Process for preparing hydrocracking catalyst

Abstract

Process for preparing a sulphided hydrocracking catalyst comprising the steps of (a) treating an amorphous silica alumina carrier with one or more Group VIB metal components, one or more Group VIII metal components and a C.sub.3-C.sub.12 polyhydric compound, (b) drying the treated catalyst carrier at a temperature of at most 200 C. to form an impregnated carrier, and (c) sulphiding the impregnated carrier to obtain a sulphided catalyst.

Claims

1. The process for preparing a sulphided hydrocracking catalyst comprising the steps of: preparing an amorphous silica-alumina carrier, containing silica in an amount in the range of from 25 to 95% by weight based on the carrier, which is dried and calcined to provide a calcined catalyst carrier; impregnating the calcined catalyst carrier with a solution, comprising one or more Group VIB metal components, one or more Group VIII metal components, and a C.sub.3-C.sub.12 polyhydric compound selected from the group consisting of sugars, sugar alcohols and sugar acids to provide an impregnated calcined catalyst carrier; drying the impregnated calcined catalyst carrier at a temperature of at most 200 C. without calcination to form a dried but uncalcined impregnated carrier; and sulfiding the dried but uncalcined impregnated carrier to obtain a sulfided catalyst; wherein the amount of Group VIB metal in the sulfided catalyst is in the range of from 6 to 19 wt %, measured as metal, and the amount of Group VIII metal is in the range of from 1 to 6 wt %, measured as metal.

2. The process according to claim 1, wherein the C.sub.3-C.sub.12 polyhydric compound is present in the sulfided catalyst in an amount of 3-30 wt %.

3. The process according to claim 2, wherein the silica-alumina carrier further contains a zeolite.

4. The process according to claim 3, wherein the carrier comprises an amount of 1 to 10 wt % of zeolite, based on total weight of the carrier.

5. The process according to claim 4, wherein the C.sub.3-C.sub.12 polyhydric compound selected from the group consisting of sucrose, gluconic acid, and combinations thereof.

6. A process for hydrocracking a hydrocarbon stream comprising contacting the hydrocarbon stream in the presence of hydrogen with a catalyst prepared by a process according to claim 1.

7. The process according to claim 6, in which the catalyst is part of a stack of multiple catalyst beds, including a top bed including an alumina-based catalyst and a bottom bed including the catalyst.

8. The process according to claim 7, wherein the volume ratio of the catalyst to the alumina-based catalyst is in a range from 1:1 to 4:1.

Description

EXAMPLES

(1) The amorphous silica-alumina carrier used in the examples was a 1.3 mm trilobe of amorphous silica-alumina extrudate having a water pore volume of 0.78 ml/g.

Example 1

Preparation of a Calcined Catalyst (not According to the Invention)

(2) 5.55 g citric acid monohydrate was dissolved in 10 ml demineralized water. 3.90 g nickel carbonate (39.80% w Ni) was added and the mixture was heated until a clear green solution was obtained. Next, 9.19 g ammonium metatungstate (70.9% w W) was added and demineralized water was added until the resulting clear solution reached a total volume of 16.2 ml. The solution was then used to impregnate 20.8 g of an amorphous silica-alumina carrier. The catalyst was then dried in a ventilated furnace at 120 C. for 2 hours, and subsequently calcined at 450 C. for 2 hours. The loading of the catalyst, in mass % on a dry weight basis, was 5.0% Ni and 21.0% W. (Denoted A)

Example 2

Preparation of a Catalyst According to the Invention

(3) 32.63 g MoO.sub.3, 6.52 g NiO, 60 g H.sub.2O and 12.18 g H.sub.3PO.sub.4 (85%) were combined and boiled for approximately 45 min. until a clear green solution was obtained. After cooling, 25.0 g gluconic acid solution (50% in H2O) was added to give a bluish dark green solution, which was briefly boiled leading to further color change to greenish dark blue. Resulting total mass of the solution was 105.7 g. One fifth of this solution (21.4 g) was diluted to the required volume (24.3 g, 15.6 ml) and used to impregnate 20.0 g of an amorphous silica-alumina carrier. The catalyst was subsequently dried at 70 C., in a vacuum stove. The loading of the catalyst, in mass % on a dry weight basis, was 3.5% Ni, 15.0% Mo, 2.2% P, and 8.53% gluconic acid. (Denoted B,)

Example 3

Preparation of a Catalyst According to the Invention

(4) 16.2 g MoO.sub.3, 3.25 g NiO, 30.0 g H.sub.2O and 5.94 g H.sub.3PO.sub.4 (85%) were combined and boiled for approximately 45 min., allowing some evaporation of water, until a clear green solution was obtained, with a total mass of 46.5 g. This was allowed to cool and split in two equal portions of 23.25 g. To one of the portions was added 3.13 g sucrose to give a bluish dark green solution, which was briefly boiled leading to further color change to dark blue. This solution was diluted to the required volume (29.0 g, 19.0 ml) and used to impregnate 25.0 g of an amorphous silica-alumina carrier. The catalyst was subsequently cooled in an IPA/CO.sub.2 bath and freeze dried overnight. The loading of the catalyst, in mass % on a dry weight basis, was 3.5% Ni, 15.0% Mo, 2.2% P, and 8.53% sucrose. (Denoted C)

