Resid hydrotreating catalyst
Catalyst supports, supported catalysts, and a method of preparing and using the catalysts for the demetallation of metal-containing heavy oil feedstocks are disclosed. The catalyst supports comprise precipitated alumina prepared by a low temperature pH swing process. A large portion of the pore volume of the catalyst supports has pores with a diameter in the range of about 200 Å to about 500 Å. Catalysts prepared from the supports of the invention exhibit improved catalytic activity and stability to remove metals from heavy hydrocarbon feedstocks during a hydroconversion process. The catalysts also exhibit increased sulfur and MCR conversion during the hydroconversion process.
1. A process comprising:
(I) contacting acidic and alkaline compounds capable of forming alumina by conducting pH swing cycles comprising:
(a) forming an aqueous slurry by combining at least one acidic compound and water in amounts sufficient to provide a pH of less than 5;
(b) adding at least one alkaline compound to (a) in an amount sufficient to provide a pH greater than 7 and to precipitate seed alumina in the form of a second alumina-containing slurry;
steps (a) and (b) comprising pH swing;
(c) repeating steps (a) to (b) at least 1 pH swing to provide an alumina-containing slurry having pH greater than 7;
(d) adding an acidic compound to the alumina containing slurry of step (c) in an amount sufficient to provide an alumina-containing slurry having a pH of less than 5;
(e) adding an alkaline compound to the alumina-containing slurry of step (d) in an amount sufficient to provide a final alumina-containing slurry having a pH of at least about 9; and
(f) recovering precipitated alumina from the final alumina-containing slurry; wherein the temperature during steps (a)-(e) is maintained at about 72° C. or less;
(II) wherein the precipitated alumina exhibits a crystalline structure, which is used for preparing a catalyst support, wherein the support has a total pore volume in the range of from about 0.8 cc/g to about 1.2 cc/g, wherein at least 5% of the volume of pores has a diameter above 1500 A.
2. The process of claim 1 wherein the temperature is maintained at about 48° C. to about 72° C. during steps (a)-(e).
3. The process of claim 1 wherein the temperature is maintained at about 52° C. to about 66° C. during steps (a)-(e).
4. The process of claim 1 wherein the acidic compound is selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, aluminum sulfate, aluminum nitrate, aluminum chloride, ammonia sulfate, aluminum chlorohydrate, and combinations thereof.
5. The process of claim 1 wherein the acid compound is aluminum sulfate.
6. The process of claim 1 wherein the alkaline compound is selected from the group consisting of sodium aluminate, aluminum hydroxide, sodium hydroxide, ammonium hydroxide and combinations thereof.
7. The process of claim 1 wherein the alkaline compound is sodium aluminate.
8. The process of claim 1 wherein the pH in at least one of steps (a), (b), (c), (d) and (e) is controlled as follows:
(i) step (a) ranges from about 2.0 to about 4.5;
(ii) step (b) ranges from about 7.5 to about 10;
(iii) step (c) ranges from about 7.5 to about 10;
(iv) step (d) ranges from about 2.0 to about 4.5; and
(v) step (e) ranges from about 9 to about 9.5.
9. The process of claim 1 , step (c) is repeated from about 3 to about 7 pH swings.
10. The process of claim 1 , where the time period between two addition steps in a pH swing is from about 1 minute to about 10 minutes.
11. The process of claim 1 , where the final slurry in step (e) comprises Al 2 O 3 solids content of about 1 weight percent to about 10 weight percent, based upon the total weight of the slurry.
12. The process of claim 1 , wherein the precipitated alumina of (II) is dried, the dried alumina is peptized, the peptized alumina is extruded, and the extrudate is calcined to obtain an extrudate suitable for use as a catalyst support.
13. The process of claim 12 , where the alumina extrudate is calcined at a temperature from about800° C. to about 1100° C.
14. The process of claim 1 , wherein the precipitated alumina of (II) comprises spherical or substantially spherical shaped particles exhibiting a crystalline structure having a first dimension as measured along a 120 XRD plane and a second dimension as measured along a 020 XRD plane, wherein the ratio of the second dimension to the first dimension is less than 1.0.
15. The process of claim 13 , wherein the precipitated alumina of (II) comprises spherical or substantially spherical shaped particles exhibiting a crystalline structure having a first dimension as measured along a 120 XRD plane and a second dimension as measured along a 020 XRD plane, wherein the ratio of the second dimension to the first dimension is less than 1.0.