil retentate has a concentration of lower boiling components and higher boiling components greater than the second oil permeate.

[00150] Embodiment 58. The method of embodiment 57 wherein the first selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers, and the second selectively permeable membrane has an average pore size from about 0.1 nanometers to about 5 nanometers.

[00151] Embodiment 59. The method of embodiment 57 wherein fractionation in the vacuum distillation column gives a light naphtha vacuum gas oil (VGO) product, a medium naphtha vacuum gas oil (VGO) product, and a heavy naphtha vacuum gas oil (VGO) product. [00152] Embodiment 60. The method of embodiment 57 wherein the second selectively permeable membrane gives a first stream comprising a wide-cut vacuum gas oil (VGO) product, and a second stream comprising fuel components.

[00153] Embodiment 61. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; e) contacting the stream having removed water and light ends from d) with the first surface of a first selectively permeable membrane at a first feed flow rate, a first feed pressure and a first feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a first oil permeate contacting the second surface and a first oil retentate contacting the first surface; f) contacting the first oil permeate from e) with the first surface of a second selectively permeable membrane at a second feed flow rate, a second feed pressure and a second feed temperature, to separate fuel components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a second oil permeate contacting the second surface and a second oil retentate contacting the first surface; and g) contacting the second permeate from f) with the first surface of a third selectively permeable membrane at a third feed flow rate, a third feed pressure and a third feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide a third oil permeate contacting the second surface and a third oil retentate contacting the first surface; wherein the first feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the first feed pressure is from about 200 psig to about 1200 psig, and the first feed temperature is from about 50°C to about 250°C; wherein the second feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the second feed pressure is from about 200 psig to about 1200 psig, and the second feed temperature is from about 30°C to about 200°C; wherein the third feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the third feed pressure is from about 200 psig to about 1200 psig, and the third feed temperature is from about 30°C to about 200°C; and wherein the third oil permeate has a concentration of lubricant-range hydrocarbon components greater than the third oil retentate, and the third oil retentate has a concentration of lower boiling components and higher boiling components greater than the third oil permeate. [00154] Embodiment 62. The method of embodiment 61 wherein the first selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers, the second selectively permeable membrane has an average pore size from about 0.1 nanometers to about 5 nanometers, and the third selectively permeable membrane has an average pore size from about 0.1 nanometers to about 5 nanometers.

[00155] Embodiment 63. The method of embodiment 61 wherein the third oil permeate comprises a light vacuum gas oil (VGO) product and a heavy vacuum gas oil (VGO) product.

[00156] Embodiment 64. The method of embodiment 61 wherein the second selectively permeable membrane gives a first stream comprising a wide-cut vacuum gas oil (VGO) product, and a second stream comprising fuel components.

[00157] Embodiment 65. A system for separating components in a used oil, said system comprising: a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; at least one filtration unit; at least one flash distillation column; and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; wherein the used oil is passed to the filtration unit to remove solids; the stream having removed solids is passed to the flash distillation column to remove water and light ends; and the stream having removed water and light ends is contacted with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C; and wherein the oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[00158] Embodiment 66. The system of embodiment 65 wherein the oil permeate comprises a wide-cut vacuum gas oil (VGO) product.

[00159] Embodiment 67. The system of embodiment 65 wherein the oil permeate comprises a wide-cut vacuum gas oil (VGO) product and fuel-range molecules.

[00160] Embodiment 68. The system of embodiment 65 further comprising one or more additional selectively permeable membranes, one or more defuel distillation columns, one or more vacuum distillation columns, or combinations thereof, in which the oil permeate is contacted with one or more additional selectively permeable membranes, one or more defuel distillation columns, one or more vacuum distillation columns, or combinations thereof, to remove fuel-range molecules from the oil permeate.

[00161] Embodiment 69. The system of embodiment 65 wherein low boiling components comprise entrained fuels, cracked molecules, and water.

[00162] Embodiment 70. The system of embodiment 65 wherein high boiling components comprise sludge and spent additives.

[00163] Embodiment 71. The system of embodiment 70 wherein the spent additives comprise detergents, antioxidants, dispersants, corrosion inhibitors, friction modifiers, and/or anti-wear agents.

[00164] Embodiment 72. The system of embodiment 65 wherein the oil retentate has a concentration of heteroatoms and metals greater than the oil permeate.

[00165] Embodiment 73. The system of embodiment 65 wherein the oil permeate has a boiling point distribution from about 350°F to about 1050°F. [00166] Embodiment 74. The system of embodiment 65 wherein the oil permeate has a boiling point distribution from about 450°F to about 1050°F.

