IMPROVED BUTANEDIOL MANUFACTURING PROCESS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority filing date of U.S. Provisional application serial number 61/983,665, filed April 24, 2014, the disclosures of which are specifically incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

[0002] The disclosed process relates to an improved process for manufacturing and recovering butanediol from feedstock comprising butynediol. More particularly, the disclosed process relates to an improved process for manufacturing and recovering butanediol from feedstock comprising butynediol in a reaction zone at reaction conditions, comprising the steps of reacting butynediol in the liquid phase and hydrogen in a reaction zone containing hydrogenation catalyst, recovering liquid phase product from the reaction zone, passing the recovered liquid phase product into a first liquid pressure let down vessel maintained at specific conditions, recovering first and second streams from the first liquid pressure let down vessel as liquid bottoms and overhead vent gas, respectively, passing the first stream liquid bottoms recovered to a second liquid pressure let down vessel maintained at specific conditions, and the second stream vent gas recovered to a vent gas cooler maintained at specific conditions, passing the gas from the vent gas cooler to a hydrogen recovery zone comprising a particular membrane filter, whereby the permeate comprises high purity hydrogen gas and the retentate comprises contaminants, recycling the permeate to the reaction zone, and recovering first and second streams from the second liquid pressure let down vessel as liquid bottoms comprising butanediol and overhead vent gas, respectively.

BACKGROUND OF THE INVENTION

[0003] In current processes for manufacturing butanediol by hydrogenation of butynediol, the hydrogenation reaction operates with a large excess, such as, for example, up to five times stoichiometric, of hydrogen recirculated by a recycle compressor operating with an iniet pressure of approximately 290 bar and compressing to 300 bar (for example, see GB Patent No. 1 ,242,358A). However, to maximize the hydrogen partial pressure and hence product quality, it is necessary in such a process to conduct a constant purge to ensure a low concentration of inert and byproduct compounds (for example, carbon dioxide, methane, methanol, etc.). Failure to manage hydrogen purity in this way results in lower conversion of butynediol to butanedio! and can result in passing byproducts and/or contaminants to the product stream. This purge typically is in the range of 2-30 % of the hydrogen fed to the hydrogenation process reaction, purged as a combination of physical losses with the reactor effluent (i.e. product) exiting the reaction zone, liquid condensate from cooling the recirculating hydrogen gas and deliberate purging from the gas loop.

[0004] Because the hydrogen contains/carries impurities, a usual way to extract some value from the purge stream is to use the vented gas as fuel gas, for example for site flares. However, this uses hydrogen, a high unit cost material, in a way which is dearly not cost effective.

[0005] U. S. Patent No. 8,552,234 B2 describes use of a hydrogen permeable membrane to recover and recycle hydrogen from a carboxylic acid hydrogenation process. In a further example, U. S. Patent No. 8,168,685 B2 describes a method of methanol production from syngas that utilizes membrane separation to remove excess hydrogen from the syngas.

[0006] International Application Publication No. WO2012095777A1 discloses a process for hydrogenating 1 ,4-butynediol to give mixtures comprising tetrahydrofuran, 1 ,4- butanediol and v-butyrolactone in the gas phase. After the hydrogenation, the gas stream is cooled, the product is largely separated from hydrogen. The remaining hydrogen is partly discharged and part is circulated, preferably as recycle gas. Part of the recycle gas is discharged to remove inert compounds. [0007] U.S Patent No. 6,171 ,472B1 relates to improved contaminant removal and hydrogen reuse in hydrocarbon conversion reactors, by passing gases in the reactor recycle loop across selective membranes.

[0008] Feedstock butynediol for use in the present process may be manufactured from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene and suspended catalyst in a reaction vessel. For example, U. S. Patent No. 4,584,418A describes a means of making a copper acetylide catalyst for synthesis of butynediol in a single vessel wherein acetylene is bubbled through the reactor at 90 °C and atmospheric pressure. In a further example, U. S. Patent No. 5,444, 169A discloses a process for synthesizing butynediol from an aqueous solution containing formaldehyde by reaction with acetylene in the presence of a suspended catalyst, wherein the solution is conveyed in a cascade by several reactors, the solution drawn off from the first through the penultimate reactor of the cascade being fed to the next reactor in the cascade, acetylene being introduced into each of the reactors, and a butynediol-rich solution being drawn off only from the last reactor in the cascade. The catalyst is separated from the solution in each individual reactor of the cascade above the last reactor to prevent the catalyst from escaping the reactor.

