Catalytic Conversion Of Light Hydrocarbons

Abstract

A process for converting light hydrocarbons into hydrogen and other valuable hydrocarbons includes reacting the light hydrocarbons with a catalyst in a reactor vessel at a reaction temperature and pressure to produce an intermediate product stream comprising hydrogen, methane, ethylene, acetylene, benzene, and polynuclear aromatics. The intermediate product stream is quenched and compressed after which the constituents of the intermediate product stream are separated.

Claims

1. A process for converting C.sub.1-C.sub.3 alkane, the process comprising: providing at a feed inlet of a reactor vessel a feed comprising the C.sub.1-C.sub.3 alkane, wherein the reactor contains a catalyst; reacting the C.sub.1-C.sub.3 alkane with the catalyst in the reactor vessel for a period of 0.01 to 60 seconds to produce an intermediate product stream comprising hydrogen, methane, ethylene, acetylene, benzene, and polynuclear aromatics, the reacting occurring while maintaining a temperature within the reactor vessel of 600 to 1200 C. and a pressure of 1 bar to 5 bar, the intermediate product stream; quenching the intermediate product stream to cool the intermediate product stream to an intermediate temperature of 300 to 950 C.; removing aromatics from the intermediate product stream; compressing the intermediate product stream to an intermediate pressure of 5 bar to 500 bar; and separating hydrogen from the intermediate product stream to produce a hydrogen stream.

2. The process of claim 1, further comprising separating ethylene, acetylene, and olefins of C.sub.3 or greater from the intermediate product stream with a separator.

3. The process of claim 1, further comprising returning methane remaining in the intermediate product stream to the feed inlet.

4. The process of claim 1, further comprising preheating the feed before providing it to the reactor.

5. The process of claim 1, further comprising, following quenching of the intermediate product stream, purifying aromatic condensates with a distillation column or a sulfone absorption column to produce a benzene stream, a polynuclear aromatics stream, and other aromatic product streams.

6. The process of claim 5, wherein the polynuclear aromatics stream is used as fuel to heat the reactor vessel.

7. The process of claim 5, further comprising converting the polynuclear aromatics stream to transportation fuels in a hydrocracker.

8. The process of claim 1, further comprising trimerizing acetylene in the intermediate product stream to produce benzene.

9. The process of claim 1, further comprising converting acetylene in the intermediate product stream to ethylene using a selective hydrogenation unit.

10. The process of claim 1, wherein the reactor vessel is a component of a fluidized bed system.

11. The process of claim 1, further comprising: moving the catalyst from the reactor vessel to a regenerator; regenerating the catalyst with an oxidation reaction in the regenerator; and after regenerating the catalyst, returning the catalyst to the reactor vessel.

12. The process of claim 1, wherein the reactor vessel is a component of a fixed bed reactor.

13. The process of claim 12, further comprising: turning off the feed comprising the C.sub.1-C.sub.3 alkane to the reactor vessel; providing at an oxidant inlet of the reactor vessel a feed of an oxidant, wherein the oxidant oxidizes coke within the reactor and regenerates the catalyst; and removing at an exhaust outlet of the vessel an exhaust from oxidation of the coke within the vessel.

14. The process of claim 1, wherein the reactor vessel is a component of a monolith catalyst block reactor.

15. The process of claim 14, wherein the monolith catalyst block reactor comprises two or more reactor vessels alternating between reaction and catalyst regeneration modes.

16. A system for converting light hydrocarbons, the system comprising: a fluidized bed reactor vessel comprising a catalyst; a heating system to supply heat to the fluidized bed reactor vessel; a feed inlet that provides a feed comprising C.sub.1-C.sub.3 alkane to the catalyst; a product outlet from which an intermediate product stream exits the fluidized bed reactor vessel, the intermediate product stream comprising hydrogen, methane, ethylene, acetylene, benzene, and polynuclear aromatics; a quencher that cools the intermediate product stream exiting the fluidized bed reactor vessel to an intermediate temperature of 300 to 950 C.; a compressor that compresses the intermediate product stream to an intermediate pressure of 5 bar to 500 bar; and a separation system that separates the hydrogen from the intermediate product stream.

17. The system of claim 16, wherein the separation system further separates the methane, ethylene, acetylene, benzene, and polynuclear aromatics from the intermediate product stream.

18. The system of claim 16, further comprising a fluidized bed catalyst regenerator that regenerates the catalyst, wherein heat from the fluidized bed catalyst regenerator is used to preheat the feed comprising C.sub.1-C.sub.3 alkane.

19. A system for converting light hydrocarbons, the system comprising: a fixed bed reactor vessel comprising a catalyst; a heating system to supply heat to the fixed bed reactor vessel; a feed inlet that provides a feed comprising C.sub.1-C.sub.3 alkane to the catalyst; a product outlet from which an intermediate product stream exits the fixed bed reactor vessel, the intermediate product stream comprising hydrogen, methane, ethylene, acetylene, benzene, and polynuclear aromatics; a quencher that cools the intermediate product stream exiting the fixed bed reactor vessel to an intermediate temperature of 300 to 950 C.; a compressor that compresses the intermediate product stream to an intermediate pressure of 5 bar to 500 bar; and a separation system that separates the hydrogen from the intermediate product stream.

20. The system of claim 19, wherein the separation system further separates the methane, ethylene, acetylene, benzene, and polynuclear aromatics from the intermediate product stream.

21. A system for converting light hydrocarbons, the reactor comprising: a vessel; at least one catalyst block within the vessel; a heating system to supply heat to the at least one catalyst block; a feed inlet at a first end of the vessel that provides a feed comprising C.sub.1-C.sub.3 alkane to the at least one catalyst block; a product outlet from which an intermediate product stream exits the vessel, the intermediate product stream comprising hydrogen, methane, ethylene, acetylene, benzene, and polynuclear aromatics; a quencher that cools the intermediate product stream exiting the vessel to an intermediate temperature of 300 to 950 C.; a compressor that compresses the intermediate product stream to an intermediate pressure of 5 bar to 500 bar; and a separation system that separates the hydrogen from the intermediate product stream.

22. The system of claim 21, wherein the separation system further separates the methane, ethylene, acetylene, benzene, and polynuclear aromatics from the intermediate product stream.