[00167] Embodiment 75. The system of embodiment 65 wherein the oil permeate has a boiling point distribution from about 650°F to about 1050°F.

[00168] Embodiment 76. The system of embodiment 65 wherein the feed flow rate is from about 0.5 gal/min to about 2.5 gal/min per membrane leaf.

[00169] Embodiment 77. The system of embodiment 65 wherein the feed flow rate is from about 1.0 gal/min to about 2.0 gal/min per membrane leaf.

[00170] Embodiment 78. The system of embodiment 65 wherein the feed pressure is from about 500 psig to about 1000 psig.

[00171] Embodiment 79. The system of embodiment 65 wherein the feed pressure is from about 700 psig to about 900 psig.

[00172] Embodiment 80. The system of embodiment 65 wherein the feed temperature is from about 130°C to about 220°C.

[00173] Embodiment 81. The system of embodiment 65 wherein the feed temperature is from about 150°C to about 200°C.

[00174] Embodiment 82. The system of embodiment 65 having a permeate pressure from about 0 psig to about 50 psig.

[00175] Embodiment 83. The system of embodiment 65 having a permeate pressure from about 0 psig to about 30 psig.

[00176] Embodiment 84. The system of embodiment 65 having a permeate temperature from about 50°C to about 250°C.

[00177] Embodiment 85. The system of embodiment 65 having a permeate temperature from about 130°C to about 220°C.

[00178] Embodiment 86. The system of embodiment 65 having a permeate yield or stage cut from about 5 wt% to about 80 wt% of a whole used oil feed.

[00179] Embodiment 87. The system of embodiment 65 having a permeate yield or stage cut from about 5 wt% to about 75 wt% of a whole used oil feed.

[00180] Embodiment 88. The system of embodiment 65 having a permeate yield or stage cut from about 75 wt% to about 80 wt% of a whole used oil feed.

[00181] Embodiment 89. The system of embodiment 65 wherein the selectively permeable membrane comprises a material chosen from polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic).

[00182] Embodiment 90. The system of embodiment 65 wherein the selectively permeable membrane comprises a material selected from polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polysulfone, polyethersulfone, polyacrylonitrile, polyamide, polyimide, polyamideimide, polyetherimide, cellulose acetate, polyaniline, polypyrrole, polyetheretherketone (PEEK), polybenzimidazole, and mixtures thereof.

[00183] Embodiment 91. The system of embodiment 65 wherein the selectively permeable membrane comprises a polyimide.

[00184] Embodiment 92. The system of embodiment 65 wherein the selectively permeable membrane is a composite material comprising a support and a selectively permeable layer, wherein the selectively permeable layer comprises a material chosen from- polydimethylsiloxane (PDMS) based elastomers, ethylene-propylene diene (EPDM) based elastomers, polynorborene based elastomers, polyoctenamer based elastomers, polyurethane based elastomers, butadiene and nitrile butadiene rubber based elastomers, natural rubber, butyl rubber based elastomers, polychloroprene (Neoprene) based elastomers, epichlorohydrin elastomers, polyacrylate elastomers, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF) based elastomers, polyetherblock amides (PEBAX), polyurethane elastomers, crosslinked polyether, polyamide, polyaniline, polypyrrole, and mixtures thereof.

[00185] Embodiment 93. The system of embodiment 65 wherein the selectively permeable membrane comprises an inorganic material selected from silicon carbide, silicon oxide, zirconium oxide, titanium oxide, and zeolites.

[00186] Embodiment 94. The system of embodiment 65 wherein the selectively permeable membrane comprises a polymer membrane with dispersed organic or inorganic matrices in the form of powdered solids present in amounts up to about 20 wt % of the polymer membrane.

[00187] Embodiment 95. The system of embodiment 65 wherein the selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers.

[00188] Embodiment 96. The system of embodiment 65 wherein the selectively permeable membrane has an average pore size from about 0.2 nanometers to about 10 nanometers.

[00189] Embodiment 97. The system of embodiment 65 wherein the selectively permeable membrane has an average pore size from about 0.5 nanometers to about 5 nanometers.

[00190] Embodiment 98. The system of embodiment 65 wherein the selectively permeable membrane has a molecular weight cut-off of between 200 and 100,000 Daltons.

[00191] Embodiment 99. The system of embodiment 65 wherein the selectively permeable membrane has a molecular weight cut-off of between 400 and 1800 Daltons.

[00192] Embodiment 100. The system of embodiment 65 wherein the used oil comprises a petroleum-based oil selected from the group consisting of a natural oil, a mineral oil, and a synthetic oil.

