Preparation of catalyst

Abstract

A process for preparing a hydrocarbon conversion catalyst that comprises a specially made silica-alumina composition and a metal or metal compound selected from Group VIB and Group VIII metals. The silica-alumina composition is made by preparing an aqueous mixture containing aluminum sulfate followed by adding alkali metal aluminate to the mixture to enhance the pH to within specified range and then adding aluminum sulfate to the mixture to lower the pH. Then alkali metal silicate is added followed by several other pH swings to provide a mixture containing silica-alumina. The resulting mixture is treated with an alkaline solution to provide a precipitate solid that is recovered to obtain a silica-alumina composition containing of from 30 to 70% wt silica and of from 70 to 30% wt of alumina.

Claims

1. A process for hydrocracking a hydrocarbonaceous feedstock, which process comprises: contacting a gaseous feedstock at a reaction temperature in the range of 250 to 500? C. and a total pressure at the reactor inlet in the range of from 3?10.sup.6 to 3?10.sup.7 Pa in the presence of hydrogen with a hydroconversion catalyst in which the gaseous feedstock contains less than 150 parts per million by weight of ammonia; wherein said hydroconversion catalyst is made by the method comprising; (a) preparing an aqueous mixture containing aluminum sulfate and having a pH in the range of from 1.0 to 6.5; (b) adding alkali metal aluminate to the mixture obtained in step (a) to increase the pH of the mixture to within the range of from 7.1 to 12; (c) adding aluminum sulfate to the mixture obtained in step (b) to lower the pH of the mixture to within the range of from 1.5 to 6.5; (d) adding alkali metal silicate to the mixture obtained in step (c) to increase the pH of the mixture to within the range of from 6.5 to 11; (e) adding aluminium sulfate to the mixture obtained in step (d) to lower the pH of the mixture to within the range of from 1.5 to 7.0; and (f) adding alkali metal aluminate to the mixture obtained in step (e) to increase the pH of the mixture to within the range of from 7.5 to 12, wherein the final steps of the preparation process are; (v) adding aluminum sulfate to the mixture obtained in a process comprising steps (a)-(d) to lower the pH of the mixture to within the range of from 2 to 8; (w) adding alkali metal silicate to the mixture obtained in step (v) to increase the pH of the mixture, (x) adding to the mixture obtained in step (w) (i) alkali metal aluminate to change the pH of the mixture to of from 7.8 to 12 and (ii) aluminum sulfate to change the pH of the mixture to within the range of from 1.5 to 7.7, wherein step (i) can precede or succeed step (ii), (y) treating the mixture obtained in step (x) with an alkali metal hydroxide solution having a pH of from 7.5 to 12, (z) recovering a precipitate solid from the mixture obtained in step (y) to provide a recovered precipitate; (zz) washing with water the recovered precipitate and drying the recovered and washed precipitate by flash drying, belt drying or spray drying to obtain a dried silica-alumina composition containing of from 30 to 70% wt silica and of from 70 to 30% wt of alumina, and having a surface area of from 320 m.sup.2/g to 450 m.sup.2/g, and subsequently shaping the dried silica-alumina composition to provide a shaped silica-alumina composition and compositing the shaped silica-alumina composition with one or more metals or metal compounds which metals have been selected from the group consisting of Group VIB and Group VIII metals to obtain a hydrocarbon conversion catalyst.

2. The process according to claim 1, which process comprises belt drying or flash drying the solid precipitate obtained in step (z).

3. The process according to claim 1, wherein the silica-alumina composition obtained in step (z) has a surface area of from 330 m.sup.2/g to 420 m.sup.2/g.

4. The process according to claim 1, wherein alkali metal aluminate is sodium aluminate.

5. The process according to claim 1, wherein alkali metal silicate is sodium silicate.

6. The process according to claim 1, which process comprises calcining the dried silica-alumina composition at a temperature of from 600 to 850? C.

7. The process according to claim 1, which shaping step includes mixing the dried silica-alumina with water and acid to provide an extrusion mixture and subsequently extruding the extrusion mixture to yield the shaped silica-alumina composition.

8. The process according to claim 7, in which process the acid is an inorganic acid.

9. The process according to claim 1, which process further comprises drying and/or calcining the shaped silica-alumina composition.

10. The process according to claim 9, which process comprises calcining the shaped silica-alumina composition at a temperature of from 600 to 850? C.