23. The system of claim 21, wherein the heating system is at least one electric heater that passes through the at least one catalyst block.

24. The system of claim 21, further comprising: an oxidant inlet through which an oxidant enters the vessel and oxidizes coke accumulated within the at least one catalyst block; and an exhaust outlet through which exhaust from oxidation of the coke exits the vessel, wherein the exhaust is used to preheat the feed comprising C.sub.1-C.sub.3 alkane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings illustrate only example embodiments of processes and reactors for catalytic conversion of light hydrocarbons to produce hydrogen and C.sub.2-C.sub.10 hydrocarbons and therefore are not to be considered limiting of the scope of this disclosure. The principles illustrated in the example embodiments of the drawings can be applied to alternate methods and apparatus. Additionally, the elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Certain dimensions or positions may be exaggerated to help visually convey such principles. In the drawings, the same reference numerals used in different embodiments designate like or corresponding, but not necessarily identical, elements.

[0011] FIG. 1 illustrates components and a method of a system for production of hydrogen and C.sub.2-C.sub.10 hydrocarbons in accordance with a first example embodiment of the disclosure.

[0012] FIG. 2 illustrates components and a method of a system for production of hydrogen and C.sub.2-C.sub.10 hydrocarbons in accordance with a second example embodiment of the disclosure.

[0013] FIG. 3 illustrates components and a method of a system for production of hydrogen and C.sub.2-C.sub.10 hydrocarbons in accordance with a third example embodiment of the disclosure.

[0014] FIG. 4 illustrates components and a method of a system for production of hydrogen and heavy hydrocarbons in accordance with a fourth example embodiment of the disclosure.

[0015] FIG. 5 illustrates a side cross-sectional view of an example fluidized bed reactor and catalyst regenerator for production of hydrogen in accordance with the example embodiments of the disclosure.

[0016] FIG. 6 illustrates a side cross-sectional view of an example multi-tube fixed bed reactor for production of hydrogen in accordance with a sixth example embodiment of the disclosure.

[0017] FIGS. 7A and 7B illustrate side and top cross-sectional views, respectively, of an example monolith reactor for production of hydrogen in accordance with a seventh example embodiment of the disclosure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0018] The example embodiments discussed herein address one or more of the challenges identified above by providing comprehensive approaches to the problem of catalytic conversion of light hydrocarbons. The comprehensive approaches provided herein can encompass one or more of reactor design, catalyst regeneration, heat management, product separation, and the potential for downstream reactions such as hydrogenation, aromatization, or hydrocracking. The example embodiments are directed to processes and reactors that convert light hydrocarbons, such as C.sub.1-C.sub.3 alkane, into hydrogen and C.sub.2-C.sub.10 hydrocarbons. Several example embodiments of processes and reactors are described herein. The example embodiments provide improved energy efficiency and provide for a regeneration process to remove coke that accumulates within the reactor and on the catalyst.

[0019] In the following paragraphs, particular embodiments will be described in further detail by way of example with reference to the drawings. The embodiments described can be implemented separately, or in combination with other embodiments in the description. In the description, well-known components, methods, and/or processing techniques are omitted or briefly described. Furthermore, reference to various feature(s) of the embodiments is not to suggest that all embodiments must include the referenced feature(s).

General Process

[0020] The example processes and reactors described herein pertain to a process for converting a light hydrocarbon feed comprising primarily C.sub.1-C.sub.3 alkane to a C.sub.2-C.sub.10 product and hydrogen. The C.sub.1-C.sub.3 alkane is not particularly limited and may include, for example, natural gas, methane, ethane, propane, or mixtures thereof. As used herein natural gas comprises methane and potentially higher alkanes, carbon dioxide, nitrogen or other gases, and/or sulfide compounds such as hydrogen sulfide, and mixtures thereof. The process generally comprises first flowing the light hydrocarbon feed comprising the C.sub.1-C.sub.3 alkane over a catalyst within a reactor vessel. As non-limiting examples, the catalyst may be: a) a metal oxide catalyst, b) a silicon dioxide catalyst which does not contain metal, or c) a matrix comprising fused silica and a metal dopant such as iron. The catalyst facilitates a reaction that converts the C.sub.1-C.sub.3 alkane to a product gas stream primarily comprising methane, ethylene, acetylene, benzene, polynuclear aromatics (PNAs), and hydrogen, as well as lesser components that may include ethane, propylene, propadiene, methyl acetylene, butadiene, and impurities. The product gas stream from the reaction with the catalyst can be further processed to yield hydrogen and C.sub.2-C.sub.10 product. The C.sub.2-C.sub.10 product is not particularly limited and could be saturated, unsaturated, aromatic, or a mixture of such compounds. In some embodiments the C.sub.2-C.sub.10 product may comprise ethylene, benzene, naphthalene, and various mixtures thereof depending upon the desired products and reactions used.

[0021] The C.sub.1-C.sub.3 alkane is usually heated in a reactor under suitable conditions in the presence of the catalyst to produce the product gas stream. Suitable conditions may vary depending upon the reactants, desired products, catalysts, and equipment employed. Typically, the reactor conditions include a temperature of from 600 C., or from 700 C., up to 1000 C. or up to 1200 C., and a pressure of from 1 bar up to 3 bar, or up to 5 bar, or up to 10 bar, or up to 100 bar may be employed to produce the product gas stream and ultimately the C.sub.2-C.sub.10 product that may comprise ethylene, acetylene, benzene, naphthalene, or a mixture thereof and hydrogen. Preferably, the pressure in the reactor is at about 5 bar. The C.sub.1-C.sub.3 alkane typically reside in the reactor for a residence time in a range of 0.01 to 60 seconds. In a preferred embodiment, the C.sub.1-C.sub.3 alkane is catalyzed in a reactor wherein the temperature is 600 C. to 1200 C., the pressure is 1 bar to 5 bar, and the C.sub.1-C.sub.3 alkane resides in the reactor for a residence time of 0.1 to 10 seconds. The C.sub.1-C.sub.3 alkane may be heated by one or more of a variety of sources, such as an electric heater or a combustion heating process.