[00193] Embodiment 101. The system of embodiment 65 wherein the selectively permeable membrane is regenerated to control fouling thereof.

[00194] Embodiment 102. The system of embodiment 101 wherein the selectively permeable membrane is regenerated by solvent backflushing.

[00195] Embodiment 103. The system of embodiment 66 further comprising a guard bed to enable co-processing of the wide-cut vacuum gas oil (VGO) product into an existing refinery.

[00196] Embodiment 104. The system of embodiment 66 in which the wide-cut vacuum gas oil (VGO) product is treated via solvent extraction or hydroprocessing to produce a base stock.

[00197] Embodiment 105. The system of embodiment 104 wherein the base stock is a Group I base stock, or a Group II base stock, or a Group III base stock.

[00198] Embodiment 106. A composition comprising a wide-cut vacuum gas oil

(VGO) product, said composition produced by a process comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; and e) contacting the stream having removed water and light ends from d) with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C; and wherein the oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[00199] Embodiment 107. The composition of embodiment 106 wherein, in the process, the oil permeate comprises vacuum gas oil (VGO) range hydrocarbons.

[00200] Embodiment 108. The composition of embodiment 106 wherein, in the process, the oil permeate comprises a wide-cut vacuum gas oil (VGO) product and fuel-range molecules.

[00201] Embodiment 109. The composition of embodiment 106 wherein said process further comprises contacting the oil permeate with one or more selectively permeable membranes, one or more defuel distillation columns, one or more vacuum distillation columns, or combinations thereof, for removing fuel-range molecules from the oil permeate.

[00202] Embodiment 110. The composition of embodiment 106 wherein, in the process, the low boiling components comprise entrained fuels, cracked molecules, and water.

[00203] Embodiment 111. The composition of embodiment 106 wherein, in the process, the high boiling components comprise sludge and spent additives.

[00204] Embodiment 112. The composition of embodiment 111 wherein the spent additives comprise detergents, antioxidants, dispersants, corrosion inhibitors, friction modifiers, and/or anti-wear agents.

[00205] Embodiment 113. The composition of embodiment 106 wherein, in the process, the oil retentate has a concentration of heteroatoms and metals greater than the oil permeate. [00206] Embodiment 114. The composition of embodiment 106 wherein, in the process, the oil permeate has a boiling point distribution from about 350°F to about 1050°F.

[00207] Embodiment 115. The composition of embodiment 106 wherein, in the process, the oil permeate has a boiling point distribution from about 450°F to about 1050°F.

[00208] Embodiment 116. The composition of embodiment 106 wherein, in the process, the oil permeate has a boiling point distribution from about 650°F to about 1050°F.

[00209] Embodiment 117. The composition of embodiment 106 wherein, in the process, the feed flow rate is from about 0.5 gal/min to about 2.5 gal/min per membrane leaf.

[00210] Embodiment 118. The composition of embodiment 106 wherein, in the process, the feed flow rate is from about 1.0 gal/min to about 2.0 gal/min per membrane leaf.

[00211] Embodiment 119. The composition of embodiment 106 wherein, in the process, the feed pressure is from about 500 psig to about 1000 psig.

[00212] Embodiment 120. The composition of embodiment 106 wherein, in the process, the feed pressure is from about 700 psig to about 900 psig.

[00213] Embodiment 121. The composition of embodiment 106 wherein, in the process, the feed temperature is from about 130°C to about 220°C.

[00214] Embodiment 122. The composition of embodiment 106 wherein, in the process, the feed temperature is from about 150°C to about 200°C.

[00215] Embodiment 123. The composition of embodiment 106 wherein the process a permeate pressure from about 0 psig to about 50 psig.

[00216] Embodiment 124. The composition of embodiment 106 wherein the process a permeate pressure from about 0 psig to about 30 psig.

[00217] Embodiment 125. The composition of embodiment 106 wherein the process has a permeate temperature from about 50°C to about 250°C.

[00218] Embodiment 126. The composition of embodiment 106 wherein the process has a permeate temperature from about 130°C to about 220°C.

[00219] Embodiment 127. The composition of embodiment 106 wherein the process has a permeate yield or stage cut from about 5 wt% to about 80 wt% of a whole used oil feed.

[00220] Embodiment 128. The composition of embodiment 106 wherein the process has a permeate yield or stage cut from about 5 wt% to about 75 wt% of a whole used oil feed.

[00221] Embodiment 129. The composition of embodiment 106 wherein the process has a permeate yield or stage cut from about 75 wt% to about 80 wt% of a whole used oil feed.

[00222] Embodiment 130. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane comprises a material chosen from polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic).