Description

EXAMPLE 1

(1) This Example illustrates the pH swing method according to the present invention and the physical properties of amorphous silica-alumina product made by the pH swing method.

(2) The amorphous silica-alumina powder was prepared using a pH swing precipitation process that included four or five pH swings conducted in a single, so-called strike tank. In the preparation procedure, a water heel was first added to the empty strike tank. Subsequently, aqueous solutions of aluminum sulfate, sodium alumina, and sodium silicate were added in a sequential manner in the order and relative amounts as presented in Tables 1-5 to the liquor contained in the strike tank thereby attaining the liquor pH as also indicated in each of the Tables. Table 1 describes the preparation of Composition A, Table 2 describes the preparation of Composition B, Table 3 describes the preparation of Composition C and Table 4 describes the preparation of Composition D.

(3) Table 5 describes the Comparative Composition prepared according to claim 5 of WO-A-2009/029580 except that the precipitates were washed with alkaline solution instead of water.

(4) The various pH swings were performed at a temperature of approximately 55? C. and a constant agitation rate of 43 rpm. The addition and mixing time for each step approximated five minutes. At the end of the last pH swing, the solids content of the final liquor, or slurry, was around 6 wt %. A 10% wt sodium hydroxide solution having a pH of 9.5 was added to the mixture obtained and the solids were recovered and washed with water. The recovered and washed solids were subjected to ion exchange, washed, and, then, flash-dried to form the final amorphous silica-alumina powder.

(5) TABLE-US-00001 TABLE 1 Composition A Relative Mass pH of Step Added of Added Liquor after pH Swing No. Component Component Addition 1 Water heel 60.4 7 First pH 2 Aluminum sulfate 5.4 1.8 swing 3 Sodium aluminate 3.3 8.9 Second pH 4 Aluminum sulfate 1.9 3.8 swing 5 Sodium silicate 5.4 8.1 Third pH 6 Aluminum sulfate 5.3 3.5 swing 7 Sodium aluminate 4.0 9.4 Fourth pH 8 Aluminum sulfate 1.9 6.4 swing 9 Sodium silicate 5.4 8.5 Fifth pH 10 Aluminum sulfate 4.6 4.1 swing 11 Sodium aluminate 2.4 8.5

(6) TABLE-US-00002 TABLE 2 Composition B Relative Mass pH of Step Added of Added Liquor after pH Swing No. Component Component Addition 1 Water heel 64.9 7 First pH 2 Aluminum sulfate 5.8 2.5 swing 3 Sodium aluminate 3.5 7.8 Second pH 4 Aluminum sulfate 2.1 3.6 swing 5 Sodium silicate 5.8 7.7 Third pH 6 Aluminum sulfate 5.6 3.3 swing 7 Sodium silicate 5.8 3.8 Fourth pH 8 Sodium aluminate 4.3 10.3 swing 9 Aluminum sulfate 2.1 7.1

(7) TABLE-US-00003 TABLE 3 Composition C Relative Mass pH of Step Added of Added Liquor after pH Swing No. Component Component Addition 1 Water heel 60.4 7 First pH 2 Aluminum sulfate 5.4 1.8 swing 3 Sodium aluminate 3.3 8.9 Second pH 4 Aluminum sulfate 1.9 3.8 swing 5 Sodium silicate 5.4 8.1 Third pH 6 Aluminum sulfate 5.3 3.5 swing 7 Sodium aluminate 4.0 9.4 Fourth pH 8 Aluminum sulfate 1.9 6.4 swing 9 Sodium silicate 5.4 8.5 Fifth pH 10 Sodium aluminate 2.4 10.4 swing 11 Aluminum sulfate 4.6 5.4

(8) TABLE-US-00004 TABLE 4 Composition D Relative Mass pH of Step Added of Added Liquor after pH Swing No. Component Component Addition 1 Water heel 57.7 7 First pH 2 Aluminum sulfate 5.1 1.8 swing 3 Sodium aluminate 3.1 8.9 Second pH 4 Aluminum sulfate 1.8 3.8 swing 5 Sodium silicate 5.2 8.1 Third pH 6 Aluminum sulfate 5.0 3.5 swing 7 Sodium aluminate 3.8 9.4 Fourth pH 8 Aluminum sulfate 1.8 6.4 swing 9 Sodium silicate 5.2 8.5 Fifth pH 10 Aluminum sulfate 4.4 4.1 swing 11 Sodium aluminate 2.3 8.5

(9) TABLE-US-00005 TABLE 5 Comparative Composition Relative Mass pH of Step Added of Added Liquor after pH Swing No. Component Component Addition 1 Water heel 64.3 First pH 2 Aluminum sulfate 6.0 3.2 swing 3 Sodium aluminate 3.3 8.3 Second pH 4 Aluminum sulfate 2.1 4.1 swing 5 Sodium silicate 6.0 9.1 Third pH 6 Aluminum sulfate 6.2 3.6 swing 7 Sodium aluminate 4.1 9.1 Fourth pH 8 Aluminum sulfate 2.0 6.5 swing 9 Sodium silicate 6.1 9.6

(10) Table 6 shows physical properties of the powders obtained. The new materials display higher surface area compared to the composition prepared according to claim 5 of WO-A-2009/29580.

(11) TABLE-US-00006 TABLE 6 Physical properties Type Surface area (m2/g) Wt. % Al.sub.2O.sub.3 Wt. % SiO.sub.2 Comparative 234 46.3 51.6 Sample A 366 53.5 45.7 Sample B 369 43.0 50.2 Sample C 355 54.5 46.3 Sample D 393 55.9 44.3

EXAMPLE 2

(12) Catalysts A, B and C were prepared by adding water, nitric acid and Methocel cellulose ethers as extrusion aid (Methocel is a trade mark of Dow Chemical Co.) to the above Compositions A, B and C. The mixture was mulled in a mix-muller until an extrudable mix was obtained. After the mulling step, the catalysts were extruded into a trilobe shape. The calcination of the final extrudates was carried out by drying at 120? C. for 2 hours and calcination at 600? C. for 2 hours.

(13) The extrudates obtained were impregnated with a homogenized aqueous solution of nickel nitrate and ammonium metatungstate. Citric acid was incorporated into the solution. The impregnated extrudates were dried at ambient conditions in hot circulating air for 1 hour, at 120? C. for 2 hours and finally calcined at 450? C. for 2 hours. The catalysts obtained contained 5% wt of nickel, calculated as nickel oxide, and 21% wt of tungsten, calculated as tungsten oxide.

(14) The catalysts were used in a hydrocracking test under so-called two-stage conditions and compared to a commercial reference catalyst based on co-precipitated amorphous silica alumina and containing 5% wt of nickel, calculated as nickel oxide, and 21% wt of tungsten, calculated as tungsten oxide.

(15) In this design H.sub.2S and NH.sub.3 are removed in a fractionator after the first stage allowing very low levels of ammonia in the second stage. The ammonia level of below 150 ppm allows a lower reaction temperature for hydrocracking in the last reactor. These operating conditions are especially beneficial for high diesel selective hydrocrackers with amorphous catalysts.

(16) The hydrocracking performance of the catalysts was assessed in a two-stage simulation tests. The testing was carried out in once-through nanoflow equipment using 0.8 ml of catalyst as extrudates diluted with 0.8 ml of 0.1 mm zirconia particles. The catalysts were presulphided prior to testing.

(17) The feedstock used was a heavy vacuum gas oil as described in Table 7 below. The process conditions comprised a space velocity of 1.5 kg heavy gas oil per liter catalyst per hour (kg.Math.l.sup.?1.Math.h.sup.?1), a hydrogen gas/heavy oil ratio of 1500 Nl/kg. Sulfrzol sulphiding agent (Sulfrzol is a trade mark of Brenntag) was added at an amount of 3.936 g/kg.sub.feed to achieve a partial pressure of 0.14 bar H.sub.2S at a total pressure of 140 bar.

(18) TABLE-US-00007 TABLE 7 Feed properties Carbon content 86.63% wt Hydrogen content 13.37% wt Sulphur (S) content 0.0175% wt Nitrogen (N) content 20 ppmw Density 70/4? C. 0.8459 g .Math. ml Initial boiling point 172? C. 50% w boiling point 468? C. Final boiling point 583? C.
Hydrocracking performance was assessed at conversion levels between 40 and 90% wt net conversion of feed components boiling above 370? C. To compare activity, the obtained results, expressed as the temperature required to obtain 55% wt net conversion of feed components boiling above 370? C., are shown in Table 8.

(19) TABLE-US-00008 TABLE 8 Performance results Catalyst Commercial Catalyst A Catalyst B Catalyst C reference Temperature 377 384 386 388 required (? C.)