[0022] A variety of reactors may be used with the example processes described herein. As will be described further below, the reactors may include a fluidized bed reactor, a fixed bed reactor, or a monolithic reactor. Several enhancements to the foregoing general process also will be described below.

[0023] Referring now to FIG. 1, an example process and system 100 are illustrated in accordance with an embodiment of the disclosure. The process and system 100 convert a light hydrocarbon feed to H.sub.2, C.sub.2H.sub.4, C.sub.2H.sub.2, and C.sub.6H.sub.6 as the final products. The following Table 1 explains the components of the system illustrated in FIG. 1.

TABLE-US-00001 TABLE 1 Components P1 Preheater with the heat generated from any of various sources R1 Fluidized bed reactor with heat generated from catalyst regeneration Q1 quencher for cooling product gas stream to <950 C. and a subsequent heat exchanger for further cooling C1 Compressor to increase gas stream pressure from 1-5 bar to 10- 500 bar A1 Aromatic recovery by sulfone absorption column, or distillation, or gas-liquid separation A2 Distillation column for purification of aromatics H1 Pressure swing absorption, membrane section, or other separator for H.sub.2 purification E1 Cryogenic section for purification of C.sub.2H.sub.4 and C.sub.2H.sub.2

[0024] The following Table 2 explains the compositions of the fluid streams illustrated in the process and system 100.

TABLE-US-00002 TABLE 2 Compositions #1 Fresh light hydrocarbon feed #2 Light hydrocarbon feed containing recycled gas #3 Preheated feed #4 Product gas (also called intermediate product) stream consisting mainly of CH.sub.4, C.sub.2H.sub.4, C.sub.2H.sub.2, C.sub.6H.sub.6, PNAs, H.sub.2 #5 Quenched product gas stream #6 product stream (1~5 bar) with most aromatic condensates removed #7 Recovered Aromatic such as C.sub.6H.sub.6 and PNAs #8 Condensed aromatics recovered from compressor such as C.sub.6H.sub.6 and PNAs #9 Compressed Product gas stream (10-500 bar) consisting of CH.sub.4, C.sub.2H.sub.4, C.sub.2H.sub.2, H.sub.2 #10 Product gas stream consisting of CH.sub.4, C.sub.2H.sub.4, C.sub.2H.sub.2 #11 Recycle gas stream consisting of unreacted CH.sub.4 #12 Fuel for reactor heat #13 Recovered PNAs #14 Recovered high-purity C.sub.6H.sub.6 #15 Recovered high-purity H.sub.2 #16 Recovered high-purity C.sub.2H.sub.4 #17 Recovered high-purity C.sub.2H.sub.2

[0025] Features and enhancements of the process and system 100 will now be described in greater detail.

Reactor Design

[0026] The process and system 100 may be implemented with a variety of reactors. One example is a fluidized bed reactor, as indicated by R1 in Table 1 above and as illustrated in FIG. 1. An example of a more detailed illustration of a fluidized bed reactor is provided in FIG. 5 and is described further below. The bed within the reactor includes the catalyst. Non-limiting examples of the catalyst include: a) a metal oxide catalyst (e.g., white alumina), b) a silicon dioxide catalyst which does not contain metal, or c) a matrix comprising fused silica and a metal dopant such as iron. A fluidized bed reactor is configured to enhance heat transfer efficiency and reduce the risk of reactor plugging compared to other reactor designs.

[0027] Another example reactor that may be used with the process and system of FIG. 1 is a monolithic reactor, such as the monolithic reactor illustrated in FIGS. 7A and 7B. As described further below, a monolithic reactor includes a vessel containing one or more monolith blocks comprising catalyst. The reactor vessel may have refractories on the vessel wall to protect the external metal surface from high temperatures. The one or more monolithic blocks within the reactor vessel may have internal channel surfaces washcoated with active catalysts for light hydrocarbon catalytic cracking reactions. The light hydrocarbon feed, such as natural gas, may be injected and uniformly distributed along the one or more monolith blocks. The light hydrocarbon feed may flow either downwards or upwards through the one or more monolith blocks. The reaction heat can be provided by one or more electric heaters as illustrated in FIGS. 7A and 7B. Alternatively, in other embodiments, reaction heat can be supplied by burning fuels outside of reaction tubes within the vessel, making the entire reaction vessel a furnace. Suitable fuels may be natural gas, produced hydrogen, and/or tail gas. The exhaust from the combustion may be further sent to heat exchangers to recover residual heating value.

[0028] Yet another example of a reactor that may be used with the process and system of FIG. 1 is a fixed bed reactor. Details of an example fixed bed reactor are provided below in connection with the description of FIG. 6.

Catalyst Regeneration

[0029] The process and system 100 may be implemented with catalyst regeneration. For a process and system using a fluidized bed reactor, the catalyst regenerator may be located near the reactor vessel as illustrated in FIG. 5 and as described further below. One or more conduits may facilitate the transfer of spent catalyst from the reactor vessel to the regenerator, preventing gas rising in the conduits and ensuring efficient regeneration of the catalyst. The catalyst regenerator may equipped with refractories on the wall for protecting the external metal surface from high reaction temperatures.

[0030] For the monolithic reactor or fixed bed reactor, two or more reactors may be used in an alternating manner for smooth operation, with one or more in reaction mode and the other reactor(s) in regeneration mode. In one embodiment, after the reaction conversion for one reactor is determined to be too low, that reactor will be isolated and put in catalyst regeneration mode with hydrocarbon feed pulled from that reactor while in catalyst regeneration mode. A calculated flow rate of oxidant, such as air, oxygen, steam, or CO.sub.2, will be injected over the deactivated catalyst, where carbon deposited on the catalyst surface will be removed. The heat generated from the oxidation will also heat up the reactor and the monolith block thereby providing additional heat for the light hydrocarbon catalytic reaction after the reactor is returned to the reaction mode. In another embodiment, the one or more reactors are operated in alternating manner between the reaction mode and catalyst regeneration mode.