[00223] Embodiment 131. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane comprises a material selected from polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polysulfone, polyethersulfone, polyacrylonitrile, polyamide, polyimide, polyamideimide, polyetherimide, cellulose acetate, polyaniline, polypyrrole, polyetheretherketone (PEEK), polybenzimidazole, and mixtures thereof.

[00224] Embodiment 132. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane comprises a polyimide.

[00225] Embodiment 133. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane is a composite material comprising a support and a selectively permeable layer, wherein the selectively permeable layer comprises a material chosen from-polydimethylsiloxane (PDMS) based elastomers, ethylene-propylene diene (EPDM) based elastomers, polynorborene based elastomers, polyoctenamer based elastomers, polyurethane based elastomers, butadiene and nitrile butadiene rubber based elastomers, natural rubber, butyl rubber based elastomers, polychloroprene (Neoprene) based elastomers, epichlorohydrin elastomers, polyacrylate elastomers, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF) based elastomers, polyetherblock amides (PEBAX), polyurethane elastomers, crosslinked polyether, polyamide, polyaniline, polypyrrole, and mixtures thereof.

[00226] Embodiment 134. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane comprises an inorganic material selected from silicon carbide, silicon oxide, zirconium oxide, titanium oxide, and zeolites.

[00227] Embodiment 135. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane comprises a polymer membrane with dispersed organic or inorganic matrices in the form of powdered solids present in amounts up to about 20 wt % of the polymer membrane.

[00228] Embodiment 136. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane has an average pore size from about 0.1 nanometers to about 20 nanometers.

[00229] Embodiment 137. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane has an average pore size from about 0.2 nanometers to about 10 nanometers.

[00230] Embodiment 138. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane has an average pore size from about 0.5 nanometers to about 5 nanometers.

[00231] Embodiment 139. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane has a molecular weight cut-off of between 200 and 100,000 Daltons.

[00232] Embodiment 140. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane has a molecular weight cut-off of between 400 and 10,000 Daltons.

[00233] Embodiment 141. The composition of embodiment 106 wherein, in the process, the used oil comprises a petroleum-based oil selected from the group consisting of a natural oil, a mineral oil, and a synthetic oil.

[00234] Embodiment 142. The composition of embodiment 106 wherein, in the process, the selectively permeable membrane is regenerated to control fouling thereof.

[00235] Embodiment 143. The composition of embodiment 142 wherein the selectively permeable membrane is regenerated by solvent backflushing.

[00236] Embodiment 144. The composition of embodiment 107 wherein, in the process, a guard bed is provided to enable co-processing of the wide-cut vacuum gas oil (VGO) product into an existing refinery.

[00237] Embodiment 145. The composition of embodiment 107 wherein, in the process, the wide-cut vacuum gas oil (VGO) product is treated via solvent extraction or hydroprocessing to produce a base stock.

[00238] Embodiment 146. The composition of embodiment 145 wherein the base stock is a Group I base stock, or a Group II base stock, or a Group III base stock.

[00239] Embodiment 147. A composition comprising a wide-cut vacuum gas oil (VGO), said composition having a kinematic viscosity at 40°C from about 20 cSt to about 24 cSt, a kinematic viscosity at 100°C from about 4.5 cSt to about 4.75 cSt, a viscosity index from about 116 to about 160, a pour point of -16°C or greater, a total acid number from about 0.40 mg KOH/g to about 0.80 mg KOH/g, total oxygen in hydrocarbons from about 0.30 wt% to about 0.60 wt%, and total aromatics from about 130 mmol/kg to about 545 mmol/kg.

[00240] Embodiment 148. The composition of embodiment 147 further having a sulfur content from about 495 ppm to about 695 ppm, a nitrogen content from about 265 ppm to about 310 ppm, a calcium content less about 10 ppm, a chlorine content from about 10 ppm to about 40 ppm, a magnesium content less than about 10 ppm, a phosphorus content from about 20 ppm to about 50 ppm, a zinc content less than about 10 ppm, and a copper content less than about 10 ppm.

[00241] Embodiment 149. The method of embodiments 1-64 wherein the selectively permeable membrane is a nanofiltration membrane or an ultrafiltration membrane. [00242] Embodiment 150. The system of embodiments 65-105 wherein the selectively permeable membrane is a nanofiltration membrane or an ultrafiltration membrane. [00243] Embodiment 151. The composition of embodiments 106-146 wherein the selectively permeable membrane is a nanofiltration membrane or an ultrafiltration membrane. [00244] The following non-limiting examples are provided to illustrate the disclosure.