Example 4

Testing of the Catalysts

(5) The catalysts A-C were tested for the hydrocracking, hydrodesulfurization and hydrodenitrogenation activity in a first stage hydrocracking simulation test using a heavy gasoil feedstock having the properties shown in the following Table:

(6) TABLE-US-00001 Feedstock Properties Density at 15/4 C., g/ml 0.9198 Density at 70/4 C., g/ml 0.8856 Kin. viscosity at 100 C., cSt 6.995 Carbon content, % w 85.28 Hydrogen content, % w 12.07 Sulphur content, % w 2.65 Total nitrogen content, ppmw 780 Aromatics content % w 15.1 Initial boiling point C. 281 10% w boiling point C. 369 50% w boiling point C. 441 90% w boiling point C. 516 Final boiling point C. 580 Fraction boiling below 370 C. % w 10.3 Fraction boiling above 540 C. % w 3.6

(7) The testing was carried out in once-through microflow equipment loaded with a catalyst bed comprising a top bed of 15 ml Criterion DN-3300 catalyst, 1.3 mm trilobes, diluted with an equal volume of 0.05 mm silicon carbide particles, and a bottom bed of 5 ml of the catalyst under scrutiny, also diluted with an equal volume of 0.05 mm silicon carbide particles.

(8) Prior to the testing, the catalyst was liquid-phase presulfided using a gasoil feed and a mixture of hydrogen and hydrogen sulfide at a pressure of 112 bar and with a temperature profile rising from ambient (22 C.) to a final temperature of 345 C.

(9) To measure hydrocracking, hydrodesulfurization and hydrodenitrogenation activity, the heavy gas oil feedstock was contacted with the catalyst bed in a once-through operation at a weight hourly space velocity of 1.36 kg heavy gasoil per litre catalyst per hour (kg/l/h); a hydrogen gas/heavy gasoil ratio of 900 Nl/kg; and a total pressure of 112 bar (11.2 MPa). Hydrocracking performance was assessed in terms of the conversion of feedstock components having a boiling point of 370 C. or above to material boiling at less than 370 C., by analyzing product obtained at a catalyst bed temperature of 380 C. and after 620 hours on stream.

(10) Hydrodesulfurization and hydrodenitrogenation performance was assessed on the same product, by measuring residual sulfur and nitrogen levels, respectively. From the results, shown in the following Table, it can be seen that catalysts B and C are significantly more active in hydrocracking, hydrodesulfurization and hydrodenitrogenation.

(11) TABLE-US-00002 Catalyst A B C Conversion of 370 C.+ (% w on feed, net) 17.84 19.74 19.32 Sulphur in liquid product (ppmw) 322 241 298 Nitrogen in liquid product (ppmw) 25 14 16

Example 5

Preparation of a Catalyst not According to the Invention

(12) 16.55 g MoO.sub.3, 3.27 g NiO, 25 g H.sub.2O and 6.02 g H.sub.3PO.sub.4 (85%) were combined and boiled for approximately 45 min. until a clear green solution was obtained. After cooling, total mass of the solution was determined to be 40.25 g. A 12.08 g portion of this solution was diluted to the required volume (13.2 ml) and used to impregnate 15.0 g of an amorphous silica-alumina carrier. The catalyst was subsequently dried at 70 C., in a vacuum stove. The loading of the catalyst, in mass % on a dry weight basis, was 3.5% Ni, 15.0% Mo and 2.2% P. (Denoted D)

Example 6

Dibenzothiophene Hydrodesulfurization Performance Test (DBT Test)

(13) Dibenzothiophene hydrodesulphurisation experiments were carried out in trickle flow, in a nanoflow reactor setup with six reactors. Each reactor was loaded with 385 mg of crushed and sieved catalyst particles (30-80 mesh), diluted with inert material to ensure proper hydrodynamic behaviour. Prior to testing, the catalysts were in situ presulfided with a mixture of hexadecane and 5.4 wt % of ditertiononylpentasulfide fed at 0.75 ml/min, in trickle flow with H.sub.2 at a flow rate of 250 ml/g feed, heated at 20 C./h to 280 C. then maintaining it for 5 h, next heating at 20 C./h to 340 C. and maintaining it for 2 h. The test feed was a mixture of 5 wt % dibenzothiophene (DBT), 1.75 wt % dodecane and the remainder hexadecane, fed at 0.75 ml/min, in trickle flow with H.sub.2 at a flow rate of 250 ml/g feed.

(14) Results are summarized in the following Table.

(15) TABLE-US-00003 DBT conversion (%) k.sub.DBT (g .Math. min/ml) Catalyst 230 C. 245 C. 260 C. 270 C. 230 C. 245 C. 260 C. 270 C. A 70.4 1.55 B 29.3 65.4 96.3 99.7 0.49 1.49 4.63 8.37 D 14.7 34.7 55.8 73.6 0.22 0.60 1.14 1.87

(16) The reaction constant for DBT conversion (k.sub.DBT) was calculated assuming first order reaction kinetics in DBT conversion. From the results it is clear that catalyst B is significantly more active in DBT hydrodesulfurization than both comparative catalysts A and D.