Heat Management

[0031] In embodiments in which the process and system 100 use a fluidized bed reactor, heating of the light hydrocarbon feed can be accomplished with any of a variety of heating sources. Examples of heat sources include a resistive or inductive heating element or a heat exchanger. In the example illustrated in FIG. 1, the preheater P1 may represent a heat exchanger. The heat exchanger enables transfer of heat from the hot gas effluent to the relatively cold light hydrocarbon feed. This heating process efficiently heats the light hydrocarbon feed to the desired reaction temperature.

[0032] For embodiments in which the process and system use monolithic reactors or fixed bed reactors, a calculated flow rate of oxidant, such as air, oxygen, steam, or CO.sub.2, will be injected over the deactivated catalyst during the catalyst regeneration mode as described above. The oxidation reaction removes carbon deposits from the catalyst and generates heat. The heat generated from the oxidation reaction also heats up the reactor and the catalyst thereby providing additional heat for the light hydrocarbon catalytic reaction after the reactor is returned to the reaction mode.

Quencher

[0033] As illustrated in FIG. 1 and as indicated in Tables 1 and 2 above, the quencher Q1 receives the product gas (or intermediate product) stream from the reactor R1. The quencher cools the product gas stream to under 950 C., e.g., in a range of 200 C. to 950 C., to stabilize the mixture of the product gas stream and prevent further cracking and coke formation and fouling of equipment. The quenched product stream may be further cooled with the light hydrocarbon feed stream in a heat exchanger. Many thermally stable fluids can be used to quench the hot product gas stream, including but not limited to steam, nitrogen, natural gas, heavy diesel, light aromatics such as benzene, xylene, etc.

Aromatic Recovery

[0034] In one embodiment, after quenching, the remaining aromatic species are removed in an absorption column using sulfone as absorbent as indicated by the aromatic recovery element A1 in FIG. 1. After regeneration of the sulfolane, the aromatic streams from the condensate separators as well as the absorption section are mixed and upgraded by a distillation column A2 to yield the products benzene, ethylbenzene, xylenes, and polynuclear aromatics (PNA) like naphthalene. In another embodiment, the quenched reactor effluent stream can be injected to a distillation column directly without using an absorption column to effectively remove aromatics from the product gas stream while separating and purifying benzene and other light high value aromatics from heavy low value aromatics. In one embodiment, as indicated by stream #13 in FIG. 1, a portion of the recovered PNA stream can be split off to burn in both furnace and the reactor to cover the heat duty, with the remainder of the PNAs in the stream. In another embodiment, as indicated by stream #14, the benzene stream is cooled and treated in a purification separator phase separator to reach the desired final product purity, for example, of 99.8% or higher.

Compression

[0035] As illustrated in FIG. 1 and as indicated in Tables 1 and 2 above, the compressor C1 receives intermediate product stream after quenching and after aromatics are removed. As explained previously, the catalytic reactions in the reactor take place at a pressure less than 100 bar and preferably at about 5 bar. At the compressor, the quenched product gas is compressed to a range of 10 bar to 500 bar. The compressor may include interstage coolers and condensate separators to remove any aromatic condensates.

Separation of Products

[0036] As illustrated in FIG. 1 and as indicated in Tables 1 and 2 above, after compression by the compressor C1, the quenched product stream (also referred to an intermediate product stream) is separated into components. The example process and system 100 of FIG. 1 incorporates a series of separators, enabling efficient separation of hydrogen and main products from the quenched product stream. The separators ensure high purity and facilitate downstream utilization of the desired products. As indicated by stream #9 (intermediate product stream) in FIG. 1, the compressed, aromatic-free product stream continues to the hydrogen separation system H1. As examples, the hydrogen separation system H1 may be a pressure swing absorption system, or a membrane section system or a combination of both. At the hydrogen separation system H1 a purified hydrogen (stream #15) is produced. The remaining hydrocarbon stream, consisting mainly of methane, ethylene, and acetylene is subjected to a cryogenic separator E1 to recover ethylene (stream #16) and acetylene (stream #17). A heavy olefin stream, such as propylene and butene, may also be recovered as described in connection with FIGS. 2, 3, and 4 below. The remaining gas stream (#11) containing mostly methane is recycled to the reactor inlet (#2) and mixed with the fresh feed stream #1.

[0037] FIG. 2 illustrates another example embodiment of a process and system 200. Process and system 200 include many of the same elements and streams of FIG. 1. For the elements and product streams of FIG. 2 having the same reference numbers as those in FIG. 1, unless otherwise indicated, the descriptions provided for FIG. 1 apply to those similar elements and product streams of FIG. 2 and will not be repeated.

[0038] The process and system 200 of FIG. 2 differs from the process and system 100 of FIG. 1 in the following respects. Table 3 explains the components of system 200 that differ from FIG. 1 and Table 4 explains the compositions of system 200 that differ from FIG. 1.

TABLE-US-00003 TABLE 3 Components T1 Trimerization unit that converts C.sub.2H.sub.2 to C.sub.6H.sub.6 with high conversion/ selectivity.

TABLE-US-00004 TABLE 4 Compositions #17 Product gas stream consisting of CH.sub.4, C.sub.2H.sub.4, C.sub.6H.sub.6 #18 Product gas stream consisting of CH.sub.4, C.sub.2H.sub.4

[0039] The process and system 200 of FIG. 2 converts a light hydrocarbon feed #1 into hydrogen, ethylene, and benzene as final products. One difference from the process and system of FIG. 1 is that process and system 200 includes an acetylene trimerization component T1 that converts intermediate product acetylene to benzene yielding stream #17 comprising methane, ethylene, and benzene. Following the acetylene trimerization unit T1 is a second aromatic recovery unit A1 that absorbs benzene from stream #17 and produces stream #18 comprising methane and ethylene. As examples, the second aromatic recovery unit A1 may be implemented as a gas-liquid separator or as a sulfone absorption column. Byproducts from the second aromatic recovery unit A1 such as PNAs may be combined with stream #13 used with fuel gas for burning to service the reactor R1.

[0040] FIG. 3 illustrates another example embodiment of a process and system 300. Process and system 300 includes many of the same elements and streams of FIG. 1. For the elements and product streams of FIG. 3 having the same reference numbers as those in FIG. 1, unless otherwise indicated, the descriptions provided for FIG. 1 apply to those similar elements and product streams of FIG. 3 and will not be repeated.