Examples

One-Stage Membrane Process

[00245] As shown in Fig. 1, conventional used oil pretreatment comprises four steps: (1) filtration to remove solids, (2) flash distillation to remove water and light ends, (3) moderate vacuum distillation to remove fuel-range molecules, and (4) deep vacuum distillation + thin film evaporation to recover lube-range hydrocarbons and remove heavies, including spent additives. An illustrative membrane-based process of this disclosure, as shown in Fig. 2, retains the filtration and dehydration steps as in the conventional technology, eliminates the de-fuel tower, and replaces the vacuum distillation + thin film evaporator heavies rejection step with a nanofiltration membrane. A single wide-cut VGO product results from the membrane-based process. In the illustrative process depicted in Fig. 2, the fuel molecules are not separated, but are instead passed downstream with the VGO to be separated, e.g., in a fluid catalytic cracking (FCC) main column or during lubes fractionation. [00246] For a 3 thousand barrels per day (kbd) used oil pretreatment plant, an economic analysis shows a potential CAPEX advantage for a membrane over vacuum distillation + thin film evaporation, if an average membrane flux of 4 gal/ft ² /day is obtained.

[00247] To enable co-processing of the pretreated VGO from used oil into existing refineries, a guard bed can be used to protect the existing assets. This was already expected for VGO from conventional used oil pretreatment, and is likely to remain true for VGO from membrane pretreatment. The competitive advantage comes from eliminating the de-fuel tower and replacing the de-contaminate tower + thin film evaporator with a less capital intensive membrane. The guard bed can be inserted anywhere within the pretreatment process, and there may be advantages to moving it earlier in the process.

[00248] Used oil pretreatment can be a highly fouling service, with the flux declining over a period of time. The membrane-based process of this disclosure can utilize equipment for regular membrane regeneration, e.g. via solvent backflushing.

[00249] A number of commercial and near-commercial nanofiltration membranes for separating the used oil were tested using a batch coupon screening apparatus. A typical experiment is as follows. Approximately 100 g of feed is loaded onto the feed side of a chamber containing a membrane as a 2-inch disc. The chamber is sealed, heated to the desired temperature (typically 50-150°C), pressurized with nitrogen to 400-800 psig, and stirred at a rate of 400 rpm to keep the feed fluid homogeneous. The pressure differential causes fluid molecules to pass through the membrane, where they are collected in a beaker attached to a scale to monitor the rate of permeate accumulation. The feed-side composition changes as material selectivity permeates through the membrane, allowing the experiment to visit the entire composition range that would be present in commercial operation. The experiment ends when the target permeate yield (“stage cut”) is obtained, and so the run length is typically only a few hours to a few days.

[00250] Several polymer, ceramic, and hybrid membranes have demonstrated high flux and selectivity at high yields for this separation, from multiple membrane vendors. Fig. 3 shows the observed fluxes through four of the screened membranes as a function of the stage cut (the fraction of the feed that exits in the permeate) for initial screening experiments at 130- 135°C and 700 psig. All three materials show fluxes within a factor of 2-4 of the commercial target, with the highest flux having an average of 2.2 gal/ft ² /day up to 75 wt% stage cut.

[00251] Fig. 4 shows the measured boiling point distribution as obtained via simulated distillation of the raw used oil feed (black link) and the permeates obtained from the same four membranes. The permeate yields in each run varied, so the distributions were weighted to a 75% stage cut to facilitate comparison. All of the membranes show a strong rejection of 1050°F+ material, with effectively zero concentration above 1100°F. Overall the three membranes yielded similar boiling point distributions, with perhaps a modest trade-off between flux and selectivity observed.

[00252] One of the key objectives of the pretreatment is to remove the spent additives from the used oil. Additives generally incorporate metals and other heteroatoms in order to achieve their performance modification; for example, detergents commonly contain calcium and magnesium metals, while zinc is often found in antioxidants and anti-wear agents. As a result, heteroatom analysis can be used to gauge the effectiveness of the membrane in rejecting the additive molecules. Fig. 5 shows the heteroatom content of the raw used oil feed and the permeates from experiments with various membranes. The last column shows a representative pretreated light VGO obtained from a re-refiner that uses vacuum distillation + thin film evaporator. All three membranes do a remarkable job of removing calcium and magnesium, each from hundreds of ppm to near or below the detection limit. The membranes also substantially reduce the nitrogen, sulfur, and phosphorus levels, but more processing is needed for further reduction. Overall the membranes produce a wide-cut VGO that is of competitive quality with that achieved via traditional pretreatment.

[00253] Fig. 6 shows representative photos of samples of the raw used oil and the membrane permeate and retentate products. The permeate color is markedly improved, going from nearly black to a deep amber. The remaining retentate is very viscous and an opaque black color.

