FCC catalyst, its preparation and use

Abstract

A process for preparing a catalyst is disclosed. The process generally comprises the steps of: (a) preparing a slurry comprising clay, zeolite, a sodium-free silica source, quasi-crystalline boehmite, and micro-crystalline boehmite, provided that the slurry does not comprise peptized quasi-crystalline boehmite; (b) adding a monovalent acid to the slurry; (c) adjusting the pH of the slurry to a value above about 3, and (d) shaping the slurry to form particles. This process results in attrition resistant catalysts with a good accessibility.

Claims

1. A process for the preparation of a catalyst comprising the steps of: a) preparing a slurry comprising clay, zeolite, a sodium-free silica source, quasi-crystalline boehmite, and micro-crystalline boehmite, provided that the slurry does not comprise peptised quasi-crystalline boehmite, b) adding a monovalent acid to the slurry, c) adjusting the pH of the slurry to a value above 3, and d) shaping the slurry to form particles; wherein the slurry contains 1 to 50 wt % of quasi-crystalline boehmite, and 1 to 50 wt % of micro-crystalline boehmite, wherein the weight percentages are based on dry solids content and calculated as oxides.

2. The process according to claim 1 wherein the sodium-free silica source is selected from the group consisting are sodium-free silica sol, polysilicic acid, potassium silicate, lithium silicate, calcium silicate, magnesium silicate, barium silicate, strontium silicate, zinc silicate, phosphorus silicate, and borium silicate, polyorganosiloxanes, methyl chlorosilane, dimethyl chlorosilane, trimethyl chlorosilane, and mixtures thereof.

3. The process according to claim 1 wherein the pH in step c) is adjusted to a value of between 4 and 7.

4. A catalyst composition comprising clay, zeolite, a sodium-free silica source, quasi and micro-crystalline boehmite, wherein the composition is prepared by a) preparing a slurry comprising clay, zeolite, a sodium-free silica source, quasi-crystalline boehmite, and micro-crystalline boehmite, provided that the slurry does not comprise peptised quasi-crystalline boehmite; b) adding a monovalent acid to the slurry; c) adjusting the pH of the slurry to a value above about 3, and d) shaping the slurry to form particles; wherein the slurry contains 1 to 50 wt % of quasi-crystalline boehmite, and 1 to 50 wt % of micro-crystalline boehmite, wherein the weight percentages are based on dry solids content and calculated as oxides.

5. A catalyst composition comprising micro-crystalline boehmite, quasi-crystalline boehmite, zeolite, and silica, wherein the composition contains 1 to 50 wt % of quasi-crystalline boehmite, and 1 to 25 wt % of micro-crystalline boehmite, wherein the weight percentages are calculated as oxides.

6. The process according to claim 1 wherein the zeolite is selected from the group consisting of Y-zeolite, ZSM-5, phosphorus-activated ZSM-5, ion-exchanged ZSM-5, MCM-22, and MCM-36, metal-exchanged zeolites, ITQs, SAPOs, ALPOs, and mixtures thereof.

7. The process according to claim 1 wherein the zeolite has a sodium content of less than 1.5 wt % Na.sub.2O.

Description

EXAMPLES

Accessibility Measurement

(1) The accessibility of the catalysts prepared according to the Examples below was measured by adding 1 g of the catalyst to a stirred vessel containing 50 g of a 15 g/l Kuwait vacuum gas oil (KVGO) in toluene solution. The solution was circulated between the vessel and a spectrophotometer, in which process the KVGO-concentration was continuously measured.

(2) The accessibility of the catalysts to KVGO was quantified by the Akzo Accessibility Index (AAI). The relative concentration of KVGO in the solution was plotted against the square root of time. The AAI is defined as the initial slope of this graph:
AAI=d(C.sub.t/C.sub.0)/d(t.sup.1/2)*100%

(3) In this equation, t is the time (in minutes) and C.sub.0 and C.sub.t denote the concentrations of high-molecular weight compound in the solvent at the start of the experiment and at time t, respectively.

(4) Attrition Resistance Measurement

(5) The attrition resistance of the catalysts was measured by the standard Attrition Test. In this test the catalyst bed resides on an attrition plate with three nozzles. The attrition plate is situated within an attrition tube which is at ambient temperature. Air is forced to the nozzles and the resulting jets bring about upward transport of catalyst particles and generated fines. On top of the attrition tube is a separation chamber where the flow dissipates, and most particles larger than about 16 microns fall back into the attrition tube. Smaller particles are collected in a collection bag.

(6) This test is conducted after calcination of the catalyst samples at 600 C., and it is first run for 5 hours and the weight percentage of fines collected in the collection bag, based on an imaginary intake of 50 grams, is determined. This is the initial attrition. The test is then conducted for another 15 hours and the weight percentage of fines in this time period (5-20 hours) is determined. This is the inherent attrition. The Attrition Index (AI) is the extrapolated wt % fines after 25 hours. So, the more attrition resistant the catalyst is, the lower the AI value.

Comparative Example 1

(7) An aqueous slurry containing peptisable QCB (13.3 kg) was mixed with water and peptised by acidification with formic acid. The pH of the resulting mixture was 2. The mixture was stirred for 15 minutes. Next, MCB (highly crystalline alumina, 5 kg), zeolite Y slurry (8 kg), kaolin (4.17 kg), sodium-free silica sol (2.4 kg), and water were added and blended with the peptised QCB. The final pH of the slurry was 3.2. The slurry was then sent to a spray-dryer at 1 kg/min, inlet temperature 500 C., and outlet temperature 120 C.

(8) The resulting material comprised 20 wt % zeolite, 24 wt % QCB, 14 wt % MCB, 6% SiO.sub.2, and balance kaolin. The powder had a d50 around 65 m.

(9) The attrition index (AI), the accessibility index (AAI), and their ratio are indicated in the Table below.

Example 2

(10) An aqueous slurry containing non-peptised but peptisable QCB (13.3 kg), MCB (highly crystalline alumina, 5.4 kg), a zeolite Y slurry (8 kg), kaolin (4.17 kg), sodium-free silica sol, and water were blended together. Nitric acid was then added to the total reaction mixture to reach pH 3.3. The slurry was then sent to a spray-dryer at 1 kg/min, inlet temperature 500 C., and outlet temperature 120 C.

(11) The resulting material comprised 20 wt % zeolite, 24 wt % QCB, 14 wt % MCB, 6% SiO.sub.2, and balance kaolin. The powder had a d50 around 65 m.

(12) The attrition index, the accessibility index, and their ratio are indicated in the Table below.

Comparative Example 3

(13) An aqueous slurry containing peptisable QCB (16.6 kg) was mixed with water and peptised by acidification with formic acid. The pH of the resulting mixture was 2. The mixture was stirred for 15 minutes. Next, MCB (highly crystalline alumina, 5.4 kg), zeolite Y slurry (7.2 kg), kaolin (4.17 kg), sodium-free silica sol (2.4 kg), and water were added and blended with the peptised QCB. The final pH of the slurry was 3.2. The slurry was then sent to a spray-dryer at 1 kg/min, inlet temperature 500 C., and outlet temperature 120 C.

(14) The resulting material comprised 18 wt % zeolite, 30 wt % QCB, 15 wt % MCB, 4% SiO.sub.2, and balance kaolin. The powder had a d50 around 65 m.

(15) The attrition index, the accessibility index, and their ratio are indicated in the Table below.

Example 4

(16) An aqueous slurry containing non-peptised but peptisable QCB (16.6 kg), MCB (highly crystalline alumina, 5.4 kg), a zeolite Y slurry (8 kg), kaolin (4.17 kg), sodium-free silica sol, and water were blended together. Nitric acid was then added to the total reaction mixture to reach pH 3.2. The slurry was then sent to a spray-dryer at 1 kg/min, inlet temperature 500 C., and outlet temperature 120 C.

(17) The resulting material comprised 18 wt % zeolite, 30 wt % QCB, 15 wt % MCB, 4% SiO.sub.2, and balance kaolin. The powder had a d50 around 65 m.

(18) The attrition index, the accessibility index, and their ratio are indicated in the Table below.

Comparative Example 5

(19) An aqueous slurry containing peptisable QCB (16.6 kg) was mixed with water and peptised by acidification with formic acid. The pH of the resulting mixture was 2. The mixture was stirred for 15 minutes. Next, MCB (highly crystalline alumina, 5.4 kg), zeolite Y slurry (9.6 kg), kaolin (4.17 kg), sodium-free silica sol (2.4 kg), and water were added and blended with the peptised QCB. The final pH of the slurry was 3.2. The slurry was then sent to a spray-dryer at 1 kg/min, inlet temperature 500 C., and outlet temperature 120 C.

(20) The resulting material comprised 24 wt % zeolite, 30 wt % QCB, 15 wt % MCB, 4% SiO.sub.2, and balance kaolin. The powder had a d50 around 65 m.

(21) The attrition index, the accessibility index, and their ratio are indicated in the Table below.

Example 6

(22) An aqueous slurry containing non-peptised but peptisable QCB (16.6 kg), MCB (highly crystalline alumina, 5.4 kg), a zeolite Y slurry (9.6 kg), kaolin (4.17 kg), sodium-free silica sol, and water were blended together. Nitric acid was then added to the total reaction mixture to reach pH 3.3. The slurry was then sent to a spray dryer at 1 kg/min, inlet temperature 500 C., and outlet temperature 120 C.

(23) The resulting material comprised 24 wt % zeolite, 30 wt % QCB, 15 wt % MCB, 4% SiO.sub.2, and balance kaolin. The powder had a d50 around 65 m.

(24) The attrition index, the accessibility index, and their ratio are indicated in the Table below.

(25) TABLE-US-00001 TABLE Example AI AAI AAI/AI 1 (comparative) 18 15 0.8 2 8.1 12 1.5 3 (comparative) 15.8 14 0.9 4 6.8 11 1.6 5 (comparative) 20.2 18 0.9 6 9.5 14 1.5

(26) This Table shows that the process of the present invention results in more attrition resistant catalysts (reduced AI) and a higher AAI/AI ratio compared to a process which uses pre-peptised boehmite.