[0041] The process and system 300 of FIG. 3 differs from the process and system 100 of FIG. 1 in the following respects. Table 5 explains the components of system 300 that differ from FIG. 1 and Table 6 explains the compositions of system 300 that differ from FIG. 1.

TABLE-US-00005 TABLE 5 Components S1 Selective hydrogenation unit that hydrogenates C.sub.2H.sub.2 to C.sub.2H.sub.4.

TABLE-US-00006 TABLE 6 Compositions #10 Product gas stream consisting of CH.sub.4, C.sub.2H.sub.4, H.sub.2 #16 Recovered high-purity CH.sub.4, C.sub.2H.sub.4 #17 Product gas stream consisting of C.sub.2H.sub.4

[0042] The process and system 300 of FIG. 3 converts a light hydrocarbon feed #1 into hydrogen, ethylene, and benzene as final products. One difference from the process and system of FIG. 1 is that process and system 300 includes selective hydrogenation unit Si that hydrogenates intermediate product acetylene to ethylene. The selective hydrogenation unit Si yields product stream #10 comprising methane, ethylene, and hydrogen. Product stream #10 is fed to hydrogen separation system H1 for recovering high-purity hydrogen as stream #15. As explained previously, the hydrogen separation system H1 may be a pressure swing absorption system or a membrane section system or a combination of both. The remaining stream from the hydrogen separation system H1 is product stream #16 comprising methane and ethylene. Ethylene stream #17 is recovered from stream #16 by the ethylene recovery unit E1 and the remaining gas stream #11 comprising methane is recycled to be combined with the light hydrocarbon feed at stream #2. In another embodiment, the hydrogen recovery unit may be placed upstream of the selective hydrogenation of acetylene unit. In the other words, hydrogen in the intermediate product stream (#9) is recovered in the hydrogen recovery unit first, before selectively hydrogenating acetylene into ethylene.

[0043] FIG. 4 illustrates another example embodiment of a process and system 400. Process and system 400 includes many of the same elements and streams of FIG. 3. For the elements and product streams of FIG. 4 having the same reference numbers as those in FIG. 3, unless otherwise indicated, the descriptions provided for FIG. 3 apply to those similar elements and product streams of FIG. 4 and will not be repeated.

[0044] The process and system 400 of FIG. 4 differs from the process and system 300 of FIG. 3 in the following respects. Table 7 explains the components of system 400 that differ from FIG. 3 and Table 8 explains the compositions of system 400 that differ from FIG. 3.

TABLE-US-00007 TABLE 7 Components R2 Monolithic reactor with heat generated from fuel combustion HCR1 Hydrocracker

TABLE-US-00008 TABLE 8 Compositions #18 Transportation fuels from VGO hydrocracker

[0045] The process and system of FIG. 4 utilizes two alternating monolithic reactor vessels R1 and R2 to convert a light hydrocarbon feed #1 into hydrogen, ethylene, benzene, and transportation fuels as final products. The two monolithic reactor vessels R1 and R2 can operate in an alternating manner whereby one reactor operates in a reaction mode while the other reactor operates in a regeneration mode so that the combination of the reactors can continuously produce the final products. As illustrated in FIG. 4, valves can be used to control the flow of the light hydrocarbon feed between the two reactor vessels. Another distinction in FIG. 4 is the use of a hydrocracker HCR1. Hydrocracker HCR1 receives stream #13 comprising intermediate product PNA, blends stream #13 with vacuum gas oil, and cracks the blend to produce transportation fuels as stream #18.

[0046] Separately, as in FIG. 3, a selective hydrogenation unit Si hydrogenates intermediate product acetylene to ethylene yielding product stream #10 comprising methane, ethylene, and hydrogen. Product stream #10 is fed to the hydrogen separation system H1 recovering high-purity hydrogen as stream #15. The remaining stream from the hydrogen separation system H1 is product stream #16 comprising methane and ethylene. Ethylene stream #17 is recovered from stream #16 by the ethylene recovery unit E1 and the remaining gas stream #11 comprising methane is recycled to be combined with the light hydrocarbon feed at stream #2.

Example Reactors

[0047] Non-limiting examples of three types of reactors that may be used in the systems and processes of FIGS. 1-4 will be now be described in connection with FIGS. 5-7B. Variations of the reactors illustrated in FIGS. 5-7B also may be used with the systems and processes of FIGS. 1-4.

[0048] Referring to FIG. 5, a side cross-sectional view of a system 100 for production of hydrogen in accordance with an example embodiment of the disclosure is illustrated. System 100 comprises an example of a fluidized bed reactor with a catalyst regeneration component. The fluidized bed reactor includes a cracking catalyst that facilitates the conversion of a light hydrocarbon feed (e.g., C.sub.1-C.sub.3 alkane) to C.sub.2-C.sub.10 product and hydrogen. As non-limiting examples, the catalyst may be: a) a metal oxide catalyst, b) a silicon dioxide catalyst which does not contain metal, or c) a matrix comprising fused silica and a metal dopant such as iron.

[0049] Referring now to the drawings in more detail, FIG. 5 illustrates a fluidized bed reactor system 100 including at least a fluidized bed reactor 102, a riser 126 and a catalyst regeneration unit 145. It is to be understood that fluidized bed reactor system 100 including at least fluidized bed reactor 102, riser 126 and catalyst regeneration unit 145 are not limited to the configuration of the embodiments shown in FIG. 5, and other configurations are contemplated herein.

[0050] Fluidized bed reactor system 100 includes fluidized bed reactor 102 having a reactor wall 104. In a non-limiting illustrative embodiment, fluidized bed reactor 102 may have a cylindrical configuration with a constant diameter along all or a portion of its length of reactor wall 104, which may constitute a majority of its length. In some embodiments, fluidized bed reactor 102 may have a cylindrical configuration from a top of fluidized bed reactor 102 to a bottom of fluidized bed reactor 102 with a uniform diameter. However, as one skilled in the art will appreciate, the cylindrical configurations are merely illustrative and any other suitable shape of the same or varying diameters are contemplated herein.