[00254] In accordance with this disclosure, it is desired to increase the flux through the membrane while minimizing the impact on the selectivity. One way is to increase the operating temperature of the membrane, as previous nanofiltration experience with other hydrocarbon feeds have shown a strong inverse correlation of flux with feed viscosity. Also, membrane materials with different pore sizes and supports can be used, as increasing the pore size generally leads to increased flux (but potentially decreased selectivity).

Impact of Feed Temperature

[00255] Diffusivity is a significant factor in the permeability of molecules through a nanofiltration membrane. The membrane flux is inversely correlated with the viscosity of the feed. As a result, increasing the operating temperature of the membrane is one means of increasing the flux. This is illustrated in Fig. 7, which shows membrane flux as a function of stage cut from batch membrane experiments with dewatered used oil feed at three temperatures with a membrane. The average membrane flux at 75% stage cut increases from 2.1 to 2.4 to 3.6 gal/ft ² /day at 135, 150, and 175°C, respectively. Fig. 8 shows measured viscosity data for each permeate from the three runs; the values are nearly identical at all temperatures, indicating minimal loss of selectivity. This is further confirmed from the minimal impact of temperature on the permeate metal s/heteroatom concentrations, shown in Fig. 9.

Impact of Feed Pressure

[00256] The driving force for molecular transport across a nanofiltration membrane is established using a pressure differential, usually by increasing the feed pressure using a pump. For a given permeate pressure, increasing the feed pressure should increase the flux across the membrane due to the increased driving force. Fig. 10 shows flux vs. stage cut data for two experiments at different feed pressures of 700 and 850 psig using the dewatered used oil feed and a membrane at 150°C. The -25% increase in flux of is similar to the -20% increase in pressure differential. Viscosity and heteroatom measurements of the permeates at 75% stage cut from the two runs, shown in Fig. 11 and Fig. 12, returned nearly identical values, indicating negligible loss in selectivity. Therefore, pressure is an additional process knob that is available to increase the membrane flux, though it may be bounded from above by the module materials or design.

Impact of Stage Cut/Yield

[00257] It is important to the process economics to obtain a high yield of VGO molecules. In particular, there is a significant margin between VGO molecules and asphalt blendstock, so every molecule of VGO that slips into the asphalt product stream is a substantial downgrade. Fig. 13 shows the flux vs. stage cut data of a batch experimental run which pushed the stage cut as high as possible. This run used raw used oil feed and a membrane at 135°C and 700 psig feed conditions. As stage cut increases the flux decreases, likely due to the increasing viscosity of the feed. At 75% stage cut, an order of magnitude increase in retentate viscosity compared to the feed viscosity is observed, and often the flux is 5-1 Ox lower at this stage cut than at the start of the experiment. This rapidly worsens as the stage cut increases beyond 75%, and by 85% the flux has effectively decreased to zero.

[00258] In this experiment, the permeate was divided into three samples: 0-10%, 10- 75%, and 75-85%. A histogram of the boiling point distribution of each of these permeates compared to the feed is shown in Fig. 14. The 10-75% permeate looks very similar to the 0-10% permeate; in particular, the fraction of molecules with boiling points above 1050°F is nearly unchanged. The 1050°F+ fraction indicates how effective the membrane is at rejecting the spent additives and other molecules that reside in the residue fraction. However, the 75- 85% permeate shows a significant increase in the 1050°F+ fraction, indicating that the slip of these molecules into the VGO product has begun.

[00259] As a result of both flux and separation factor, the target stage cut for this used oil feed appears to be 75-80%. However, the simulated distillation of the feed indicates that there only 5-10% of the molecules reside in the 1050°F+ fraction. Thus there appears to be some giveaway of VGO molecules required when using membranes as a pretreatment step, compared to distillation.

Ordering of Dewater and Membrane Steps

[00260] It may be advantageous to reverse the order of the dewater flash drum and the nanofiltration membrane. For example, placing the membrane first could enable increased fluxes by taking advantage of the very light hydrocarbon molecules that exist with the water to lower the feed viscosity. Fig. 15 shows the membrane flux profiles as a function of the stage cut for batch screening experiments with a membrane using both the raw used oil feed and a distilled used oil feed to remove the water and other 300°F- molecules. The raw feed shows a higher flux in the first 0-20% of stage cut, likely due to the reduced feed viscosity of the raw used oil feed as a result of the 300°F- molecules. The 300°F- molecules are the fastest permeating components, and as they become depleted, the flux of the raw feed approaches that of the dewatered feed. Ultimately the difference over the entire 75% stage cut is modest: 2.2 vs. 2.1 gal/ft ² /day.

