Method and apparatus for regenerating an iron-based Fischer-Tropsch catalyst
View Patent ↗Solvent extraction is used to remove wax and contaminants from an iron-based Fischer-Tropsch catalyst in a natural circulation continuous-flow system. The wax-free catalyst is then subjected to controlled oxidation to convert the iron to its initial oxidized state, Fe 2 O 3 . Reactivation of the oxide catalyst precursor is carried out by addition of synthesis gas.
1. A method for regenerating a deactivated iron-based Fischer-Tropsch catalyst from a slurry bubble column reactor, said method comprising the steps of:
placing a slurry comprising wax and deactivated catalyst into a first vessel;
feeding an inert gas into the bottom of the first vessel, thereby producing a three-phase bubble column in said first vessel wherein overhead gases are discharged to a separator;
removing a degassed catalyst and wax bearing slurry from an upper portion of the first vessel and allowing the degassed catalyst and wax bearing slurry to flow under natural circulation through a catalyst settling vessel into a lower portion of the first vessel, whereby said deactivated catalyst having undergone settling is returned to said first vessel;
adding an extraction solvent to said first vessel to maintain a desired level of catalyst bearing slurry as a catalyst-free wax and solvent mixture is removed from the catalyst settling vessel;
separating wax and solvent in said catalyst-free wax and solvent mixture in a flash vessel, thereby generating a separated wax and a recovery solvent;
recovering said separated wax;
returning said recovery solvent to said first vessel;
separating a dewaxed catalyst from the extraction solvent in said first vessel, thereby generating a wax-free catalyst-free solvent which undergoes vaporization and condensation for liquid storage;
oxidizing said dewaxed catalyst in said first vessel under controlled conditions;
mixing said dewaxed catalyst with a solvent containing an alkali promoter, thereby forming an oxide catalyst precursor;
drying said oxide catalyst precursor to form a catalyst precursor powder;
mixing said catalyst precursor powder with a liquid medium to form a catalyst precursor slurry; and
treating the catalyst precursor slurry with a synthesis gas to form an active catalyst containing iron carbides, thereby regenerating said deactivated catalyst.
2. The method as in claim 1 further comprising the step of removing said active catalyst from said first vessel.
3. The method as in claim 1 , wherein the first vessel is a bubble column reactor.
4. The method as in claim 1 , wherein the liquid medium further comprises wax or oil.
5. The method as in claim 1 , wherein the deactivated catalyst is unsupported precipitated iron.
6. The method as in claim 1 , wherein the inert gas is selected from the group consisting of nitrogen, carbon dioxide, and sulfur-free natural gas.
7. The method as in claim 1 , wherein the extraction solvent is selected from the group consisting of hexane, hexene, heptane, heptene, Fischer-Tropsch naphtha, and tetrahydrofuran.
8. The method as in claim 1 further comprising the step of heating the catalyst-free wax and solvent mixture entering said flash vessel to a temperature between about 125 and about 225° C.
9. The method as in claim 1 , wherein said oxidation step further comprises an oxidation gas having between about 1 and about 5 percent by volume oxygen.
10. The method of claim 1 , wherein said oxidation step further comprises a gas pressure between about 0.1 and about 0.7 MPaa.
11. The method of claim 1 , wherein the oxidation step further comprises a gas temperature between about 200 and about 250° C.
12. The method of claim 1 , wherein the activation step further comprises maintaining a slurry temperature of about 275° C. for a length of time between about 2 and about 5 hours.
13. The method as in claim 1 , wherein the step of feeding the inert gas into the bottom of the first vessel further comprises distributing gas bubbles in said inert gas uniformly across a cross sectional area of said first vessel.
14. The method as in claim 1 further comprising the step of recovering solvent present in said overhead gases.
15. The method of claim 1 , wherein the synthesis gas has a H 2 :CO ratio between about 1.2 and about 1.4.
16. The method of claim 1 , wherein the pressure of the first vessel is between about 0.8 and about 1.0 MPaa.
17. The method as in claim 1 , wherein the deactivated catalyst is iron dispersed on a support.
18. The method as in claim 17 , wherein the support further comprises aluminum oxide.
19. The method as in claim 17 , wherein the deactivated catalyst further comprises potassium and copper.
20. The method as in claim 1 , wherein the promoter is chosen from the group consisting of potassium, copper, magnesium, aluminum, and silicon.
