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Title:
PROCESSES FOR OXIDATIVE PYROLYSIS OF HYDROCARBONS TO PRODUCE SYNGAS AND C2 HYDROCARBONS
Document Type and Number:
WIPO Patent Application WO/2019/162781
Kind Code:
A1
Abstract:
Systems and processes to produce ethylene and synthesis gas having a H2:CO2 ratio of 1.9:1 to 2.1:1 and less than 5 wt.% CH4 from oxidative pyrolysis of methane are described.

Inventors:
MAMEDOV, Aghaddin (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
NAIR, Balamurali (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
HUCKMAN, Michael E. (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
PENG, Kuang-Yao Brian (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
LIU, Zheng (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
Application Number:
IB2019/050835
Publication Date:
August 29, 2019
Filing Date:
February 01, 2019
Export Citation:
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Assignee:
SABIC GLOBAL TECHNOLOGIES B.V. (Plasticslaan 1, 4612 PX Bergen op Zoom, 4612 PX, NL)
MAMEDOV, Aghaddin (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
NAIR, Balamurali (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
HUCKMAN, Michael E. (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
PENG, Kuang-Yao Brian (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
LIU, Zheng (SABIC T&I, 1600 Industrial Blvd.Sugar Land, Texas, 77478, US)
International Classes:
C01B3/36; C01B3/24; C07C4/02; C07C11/24
Attorney, Agent or Firm:
NORTON ROSE FULBRIGHT US LLP (98 San Jacinto Blvd, Suite 1100Austin, Texas, 78701, US)
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Claims:
CLAIMS

1. An oxidative pyrolysis process, the process comprising:

(a) providing heat from combustion of a hydrocarbon to a methane stream at a temperature sufficient to pyrolyze the methane and produce a gaseous stream comprising hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and hydrocarbons having 2 carbon atoms (C2 hydrocarbons);

(b) quenching the gaseous stream with a quenching fluid comprising water (H2O) to form a quenched gaseous product stream comprising the H2, CO, CO2, C2 hydrocarbons, CH4, and quenching fluid;

(c) separating the C2 hydrocarbons from the quenched gaseous product stream to form a C2 hydrocarbons stream and a separated gaseous stream comprising H2, CO, > 5 mol.% CH4, and quenching fluid; and

(d) steam reforming the separated gaseous stream with heat from step (a) to produce a synthesis gas (syngas) product stream comprising H2, CO, and < 5 mol.% of CH .

2. The process of claim 1, wherein the step (a) pyrolysis temperature is at least 2500 °C, and wherein the gaseous product stream has a temperature of 1300 °C to 1500 °C or 1400 °C to 1450 °C.

3. The process of claim 1, wherein the step (a) gaseous stream comprises at least 10 mol.% of CO2, preferably 15 to 40 mol.% of CO2, more preferably 20-30 mol.% of CO2.

4. The process of claim 1, wherein the step (b) quenched gaseous product stream has a temperature of 700 °C to 800 °C or 725 °C to 775 °C.

5. The process of claim 1, wherein the step (c) separation comprises:

(i) contacting the quenched gaseous product stream with a solvent to solubilize the C2 hydrocarbons in the solvent and form a C2 hydrocarbons/solvent stream, wherein the C2 hydrocarbons comprise acetylene (C2H2);

(ii) contacting the C2 hydrocarbons/solvent stream with a hydrogenation catalyst and H2 to produce a hydrogenated stream comprising ethylene (C2H4), solvent; and

(iii) separating the C2TL from the hydrogenated stream to form a C2TL product stream, wherein the C2TL product stream comprises at least 90 wt.% C2TL, preferably 95 wt.% C2TL, more preferably 99 wt.% C2TL.

6. The process of claim 5, wherein the separated C2 hydrocarbons stream further comprises CO2 and the hydrogenated stream has a C2H4 to CO2 molar ratio of 1.2: 1 to 1 : 1.

7. The process of claim 1, further comprising combusting a portion of the step (c) separated gas stream to produce heat and providing the produced heat to the step (d) reforming.

8. The process of claim 1, further comprising providing steam during the step (d) reforming.

9. The process of claim 8, further comprising producing the steam by heating water with the produced heat of step (a) or by heating water with heat exchange.

10. The process of claim 1, further comprising heat exchanging a portion of the step (c) separated stream, a portion of the step (d) syngas stream, or both to the gaseous stream during step (b) to cool the gaseous stream.

11. The process of claim 1, further comprising providing the syngas stream having < 5 mol.% of CH4 to a methanol production process or an olefins production process.

12. The process of claim 1, wherein the step (a) gaseous product stream comprises 25 to 40 mol.% H2, 15 to 25 mol.% CO2, 10 to 20 mol.% CTri, 1 to 10 mol.% C2 hydrocarbons, and 15 to 30 mol.% CO.

