HYDROCARBONS & SYNGAS MIXTURE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/257,414, filed November 19, 2015. The contents of the referenced application are incorporated into the present application by reference.

FIELD

[0002] The presently disclosed subject matter relates to methods of oxidative conversion of variable hydrocarbon feed to C2-C3 olefins, syngas, low molecular weight paraffinic hydrocarbons and aromatic hydrocarbons.

BACKGROUND

[0003] The petrochemicals industry has provided the chemical industry with certain basic building blocks of chemical technology, i.e., hydrocarbon intermediates such as C2-C3 olefins, methanol, and aromatics. Crude oil and natural gas are two major source materials for conversion into such hydrocarbon intermediates.

[0004] Natural gas is often first converted through steam reforming into syngas gas, a gas mixture consisting primarily of hydrogen (H ₂ ) and carbon monoxide (CO) and may further contain other gas components such as carbon dioxide (C0 ₂ ), water (H ₂ 0), methane (CH ₄ ) and/or nitrogen (N ₂ ). Syngas can be subsequently used in the production of methanol and other important hydrocarbon intermediates.

[0005] Certain conventional processes to convert oil to chemicals involves refinery and Fluid Catalytic Cracker (FCC) processes which produce light olefins as one of the byproducts in parallel with light naphtha and gasoline range hydrocarbons. Industrial scale C2-C3 olefins are produced by steam cracking of C2-C3 paraffins in Gulf region countries and steam cracking of naphtha in European countries.

[0006] However, steam reforming is not necessarily an energy efficient process and the two step refinery -FCC approach is not a cost efficient means to produce petrochemicals. There is a need to replace steam reforming with more energy efficient processes and to remove the extra refining step in petrochemical production.

[0007] Certain steam reforming alternatives for generating olefins are known in the art. For example, U.S. Patent Application Publication No. 2011/0137095 discloses a process for producing lower olefins (ethylene/propylene) from a feed comprising hydrocarbons and C0 ₂ and further discloses synthesis of oxygenates from the feed. U.S. Patent Application Publication No. 2011/0137053 discloses a process for producing ethylene oxide by recycling the resulting C0 ₂ from synthesizing oxygenates. Great Britain Patent No. 853596 discloses cracking hydrocarbon oils in a fluidized bed with oxygen, at high temperatures to produce unsaturated gaseous hydrocarbons and syngas. The lower boiling point products react with oxygen above 700°C to form syngas. U.S. Patent No. 4,166,830 discloses a continuous process for producing ethylene by diacritic cracking of heavy hydrocarbons feeds in a non- tubular multi-zone reactor at elevated pressure. U.S. Patent Application Publication No. 2013/0224808 discloses a method of producing olefins, e.g., ethylene, wherein syngas is first produced from a carbonaceous feedstock.

[0008] There remains a need for a flexible and energy efficient method for converting a variable hydrocarbon feed into hydrocarbon chemical intermediates.

SUMMARY OF THE DISCLOSED SUBJECT MATTER

[0009] The presently disclosed subject matter provides methods of oxidative conversion of variable hydrocarbon feed to C2-C3 olefins, syngas, low molecular weight paraffinic hydrocarbons and aromatic hydrocarbons. [0010] In certain embodiments, methods of converting a hydrocarbon feed can involve combining the hydrocarbon feed, oxygen source, and carbon dioxide within a reactor including a catalyst; and converting the hydrocarbon feed into one or more olefins, aromatic hydrocarbons, C2-C3 paraffinic hydrocarbons, linear hydrocarbons greater than C4, and/or syngas. In certain embodiments, the methods can further include separating the one or more olefins, aromatic hydrocarbons, C2-C3 paraffinic hydrocarbons, linear hydrocarbons greater than C4, and/or syngas; and returning C2-C3 paraffinic hydrocarbons and/or linear hydrocarbons greater than C4 to be used as part of the hydrocarbon feed. In certain embodiments, the produced syngas can be further converted into methanol.

[0011] In certain embodiments, the hydrocarbon feed includes methane, ethane, propane, linear hydrocarbons greater than C4, or crude oil. In certain embodiments, the hydrocarbon feed includes Naphtha.