21. The method as in claim 1 , wherein the promoter is a mixture of potassium and copper.
22. The method as in claim 21 , wherein the promoter also contains magnesium and aluminum.
23. A method for regenerating a deactivated iron-based Fischer-Tropsch catalyst from a slurry bubble column reactor, said method comprising the steps of:
placing a slurry comprising wax and deactivated catalyst into a first vessel;
intimately mixing an extraction solvent with the slurry at a superficial velocity above about 2.5 cm/sec;
extracting the wax from the slurry by passing a degassed catalyst bearing slurry through a catalyst settling vessel, whereby a catalyst-bearing slurry is returned to said first vessel, and by passing a catalyst-free wax and solvent mixture to a flash vessel for separating wax and solvent;
separating a wax-free catalyst from an extraction solvent in said first vessel;
oxidizing said wax-free catalyst in the first vessel under controlled conditions;
mixing said wax-free catalyst with a solvent containing an alkali promoter, thereby forming an oxide catalyst precursor;
drying said oxide catalyst precursor to form a catalyst precursor powder;
mixing said catalyst precursor powder with a liquid medium to form a catalyst precursor slurry; and
treating the catalyst precursor slurry with a synthesis gas to form an active catalyst containing iron carbides, thereby regenerating said deactivated catalyst.
24. The method as in claim 23 , wherein the step of extracting the wax further comprises adding an extraction solvent to said first vessel to maintain a desired level of catalyst bearing slurry as the catalyst-free wax and solvent mixture is passed to the flash vessel.
25. The method of claim 23 , wherein the first vessel is a bubble column reactor.
26. The method of claim 23 wherein the mixing step further comprises feeding an inert gas into the bottom of the first vessel.
27. The method as in claim 26 , wherein the inert gas is selected from the group consisting of nitrogen, carbon dioxide, and sulfur-free natural gas.
28. The method of claim 23 , wherein the degassed catalyst bearing slurry flows to the catalyst settling vessel by means of natural circulation.
29. The method of claim 23 , wherein the catalyst-bearing slurry flows to the first vessel by means of natural circulation.
30. The method of claim 23 further comprising the step of recovering the extracted wax.
31. The method of claim 23 further comprising the step of returning solvent recovered from the flash vessel to the first vessel.
32. The method of claim 23 , wherein the catalyst settling vessel is a dynamic settler.
33. The method as in claim 23 further comprising the step of removing said active catalyst from said first vessel.
34. The method as in claim 23 , wherein the liquid medium further comprises wax or oil.
35. The method as in claim 23 , wherein the deactivated catalyst is un supported precipitated iron.
36. The method as in claim 24 , wherein the extraction solvent is selected from the group consisting of hexane, hexene, heptane, heptene, Fischer-Tropsch naphtha, and tetrahydrofuran.
37. The method as in claim 23 further comprising the step of heating the catalyst-free wax and solvent mixture entering said flash vessel to a temperature between about 125 and about 225° C.
38. The method as in claim 23 , wherein said oxidation step further comprises an oxidation gas having between about 1 and about 5 percent by volume oxygen.
39. The method of claim 23 , wherein said oxidation step further comprises a gas pressure between about 0.1 and about 0.7 MPaa.
40. The method of claim 23 , wherein the oxidation step further comprises a gas temperature between about 200 and about 250° C.
41. The method of claim 23 , wherein the activation step further comprises maintaining a slurry temperature of about 275° C. for a length of time between about 2 and about 5 hours.
42. The method as in claim 26 , wherein the step of feeding the inert gas into the bottom of the first vessel further comprises distributing gas bubbles in said inert gas uniformly across a cross sectional area of said first vessel.
43. The method as in claim 23 further comprising the step of recovering solvent present in said overhead gases.
44. The method of claim 23 , wherein the synthesis gas has a H 2 :CO ratio between about 1.2 and about 1.4.
45. The method of claim 23 , wherein the pressure of the first vessel is between about 0.8 and about 1.0 MPaa.
46. The method as in claim 23 , wherein the deactivated catalyst is iron dispersed on a support.
47. The method as in claim 46 , wherein the support further comprises aluminum oxide.
48. The method as in claim 46 , wherein the deactivated catalyst further comprises potassium and copper.
49. The method as in claim 23 , wherein the promoter is chosen from the group consisting of potassium, copper, magnesium, aluminum, and silicon.
50. The method as in claim 23 , wherein the promoter is a mixture of potassium and copper.
51. The method as in claim 50 , wherein the promoter also contains magnesium and aluminum.