13. The process of claim 12, wherein the C2 hydrocarbons have less than 1 mol.% ethylene.

14. The process of claim 1, wherein the separated gaseous stream further comprises CO2 and includes 25 to 40 mol.% H2, 15 to 25 mol.% CO2, 10 to 20 mol.% CH4, and 15 to 30 mol.% CO, preferably 35 to 40 mol.% H2, 20 to 25 mol.% CO2, 15 to 20 mol.% CH4, and 25 to 30 mol.% CO.

15. The process of claim 1, wherein the step (c) separated gaseous stream has a H2 to CO molar ratio of 1 : 1 to 2: 1.

16. The process of claim 1, wherein the step (d) produced syngas stream has a H2 to CO molar ratio of 1.9: 1 to 2.1 : 1.

17. The process of claim 1, wherein quenching comprises adding the quenching fluid and/or heat exchanging the gaseous product stream with a coolant during addition of the quenching fluid at a rate sufficient to inhibit decomposition of the C2 hydrocarbons.

18. The process of claim 1, wherein the hydrocarbon fuel is methane and the process further comprises separating the methane stream into the first methane stream and a second methane stream and providing the first methane stream to step (a) as fuel and the second methane stream to step (b).

19. An oxidative pyrolysis process, the process comprising:

(a) providing heat from combustion of a hydrocarbon to a methane containing stream at a temperature sufficient to pyrolyze the methane and produce a gaseous stream comprising hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and hydrocarbons having 2 carbon atoms (C2 hydrocarbons);

(b) separating the C2 hydrocarbons from the gaseous stream to produce a second gaseous stream comprising H2, CO, > 5 mol.% CH4, and optional H2O; and

(c) steam reforming the step (b) second gaseous stream with heat from step (a) to produce a synthesis gas (syngas) product stream comprising H2, CO, and < 5 mol.% of CH4.

20. A system to produce synthesis gas using any one of the processes of claims 1 or 19, the system comprising:

(a) a pyrolysis unit comprising:

(i) a combustion zone capable of combusting a hydrocarbon fuel source to produce heat;

(ii) a pyrolysis zone in fluid communication with the combustion zone and capable of cracking methane to produce the gaseous stream; and

(iii) a quenching zone in fluid communication with the gaseous stream and capable of providing a quenching fluid comprising water (H2O), syngas, or both at a rate sufficient to quench the gaseous stream and inhibit decomposition of the C2 hydrocarbons and produce the quenched gaseous stream;

(b) a separation unit in fluid communication with the quenched gaseous stream and capable of separating the C2 hydrocarbons from the quenched gaseous stream and forming the separated stream comprising CO, H2, H2O, and at least 5 mol.% CH4; and (c) a steam reforming unit in fluid communication with the separated stream comprising CH4, CO, H2, and H2O and capable of producing the syngas stream comprising CO, H2, and less than 5 mol.% CH4.

Description:
PROCESSES FOR OXIDATIVE PYROLYSIS OF HYDROCARBONS TO PRODUCE

SYNGAS AND C2 HYDROCARBONS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/635,141 filed February 26, 2018, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

A. Field of the Invention

[0002] The invention generally concerns processes for the oxidative pyrolysis of hydrocarbons to produce C2 hydrocarbons and synthesis gas (syngas) suitable for methanol or olefin production processes. The syngas product stream can include hydrogen gas, carbon monoxide, and less than 5 mol.% of methane.

B. Description of Related Art

[0003] High-temperature pyrolysis has been used for converting methane to acetylene. Depending on the method used to supply the necessary heat for pyrolysis, the methane and/or hydrocarbon pyrolysis to acetylene process is broadly categorized into one-step and two-step processes.

[0004] In a one-step acetylene production process, natural gas substantially containing methane serves for the hydrocarbon feed and pure oxygen as the oxidant. See, for example, U.S. Pat. Nos. 5,824,834 to Bachtler et al. and 5,789,644 to Passler et al. As a whole, the partial oxidation reactor system includes three major parts: a top part, which is a mixing zone with a special diffuser; an underneath part, which is a water-jacketed burner immediately followed by a reaction zone; and the third part is a quenching zone using water or heavy oil as a coolant. These types of processes suffer from soot formation, which cannot be entirely or effectively eliminated from this process.

[0005] In a two-stage high temperature pyrolysis (HTP) process, a reaction zone can serve as a stoichiometric combustor to supply the necessary heat for hydrocarbon pyrolysis taking place in the second reaction zone, into which a fresh hydrocarbon feed such as methane is introduced See, for example, U.S. Patent Nos. 8,080,697 to Lin et al. and 8,013,196 to Mamedov et. al. , Great Britain Patent Nos. 921,305 and 958,046 assigned to Hoechst AG. In the quenching zone, water or heavy oil is used as a coolant to cool down instantaneously the hot product gas from the pyrolysis zone. Similarly, a certain quantity of carbon is formed in this two-step pyrolysis process. The acetylene concentration produced in the two step pyrolysis method is about double the acetylene produced in the one stage partial oxidation process. In these processes, the by-product stream that includes carbon dioxide (CO2), CO and/or H2 is recycled back to the combustion zone of the pyrolysis unit, sent to a CO2 (dry) reforming unit to produce synthesis gas and/or burned to generate heat for other processing units. Dry reforming is endothermic and requires a substantial amount of heat. The synthesis gas streams produced from dry reforming reactions are usually high in hydrocarbon content and not suitable for methanol or olefins synthesis unless further purification is performed.