[0012] In certain embodiments, methods of converting a hydrocarbon feed can involve Ni based catalysts. In certain embodiments, the catalyst can be a Ni based catalyst on a support. In certain embodiments, the support can be MgO, La ₂ 0 ₃ , A1 ₂ 0 ₃ , or any combinations thereof. In certain embodiments, the catalyst can be Ni on a La ₂ 0 ₃ support. In certain embodiments, the amount of Ni can range from 5% to 15% by weight of the catalyst. In certain embodiments, the catalyst can further include 0.1% to 2% by weight noble metal. In certain embodiments, the noble metal can be Pt, Ru, and combinations thereof.

[0013] In certain embodiments, the oxygen used in the presently disclosed subject matter can be supplied with air. In certain embodiments, the reactor temperature can range from about 700 to 750 °C, from about 750 to 800 °C, or from about 800 to 820 °C.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic diagram depicting an exemplary embodiment of the disclosed subject matter. DETAILED DESCRIPTION

[0015] The presently disclosed subject matter provides methods of oxidative conversion of variable hydrocarbon feed into C2-C3 olefins, syngas, low molecular weight paraffinic hydrocarbons and aromatic hydrocarbons.

[0016] For the purpose of illustration and not limitation, FIG. 1 is a schematic representation of a non-limiting embodiment of the disclosed subject matter. In certain embodiments, methods of converting a variable hydrocarbon feed can involve oxidative dry reforming of a feed mixture 101 of the hydrocarbon feed, oxygen source, and carbon dioxide in a reactor 102.

[0017] In certain embodiments, the hydrocarbon feed can contain hydrocarbons of various length from methane to crude oil hydrocarbons. In certain embodiments, the hydrocarbon feed can contain methane. Syngas and ethylene can be generated through oxidative dry reforming of methane, according to the reaction as follows:

CH ₄ + C0 ₂ + 0 ₂ → C ₂ H ₄ + Syngas + H ₂ 0 (1)

[0018] In certain embodiments, the hydrocarbon feed can contain low molecular weight C2-C3 paraffins. Both ethane and propane can be converted into olefins and syngas through oxidative dry reforming, according to the respective reaction as follows:

C ₂ H ₆ + C0 ₂ + 0 ₂ → C ₂ H ₄ + Syngas + H ₂ 0 (2) C ₃ H ₈ + C0 ₂ + 0 ₂ → C ₃ H ₆ + Syngas + H ₂ 0 (3)

[0019] In certain embodiments, the hydrocarbon feed can contain >C4 linear hydrocarbons such as Naphtha, which can be converted into olefins, paraffins, aromatics, and syngas, according to the reaction as follows:

Naphtha + C0 ₂ + 0 ₂ → C2-C3 olefins + C2-C3 paraffins + aromatics + Syngas (4) [0020] In certain embodiments, the hydrocarbon feed can contain crude oil (>C6), which can also be converted to olefins, paraffins, aromatics, and syngas, according to the reaction as follows:

Crude oil + C0 ₂ + 0 ₂ → C2-C3 olefins + C2-C3 paraffins + aromatics + Syngas (5)

[0021] These reactions involve exothermic reactions of hydrocarbon with oxygen and endothermic reaction with C0 ₂ facilitated by a common catalyst in the reactor 102. Such design can result in an efficient in-situ heat transfer from the exothermic reaction to the endothermic processes and can be more energy efficient than the conventional dry reforming or steam reforming processes. The endothermic nature of the reforming reactions with C0 ₂ can further facilitate temperature control so as to prevent unwanted deep oxidation reactions of the feed. The disclosed subject matter can be flexible in adjusting the process parameters for conversion of the hydrocarbon feed of all compositions according to the availability of the hydrocarbons. This flexible process can be used for direct conversion of crude oil and have an advantage over certain conventional oil-to-chemicals processes, where step-wise refining and fluid catalytic cracking processes are usually necessary. In certain embodiments, the hydrocarbon feed can be treated to remove harmful impurities, particulates, and/or silica before subject to oxidative dry reforming process.