[0051] In illustrative embodiments, fluidized bed reactor 102 includes reactor wall 104 that surrounds the interior. In some embodiments, reactor wall 104 may be formed from a reactor lining having one or more layers of a refractory material that line the interior of reactor wall 104 to reduce heat loss and sustain the high temperatures of fluidized bed reactor 102. The reactor lining provides thermal and abrasion resistance, and may extend over all or a portion of each of the components of fluidized bed reactor system 100 including at least fluidized bed reactor 102, riser 126 and catalyst regeneration unit 145. For example, fluidized bed reactor 102 may operate at high or even extremely high temperatures, and further includes a flowing heated regenerated catalyst and heated light hydrocarbon feed stream 138, such as the previously described C.sub.1-C.sub.3 alkane feed.

[0052] Fluidized bed reactor 102 further includes separators 108 located at the top of fluidized bed reactor 102. Separators 108 receive the product effluent stream comprising hydrogen and spent catalyst comprising coke deposits produced from cracking the heated light hydrocarbon feed stream in the presence of the heated regenerated catalyst. Separators 108, e.g., cyclones, then separate a spent catalyst 113 from the product effluent stream to generate an intermediate product stream comprising hydrogen which then exits fluidized bed reactor 102 via line 128. Spent catalyst 113 then flows downward from separators 108 and to a reactor stripper 110 through conduits 114. In some embodiments, spent catalyst 113 flows downward by, for example, gravity forces.

[0053] Fluidized bed reactor system 100 further includes catalyst regeneration unit 145 for receiving spent catalyst 113 from reactor stripper 110 which is in fluid communication with fluidized bed reactor 102 and riser 126. As discussed above, coke is formed on the surface of spent catalyst 113 comprising the catalyst and coke deposits. Spent catalyst 113 is continuously introduced to catalyst regeneration unit 145 via reactor stripper 110 where spent catalyst 113 is subjected to coke burning conditions to burn most, if not all, of the coke from spent catalyst 113 and provide a regenerated catalyst, which can be split into a regenerated catalyst 118-1 and an optional regenerated catalyst 118-2.

[0054] In an illustrative embodiment, catalyst regeneration unit 145 includes a regeneration gas inlet adapted to receive an oxidizing stream 140 into catalyst regeneration unit 145. The regeneration gas inlet may be disposed at the bottom of catalyst regeneration unit 145. However, this is merely illustrative and other locations for the regeneration gas inlet are contemplated herein. Oxidizing stream 140 enters catalyst regeneration unit 145 through heating unit 142 to generate a heated oxidizing stream 144. Oxidizing stream 140 can contain, for example, air, oxygen, nitrogen, methane or combinations thereof or a steam/air mixture.

[0055] Heating unit 142 can be any conventional heating unit known in the art that is configured to heat oxidizing stream 140 to generate heated oxidizing stream 144 having a temperature sufficient to combust spent catalyst 113 and produce the regenerated catalyst.

[0056] Catalyst regeneration unit 145 further includes a flow distributor 146 which is configured to inject heated oxidizing stream 144 amongst spent catalyst 113 disposed in catalyst regeneration unit 145. The coke can be burned from spent catalyst 113 by exposing spent catalyst 113 to heated oxidizing stream 144 at appropriate high temperature and time duration conditions to burn off and remove substantially all coke deposits from the catalyst. In an illustrative embodiment, a temperature can range from about 450 C. to about 1400 C., and a time period can range from about 10 minutes to about 600 minutes.

[0057] In some embodiments, catalyst regeneration unit 145 is operated as a moving bed with spent catalyst 113 continuously moving downwards. In some embodiments, catalyst regeneration unit 145 is operated as a fluidized bed.

[0058] The coke burn causes the spent catalyst to be heated to an elevated temperature, e.g., a temperature of from about 450 C. to about 1400 C., to provide a heated regenerated catalyst relatively free or free of coke wherein the catalyst particles are heated, and sent to riser 126. The coke burn also generates a flue gas which will pass through a series of separators 148, where the solid particulates carried over in the flue gas are separated and drained back down to the lower section of catalyst regeneration unit 145 and generate a flue gas stream 150 free of particulates exiting through a top portion of catalyst regeneration unit 145. In some embodiments, flue gas stream 150 is composed of, for example, carbon dioxide and nitrogen.

[0059] In addition, heated oxidizing stream 144 is used to fluidize the regenerated catalyst in catalyst regeneration unit 145. The regenerated catalyst is continuously introduced to riser 126 at an elevated temperature relative to the temperature of the spent catalyst. The heat generated by the coke burn in catalyst regeneration unit 145 is continuously transferred with the regenerated catalyst to riser 126.

[0060] In some embodiments, catalyst regeneration unit 145 may further have one or multiple conduits between catalyst regeneration unit 145 and different locations in riser 126 that allows the heated regenerated catalyst to be transferred to different locations of riser 126. For example, the regenerated catalyst can be split into two or more streams such as regenerated catalyst 118-1 and regenerated catalyst 118-2. In some embodiments, regenerated catalyst 118-1 or regenerated catalyst 118-2 can have a temperature ranging from about 600 C. to about 1500 C. In some embodiments, the one or multiple conduits can have valves to adjust the regenerated catalyst flow. For example, the flow of regenerated catalyst 118-1 can be controlled by adjusting valve 120. In some embodiments, regenerated catalyst 118-1 is introduced through a first conduit in a bottom portion of riser 126 where it is contacted with light hydrocarbon feed stream 101 as discussed below, and regenerated catalyst 118-2 enters through a second conduit located upwards of the first conduit and flows upwards with the heated regenerated catalyst and heated light hydrocarbon feed stream 138 as discussed below.

[0061] Fluidized bed reactor system 100 includes riser 126 for receiving regenerated catalyst 118-1 and optionally regenerated catalyst 118-2 from catalyst regeneration unit 145.

[0062] In some embodiments, riser 126 has a first diameter and fluidized bed reactor 102 has a second diameter greater than the first diameter. By riser 126 having a smaller diameter than fluidized bed reactor 102, regenerated catalyst 118-1 and regenerated catalyst 118-2 can be substantially or fully fluidized when contacting with the light hydrocarbon feed stream 101 to carry out the direct light hydrocarbon conversion reactions.