SUMMARY OF THU INVENTION

[0006] A discovery has been made that provides a solution to the quality of synthesis gas produced from the aforementioned two-stage HTP process. The solution is premised on the use of a two-step oxidative pyrolysis process to produce a product stream. The product stream can be further processed in an elegant energy efficient manner to produce C2 hydrocarbons (e.g, acetylene and ethylene) and syngas having less than 5 mol.% methane (e.g, less than 2 mol.% CH4), which is suitable for use in methanol or olefin synthesis processes.

[0007] In one aspect of the present invention, an oxidative pyrolysis process to produce C2 hydrocarbons and syngas is described. The process can include several steps. In step (a), heat from combustion of a hydrocarbon can be provided to a methane stream at a temperature sufficient to pyrolyze the methane and produce a gaseous stream that can include hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH 4 ), and hydrocarbons having 2 carbon atoms (C2 hydrocarbons). In step (b), the gaseous stream can be quenched with a quenching fluid to form a quenched gaseous product stream that can include the H2, CO, CO2, C2 hydrocarbons, CH 4 , and quenching fluid. In step (c), the C2 hydrocarbons can be separated from the quenched gaseous product stream to form a separated gaseous stream that can include H2, CO, > 5 mol.% CH 4 , quench fluid and optional CO2, and a C2 hydrocarbons stream that can include optional CO2. In a preferred embodiment, the quench fluid is water or syngas. Step (d) can include steam reforming the separated gaseous stream with heat from step (a) to produce a synthesis gas (syngas) product stream that can include H2, CO, and < 5 mol.% of CH 4 . In some embodiments, the hydrocarbon fuel can be methane, and the process can include separating the methane stream into the first methane stream and a second methane stream and providing the first methane stream to step (a) as fuel and the second methane stream to step (b). Pyrolysis conditions in step (a) can include a temperature of at least 2500 °C. The step (a) gaseous product stream can have temperature of 1300 °C to 1500 °C or 1400 °C to 1450 °C. The gaseous product stream can include at least 10 mol.% of CO2, preferably 15 to 40 mol.% of CO2, more preferably 20 to 30 mol.% of CO2. In some embodiments, the gaseous product stream can include 25 to 40 mol.% H2, 15 to 25 mol.% CO2, 10 to 20 mol.% CH 4 , 1 to 10 mol.% C2 hydrocarbons, and 15 to 30 mol.% CO. In one instance, the C2 hydrocarbons produced by the method of the invention can include less than 1 mol.% ethylene.

[0008] Quenching in step (b) can produce a quenched stream having a temperature of 700 °C to 800 °C or 725 °C to 775 °C. The quenching fluid can include water (H2O) and/or hydrocarbons ( e.g hydrocarbon fuel, syngas, heavy hydrocarbons (e.g., hydrocarbons having a carbon number of at least 10), methanol, or mixtures thereof). In a preferred instance, the quenching fluid is water and/or syngas, thereby eliminating any new species in the product stream and conserving raw materials for sustainability. The syngas can be obtained from the methane reforming reaction. Quenching can include adding the quenching fluid at a rate sufficient to inhibit decomposition of the C2 hydrocarbons and/or heat exchanging the gaseous product stream with a coolant during addition of the quenching fluid at a rate sufficient to inhibit decomposition of the C2 hydrocarbons.

[0009] Separating the CO2 and the C2 hydrocarbons from the quenched gaseous product stream can include contacting the CO2/C2 hydrocarbons stream with a solvent to solubilize the C2 hydrocarbons and CO2 in the solvent and form a C2 hydrocarbons/C02/solvent stream. The C2 hydrocarbons can include acetylene (C2H2). The C2 hydrocarbons/C02/solvent stream can be contacted with a hydrogenation catalyst and H2 to produce a hydrogenated stream that can include ethylene (C2H4), solvent, and CO2. The hydrogenated stream can have a C2H4 to CO2 molar ratio of 1.2: 1 to 1 : 1. Separation of the C2H4 from the hydrogenated stream can form a C2H4 product stream, which can have at least 90 wt.% C2H4, preferably 95 wt.%, more preferably 99 wt.%. The step (c) separated gaseous stream can have a H2 to CO molar ratio of 1 : 1 to 2: 1. In some embodiments, a portion of the separated gaseous stream can be combusted to produce additional heat and the produced heat can be provided to the step (d) reforming reaction. Heat exchange of a portion of the step (c) separated stream, a portion of the step (d) syngas stream, or both to the gaseous stream can be performed during step (b) to cool the gaseous stream.

[0010] Reforming of the separated gaseous stream can be a methane steam reforming process. The steam used in the reforming process can be provided from an external source. In some embodiments, the steam is provided by heating water with the step (a) produced heat or by heating the water through heat exchange from the step (b) quenching process. The produced syngas stream can have a H 2 to CO molar ratio of 1.9: 1 to 2.1 : 1. A portion of the produced syngas stream can be recycled to the reforming unit.

[0011] In yet another aspect of the present invention, an oxidative pyrolysis process is described that includes: (a) providing heat from combustion of a hydrocarbon to a methane stream at a temperature sufficient to pyrolyze the methane and produce a gaseous stream that includes Eb, CO, C0 2 , CH 4 , and C2 hydrocarbons; (b) separating the C0 2 and the C2 hydrocarbons from the gaseous stream to produce a second gaseous stream that can include H 2 , CO, > 5 mol.% CEb, and optional H 2 0; and (c) steam reforming the step (b) second gaseous stream with heat from step (a) to produce a syngas product stream that includes H 2 , CO, and less than 5 mol.% of CH 4 .

[0012] Systems to employ the methods of the present invention are also described. A system can include (a) a pyrolysis unit, (b) a separation unit, and (c) a reforming unit. The pyrolysis unit can include (i) a combustion zone capable of combusting the hydrocarbon fuel source to produce heat, (ii) a pyrolysis zone in fluid communication with the combustion zone and capable of cracking methane to produce the gaseous stream, and (iii) a quenching zone in fluid communication with the gaseous stream and capable of providing a quenching fluid that can include H 2 0, syngas, or both at a rate sufficient to quench the gaseous stream and inhibit decomposition of the C2 hydrocarbons and produce the quenched gaseous stream. The separation unit can be in fluid communication with the quenched gaseous stream and capable of separating the C2 hydrocarbons and C0 2 from the quenched gaseous stream and form the separated stream that includes CO, H 2 , EbO, and at least 5 mol.% CH 4 . The steam reforming unit can be in fluid communication with the separated stream that includes CH 4 , CO, H 2 , and H 2 0, and capable of producing the syngas stream that can include CO, H 2 , and less than 5 mol.% CH .

[0013] In the context of the present invention 20 embodiments are described. Embodiment

1 is an oxidative pyrolysis process, the process comprising: (a) providing heat from combustion of a hydrocarbon to a methane stream at a temperature sufficient to pyrolyze the methane and produce a gaseous stream comprising hydrogen (H 2 ), carbon monoxide (CO), carbon dioxide (C0 2 ), methane (CEE), and hydrocarbons having 2 carbon atoms (C2 hydrocarbons); (b) quenching the gaseous stream with a quenching fluid comprising water (EbO) to form a quenched gaseous product stream comprising the Eb, CO, C0 2 , C2 hydrocarbons, CEb, and quenching fluid; (c) separating the C2 hydrocarbons from the quenched gaseous product stream to form a C2 hydrocarbons stream and a separated gaseous stream comprising H 2 , CO, > 5 mol.% CH 4 , and quenching fluid; and (d) steam reforming the separated gaseous stream with heat from step (a) to produce a synthesis gas (syngas) product stream comprising EE, CO, and < 5 mol.% of CEE. Embodiment 2 is the process of embodiment 1, wherein the step (a) pyrolysis temperature is at least 2500 °C, and wherein the gaseous product stream has a temperature of 1300 °C to 1500 °C or 1400 °C to 1450 °C. Embodiment 3 is the process of any one of embodiments 1 or 2, wherein the step (a) gaseous stream comprises at least 10 mol.% of C0 2 , preferably 15 to 40 mol.% of C0 2 , more preferably 20-30 mol.% of C0 2 . Embodiment 4 is the process of any one of embodiments 1 to 3, wherein the step (b) quenched gaseous product stream has a temperature of 700 °C to 800 °C or 725 °C to 775 °C. Embodiment 5 is the process of any one of embodiments 1 to 4, wherein the step (c) separation comprises: (i) contacting the quenched gaseous product stream with a solvent to solubilize the C2 hydrocarbons in the solvent and form a C2 hydrocarbons/solvent stream, wherein the C2 hydrocarbons comprise acetylene (C 2 H 2 ); (ii) contacting the C2 hydrocarbons/solvent stream with a hydrogenation catalyst and H 2 to produce a hydrogenated stream comprising ethylene (C 2 H 4 ), solvent; and (iii) separating the C 2 H 4 from the hydrogenated stream to form a C 2 H 4 product stream, wherein the C 2 H 4 product stream comprises at least 90 wt.% C 2 H 4 , preferably 95 wt.% C 2 H 4 , more preferably 99 wt.% C 2 H 4 . Embodiment 6 is the process of embodiment 5, wherein the separated C 2 hydrocarbons stream further comprises C0 2 and the hydrogenated stream has a C 2 H 4 to C0 2 molar ratio of 1.2: 1 to 1 : 1. Embodiment 7 is the process of any one of embodiments 1 to 6, further comprising combusting a portion of the step (c) separated gas stream to produce heat and providing the produced heat to the step (d) reforming. Embodiment 8 is the process of any one of embodiments 1 to 7, further comprising providing steam during the step (d) reforming. Embodiment 9 is the process of embodiment 8, further comprising producing the steam by heating water with the produced heat of step (a) or by heating water with heat exchange. Embodiment 10 is the process of any one of embodiments 1 to 9, further comprising heat exchanging a portion of the step (c) separated stream, a portion of the step (d) syngas stream, or both to the gaseous stream during step (b) to cool the gaseous stream. Embodiment 11 is the process of any one of embodiments 1 to 10, further comprising providing the syngas stream having < 5 mol.% of CEE to a methanol production process or an olefins production process. Embodiment 12 is the process of any one of embodiments 1 to 11, wherein the step (a) gaseous product stream comprises 25 to 40 mol.% EE, 15 to 25 mol.% C0 2 , 10 to 20 mol.% CEE, 1 to 10 mol.% C2 hydrocarbons, and 15 to 30 mol.% CO. Embodiment 13 is the process of embodiment 12, wherein the C2 hydrocarbons have less than 1 mol.% ethylene. Embodiment 14 is the process of any one of embodiments 1 to 13, wherein the separated gaseous stream further comprises CO2 and includes 25 to 40 mol.% Eh, 15 to 25 mol.% CO2, 10 to 20 mol.% CEh, and 15 to 30 mol.% CO, preferably 35 to 40 mol.% Eh, 20 to 25 mol.% CO2, 15 to 20 mol.% CEh, and 25 to 30 mol.% CO. Embodiment 15 is the process of any one of embodiments 1 to 14, wherein the step (c) separated gaseous stream has a Eh to CO molar ratio of 1 : 1 to 2: 1. Embodiment 16 is the process of any one of embodiments 1 to 15, wherein the step (d) produced syngas stream has a El 2 to CO molar ratio of 1.9: 1 to 2.1 : 1. Embodiment 17 is the process of any one of embodiments 1 to 16, wherein quenching comprises adding the quenching fluid and/or heat exchanging the gaseous product stream with a coolant during addition of the quenching fluid at a rate sufficient to inhibit decomposition of the C2 hydrocarbons. Embodiment 18 is the process of any one of embodiments 1 to 17, wherein the hydrocarbon fuel is methane and the process further comprises separating the methane stream into the first methane stream and a second methane stream and providing the first methane stream to step (a) as fuel and the second methane stream to step (b).

[0014] Embodiment 19 is an oxidative pyrolysis process, the process comprising: (a) providing heat from combustion of a hydrocarbon to a methane containing stream at a temperature sufficient to pyrolyze the methane and produce a gaseous stream comprising hydrogen (EE), carbon monoxide (CO), carbon dioxide (CO2), methane (CEE), and hydrocarbons having 2 carbon atoms (C2 hydrocarbons); (b) separating the C2 hydrocarbons from the gaseous stream to produce a second gaseous stream comprising EE, CO, > 5 mol.% CEE, and optional EEO; and (c) steam reforming the step (b) second gaseous stream with heat from step (a) to produce a synthesis gas (syngas) product stream comprising EE, CO, and < 5 mol.% of CEE.

[0015] Embodiment 20 is a system to produce synthesis gas using any one of the processes of embodiments 1 to 19, the system comprising: (a) a pyrolysis unit comprising: (i) a combustion zone capable of combusting a hydrocarbon fuel source to produce heat; (ii) a pyrolysis zone in fluid communication with the combustion zone and capable of cracking methane to produce the gaseous stream; and (iii) a quenching zone in fluid communication with the gaseous stream and capable of providing a quenching fluid comprising water (EEO), syngas, or both at a rate sufficient to quench the gaseous stream and inhibit decomposition of the C2 hydrocarbons and produce the quenched gaseous stream; (b) a separation unit in fluid communication with the quenched gaseous stream and capable of separating the C2 hydrocarbons from the quenched gaseous stream and forming the separated stream comprising CO, H 2 , H 2 0, and at least 5 mol.% CH 4 ; and (c) a steam reforming unit in fluid communication with the separated stream comprising CH 4 , CO, H2, and H2O and capable of producing the syngas stream comprising CO, H2, and less than 5 mol.% CH 4 .

[0016] Other embodiments and aspects of the invention are discussed throughout this application. Any embodiment discussed with respect to one aspect of the invention applies to other aspects of the invention as well and vice versa. Each embodiment described herein is understood to be embodiments of the invention that are applicable to other aspects of the invention. It is contemplated that any embodiment or aspect discussed herein can be implemented with respect to any method or composition of the invention, and vice versa. Furthermore, compositions and systems of the invention can be used to achieve methods of the invention.

[0017] The following includes definitions of various terms and phrases used throughout this specification.

[0018] The terms“about” or“approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0019] The terms “wt.%”, “vol.%”, or“mol.%” refers to a weight percentage of a component, a volume percentage of a component, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0020] The term“substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0021] The terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0022] The term“effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0023] The use of the words“a” or“an” when used in conjunction with any of the terms “comprising,”“including,”“containing,” or“having” in the claims, or the specification, may mean“one,” but it is also consistent with the meaning of“one or more,”“at least one,” and “one or more than one.”

[0024] The words“comprising” (and any form of comprising, such as“comprise” and “comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“includes” and“include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0025] The process and systems of the present invention can “comprise,” “consist essentially of,” or“consist of’ particular ingredients, components, compositions, steps, etc. disclosed throughout the specification. With respect to the transitional phrase“consisting essentially of,” in one non-limiting aspect, a basic and novel characteristic of the processes and the systems of the present invention are their abilities to produce an ethylene stream and a syngas stream having less than 5 mol.% of CH 4 from methane.

[0026] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0028] FIG. 1 is a schematic of the present invention to produce an ethylene product stream and a syngas product stream having less than 5 mol.% methane.

[0029] FIG. 2 is a schematic of the present invention to produce an ethylene product stream and a syngas product stream having less than 5 mol.% methane using direct heat exchange from the combustion of hydrocarbon fuel to make steam for the reforming reaction. [0030] FIG. 3 is schematic of the present invention using the process of FIG. 2 in combination with combustion of the separated gas stream that includes Fh, CO, and CFh to produce heat for the reforming reaction.

[0031] FIG. 4 is schematic of the present invention using the process of FIG. 2 in combination with combustion of hydrocarbon fuel to produce heat for the reforming reaction.

[0032] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DFTATFFD DESCRIPTION OF TTTF TNVFNTTON

[0033] A discovery has been made that provides a solution to the problems associated with by-products produced from the oxidative pyrolysis of methane to produce acetylene and ethylene. The solution is premised on separation of C2 hydrocarbons from a product stream that includes CO2, C2 hydrocarbons, Fh, CO, and quenching fluid ( e.g FhO) to form a gaseous stream that include Fh, CO, and quenching fluid (e.g., FhO). The CO2 can be separated from the product stream, processed with the C2 hydrocarbons, or be present in the gaseous stream. The separated gaseous stream is then used as a feed stream for a methane steam reforming reaction to produce a synthesis gas stream having a Fh:CO ratio of 1.9: 1 to 2.1 : 1 with less than 5 mol.% methane.

[0034] Conversion of methane to acetylene by thermal pyrolysis using combustion produces heat, which can then be used for high temperature pyrolysis of methane to acetylene. Reaction equations 1, 2, and 3 show the overall chemical reactions for the two-step process using methane as the hydrocarbon fuel.

2CH 4 + 3.50 2 -► C0 2 + CO + 4 H 2 0 DH= -l57 kcal/mol (1)

2CH 4 - C 2 H 2 + H 2

DH = 45 kcal/mol (2)

4CH 4 + 3.50 2 C 2 H 2 + H 2 + C0 2 + CO + 4 H 2 0

(3)

As shown in equation (3), the total reaction products are C2H2, CO, H2, and CO2. These reaction products can be further converted to ethylene and syngas using the process of the present invention without addition of other materials to the product stream. This allows for conserving raw materials and for producing a sustainable process. [0035] These and other non-limiting aspects of the present invention are discussed in further detail in the following paragraphs with reference to the figures.

[0036] Referring to FIG. 1, a system and process to produce ethylene and syngas suitable for use in methanol and/or olefins synthesis is described. System 100 can include a pyrolysis unit 102, a quenching unit 104, a separations unit 106, a methane steam reforming unit 108. Pyrolysis unit 102 can include combustion zone 110 and thermal conversion zone 112. Hydrocarbon fuel stream 114 and oxidant source ( e.g ., O2, air, or O2 enriched air) 116 can enter combustion zone 110. Hydrocarbon fuel can be methane, natural gas, natural gas enriched in methane, or hydrocarbons having a carbon number less than 5 (e.g., ethane, ethylene, propane, butane, etc.). In some embodiments, hydrocarbon fuel stream 114 and oxidant source 116 can be preheated to a temperature from 550 °C to 650 °C and can be fed in a stoichiometric ratio or with the oxygen content of the oxygen source slightly below the stoichiometric ratio. By way of example, from 0.5 to 0.7, or any value or range there between, preferably about 0.62 of the stoichiometric ratio can be used. The ratio of oxygen to methane can be varied to control coke and soot formation. In combustion zone 110, the hydrocarbons react with the oxygen to form hot combustion gaseous stream 118 and heat 120. Combustion zone 100 reaction conditions can include a temperature of at least any one of, equal to any one of, or between any two of 2500 °C, 2600 °C, 2700 °C, 2800 °C, 2900 °C to and 3000 °C and/or a pressure in the range of 0.05 to 0.5 MPa. Gaseous stream 118 can include at least any one of, equal to any one of, or between any two of 10%, 15%, 20%, 25%, 30%, 35%, and 40 mol.% CO2, or 15% to 40 mol% CO2, or more preferably 20% to 30 mol.% CO2. Gaseous product stream 118 can include at least any one of, equal to any one of, or between any two of 25, 30, 35, and 40 mol.% H2. A methane content of gaseous stream 118 can be at least any one of, equal to any one of, or between any two of 5, 10, 15, and 20 mol.%. The C2 hydrocarbon content in gaseous stream 118 can be at least any one of, equal to any one of, or between any two of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mol.%. Gaseous stream 118 can include at least any one of, equal to any one of, or between any two of 15, 20, 25, and 30 mol.% CO.

[0037] Hot gaseous stream 118 can be passed into pyrolysis zone 112. Methane containing stream 122 can enter pyrolysis zone 112, and heat from gaseous stream 118 can promote the thermal cracking of the methane to form acetylene (C2H2). In some embodiments, the methane- containing stream 122 can be pre-heated to 600 °C to 700 °C. Reaction conditions in pyrolysis zone 112 can include a temperature of at least any one of, equal to any one of, or between any two of 1300 °C, 1400 °C, 1500 °C, and 1600 °C, and/or a pressure of in the range of 0.05 to 0.5 MPa, or any value or range there between, or about 0.2 MPa. The contact time in pyrolysis zone 112 can be determined using known engineering methods. Non-limiting examples of contact time include 1 to 50 millisecond, 5 to 40 milliseconds or 10 to 30 milliseconds. The acetylene and combustion gases can exit pyrolysis zone 112 as gaseous stream 124. A temperature of gaseous product stream 124 as it exits pyrolysis zone 112 can be at least any one of, equal to any one of, or between any two of 1300 °C, 1400 °C, 1450 °C, and 1500 °C, or 1300 °C to 1500 °C or 1400 °C to 1450 °C. A weight ratio of the acetylene to CO2 can be from 1.3: 1 to 1.45: 1, or any range or value there between, or about 1.4: 1.

[0038] Gaseous stream 124 can enter quenching unit 104 and be quenched by contact with quenching fluid 126. Quenching fluid can include H2O, heavy hydrocarbons, a portion of the produced syngas stream from reforming unit 108, natural gas, methanol, or mixtures thereof. In a preferred embodiment, the quenching fluid includes water or syngas. In preferred instances, the quenching fluid includes at least 90 wt. % water, preferably at least 95 wt.% water, or more preferably at least 99 wt.% or 100 wt. % water. In some embodiments, the quenching fluid is sprayed into the quenching unit 104. Contact of quenching fluid 126 with the gaseous stream 124 cools the gaseous stream to a temperature of at least any one of, equal to any one of, or between any two of 700 °C, 725 °C, 750 °C, 775 °C, and 800 °C, and forms quenched gaseous product stream 128. Contact of the quenching fluid 127 with the gaseous stream 124 can inhibit further reactions of the acetylene ( e.g polymerization of acetylene). The quenched gaseous product stream 128 can includes less than 1 mol% of ethylene.

[0039] Quenched gaseous product stream 128 can exit quenching unit 104 and enter separation unit 106. In separation unit 106, quenched gaseous product stream 128 can be separated into a C2 hydrocarbons stream (not shown) and separated gaseous stream 132. Separated gaseous stream 132 can include H2, CO, > 5 mol.% CH 4 , quenching fluid (e.g., H2O and/or syngas) and optional CO2. Separation can be performed by contacting quenched gaseous product stream 128 with a solvent capable of solubilizing the C2 hydrocarbons in separation zone 134 to form a C2 hydrocarbons stream/solvent stream 130, and a non-soluble separated gas stream 132 that includes H2, CO, > 5 mol.% CH 4 , quenching fluid. Depending on the separation method, the C2 hydrocarbons stream can include the CO2, the gaseous stream can include the CO2 and/or a separate CO2 stream can be generated. Separation of these components can be done using conventional systems. The separation zone 134 can have a temperature of 10 °C to 50 °C, or any temperature there between and a pressure of 0.5 MPa to 1.5 MPa or any pressure there between. Separated gaseous stream 132 can have 25, 30, 35, 40 mol.% H 2 , 15, 20, 25 mol.% C0 2 , 10, 15, 20 mol.% CH 4 , and 15, 20, 25, 30 mol.% CO or any value or range there between. In a preferred embodiment, separated gaseous stream can include 35 to 40 mol.% H 2 , 20 to 25 mol.% C0 2 , 15 to 20 mol.% CH 4 , and 25 to 30 mol.% CO.