[0022] The C0 ₂ used in the feed mixture 101 can originate from various sources. In certain embodiments, the C0 ₂ can come from a waste gas stream, e.g., from a plant on the same site, or after recovering C0 ₂ from a gas stream. Recycling C0 ₂ as starting material in the methods of the presently disclosed subject matter can contribute to reducing the amount of C0 ₂ emitted to the atmosphere, e.g., from a chemical production site. In certain embodiments, the C0 ₂ is pressurized to have a pressure from about 1 to about 25 bar, from about 1 to about 10 bar, from about 10 bar to about 20 bar, or from about 20 bar to about 25 bar. [0023] The oxygen source used in the feed mixture 101 can be in various forms. In certain embodiments, clean dry air can be collected from the environment and used as the oxygen source. In certain embodiments, the oxygen source can be in the form of compressed air. In certain embodiments, the air is pressurized to have a pressure from about 1 to about 25 bar, from about 1 to about 10 bar, from about 10 bar to about 20 bar, or from about 20 bar to about 25 bar. In certain embodiments, the oxygen source can have enriched oxygen contents ranging from about 21% to about 100% by mole. In certain embodiments, the feed mixture 101 can further contain other gases that do not negatively affect the reaction. In certain embodiments, the feed mixture 101 can contain about 20% to 60% air and about 10% to 40% carbon dioxide.

[0024] As used herein, the term "about" or "approximately" means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, "about" can mean a range of up to 20%, up to 10%, up to 5% and/or up to 1% of a given value.

[0025] In certain embodiments, the feed mixture 101 contacts a catalyst in the reactor 102 to be converted into C2-C3 olefins, syngas, low molecular weight paraffinic hydrocarbons and/or aromatic hydrocarbons. In certain embodiments, the catalyst used in 102 includes Ni as an active constituent. In certain embodiments, the catalyst can include Ni based catalysts in the form of mixture of oxides. The catalyst compositions can further include an inert carrier or support material. Suitable supports can be any support materials, which exhibit good stability at the reaction conditions of the disclosed methods, and are known by one of ordinary skill in the art, such as MgO, La ₂ 0 ₃ , A1 ₂ 0 ₃ , or any combinations thereof. The amount of Ni on support can vary from about 5% to 15% by weight of the catalyst. An appropriate support can provide a large surface area, to which the active catalyst is affixed. In certain embodiments, the catalyst has a surface area of at least 50 m ² /g. In certain embodiments, the appropriate support can also be mildly basic materials, such as La ₂ C"3 In certain embodiments, the support catalysts can further contain small amounts of noble metal, such as Pt, Ru, or both. In certain embodiments, the support catalysts can contain noble metal in the amount from 0.1% to 2% by weight. The catalyst may further contain other inert components, like a binder material, or usual impurities, as known to the skilled person. The catalysts used in the present disclosure can be prepared by any catalyst synthesis process well known in the art. Examples include, but are not limited to, spray drying, precipitation, impregnation, incipient wetness, ion exchange, fluid bed coating, physical or chemical vapor deposition.

[0026] In certain embodiments, the oxidative dry reforming in reactor 102 can be conducted over wide range temperature range depending of the composition of the feed mixture 101. In certain embodiments, the reactions are carried at a temperature from about 600°C to 850°C, from about 700°C to 750°C, from about 720°C to 730°C, from about 800°C to 850°C, or from about 800°C to 820°C.

[0027] In certain embodiments, the reactor 102 can use any reactor type suitable for oxidative dry reforming. For example, but not by way of limitation, such reactors include fixed bed reactors, fluidized bed reactors, and riser reactors. In certain embodiments, the fixed bed reactors can be tubular type reactors or fixed bed reactors where catalysts can be loaded across the entire diameter of the bed. In certain embodiments, the reactor can include a reactant preheating zone and a catalyst reaction bed suitable for efficient heat transfer. In certain embodiments, the feed mixture can be preheated to about 450°C then fed to the reactor. The dimensions and structure of the reactor unit of the presently disclosed subject matter can vary depending on the capacity of the reactor. The capacity of the reactor unit can be determined by the reaction rate, the stoichiometric quantities of the reactants and/or the feed flow rate. The feed flow rate in reactor 102 may vary widely based on the reactor design. The space velocity can range from about 10 hour-1 to about 400 hour-1, from about 100 hour-1 to about 400 hour-1, or from about 300 hour-1 to about 400 hour-1. In certain embodiments, the reactor 102 can be operated in a wide pressure range. For example, and not by way of limitation, the pressure can be from about lOOkPa to about 200kPa, from about 200kPa to about 300kPa, from about 300kPa to about 400kPa or from about 500kPa to about 700kPa.