[0063] Riser 126 further receives light hydrocarbon feed stream 101 through an inlet in the bottom portion of riser 126. In some embodiments, light hydrocarbon feed stream 101 is at or near room temperature. The light hydrocarbon feed stream 101 flows upward where it is combined with regenerated catalyst 118-1 to form a regenerated catalyst and light hydrocarbon feed stream. The flow of regenerated catalyst 118-1 is controlled by valve 120 as discussed above. In a non-limiting illustrative embodiment, riser 126 may have a cylindrical configuration with a constant diameter along all or a portion of its length.

[0064] The regenerated catalyst and light hydrocarbon feed stream flows upwards where it can first be contacted with a heat source capable of heating regenerated catalyst and light hydrocarbon feed stream to a sufficient temperature to crack the light hydrocarbon feed stream in reaction chamber 106 of riser 126.

[0065] The heated regenerated catalyst and heated light hydrocarbon feed stream 138 flows upward in riser 126 where it is continuously sent to reaction chamber 106. In some embodiments, it may be necessary to add additional catalyst to the heated regenerated catalyst and heated light hydrocarbon feed stream 138. Thus, in some embodiments, regenerated catalyst 118-2 flows into riser 126 and is combined with heated regenerated catalyst and heated light hydrocarbon feed stream 138. Heated regenerated catalyst and heated light hydrocarbon feed stream 138 and regenerated catalyst 118-2 flow upwards to reaction chamber 106 where heated regenerated catalyst and heated light hydrocarbon feed stream 138 are subjected to cracking.

[0066] In illustrative embodiments, the heated regenerated catalyst and heated light hydrocarbon feed stream 138 are subjected to reaction conditions such as, for example, a temperature of from about 600 C. to about 1200 C., or from 700 to 1000 C. The reaction conditions can include a residence time of the heated regenerated catalyst and heated light hydrocarbon feed stream 138 in fluidized bed reactor 102 of from about 0.05 seconds to about 100 seconds, or from about 0.1 seconds to about 2 seconds. The reaction conditions can further include a pressure in the range from 1 bar up to 3, or up to 5, or up to 10 bar.

[0067] Once heated regenerated catalyst and heated light hydrocarbon feed stream 138 has been cracked, the intermediate product can be sent to separators 108 (cyclones) where the spent catalyst comprising coke deposits as well as unstripped hydrocarbon can be separated from the intermediate product comprising hydrocarbons and hydrogen. The intermediate product comprising hydrocarbons and hydrogen can then exit fluidized bed reactor 102 via line 128 for further processing as illustrated and described in connection with FIGS. 1-3.

[0068] Spent catalyst and unstripped hydrocarbons will fall to reactor stripper 110. In some embodiments, a steam stream 112 can be introduced into reactor stripper 110 to assist in separating spent catalyst 113 from unstripped hydrocarbons to generate separated unstripped hydrocarbons and spent catalyst 113. The separated unstripped hydrocarbons can then exit reactor stripper 110 as a stream 115. Spent catalyst 113 is continuously introduced into catalyst regeneration unit 145 as discussed above.

[0069] Referring to FIG. 6, a side cross-sectional view of a reactor system 200 for production of hydrogen in accordance with an example embodiment of the disclosure is illustrated. Reactor system 200 comprises an example of a multi-tube fixed bed reactor. The fixed bed reactor includes a cracking catalyst that facilitates the conversion of a light hydrocarbon feed (e.g., C.sup.1-C.sub.3 alkane) to C.sub.2-C.sub.10 product and hydrogen. As one non-limiting example, the catalyst may be a metal oxide catalyst.

[0070] Reactor system 200 comprises a reactor 202 that has a plurality of reactor tubes 203, each of which contains a fixed catalyst bed 204. Typically, the reactor 202 is generally cylindrical in shape and can have various dimensions.

[0071] As further illustrated in FIG. 6, the reactor 202 comprises a feed inlet 214 at which a light hydrocarbon feed 212 flows into the reactor 202. The light hydrocarbon feed 212 flows downward through the reactor tubes 203 and is treated by the catalyst bed 204 producing the intermediate product stream 220 that exits the reactor 202 through an outlet at the bottom portion of the reactor 202. As illustrative ranges, during the reaction, the reactor control system may maintain conditions within the reactor whereby a reaction mode temperature is in the range of from 600, or from 700, up to 1000 or up to 1200 C., and a reaction mode pressure is in the range from 1 bar up to 3, or up to 5, or up to 10 bar.

[0072] Upon exiting the reactor 602, the intermediate product comprising hydrocarbons and hydrogen can undergo further processing as illustrated and described in connection with FIGS. 1-4.

[0073] Referring to FIGS. 7A and 7B, a side cross-sectional view and a top cross-sectional view, respectively, of a reactor 500 for production of hydrogen in accordance with an example embodiment of the disclosure is illustrated. Reactor 500 comprises a cylindrical vessel 501 containing one or more catalyst blocks (also referred to as monolith catalyst blocks) coated with a cracking catalyst that facilitates the conversion of a light hydrocarbon feed (e.g., C.sub.1-C.sub.3 alkane) to C.sub.2-C.sub.10 product and hydrogen.

[0074] The catalyst block(s) is suitable for light hydrocarbon cracking reactions. The composition, form, size, shape, and properties of the catalyst blocks, may vary depending upon such parameters as the reactants, reactor type, reaction tube size and shape, reaction conditions, and/or desired products. The catalyst block(s) can comprise one or more holes or channels that increase the surface area and porosity of the catalyst blocks. With adequate porosity and pore structure the effective diffusivity for light hydrocarbons may be in the range of 510.sup.3 to 210.sup.2 cm.sup.2/s, and the catalyst effectiveness factor may be in the range of from 0.05, or from 0.1 up to 0.5, or up to 0.4. The catalyst blocks may comprise washcoated honeycomb or metal blocks in some embodiments. The catalyst blocks may comprise ceramic, silica, quartz, glass, metal, silicon carbide, silicon nitride, boron nitride, a metal oxide or any combination thereof. Suitable metal oxides may comprise alpha-alumina, titania, iron oxide, zirconia, a mixed metal oxide, or any combination thereof.

