Acid-resistant catalyst supports and catalysts
A process for preparing a catalyst comprises coating substantial internal surfaces of porous inorganic powders with titanium oxide to form titanium oxide-coated inorganic powders. After the coating, an extrudate comprising the titanium oxide-coated inorganic powders is formed and calcined to form a catalyst support. Then, the catalyst support is impregnated with a solution containing one or more salts of metal selected from the group consisting of molybdenum, cobalt, and nickel.
1. A process for preparing an acid-resistant catalyst support, the process comprising:
coating substantial internal surfaces of porous inorganic powders with titanium oxide to form titanium oxide-coated inorganic powders,
wherein a Ti/Al ratio as measured by x-ray photoelectron spectroscopy of the titanium oxide-coated inorganic powders is less than about 4.5.
2. The process of claim 1 , wherein the process further comprises
forming an extrudate comprising the titanium oxide-coated inorganic powders; and
calcining the extrudate.
3. The process of claim 2 , wherein the process further comprises, between the coating of internal surfaces and forming the extrudate,
washing the titanium oxide-coated inorganic powders to remove residual ions;
partially drying the titanium oxide-coated inorganic powders; and
forming the partially dried titanium oxide-coated inorganic powders into support particles.
4. The process of claim 2 , wherein forming the extrudate comprises:
forming an extrudable mixture comprising the titanium oxide-coated inorganic powders, an acid, and a binder; and
extruding the mixture to form the extrudate comprising the titanium oxide-coated inorganic powders.
5. The process of claim 4 , wherein the extrudate is in a form of pellet, ring, cylinder rod, or polylobe.
6. The process of claim 4 , wherein the binder is methyl cellulose.
7. The process of claim 4 , wherein the acid is nitric acid.
8. The process of claim 2 , wherein the calcining of the extrudates is performed at a temperature ranging from about 600° C. to about 800° C. for a period of from about 1 hour to about 2 hours.
9. The process of claim 1 , wherein the inorganic powders are selected from the group consisting of alumina powders, silica powders, silica-alumina powders, and mixtures thereof.
10. The process of claim 1 , wherein the coating of internal surfaces comprises:
preparing an aqueous mixture slurry comprising porous inorganic powders, a soluble titanium oxide precursor, and optionally a chelating or complexing agent with a weight ratio of the soluble titanium oxide precursor (as titanium oxide) to the porous inorganic powders in a range of about 0.1 to about 1.0;
introducing a basic solution to the mixture slurry to raise pH value of the mixture slurry to a resultant pH of between about 3.5 and about 6; and
aging the mixture slurry at a pH of 4.5 to 7.0 for at least about 1 hour to form titanium oxide-coated inorganic powders.
11. The process of claim 10 , wherein the aging comprises aging the mixture slurry for about 1 hour to 3 hours.
12. The process of claim 10 , wherein the soluble titanium oxide precursor is titanyl sulfate.
13. The process of claim 10 , wherein the basic solution is ammonium hydroxide solution.
14. The process of claim 10 , wherein the soluble titanium oxide precursor is titanium chloride.
15. The process of claim 1 , wherein the coating of internal surfaces comprises:
preparing a slurry of porous inorganic powders in water;
introducing portions of a solution comprising a soluble titanium oxide precursor and optionally a chelating or complexing agent and a basic solution alternately in 2 or more portions of each type into the slurry to form a mixture slurry; and
aging the mixture slurry at a pH of 4.5 to 7.0 for at least about 1 hour to form titanium oxide-coated inorganic powders,
wherein a resultant pH of the mixture slurry is maintained in a range of about 3.5 to about 6 during a period of introducing the soluble titanium oxide precursor and the basic solution, and
a weight ratio of the total soluble titanium oxide precursor introduced into the mixture slurry (as titanium oxide) to the porous inorganic powders is in a range of about 0.1 to about 1.0.
16. The process of claim 15 , wherein the aging comprises aging the mixture slurry for about 1 hour to 3 hours.
17. The process of claim 15 , wherein the soluble titanium oxide precursor is titanyl sulfate.
18. The process of claim 15 , wherein the basic solution is ammonium hydroxide solution.
19. The process of claim 1 , wherein the coating of internal surfaces comprises:
preparing a slurry of porous inorganic powders in water;
introducing a solution comprising a soluble titanium oxide precursor and optionally a chelating or complexing agent and a basic solution simultaneously into the slurry at a predetermined relative rate to form a mixture slurry; and
aging the mixture slurry at a pH of 4.5 to 7.0 for at least about 1 hour to form titanium oxide-coated inorganic powders,
wherein a resultant pH of the mixture slurry is maintained in a range of about 3.5 to about 6.0 during a period of introducing the soluble titanium oxide precursor and the basic solution, and
a weight ratio of the total soluble titanium oxide precursor introduced into the mixture slurry (as titanium oxide) to the porous inorganic powders is in a range of about 0.1 to about 1.0.
20. The process of claim 19 , wherein the aging comprises aging the mixture slurry for about 1 hour to 3 hours.
21. The process of claim 19 , wherein the soluble titanium oxide precursor is titanyl sulfate.
22. The process of claim 19 , wherein the basic solution is ammonium hydroxide solution.
23. The process of claim 1 , wherein the coating of internal surfaces comprises:
impregnating with incipient wetness porous inorganic powders with a solution comprising a soluble titanium oxide precursor and optionally a chelating or complexing agent;
treating the impregnated porous inorganic powders with a basic solution; and
aging the treated porous inorganic powders at a pH of 4.5 to 7.0 for at least about 1 hour to form titanium oxide-coated inorganic powders,
wherein a weight ratio of the soluble titanium oxide precursor (as titanium oxide) to the porous inorganic powders is in a range of about 0.1 to about 1.0.
24. The process of claim 23 , wherein the soluble titanium oxide precursor is titanyl sulfate.
25. The process of claim 23 , wherein the basic solution is ammonium hydroxide solution.
26. The process of claim 1 , wherein an amount of Al dissolved as measured by an acid-leaching test of an extruded support comprising the titanium oxide-coated inorganic powders is 70 ppm or less.