Hydrothermal pretreatment for increasing average pore size in a catalyst support
View Patent ↗A pretreatment method for increasing the average pore size of a catalyst support is disclosed which increases the diffusivity and effectiveness factor η. The pretreatment method includes calcining the support in moisturized air at an elevated temperature sufficient to increase the average pore size. In some embodiments, the support may be treated with an acidic/basic solution prior to the calcination step. Alternatively, the calcination step may occur in a gas mixture including water/air/acidic (or basic) gases.
1. A method for increasing the average pore size of a catalyst support, the method comprising the step of:
calcining the support in moisturized air at an elevated temperature sufficient to increase the average pore size such that the average pore size is increased by a factor of 2 to 10 during calcination and the resulting calcined support has a total pore volume equal to or less than 0.14 cc/g.
2. The method of claim 1 wherein the moisturized air comprises a mixture of air, steam, and water.
3. The method of claim 1 wherein the moisturized air comprises a mixture of air and steam or air and water.
4. The method of claim 1 wherein the moisturized air contains from about 1 to about 20 wt. percent water.
5. The method of claim 4 wherein the elevated temperature is in the range of 600 to 1300° C.
6. The method of claim 5 wherein the elevated temperature is in the range of 700 to 1000° C.
7. The method of claim 1 further including treating the support in an acidic or basic solution prior to or during the calcination step.
8. The method of claim 7 wherein the acidic or basic solution is selected from the group consisting of HCl, HNO 3, and NH 3 ·H 2 O.
9. The method of claim 1 wherein the average pore size is increased by a factor of 10.
10. The method of claim 1 wherein the support is selected from the group consisting of zirconia, stabilized zirconia, titania, yttria, silica, niobia, and vanadia.
11. The method of claim 1 wherein the support is zirconia or stabilized zirconia.
12. A partial oxidation catalyst comprising:
a porous support; and
a catalytically active metal dispersed on the support,
wherein the support has been calcined in moisturized air at an elevated temperature sufficient to increase the average pore size by a factor of 2 to 10 during calcination and the resulting calcined support has a total pore volume equal to or less than 0.14 cc/g.
13. The catalyst of claim 12 wherein the support comprises a plurality of discrete structures.
14. The catalyst of claim 13 wherein the discrete structures are particulates.
15. The catalyst of claim 13 wherein the plurality of discrete structures comprises at least one geometry chosen from the group consisting of powders, particles, granules, spheres, beads, pills, pellets, balls, noodles, cylinders, extrudates and trilobes.
16. The catalyst of claim 13 wherein at least a majority of the discrete structures each have a maximum characteristic length of less than six millimeters.
17. The catalyst of claim 16 wherein the majority of the discrete structures each have a maximum characteristic length of less than about 3 millimeters.
18. The catalyst of claim 12 wherein the support is selected from the group consisting of alumina, zirconia, stabilized zirconia, titania, yttria, silica, niobia, and vanadia.
19. The catalyst of claim 18 wherein the support is selected from the group consisting of alumina, zirconia, and combinations thereof.
20. The catalyst of claim 12 wherein the catalytically active metal is selected from the group consisting of Group VIII B metals Os, Ir, Pt, Ru, Rh, Pd, Fe, Co, Ni, and combinations thereof.
21. The catalyst of claim 12 further including a promoter metal.
22. The catalyst of claim 21 wherein the promoter metal is selected from the group consisting of lanthanides.
23. The catalyst of claim 22 wherein the catalytically active metal is selected from the group consisting of, Group VIII B metals Os, Ir. Pt, Ru, Rh, Pd, Fe, Co, Ni, and combinations thereof.
24. The catalyst of claim 12 wherein the moisturized air comprises a mixture of air, steam, and water.
25. The method of claim 12 wherein the moisturized air comprises a mixture of air and steam or air and water.
26. The catalyst of claim 12 wherein the moisturized air contains from about 1 to about 20 wt. percent water.
27. The catalyst of claim 26 wherein the elevated temperature is in the range of 600 to 1300° C.
28. The catalyst of claim 26 wherein the elevated temperature is in the range of 700 to 1000° C.
29. The catalyst of claim 12 further including treating the support in an acidic or basic solution prior to, or during the calcination step.
30. The catalyst of claim 29 wherein the acidic or basic solution is selected from the group consisting of HCl,HNO 3 , and NH 3 .H 2 O.
31. The catalyst of claim 12 wherein the average pore size is increased by a factor of 2.
32. The catalyst of claim 12 wherein the average pore size is increased by a factor of 10.
33. The catalyst of claim 12 wherein the catalytically active metal is selected from the group consisting of Rh, Os, Ir, Pt, Ru, Rh, Pd, and combinations thereof.
34. The catalyst of claim 12 wherein the support is selected from the group consisting of zirconia, stabilized zirconia, titania, yttria, silica, niobia, and vanadia.
35. The catalyst of claim 12 wherein the support is zirconia or stabilized zirconia.
36. A method for preparing a partial oxidation catalyst comprising, the method comprising the steps of:
a) calcining a support material in moisturized air at an elevated temperature sufficient to increase the average pore size by a factor of 2 to 10 during calcination and the resulting calcined support has a total pore volume equal to or less than 0.14 cc/g; and
b) loading the support material with a catalytically effective amount of a precious metal to form the partial oxidation catalyst.
37. The method of claim 36 wherein step b) is achieved through wet impregnation.