[0075] The reactor 500 comprises a cylindrical vessel 501 with catalyst blocks stacked on top of each other. FIG. 7A illustrates a first catalyst block 505 stacked on top of a second catalyst block 510. However, additional catalyst blocks also can be stacked within the vessel 501. The catalyst blocks have channels passing through each block to increase surface area. Examples of illustrative channels 507 are shown passing through the first catalyst block 505 and the second catalyst block 510. The channels can take a variety of shapes and configurations.

[0076] Reactor 500 includes electric heaters 509 extending vertically from the top to the bottom of the vessel 501 and passing through the catalyst blocks. As illustrated in FIGS. 7A and 7B, a plurality electric heaters 509 can be interspersed throughout the reactor to maintain a desired temperature profile along the length of the vessel 501 and across the diameters of the vessel 501 which can improve the yield of hydrogen and the C.sub.2-C.sub.10 hydrocarbons produced by the reactor 500. Furthermore, the power supplied to the electrical heaters 509 can be adjusted individually for more precise control of the temperature both along the length and along the diameters within the vessel 501. In order to assist with insulating the vessel and maintaining heat within the vessel, FIG. 7B additionally illustrates that a refractory layer 502 can be placed along the inner surface of the vessel 501, as well as the other example vessels described herein.

[0077] FIG. 7A further illustrate a series of feed inlets 540 that supply light hydrocarbon comprising C.sub.1-C.sub.3 alkane at a first end (the top) of the reactor. The C.sub.1-C.sub.3 alkane flows downward through each stage catalyst block and is heated as it flows from one stage catalyst block to the next. As the C.sub.1-C.sub.3 alkane flows downward through the reactor, it is converted to hydrocarbons, such as C.sub.2-C.sub.10 product, and hydrogen. The hydrogen and C.sub.2-C.sub.10 hydrocarbons produced by the reactor exit as an intermediate product at a product outlet 550. While the reactor is operating in a reaction mode, the C.sub.1-C.sub.3 alkane will flow into the reactor at the feed inlet 540, react with the catalyst blocks producing an intermediate product comprising hydrogen and C.sub.2-C.sub.10 hydrocarbons, and the intermediate product exits the reactor at the product outlet 550. Upon exiting the reactor 500, the intermediate product comprising hydrocarbons and hydrogen can undergo further processing as illustrated and described in connection with FIGS. 1-4.

[0078] Reactor 500 will be operated in a regeneration mode periodically to remove accumulated coke thereby regenerating the catalyst blocks. When operating in the regeneration mode, the supply of C.sub.1-C.sub.3 alkane to the vessel will be turned off and an oxidant such as air, oxygen, or steam, is provided to the vessel 501 at one or more oxidant inlets 545. The oxidant will react with the coke accumulated in the vessel causing the coke to burn off. The exhaust from the oxidation reaction is removed from the vessel 501 at an exhaust outlet 555. An additional benefit of the regeneration mode is that the oxidation reaction produces heat which can be retained by the catalyst blocks and used when the reactor is switched from the regeneration mode back to the reaction mode.

[0079] In certain examples of reactor 500, the catalyst blocks can be coated with multiple catalysts, wherein one catalyst is active during the reaction mode and facilitates the conversion of C.sub.1-C.sub.3 alkane to C.sub.2-C.sub.10 product and hydrogen, and the other catalyst is active during the regeneration mode and facilitates oxidation of accumulated coke. In yet another variation, in certain example embodiments the catalyst blocks can comprise two types of catalyst blocks, wherein one type of block comprises catalyst for conversion of C.sub.1-C.sub.3 alkane to C.sub.2-C.sub.10 product and hydrogen when the reactor is operating in reaction mode, and wherein the other type of block comprises catalyst for oxidation of accumulated coke when the reactor is operating in regeneration mode.

[0080] For any figure shown and described herein, one or more of the components may be omitted, added, repeated, and/or substituted. Additionally, it should be understood that in certain cases components of the example systems can be combined or can be separated into subcomponents. Accordingly, embodiments shown in a particular figure should not be considered limited to the specific arrangements of components shown in such figure. Further, if a component of a figure is described but not expressly shown or labeled in that figure, the label used for a corresponding component in another figure can be inferred to that component. Conversely, if a component in a figure is labeled but not described, the description for such component can be substantially the same as the description for the corresponding component in another figure.

[0081] With respect to the example methods described herein, it should be understood that in alternate embodiments, certain steps of the methods may be performed in a different order, may be performed in parallel, or may be omitted. Moreover, in alternate embodiments additional steps may be added to the example methods described herein. Accordingly, the example methods provided herein should be viewed as illustrative and not limiting of the disclosure.

[0082] Terms such as first, second, top, bottom, side, distal, proximal, and within are used merely to distinguish one component (or part of a component or state of a component) from another. Such terms are not meant to denote a preference or a particular orientation, and are not meant to limit the embodiments described herein. In the example embodiments described herein, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0083] The terms a, an, and the are intended to include plural alternatives, e.g., at least one. The terms including, with, and having, as used herein, are defined as comprising (i.e., open language), unless specified otherwise.

[0084] When Applicant discloses or claims a range of any type, Applicant's intent is to disclose or claim individually each possible number that such a range could reasonably encompass, including end points of the range as well as any sub-ranges and combinations of sub-ranges encompassed therein, unless otherwise specified. Numerical end points of ranges disclosed herein are approximate, unless excluded by proviso.

[0085] Values, ranges, or features may be expressed herein as about, from about one particular value, and/or to about another particular value. When such values, or ranges are expressed, other embodiments disclosed include the specific value recited, from the one particular value, and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent about, it will be understood that the particular value forms another embodiment. It will be further understood that there are a number of values disclosed therein, and that each value is also herein disclosed as about that particular value in addition to the value itself. In another aspect, use of the term about means 20% of the stated value, 15% of the stated value, 10% of the stated value, 5% of the stated value, 3% of the stated value, or 1% of the stated value.

[0086] Although embodiments described herein are made with reference to example embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope of this disclosure. Those skilled in the art will appreciate that the example embodiments described herein are not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the example embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments using the present disclosure will suggest themselves to practitioners of the art. Therefore, the scope of the example embodiments is not limited herein.