Two-Stage Membrane Process

[00261] The base process concept produces a wide-cut VGO which also contains naphtha and distillate molecules. It may be possible to pass those molecules downstream to lubricant production, and allow them to be removed using the existing lubricant fractionation equipment. However, if the lubes plant is capacity-limited by fuel-range molecules, then it may be preferred to remove the naphtha and distillate during pretreatment, as is done in distillation-based pretreatment. One embodiment of this, shown in Fig. 16, restores the defuel distillation column to the flowsheet, downstream of the membrane. This enables removal of the highly fouling components early in the process, which may lead to longer run lengths in the downstream equipment than typical of distillation-based pretreatment. This also enables use of the naphtha and distillate molecules to increase the membrane flux by decreasing the feed viscosity. These advantages can more than outweigh the disadvantage of the higher stage cut requirement in the membrane when it precedes the defuel tower.

[00262] An alternative membrane process concept, shown in Fig. 17, adds a second membrane stage for separating the fuel molecules from the VGO. This can facilitate additional heteroatom reductions, e.g., from additive molecules that are lighter than VGO or that were cracked during use as a result of thermal or shearing effects, which could reduce or eliminate aspects of a downstream guard system. Additionally, this can minimize impacts to the lubes fractionation unit by removing most of the fuel-range molecules in the pretreatment phase.

[00263] Nanofiltration membrane performance can be modeled using an empirical correlation for membrane permeability k _B T 1 j ^J > I. = ^L n'l.O0 ¹ H ¹ 1- = 1 — tanh

3ndiri 2 where Pt is the permeability of component i, D _ico is the bulk diffusivity in the fluid, and is a hindrance factor due to interactions with the membrane pore walls. The Stokes-Einstein equation can be used to calculate the bulk fluid diffusivity using Boltzmann constant fc _B , temperature T, molecular diameter d _t of component i, and fluid viscosity T , Small molecules pass through the membrane largely unimpeded, while large molecules encounter increasing degrees of resistance as the molecule increases relative to the pore size. An empirical function for the hindrance factor captures this trend, and is parameterized by the centroid and width of the switching function^ and respectively. For convenience, normal boiling point is used as a proxy for molecular size, so both A and B are expressed in units of temperature.

[00264] Fig. 18 shows preliminary modeling results for a two-stage membrane pretreatment process. The model components were petroleum fractions based on Arab Light crude, with the feed composition tuned to match the boiling point distribution in Fig. 4.

The model parameters used for the membrane separations are shown in Fig. 23. Overall the model shows potential to recover a wide-cut VGO by removing the 650°F- (fuel-range) and 1050°F+ (asphalt-range) molecules with suitable membranes.

[00265] Another process variation of the two-stage membrane process concept, shown in Fig. 19, involves reversing the order of the membrane stages, i.e., removing the fuel molecules first. The advantage of this process concept is that minimal pressurization is needed between the stages since the retentate from the first stage is the feed to the second stage. The trade-off is that removing the lightest molecules first will increase the viscosity of the feed to the asphalt-removing stage, which will likely increase the membrane area requirement. The order of these stages is a process optimization between the cost of the additional membrane area and the cost of re-pressurizing the permeate vs. the retentate between stages.

Three-Stage Membrane Process

[00266] Some lubricant plants run in blocked operation, separately processing VGO fractions of different boiling point ranges in order to access higher-value products, such as Group 111/111+ base stocks. Incorporating used oil from a membrane pretreatment process into these lubes plants would require additional separation of the wide-cut VGO into these fractions. One option for doing this, shown in Fig. 20, would be fractionation via vacuum distillation, similar to conventional used oil pretreatment. The membrane may enable elimination of the thin-film evaporator if it sufficiently removes the highly fouling components that currently limit fractionation temperatures. This could be accomplished by a dedicated grassroots fractionator for processing pretreated used oil. Also, the existing vacuum pipestill can potentially be utilized if the pretreated used oil does not adversely affect its operation.

[00267] Membranes can again serve as an alternative to distillation, here for cutting VGO into multiple grades for blocked lubes processing, as shown in Fig. 21. Fig. 22 shows PRO/II modeling results for a hypothetical three-stage concept, illustrating the potential to generate two VGO product cuts with the right membrane selectivity.

[00268] The model parameters used to generate the results in Figs. 18 and 22 are summarized in Fig. 23. The parameterization for the first-stage decontaminate membrane is consistent with the experimental performance of the membranes shown in Fig. 4.

