Method for preparing hydrocracking catalyst

Abstract

This invention discloses a preparation method of a hydrocracking catalyst. According to the method, a new functional group is modified through chemical bonds on the surface of a traditionally prepared inorganic carrier, and a VIB group metal element and a VIIIB metal element are then loaded on the carrier to prepare the hydrocracking catalyst. The hydrocracking catalyst prepared according to the invention has a higher diesel liquid yield.

Claims

1. A preparation method of a hydrocracking catalyst, comprising the following Steps: 1) mixing pseudo-boehmite, amorphous silica-alumina and a molecular sieve in a certain proportion, adding a certain amount of acid solution, kneading for 2-60 min, and then extruding and molding into strips; the strips are prepared by drying and calcining to obtain an inorganic carrier; 2) adding to the inorganic carrier obtained in Step 1) a modification reagent in an amount which is 0.5-20% of the weight of the inorganic carrier, and reacting at 10-120° C. to connect new functional groups on the surface of the inorganic carrier to obtain a surface-modified inorganic carrier; and 3) loading VIB metal elements and VIIIB metal elements on the surface-modified inorganic carrier, obtained in Step 2), by using an impregnation method, and then drying at 60-120° C. to obtain the hydrocracking catalyst.

2. The preparation method of a hydrocracking catalyst according to claim 1, wherein the weight ratio of the pseudo-boehmite, amorphous silica: alumina and molecular sieve used in Step 1) is (20-80):(20-60):(1-20).

3. The preparation method of a hydrocracking catalyst according to claim 1, wherein the amount of the acid solution used in Step 1) is 0.5-10% of the total weight of the pseudo-boehmite, the amorphous silica alumina and the molecular sieve, and the concentration of the acid solution is no more than 10 wt %; wherein the acid solution is an inorganic acid or an organic acid.

4. The preparation method of a hydrocracking catalyst according to claim 1, wherein the modification reagent in Step 2) contains two or more functional groups; one of the functional group needs to be able to react with the surface of the inorganic carrier, and the other functional group needs to be able to react with oxides or salts containing VIB metal elements or VIIB metal elements.

5. The preparation method of a hydrocracking catalyst according to claim 4, wherein the functional group which is able to react with the surface of the inorganic carrier includes any one of a hydroxyl group, a carboxyl group, anhydride, an amino group, a halogen substituent, a siloxy group, a phosphate group, a metaphosphate group, and a phosphite group.

6. The preparation method of a hydrocracking catalyst according to claim 4, wherein the functional group which is able to react with oxides or salts containing VIB metal elements or VIIB metal elements include any one of a hydroxyl group, a carboxyl group, an amino group, a sulfhydryl group, an amide group, and a halogen substituent.

7. The preparation method of a hydrocracking catalyst according to claim 1, wherein in Step 3), the loading amount of the VIB metal element on the surface-modified inorganic carrier is 5-30 wt %, and the loading amount of the VIIIB metal element on the surface-modified inorganic carrier is 1-15 wt %.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) In order to make the content of the invention more understandable, the technical solution of the invention is further described below in conjunction with specific embodiments, but the invention is not limited thereto.

(2) The molecular sieve used is an ultra-stable Y molecular sieve raw material with a Si/Al ratio (molar ratio) of 30, a unit cell size of 24.31, and a framework Al/non-framework Al ratio (.sup.27Al NMR method) of 3.6.

(3) The pseudo-boehmite used has a specific surface area (BET method) of 234 m.sup.2/g, the average pore diameter (BJH method) of 6.7 nm, the single-point adsorption pore volume of 0.65 cc/g, and the Na.sub.2O content (weight percentage) of less than 0.1%.

(4) The amorphous silica aluminum cased has the silicon content of 40% and the single point adsorption pore volume (BET) of 1.56 cc/g.

EXAMPLE 1

(5) 220 g of pseudo-boehmite (dry basis, all raw materials below are on dry basis unless otherwise specified), 160 g of amorphous silica alumina and 20 g of molecular sieve were weighed, these three solid powders were then mixed thoroughly, a pre-prepared dilute nitric acid solution (6.6 g, 67 wt % concentrated nitric acid diluted with 400 g deionized water) was added to the mixed powder, the resulting mixture was kneaded vigorously for 15 min and extruded into strips through a 2.5 mm perforated plate, and the stripes were dried at 120° C. for 8 h and then calcined in the 500° C. air atmosphere for 4 h to obtain an inorganic carrier Z0.

EXAMPLE 2

(6) 7.2 g of 3-phosphonopropionic acid was weighed and added to 70 mL of 95% ethanol solution, and the resulting solution was stirred at room temperature for 20 min so that the 3-phosphonopropionic acid was fully dissolved. Then, 40 g of the carrier Z0 prepared in Example 1 was added to the above solution, and the solution was rested to react at room temperature for 12 h, and then heated to 70° C. to react for 3 h. After the reaction, the excess ethanol solution was poured out, the obtained solid particles were rinsed 3 times with 40 mL of absolute ethanol at room temperature, and then pre-dried at 70° C. for 1 h in an air atmosphere, and then fully dried in a vacuum drying oven at 70° C. to obtain a surface-modified carrier Z1.

EXAMPLE 3

(7) 6.4 g of 3-aminopropane-1-phosphoric acid was weighed and added to 70 mL of 95% ethanol solution, and the resulting solution was stirred at room temperature for 20 min so that the 3-aminopropane-1-phosphoric acid was fully dissolved. Then, 40 g of the carrier Z0 prepared in Example 1 was added to the above solution; the reaction vessel was purged with nitrogen and the nitrogen atmosphere was maintained at a slight positive pressure; the solution was rested to react at room temperature for 12 h, and then heated to 60° C. to further react for 3 h. After the reaction, the excess ethanol solution was poured out, the obtained solid particles were rinsed 3 times with 40 mL of absolute ethanol at room temperature, and then pre-dried at room temperature for 4 h in an air atmosphere, and then fully dried in a vacuum drying oven at 70° C. to obtain a surface-modified carrier Z2.

EXAMPLE 4

(8) 5.5 g of 3-mercaptopropyl triethoxysilane was weighed and added to 80 mL of 95% ethanol solution, and the resulting solution was stirred at room temperature for 20 min so that the 3-mercaptopropyl triethoxysilane was fully dissolved. Then, 40 g of the carrier Z0 prepared in Example 1 was added to the above solution, and the solution was rested to react at room temperature for 8 h, and then heated to 80° C. to react for 4 h. After the reaction, the excess ethanol solution was poured out, the obtained solid particles were rinsed 3 times with 40 mL of absolute ethanol at room temperature, and then pre-dried at 70° C. for 1 h in an air atmosphere, and then fully dried in a vacuum drying oven at 70° C. to obtain a surface-modified carrier Z3.

EXAMPLE 5

(9) 5.4 g of 3-aminopropyltriethoxysilane was weighed and added to 80 mL of 95% ethanol solution, and the resulting solution was stirred at room temperature for 20 min so that the 3-aminopropane-1-phosphoric acid was fully dissolved. Then, 40 g of the carrier Z0 prepared in Example 1 was added to the above solution; the reaction vessel was purged with nitrogen and the nitrogen atmosphere was maintained at a slight positive pressure; the solution was rested to react at room temperature for 8 h, and then heated to 60° C. to further react for 4 h. After the reaction, the excess ethanol solution was poured out, the obtained solid particles were rinsed 3 times with 40 mL of absolute ethanol at room temperature, and then pre-dried at room temperature for 4 h in an air atmosphere, and then fully dried in a vacuum drying oven at 70° C. to obtain a surface-modified carrier Z4.

(10) The properties of the carriers obtained in Examples 1-5 are shown in Table 1.

(11) TABLE-US-00001 TABLE 1 The properties of the carriers obtained in Examples 1-5 Specific surface area Individual adsorption Average adsorption Surface functional of carrier pore volume pore size Carrier group of carrie (m.sup.2/g) (cc/g) (nm) Z0 —OH 395.2 0.771 7.39 Z1 —COOH 374.3 0.646 6.30 Z2 —NH.sub.2 365.7 0.679 6.54 Z3 —SH 372.4 0.663 6.38 Z4 —NH.sub.2 360.5 0.657 6.39

EXAMPLE 6: PREPARATION OF HYDROCRACKING CATALYST

(12) The carriers prepared in Examples 1-5 were fully dried and sampled to test their water absorption. Then, the carriers were respectively impregnated in the mixed aqueous solution of ammonium metatungstate and nickel nitrate in equal volume so that the carriers were loaded with 18% of W and 5.4% of Ni (theoretical weight), and then dried and calcined in an air atmosphere at 500° C. for 4 h. The resulting catalysts were denoted as C0, C1, C2, C3, and C4, respectively.