[0009] A simple economical process for manufacturing butanediol by hydrogenation of butynediol with hydrogen preservation is needed.

SUMMARY OF THE INVENTION

[00010] The disclosed process provides an economical improved process for manufacturing and recovering butanediol from feedstock comprising butynediol, whereby the process involves two staged pressure letdown and flash steps to enable hydrogen gas separation from reaction liquid streams in addition to a membrane recovery process, and the process has the capability to recover high quality hydrogen gas that would be lost because it is dissolved in the reactor liquid effluent. It is also possible that additional entrainment of small (micro) bubbles in the reaction liquid stream effluent would further boost losses. An embodiment of the disclosed process involves the steps of: a) reacting feedstock comprising liquid phase butynediol and feedstock comprising hydrogen in a reaction zone containing hydrogenation catalyst, hereinafter described, and maintained at specific reaction conditions, hereinafter described, b) recovering liquid phase product from the reaction zone of step a), c) passing the recovered product of step b) into a first liquid pressure let down vessel maintained at specific conditions, hereinafter described, d) recovering first and second streams from the first liquid pressure let down vessel of step c) as liquid bottoms and overhead vent gas, respectively, e) passing the first stream liquid bottoms recovered in step d) to a second liquid pressure let down vessel maintained at specific conditions, hereinafter described, and the second stream vent gas recovered in step d) to a vent gas cooler maintained at specific conditions, hereinafter described, f) passing effluent from the vent gas cooler of step e) to a hydrogen recovery zone comprising a particular membrane filter, hereinafter described, whereby the permeate comprises high purity hydrogen gas and the retentate comprises contaminants, g) recycling the permeate of step f) to step a), and h) recovering first and second streams from the second liquid pressure let down vessel of step e) as liquid bottoms comprising butanedioi and overhead vent gas, respectively.

[00011] Another embodiment of the disclosed process involves the steps of: a) reacting feedstock comprising liquid phase butynediol and feedstock comprising hydrogen in a fixed bed reactor containing catalyst comprising, but not limited to, one or more metals from Group Vlli of the Periodic Table of Elements, e.g. Ni, Cu, Pd, Pt, Ru, Rh, or combinations thereof, and maintained at specific reaction conditions, hereinafter described, b) recovering liquid phase product from the reactor of step a), c) passing the recovered product of step b) into a first liquid pressure let down vessel maintained at specific conditions, hereinafter described, d) recovering first and second streams from the first liquid pressure let down vessel of step c) as liquid bottoms and overhead vent gas, respectively, e) passing the first stream liquid bottoms recovered in step d) to a second liquid pressure let down vessel maintained at specific conditions, hereinafter described, and the second stream vent gas recovered in step d) to a vent gas cooler maintained at specific conditions, hereinafter described, f) passing effluent from the vent gas cooler of step e) to a hydrogen recovery zone comprising a membrane filter selected from the group consisting of metallic, polymeric, ceramic membranes and combinations thereof, whereby the permeate comprises from 90 to 100 volume % hydrogen and the retentate comprises one or more compounds selected from the group consisting of carbon dioxide, methane, methanol, propanoi, butanol, and combinations thereof, g) recycling the permeate of step f) to step a), and h) recovering first and second streams from the second liquid pressure let down vessel of step e) as liquid bottoms comprising butanediol and overhead vent gas, respectively,

[00012] Another embodiment of the disclosed process involves the step i) mixing the recovered second stream vent gas from step h) with the retentate of step f).

[00013] Another embodiment of the disclosed process involves a method of controlling hydrogen concentration for synthesizing product comprising butanediol from feedstock comprising butynediol in a reaction zone at reaction conditions; the method comprising: i) reacting feedstock comprising liquid phase butynediol and feedstock comprising hydrogen in a reaction zone containing hydrogenation catalyst and maintained at reaction conditions including pressure from 20 to 325 bar, and temperature of from 50 to 300°C, ii) recovering liquid phase product from the reaction zone of step i), iii) passing the recovered product of step ii) into a first liquid pressure let down vessel maintained at conditions including pressure from 30 to 270 bar, iv) recovering first and second streams from the first liquid pressure let down vessel of step iii) as liquid bottoms and overhead vent gas, respectively, v) passing the first stream liquid bottoms recovered in step iv) to a second liquid pressure let down vessel maintained at conditions including pressure from 1 to 20 bar, and the second stream vent gas recovered in step iv) to a vent gas cooler maintained at conditions including pressure from 30 to 270 bar, and temperature of from 10 to 60°C, vi) passing effluent from the vent gas cooler of step v) to a hydrogen recovery zone comprising a membrane filter, whereby the permeate comprises high purity hydrogen gas and the retentate comprises contaminants, vii) recycling the permeate of step vi) to step i), viii) removing the retentate of step vi) comprising contaminants, and viii) recovering first and second streams from the second liquid pressure let down vessel of step v) as liquid bottoms comprising butanediol and overhead vent gas, respectively. [00014] Another embodiment of the disclosed process involves a method of controlling hydrogen concentration for synthesizing product comprising butanedioi from feedstock comprising butynediol in a reaction zone at reaction conditions, further comprising replenishing the at least reacted portion of hydrogen in step i) with a make-up stream.

[00015] In an embodiment of the disclosed process involving a method of controlling hydrogen concentration for synthesizing product comprising butanedioi from feedstock comprising butynediol in a reaction zone at reaction conditions, the amount of make-up stream is regulated via a flow device to maintain hydrogen concentration in step i).

[00016] In one aspect of the disclosed process involving a method of controlling hydrogen concentration for synthesizing product comprising butanedioi from feedstock comprising butynediol in a reaction zone at reaction conditions, the permeate of step vi) comprises from about 99 to 100 volume % hydrogen purity {water free basis).

[00017] In another aspect of the disclosed process involving a method of controlling hydrogen concentration for synthesizing product comprising butanedioi from feedstock comprising butynediol in a reaction zone at reaction conditions, the contaminants of the retentate of step vi) comprise compounds selected from the group consisting of carbon dioxide, methane, methanol, propanol, butanol, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWING

[00018] Fig. 1 is a simplified schematic representation of an embodiment of the present process.

[00019] Fig. 2 is a simplified schematic representation of an embodiment of the present process.

DETAILED DESCRIPTION OF THE INVENTION

[00020] As a result of intense research in view of the above, we have found that we can - economically and effectively manufacture butanedioi from feedstock comprising butynediol. The process involves collecting the dissolved gas leaving the hydrogenation reactor in a liquid stream, and then passing the gas to a hydrogen recovery zone comprising a particular membrane filter for efficient recovery of high purity hydrogen for recycle. By using the hydrogen recovery zone comprising a particular membrane filter as in the present process, valuable hydrogen of a quality sufficient to permit efficient recycle, may be recovered, while impurities and reaction byproducts, such as methane, carbon dioxide, methanol and butanol, may be removed.

[00021] The term butynedio! ("BYD") represents the compound structure HOCH ₂ C≡CCH ₂ OH. The term butanediol ("BDO") represents one or a combination of the compound structures HOCH ₂ CH ₂ CH(OH)CH ₃ , HOCH ₂ CHOHCH2CH3, HOCH ₂ CH ₂ CH ₂ CH2 OH _, and CH ₃ CHOHCHOHCH ₃ . Percentages are in volume % unless otherwise indicated. Pressures are in bar, wherein 1 bar = 0.987 atmosphere = 98.7kPa, unless otherwise indicated. Flow rates of gaseous streams are presented in kg/hour. Flow rates of liquid streams are presented in kg/hour.

[00022] This new process involves three separate elements for collecting and purifying the gas from the BYD Hydrogenation system. First, both liquid product and condensate from the reaction gas loop, i.e., reaction zone, enters an intermediate flash vessel, i.e., first liquid pressure let down vessel, operating at above atmospheric pressure, preferably from 30 to 200 bar (3,000 to 20,000 kPa), and more specifically from 70 to 100 bar (7,000 to 10,000 kPa), where dissolved and entrained gases are separated from the liquid stream. The flash vapor is then cooled to minimize the mass of condensable species within the gas and, if desired, mixed with any direct gaseous purge from the reaction loop.

[00023] The cooled mixed gas containing a significant proportion of hydrogen, typically well in excess of 50 volume %, is then passed to a hydrogen recovery zone comprising a particular membrane where high purity hydrogen is recovered as a permeate for recycle.

[00024] By using the present arrangement, incorporating staged pressure letdown and flash steps and membrane separation technology, valuable hydrogen of a quality sufficient to permit recycle will be recovered, while impurities and reaction byproducts in the vent gas, such as methane, carbon dioxide and methanol, will be removed. It is estimated that this process can achieve in excess of 99 volume % hydrogen purity (water free basis) and in excess of 95 volume % hydrogen recovery from the gas sent to the hydrogen recovery zone comprising a particular membrane which can then be recycled to the hydrogenation reaction.

[00025] From the gas liquid separation of the intermediate pressure letdown and flash step, i.e., first liquid pressure let down vessel, liquid is flashed to a low pressure vessel, i.e., second liquid pressure iet down vessel, where any residual gas is removed and then, if desired, mixed with retentate gas from the hydrogen recovery zone comprising a particular membrane, high in impurities and byproducts and low in hydrogen. Gas from this low pressure vessel is then either vented to flare or can be utilized as fuel gas if economically justified.

[00026] The reaction zone in the disclosed process may, for example, comprise unit operations exemplified by a primary hydrogenation reaction vessel, an externa! circulation cooler wherein the cooled reaction product is partially recycled to the primary reaction vessel, a secondary hydrogenation reaction vessel, and a hydrogen circulation system for both reaction vessels. The reaction vessel for use as the reaction zone in the disclosed process may comprise one of current use in such a process. Particularly useful as a reaction vessel for use in this process is a fixed bed reactor or a mixed slurry bed reactor. These reactor vessels may be cooled or heated by heat exchanger either internal to the reactor or externally by circulation. A fixed bed reactor may be operated using any of the following types of contact: (i) co-current downflow trickle bed contact, (ii) countercurrent gas-liquid contact, or (iii) co-current upflow gas-liquid contact.

[00027] Reaction conditions in the reaction zone include a pressure of from 20 to 325 bar and temperature from 50 to 300 ^° C, for example, from 27 to 300 bar, and temperature from 100 to 145 ^° C, such as from 125 to 140 ^° C. if a mixed bed reactor is used, contents of the reaction zone may be agitated by either or both of mechanical means, for example a stirrer, or gaseous injection. [00028] Catalyst for use in the reaction zone of the present process is a hydrogenation catalyst , such as but not limited to, for example, one or more metals from Group VIM of the Periodic Table of the Elements, e.g. Ni, Cu, Pd, Pt, Ru and Rh. The catalyst composition may include an inorganic oxide materia! matrix or binder upon which the metal resides. Such matrix materials include synthetic or naturally occurring substances as well as inorganic materials such as clay, silica and/or metal oxides. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be used for this include those of the montmori!ionite and kaolin families, which families include the subbentonites and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Specific useful catalyst matrix or binder materials which may be employed herein include silica, alumina, zirconia, titania, silica-alumina, silica-magnesia, siiica-zirconia, silica-thoria, silica- beryllia, silica-titania as well as ternary compositions such as siiica-alumina-thoria, si!ica- alumina-zirconia, silica-aiumina-magnesia and silica-magnesia-zirconia. A mixture of these components could also be used. The relative proportions of hydrogenation catalyst metal and binder or matrix, if present, may vary widely with the catalyst metai content ranging from about 1 to about 90 percent by weight, and more usually in the range of about 40 to about 75 percent by weight of the total composition.

[00029] The liquid phase product recovered from the reaction zone comprises unreacted butynediol, butenediol, butanediol, entrained hydrogen, reaction byproducts and other feed impurities. Reaction byproducts include methanol, butanol, propanol, tars, and combinations thereof.