Tighter membranes can be tested to identify materials that match the parameterized selectivities for the defuel and LVGO/HVGO membranes.

[00269] Fig. 24 summarizes the product quality of a wide-cut VGO product produced by a membrane-based process of this disclosure. The left column is the raw used oil feed, the middle is a pretreated VGO obtained via distillation, while the right is the pretreated VGO from the membrane. The viscosity index and chlorine concentration are particularly notable from a process perspective; the former implies higher base stock yield/quality, while the latter decreases the amount of additional processing required to manage chlorine corrosion in the downstream process.

PCT and EP Clauses:

[00270] 1. A method for separating components in a used oil, said method comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; and e) contacting the stream having removed water and light ends from d) with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C; and wherein the oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[00271] 2. The method of clause 1 wherein the oil permeate comprises a wide-cut vacuum gas oil (VGO) product.

[00272] 3. The method of clauses 1 and 2 wherein low boiling components comprise entrained fuels, cracked molecules, and water; and wherein high boiling components comprise sludge and spent additives.

[00273] 4. The method of clauses 1-3 wherein the oil permeate has a boiling point distribution from about 350°F to about 1050°F.

[00274] 5. The method of clauses 1-4 wherein the feed flow rate is from about 0.5 gal/min to about 2.5 gal/min per membrane leaf, the feed pressure is from about 500 psig to about 1000 psig, and the feed temperature is from about 130°C to about 220°C. [00275] 6. The method of clauses 1-5 having a permeate pressure from about 0 psig to about 50 psig, a permeate temperature from about 100°C to about 250°C, and a permeate yield or stage cut from about 5 wt% to about 80 wt% of a whole used oil feed.

[00276] 7. The method of clauses 1-6 wherein the selectively permeable membrane comprises a material chosen from polymer, ceramic, or hybrid (polymer/ceramic or polymer/inorganic).

[00277] 8. The method of clauses 1-7 wherein the selectively permeable membrane is a nanofiltration membrane or an ultrafiltration membrane.

[00278] 9. The method of clauses 1-8 wherein the selectively permeable membrane has a molecular weight cut-off of between 200 and 100,000 Daltons.

[00279] 10. The method of clauses 1-9 wherein the used oil comprises a petroleumbased oil selected from the group consisting of a natural oil, a mineral oil, and a synthetic oil. [00280] 11. The method of clauses 1-10 further comprising treating the wide-cut vacuum gas oil (VGO) product via solvent extraction or hydroprocessing to produce a base stock.

[00281] 12. The method of clauses 1-11 wherein the base stock is a Group I base stock, or a Group II base stock, or a Group III base stock.

[00282] 13. A system for separating components in a used oil, said system comprising: a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; at least one filtration unit; at least one flash distillation column; and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; wherein the used oil is passed to the filtration unit to remove solids; the stream having removed solids is passed to the flash distillation column to remove water and light ends; and the stream having removed water and light ends is contacted with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C; and wherein the oil permeate has a concentration of lubricant-range hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[00283] 14. The system of clause 13 wherein the oil permeate comprises a wide-cut vacuum gas oil (VGO) product.

[00284] 15. A composition comprising a wide-cut vacuum gas oil (VGO) product, said composition produced by a process comprising: a) providing a used oil stream comprising lubricant-range hydrocarbon components, lower boiling components, and higher boiling components; b) providing at least one filtration unit, at least one flash distillation column, and at least one selectively permeable membrane; wherein the selectively permeable membrane has a first surface and a second surface opposite to the first surface; c) passing the stream of used oil to the filtration unit to remove solids; d) passing the stream having removed solids from c) to the flash distillation column to remove water and light ends; and e) contacting the stream having removed water and light ends from d) with the first surface of the selectively permeable membrane at a feed flow rate, a feed pressure and a feed temperature, to separate components in the stream by allowing one or more components of the stream to transfer from the first surface to the second surface across the membrane, to provide an oil permeate contacting the second surface and an oil retentate contacting the first surface; wherein the feed flow rate is from about 0.25 gal/min to about 3.0 gal/min per membrane leaf, the feed pressure is from about 200 psig to about 1200 psig, and the feed temperature is from about 50°C to about 250°C; and wherein the oil permeate has a concentration of lubricantrange hydrocarbon components greater than the oil retentate, and the oil retentate has a concentration of lower boiling components and higher boiling components greater than the oil permeate.

[00285] The present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present disclosure. The disclosure illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein.

[00286] While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of’ or “consist of’ the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

[00287] All priority documents are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted. Further, all documents cited herein, including testing procedures, are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted. All priority documents are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted. Further, all documents cited herein, including testing procedures, are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted.