Production of synthesis gas via fluidized bed/fixed bed process combination

• US 5,421,840 A
• Filed: 09/06/1994
• Issued: 06/06/1995
• Est. Priority Date: 09/06/1994
• Status: Expired due to Fees

• Current Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Original Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Inventors: Taylor, James H., Say, Geoffrey R.
• Primary Examiner(s): KRATZ, PETER F
• Application Number:
  US08/301,206
• Time in Patent Office: 273 Days
• Field of Search: 48/198.5, 48/198.6, 48/198.7, 48/198.8, 48/214 A, 48/215, 48/197 R, 48/198.1, 252/373, 423/418.2, 423/651, 423/602, 423/603, 423/604
• US Class Current: 48/198.6
• CPC Class Codes: C01B 3/382 Multi-step processes
• CPC Class Codes: C01B 3/44 using the fluidised bed technique
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

A mixture of hydrocarbons, oxygen and steam is reacted over a fluidized bed, in a first reaction stage, at high temperature to produce, at hydrocarbon conversion levels ranging from about 85 percent to about 92 percent, a reaction product of hydrogen and carbon monoxide in admixture with unreacted hydrocarbons, carbon dioxide and steam. The level of hydrocarbon conversion is further increased by about 0.5 to 5 percent by contacting and endothermically reacting the reaction product mixture over a fixed bed of a high void fraction catalyst in a second reaction stage.

Claims

1. In a process for the production of hydrogen and carbon monoxide, the steps comprising

contacting, in a first reaction zone, low molecular weight hydrocarbons comprising methane, oxygen, and steam, at high temperature in a net reducing atmosphere, with a fluidized bed of catalyst, or catalyst and a solids diluent, to convert from about 85 percent to about 92 percent of the hydrocarbons to hydrogen and carbon monoxide and form a reaction mixture of hydrogen, carbon monoxide and unreacted hydrocarbons, oxygen and steam,

withdrawing said reaction mixture as an effluent from said first reaction zone, and

contacting said effluent, in a second reaction zone, with a fixed bed of catalytic metal solids with a void fraction of at least about 0.9 to convert, sufficient of the unreacted hydrocarbons, oxygen, and steam and increase the hydrocarbon conversion to a level ranging from about 0.5 percent to about 5 percent above that obtained in said first reaction zone.

2. The process of claim 1 wherein, in the second reaction zone, sufficient of the unreacted hydrocarbons are converted to hydrogen and carbon monoxide to increase the hydrocarbon conversion to a level ranging from about 1 percent to about 3 percent above that of said first reaction zone.

3. The process of claim 1 wherein in the first conversion zone from about 87 percent to about 90 percent of the hydrocarbon feed is converted to hydrogen and carbon monoxide.

4. The process of claim 1 wherein in the first conversion zone from about 87 percent to about 90 percent of the hydrocarbon feed is converted to hydrogen and carbon monoxide, and in the second reaction zone, sufficient of the unreacted hydrocarbons are converted to hydrogen and carbon monoxide to increase the hydrocarbon conversion to a level ranging from about 1 percent to about 3 percent above that of said first reaction zone.

5. The process of claim 1 wherein, in the first reaction zone, the reaction is conducted at temperatures ranging from about 1500°

F. to about 1900°

F. over a nickel-on-alumina catalyst, the effluent introduced initially into the second reaction zone ranges from about 1500°

F. to about 1900°

F., the fixed bed of catalytic solids contained in the second reaction zone has a void fraction at least about 0.9 and the residence time of the effluent in said second reaction zone is less than about 1 second.

6. The process of claim 5 wherein in the temperature of the first reaction zone and effluent initially introduced into said second reaction zone ranges from about 1600°

F. to about 1800°

F., and, in the second reaction zone, the fixed bed of catalytic solids has a void fraction ranging from about 0.90 to about 0.98, and the effluent has a residence time of less than about 0.6 second.

7. The process of claim 6 wherein the residence time of the effluent within the second reaction zone ranges from about 0.3 second to about 0.6 second.

8. The process of claim 1 wherein the catalyst of the first reaction zone is comprised of nickel-on-alumina, and the catalyst of the second reaction zone is comprised of nickel.

9. The process of claim 8 wherein the surface area of the nickel contained on the catalyst of the second reaction zone ranges from about 0.2 m² /lb-mole/hr to about 4.0 m² /lb-mole/hr of synthesis gas.

10. The process of claim 9 wherein the surface area of the nickel ranges from about 0.6 m² /lb-mole/hr to about 1.7 m² /lb-mole/hr of synthesis gas.

11. The process of claim 9 wherein the catalyst is nickel coated Pall Rings, or nickel deposited on a ceramic honeycomb monolith.

12. The process of claim 1 wherein the total conversion of the low molecular weight hydrocarbon feed obtained by reaction in both the first and second reaction zones ranges from about 86 percent to about 95 percent, based on the total weight of hydrocarbon feed initially fed to the process.

13. The process of claim 12 wherein the total conversion of the low molecular weight hydrocarbon feed ranges from about 88 to about 95 percent.

14. In a process for the production of hydrogen and carbon monoxide, the steps comprising

contacting, in a first reaction zone, low molecular weight hydrocarbons, comprising methane oxygen, and steam, at temperature ranging from about 1500°

F. to about 1900°

F. in a net reducing atmosphere, with a fluidized bed of catalyst, or catalyst and a solids diluent, to convert from about 85 percent to about 92 percent of the hydrocarbons to hydrogen and carbon monoxide and form a reaction mixture of hydrogen, carbon monoxide and unreacted hydrocarbons, oxygen and steam,

withdrawing said reaction mixture as an effluent from said first reaction zone, and

contacting said effluent, in a second reaction zone, with a fixed bed of catalytic metal solids having a void fraction at least about 0.9, and providing an effluent residence time in said second reaction zone less than about 1 second to convert the unreacted hydrocarbons, oxygen, and steam and increase the hydrocarbon conversion to a level ranging from about 0.5 percent to about 5 percent above that of said first reaction zone.

15. The process of claim 14 wherein, in the second reaction zone, sufficient of the unreacted hydrocarbons are converted to hydrogen and carbon monoxide to increase the hydrocarbon conversion to a level ranging from about 1 percent to about 3 percent above that of said first reaction zone.

16. The process of claim 14 wherein in the first conversion zone from about 87 percent to about 90 percent of the hydrocarbon feed is converted to hydrogen and carbon monoxide.

17. The process of claim 14 wherein in the first conversion zone from about 87 percent to about 90 percent of the hydrocarbon feed is converted to hydrogen and carbon monoxide, and in the second reaction zone, sufficient of the unreacted hydrocarbons are converted to hydrogen and carbon monoxide to increase the hydrocarbon conversion to a level ranging from about 1 percent to about 3 percent above that of said first reaction zone.

18. The process of claim 14 wherein, in the first reaction zone, the reaction is conducted over a nickel-on-alumina catalyst, the effluent introduced initially into the second reaction zone ranges from about 1700°

F. to about 1800°

F., the fixed bed of catalytic solids contained in the second reaction zone has a void fraction ranges from about 0.90 to about 0.98, and the residence time of the effluent in said second reaction zone is less than about 0.6 second.

19. The process of claim 18 wherein in the second reaction zone, the fixed bed of catalytic solids has a void fraction ranging from about 0.93 to about 0.98.

20. The process of claim 19 wherein the residence time of the effluent within the second reaction zone ranges from about 0.3 second to about 0.6 second.