[00030] Conditions to be maintained in the first liquid pressure let down vessel include a pressure from 30 to 270 bar, for example, from 70 to 100 bar. This first liquid pressure let down vessel may comprise one of current use for such an operation. Such a liquid pressure let down vessel may be constructed from piping components, or a singie pressure (flash) vessel, or some combination thereof. Particularly useful as a liquid pressure let down vessel for use in this process is a single pressure (flash) vessel which facilitates disengagement of vapor and liquid.

[000313 The first stream recovered from the first liquid pressure let down vessel and passed to a second liquid pressure let down vessel typically comprises approximately 55 % BDO, 45 % water, plus byproducts and methanol, propanol and butanoi. The second stream overhead vent gas from the first liquid pressure let down vessel and passed to a vent gas cooler typically comprises approximately 96% hydrogen, plus inerts, byproducts and water vapor.

[00032] Conditions to be maintained in the second liquid pressure let down vessel include pressure from 1 to 20 bar, for example, from 3 to 8 bar. This second liquid pressure let down vessel may comprise one of current use for such an operation, such as that used for the first liquid pressure let down vessel. Other types of pressure let down equipment including a gas-liquid disengagement section are also suitable in this application. Such equipment may be internally staged, with packing or trays for example, and equipped with a gas-liquid disengagement zone for reduced liquid entrainment in the gas. There are no size or orientation layout restrictions other than the production scale is matched and are economical to design, build, operate and maintain at scale.

[00033] Conditions to be maintained in the vent gas cooler include a pressure from 30 to 270 bar, for example, from 75 to 100 bar, and temperature from 10 to 60 ^° C, for example from 30 to 50 ^° C. The vent gas cooler may comprise one of current use for such an operation.

[00034] Gas recovered from the vent gas cooler is passed to a recovery zone comprising a membrane filter sufficient to generate a permeate comprising high purity hydrogen gas and a retentate comprising contaminants, such as, for example, carbon dioxide, methane, and methanol. The recovered gas passed to the recovery zone comprises at least 50 volume % hydrogen, such as, for example from 50 to 95 volume % hydrogen. The membrane filter is commercially available, for example available from Air Liquide or Air Products, designed for such a recovery process. Particularly useful as the membrane filters for use in this process are, as non-iimiting examples, the MEDAL™ unit from Air Liquide, and the PRISM ^® unit from Air Products. Permeate generated from this step of the process will comprise from about 99 to 100 volume % hydrogen purity (water free basis) and in excess of about 95 volume % hydrogen recovery from the gas sent to the hydrogen recovery zone, sufficient high purity to be advantageously recycled to the reaction zone. Such recycle may be by way of the compressed hydrogen supply system from which hydrogen is supplied to the reaction zone for conversion of liquid phase butynediol to butanedioi at reaction conditions.

[00035] The first stream recovered from the second liquid pressure let down vessel is a liquid bottoms and comprises from 45 to 65 volume % butanedioi product. The second stream is overhead vent gas. The second stream overhead vent gas from the second liquid pressure let down vessel may be combined with the retentate from the hydrogen recovery zone comprising a membrane filter. The combined gases may be either vented to flare or utilized as fuel gas.

Overview of Figure 1

[00036] Referring more particularly to the drawing, Fig. 1 represents a simplified schematic of one embodiment of the disclosed process wherein feedstock comprising liquid phase butynediol and feedstock comprising hydrogen are passed via lines 1 and 2, respectively, to a reaction zone 3 containing hydrogenation catalyst and maintained at specific reaction conditions. Liquid phase product from the reaction zone 3 is passed via line 4 to a first liquid pressure let down vessel 5 maintained at specific conditions. A liquid bottoms stream is recovered from pressure let down vessel 5 via line 6, and overhead vent gas is recovered from pressure let down vessel 5 via line 7. The liquid bottoms stream is passed via line 6 to a second liquid pressure let down vessel 8 maintained at specific conditions, and the vent gas stream flows via line 7 to a vent gas cooler 9 maintained at specific conditions. The gas from the vent gas cooler 9 is passed via line 10 to a hydrogen recovery zone 1 comprising a particular membrane filter, whereby a permeate comprising high purity hydrogen gas and a retentate comprising contaminants result. The permeate is recycled via line 12 to reaction zone 3, such as by way of the source of feedstock comprising hydrogen to reaction zone 3, and the retentate is removed from hydrogen recovery zone 1 via line 13. A bottoms stream comprising butanedioi product is recovered from the second liquid pressure let down vessel 8 via line 14, and overhead vent gas is recovered from the second liquid pressure let down vessel 8 via line 15.