[0028] In certain embodiments, products of the oxidative dry reforming process can further subject to separation 103. In certain embodiments, such separation process can involve various distillation equipment known in the art. In certain embodiments, products of the oxidative dry reforming process can be separated by pressure swing adsorption, a known process in the art. In certain embodiments, the syngas mixtures can be separated from the product mixtures to be further processed to produce methanol 108 using a known process in the art. For example, syngas can be catalytically converted into methanol in the presence of appropriate copper catalysts. Because methanol production can rely on syngas produced from methane steam reforming, this alternative crude oil to methanol product path is particularly valuable in area that has limited methane supply. By removing the demand for methane to generate syngas gas, methane resources can be redirected to serve other important functions such as electricity generation. In certain embodiments, C2-C3 olefins 105 and aromatics 106 can be separated from the product mixtures for further chemical processing. In certain embodiments, C2-C3 paraffins and >C4 linear hydrocarbons 107 from the separation process can be reintroduced as part of the hydrocarbon feed in feed mixture 101.

[0029] In certain embodiments, the product mixture can include from about 10% to about 40%) methane, from about 0% to 70% syngas, from about 0 to 30%> C2-C3 olefins, from about 0 to about 20% C2-C3 paraffins, from about 0% to about 20% aromatics, from about 0%) to about 20%) carbon dioxide, and/or from about 5% to about 30%> nitrogen.

EXAMPLES

[0030] The following examples are merely illustrative of the presently disclosed subject matter and should not be considered as a limitation in any way.

Example 1:

[0031] This example describes conversion of methane in the presence of oxygen and C0 ₂ into syngas mixture.

[0032] A feed mixture that contained 28.4 % by mole of CH ₄ , 17.4% by mole of C0 ₂ , 11% by mole of 0 ₂ , and 42.8% by mole of N ₂ was fed into a lab-scale fixed bed reactor in the presence of a Ni/La ₂ 0 ₃ catalyst to produce a syngas mixture. The operating conditions were as follows: 720°C with a space velocity of 3600 h ^"1 per hour and a pressure of 1 atm. These operating conditions led to 72.7% conversion of CH ₄ and 86.1%> conversion of C0 ₂ . The products from the reactor outlet contained 22.7% by mole CO, 34.6% by mole H ₂ , 6.0% by mole CH ₄ , 3.06% by mole C0 ₂ , 33.2% by mole N ₂ , 0.43% by mole 0 ₂ .

Example 2:

[0033] This example describes conversion of Naphtha in the presence of oxygen and C0 ₂ into olefins, aromatics, and other products.

[0034] A feed mixture that contained 25% by mole of Naphtha, 30% by mole of C0 ₂ , 15% by mole of 0 ₂ , and 30%> by mole of N ₂ was fed into a lab-scale fixed bed reactor in the presence of a Ni/La ₂ 0 ₃ catalyst to undergo oxidative dry reforming. The operating conditions were as follows: 800-820°C with a space velocity of 3600 h ^"1 per hour and a pressure of 1 atm. The products from the reactor outlet contained 12.4% by mole C2-C3 olefins, 14% by mole aromatics, 21% by mole methane, 9.3% by mole C2-C3 paraffins, 7.3% by mole C0 ₂ , 28% by mole CO+H ₂ , and 8% by mole N ₂ . Example 3:

[0035] This example describes conversion of crude oil in the presence of oxygen and C0 ₂ into syngas olefins, aromatics, and other products.

[0036] Oxidative dry reforming of crude oil was conducted at the same condition as Example 2. The products from the reactor outlet contained a wide range of hydrocarbons from CI to C7 including C2-C4 olefins, aromatics, light C2-C4 hydrocarbons, and a heavy C5-C7 fraction which has a composition similar to light naphtha. The aromatics and C2-C3 olefins accounted for about 12-16% by volume. The methane product was about 23% by volume and the unreacted C0 ₂ was about 8-9%.

[0037] These examples illustrates that the presently disclosed subject matter can enable a flexible oxidative dry reforming of a variable hydrocarbon feed to produce C2-C3 olefins, syngas, and aromatic hydrocarbons.

[0038] In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having other combinations of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. The foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.

[0039] It will be apparent to those skilled in the art that various modifications and variations can be made in the systems and methods of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.