[0040] C2 hydrocarbons stream with optional C0 2 /solvent stream 130 can pass into hydrogenation zone 138 and contact a hydrogenation catalyst to produce hydrogenated stream 140. Hydrogenation stream 140 can include ethylene, optional C0 2 , and solvent. The solvent can be any polar organic solvent with high acetylene solubility. Non-limiting examples of solvents include N-methyl-2-pyrrolidone, dimethylformamide, acetone, tetrahydrofuran, dimethylsulfoxide, and monomethylamine, acetonitrile, or combinations thereof. Contact of the acetylene in the C2 hydrocarbons with the hydrogenation catalyst can produce ethylene. The hydrogenation catalyst can be any known hydrogenation catalyst, with a 0.005 to 1 wt.% palladium based catalyst being preferred. In some embodiments, separated gaseous stream 132 can be provided to hydrogenation zone 138 and any H 2 present in the separated gaseous stream can be a source of hydrogen for the reaction. In other embodiments, ethane and/or H 2 can be added to hydrogenation zone 138 as a source of hydrogen. The thermal hydrogenation reaction can occur at a temperature of 110 °C to 160 °C, or 120 °C to 150 °C, and a pressure of 1 to 2 MPa, or 1.5 to 1.8 MPa, or any range there between. In some embodiments, separation zone and hydrogenation zone are one unit and the acetylene is hydrogenated as it is solubilized in the solvent. Hydrogenated steam 140 can have a C 2 H 4 to C0 2 molar ratio of 1.2: 1 to 1 : 1. Hydrogenated stream 140 can be pass into a separation zone 142 and be separated into ethylene stream 144 and C0 2 stream 146 using known separation techniques such as membrane, pressure swing adsorption (PSA), or the like. Ethylene stream can include at least 90 wt.% ethylene, at least 95 wt.% ethylene, or at least 99 wt.% ethylene.

[0041] Separated gaseous stream 132 that includes H 2 , CO, > 5 mol.% CH 4 , and quenching fluid ( e.g H 2 0 and/or syngas) can exit separation zone 134 and enter methane steam reforming unit 108. In methane steam reforming unit 108, separated gaseous stream 132 can be contacted with a reforming catalyst to produce syngas product stream 148 having H 2 to CO molar ratio of 1.9: 1 to 2.1 : 1, or about 2: l . Heat 120 from combustion zone 102 is used to heat the reforming reaction to at least, equal to, or between any two of 800 °C, 825 °C, 850 °C, 900 °C, 925 °C, and 950 °C. In some embodiments, steam (See, FIGS. 2-4) can be added to the reforming unit. In other embodiments, the separated C0 2 stream 146 can be added to the reforming reaction and C0 2 reforming of methane can also be performed in addition to steam reforming of methane. The reforming catalyst can be any known reforming catalyst, with a nickel Ni) based catalyst being preferred. A non-limiting example of the reforming catalyst can include 10 to 20 wt.% Ni, or about 15 wt.%, 1 to 10 wt. wt.% barium (Ba) or about 5 wt.% on an alumina support. Syngas product stream 148 can exit methane steam reforming unit 108 and be stored, transported, or sold. In some embodiments, syngas product stream 148 is provided to a methanol synthesis unit or an olefins synthesis unit as a feed source.

[0042] Referring to FIG. 2, steam 202 for the reforming reaction can be generated by direct heat exchange with heat 120 from combustion zone 102 and water 204 in heat exchanger 206. Referring to FIG. 3, heat for reforming unit 108 can be generated by combusting a portion of separated gaseous stream 132 in second combustor 302 and providing heat 304 to reforming unit 108 in addition to using heat 120 from combustion zone 102 and water 204 in heat exchanger 206. In some embodiments, heat 120 is not used. Referring to FIG. 4, heat for reforming unit 108 can be generated by combusting a portion of methane stream 122 or hydrocarbon fuel stream 114 ( not shown) in second combustor 302 and providing heat 304 to reforming unit 108 and heat 120 from combustion zone 102 and water 204 in heat exchanger 206. In some embodiments heat 120 is not used.

[0043] In FIGS. 1-4 the reactors, units and/or zones can include one or more heating and/or cooling devices ( e.g ., insulation, electrical heaters, jacketed heat exchangers in the wall) or controllers (e.g., computers, flow valves, automated values, etc) that are necessary to control the reaction temperature and pressure of the reaction mixture. While only one unit or zone is shown, it should be understood that multiple reactors or zones can be housed in one unit or a plurality of reactors housed in one heat transfer unit.

EXAMPLES

[0044] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

Example 1

(Combustion of Methane and Its Pyrolysis)

[0045] Example 1 describes combustion of methane and its pyrolysis at high temperature to an acetylene and ethylene mixture, which was performed in a pilot scale reactor. Table 1 lists the conditions for combustion and the resulting cracked gas on a water free basis for four experimental runs.

Example 2

(Reformation of Separated Gas Stream)

[0046] A gas composition, containing 37.7 mol.% H 2 , 21.3 mol.% CO2, 15.4 mol.% CH 4 , and 25.7 mol.% CO with flow rate 100 mL/min was mixed with 0.024 mL/min H2O (room temperature) and fed to the fixed bed quartz reactor, containing 2 mL nickel based catalyst (l5%Ni-5%Ba/Al203), heated by an electrical furnace to the temperature 850 °C. The outlet dry gas composition was 56.75 vol.% H2, 25.31 vol.% CO, 16.50 vol.% CO2 and 1.69 vol.% CH4.

[0047] As can be seen from Examples 1 and 2, H2/CO ratio of syngas produced from methane combustion pyrolysis was less than 2 and was not suitable for methanol synthesis. But integrated methane steam reforming of gas mixture produced syngas with suitable H2/CO ratio required for methanol synthesis, with a methane content of less than 5 mol.%

[0048] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.