Overview of Figure 2

[00037] Fig. 2 represents a simplified schematic of one embodiment of the disclosed process wherein a processing zone 251 comprises of interconnected units 5, 8, 9 and 1 1 , as shown in Fig.1 . A feedstock comprising liquid phase butynediol and feedstock comprising hydrogen are passed via lines 201 and 202, respectively, to a reaction zone 203 containing hydrogenation catalyst and maintained at specific reaction conditions. Liquid phase product from the reaction zone 203 is passed via line 204 to the processing zone 251 which comprises a particular hydrogen membrane filter (not shown). The processing zone 251 produces a permeate stream 212 comprising high purity hydrogen gas and a retentate stream 213 comprising contaminants. The permeate stream 212 is recycled to the reaction zone 203 via a hydrogen management zone 255.

[00038] A hydrogen gas make-up stream 224 is connected to the hydrogen management zone 255 and regulated through a flow device 99. The combined gas feed stream 202, i.e., hydrogen gas make-up stream 224 and recycled permeate stream 212, serve as high- purity gas feedstock to reaction zone 203. A process control device 88 is connected upstream of the reaction zone 203 which monitors the hydrogen balance in the gas feed stream 202. A process control signal 77 between devices 88 and 99 regulates the necessary flow of hydrogen make-up stream 224 to the hydrogen management zone 255.

[00039] The retentate stream 213 is removed from the processing zone 251. An overhead vent gas stream 215 is also removed from the processing zone 251. The two streams, 213 and 215, may be disposed either individually or as combined. A bottom stream comprising butanedioi product is recovered from the process zone 251 via line 214.

[00040] As represented in Fig.2, the processing zone 251 effectively recovers and preserves the excess hydrogen gas in stream 204 by removing a concentrated stream of process inert and by-product contaminants 213. The recovered high purity hydrogen via stream 212 is recycled in the process instead of purging a significant portion to keep contaminants from accumulating in the system. The process control in combination with the hydrogen recovery replenishes the at least reacted hydrogen in reaction zone 203. At steady state, the hydrogen make-up stream 224 balances the reacted hydrogen in 203.

[00041] In one embodiment, the hydrogen management zone 255 may comprise of a compressed hydrogen supply system, gas mixing system, gas drying system, gas storage/header system, and such integrated industrial systems. The hydrogen may be supplied by commercial, petrochemical, biorefinary, fuel cell, water electrolysis, and/or any combinations of industrial sources.

[00042] in an embodiment, the flow device 99 may be any of commercially available flow device, such as mass flow controller or volumetric flow controller. The flow device range is appropriately selected to handle normal as well as off-normal load demands, for example, start-up gas demand. The process control device 88 may be any of commercially available gas quality measurement control system, such as continuous monitoring system (CMS), gas chromatography (GC), mass spectroscopy (MS), and other. The control system may have a provision for on-line gas sampling from the process stream and analysis. A reasonably accurate analysis of the main gas components and process contaminants may be obtained from the gas monitoring system. The process control signal 77 may provide a real-time interface between the gas quality control and the gas make-up demand. The process control loop comprising 77, 88 and 99 is an effective gas feed quality control for reaction zone 203.

EXAMPLES

Example 1

[00043] Into a high pressure liquid phase fixed bed reactor system containing 60,000 kg of Ni (Raney) on Al ₂ 0 ₃ (40/60 by weight) catalyst is passed 26,000 kg/hour of liquid feedstock comprising 54 % BYD and 3,000 kg/hour of hydrogen at a pressure of 300 bar. The hydrogen feedstock is from a compressed hydrogen supply system involving a hydrogen booster compressor and other unit operations required to provide quality high pressure hydrogen for the reaction. Reaction conditions maintained in the fixed bed reactor include a pressure of 300 bar and temperature of 135 C. Vent gas comprised of 96 % hydrogen is removed from the reactor and recycled to the hydrogen supply system at about 2,300kg/hour. Liquid phase product comprising approximately 54 % BDO is recovered from the reactor and passed to a first liquid phase iet down vessel via an isenthalpic pressure let down, maintained at a pressure of 80 bar at 26,000 kg/hour, along with about 50 to 100 kg/hour of hydrogen.

[00044] From the first liquid phase let down vessel is recovered a first stream liquid bottoms comprising product BDO and a second stream overhead vent gas comprising mainly water vapor plus residual light organics and hydrogen. The recovered first stream liquid bottoms is passed to a second liquid phase iet down vessel, maintained at a pressure of 8 bar, at approximately 20,000 kg/hour. The recovered second stream overhead vent gas is passed to a vent gas cooler maintained at a pressure of 75 bar and temperature of 35 ^° C. The gas from the vent gas cooler is passed to a hydrogen recovery zone comprising a MEDAL™ membrane filter unit. Permeate recovered from the hydrogen recovery zone, comprising 97 % hydrogen gas of 99 % hydrogen purity (water free basis), is recycled to the hydrogen supply system. The retentate recovered from the hydrogen recovery zone comprises contaminants, such as, for example, carbon dioxide, methane, and methanol.

[00045] From the second liquid phase let down vessel is recovered a first stream liquid bottoms comprising product 60 % BDO, and a second stream overhead vent gas comprising contaminants. The second stream overhead vent gas is mixed with the recovered retentate from the hydrogen recovery zone and passed on to further use.

Example 2

[00046] For comparison, into the same high pressure liquid phase fixed bed reactor system as used in Example 1 containing 60,000 kg of Ni (Raney) on AI ₂ O ₃ (40/60 by weight) catalyst is passed 26,000 kg/hour of feedstock comprising 54 % BYD and 3,000 kg/hour of hydrogen at a pressure of 300 bar. The hydrogen feedstock is from the same compressed hydrogen supply system as used in Example 1 involving a hydrogen booster compressor and other unit operations required to provide quality high pressure hydrogen for the reaction. Reaction conditions maintained in the fixed bed reactor include a pressure of 300 bar and temperature of 135 ^° C. Vent gas comprised of 96 % hydrogen is removed from the reactor and recycled to the hydrogen supply system at about 2,300 kg/hour. Liquid phase product comprising approximately 54 % BDO is recovered from the reactor and passed to a liquid phase let down vessel maintained at a pressure of 4 bar, via isenthalpic flash, at 26,000 kg/hour, along with about 50 to 100 kg/hour of hydrogen.

[00047] From this let down vessel is recovered a first stream liquid bottoms comprising approximately 54 % BDO and a second stream overhead vent gas comprising about 96 % hydrogen, water vapor and light organics. This overhead vent gas is sent to vent gas treatment for disposal or use as fuel.

[00048] As demonstrated, a benefit of the disclosed process is that using staged letdown of pressure and the hydrogen recovery zone comprising a membrane filter it is possible to purify hydrogen purge gas to a degree that makes it suitable for recycle to the hydrogenation process, in addition, appropriate selection of the intermediate vessel pressure allows direct recycle of the permeate gas (purified hydrogen) to the process hydrogen booster compressor, thus incurring no additional compression costs. Without the disclosed process, the purge gas can only be used, for example, as fuel unless it is recompressed and sent to a further external hydrogen purification facility.

[00049] All patents, patent applications, test procedures, priority documents, articles, publications, manuals, and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosed process and for all jurisdictions in which such incorporation is permitted.

[00050] When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

[00051] While the illustrative embodiments of the disclosed process have been described with particularity, it will be understood that various other modifications will be apparent to and may be readily made by those skilled in the art without departing from the spirit and scope of the disclosed process. Accordingly, it is not intended that the scope of the claims hereof be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the disc!osed process, including a!l features which would be treated as equivalents thereof by those skilled in the art to which the disclosed process pertains.