EXAMPLE 7: HYDROCRACKING REACTION OF WAX OIL

(13) The hydrocracking cycle oil was used as the wax oil raw material, and its density was 0.923 g/ml. In the raw material, the nitrogen content was 2.1 ppmw and the sulfur content was 23 ppmw. Its distillation range distribution is shown in Table 2.

(14) TABLE-US-00002 TABLE 2 Distillation range distribution Distillation range distribution Weight percentage, wt % IBP-170° C. 0 170-280° C. 2.3 280-371° C. 12.3 371-500° C. 78.3 >500° C. 7.1

(15) The hydrocracking unit adopted a one-pass hydrogenation process, and the unit was mainly composed of gas feed, liquid feed, hydrogenation reaction, gas-liquid separation and product collection. The unit was equipped with a single reactor filled with a hydrocracking catalyst and adopted a 5-stage electric furnace for heating. The reaction effluent entered a high-pressure separator and a low-pressure separator tank for gas-liquid separation. The high-fraction hydrogen-rich gas was separated by the separation tank, and the water cooling for the jacket and corresponding technical measures were adopted to allow the ammonium salt to crystallize and settle, thus preventing the downstream pipelines and equipment from being blocked. The low-pressure tail gas after the pressure control valve was measured with a gas flow meter and its composition was analyzed by online chromatography. The distillation range of the liquid product was analyzed offline.

(16) The hydrocracking reaction was carried out under the hydrogen pressure of 15 MPa with the hydrogen flow rate of 832 mL.Math.min.sup.−1 and the raw material feed rate of 70 mL.Math.h.sup.−1, wherein the hydrocracking catalyst was filled in 14 cm.sup.−3 and diluted with quartz sand to 4 times of the original volume. The test results of the prepared catalysts are shown in Table 3.

(17) TABLE-US-00003 TABLE 3 Test results of catalysts he nature and performance of the catalyst: C0 C1 C2 C3 C4 Before metal loading Carrier Z0 Z1 Z2 Z3 Z4 Surface functional —OH —COOH —NH.sub.2 —SH —NH.sub.2 After metal impregnation W, wt % 17.8 17.6 18.1 18.0 17.5 Ni, wt % 5.4 5.7 5.4 5.2 5.6 Specific suface area 252.8 249.6 258.7 247.3 247.0 m.sup.2/g Catalyst activity, (when 372 369 370 371 371 the conversion rate of the component reaches 65% at 371° C. or above) Product selectivity, (when the conversion rate of the component reaches 65% at 371° C. or above) Gaseous product  2.9%  3.2%  3.1%  2.4% 2.3% (C1-C4) Naphtha 32.4% 32.3% 32.2% 29.9% 29.6 (C5-170° C.) Diesel 64.7% 64.5% 64.7% 66.7% 68.1 (170-371° C.)

(18) The results show that, compared with the catalyst C0 prepared from the inorganic carrier Z0, the catalysts C1 and C2 obtained by replacing the surface functional groups of the inorganic carrier Z0 with carboxyl and amino groups are increased in the reaction activity by 2-3° C., but do not change significantly in the product selectivity. This is because although the performance of the metal center is improved after the functional group is replaced, the P element is introduced into the catalyst carrier and enhances the acidity of the carrier, thus improving the cracking performance of the catalyst. Therefore, the overall performance of the catalyst is improved in catalyst activity while maintaining the selectivity of various products.

(19) The catalyst activity of the catalysts C3 and C4 prepared by introducing mercapto and amino groups into the surface of the inorganic carrier Z0 by organosiloxane is slightly improved, but the product selectivity has changed significantly. Among them, the selectivity of the gaseous product and naphtha product of the catalyst C3 is decreased by 2%, and the corresponding diesel selectivity is increased by 2%; similar phenomena are also observed in the hydrocracking reaction using the catalyst C4, but the diesel yield is increased more significantly, reaching 3.4%. The reason is that different functional groups are introduced into the carriers of the catalysts C3 and C4 through organosiloxane, which significantly improves the metal performance. However, the introduction of Si element does not enhance the acidity of the carrier as much as P element, so the overall performance of the catalyst is slightly improved. But diesel selectivity has increased significantly.

(20) The above experiments prove that the introduction of new functional groups through the modification of the carrier surface weakens the strong interaction between the transition metal and the carrier surface, and does help the sulfidation of the transition metal to improve the hydrogenation/dehydrogenation performance of the metal center.

(21) The above description is only the preferred embodiments of the invention, and all equivalent changes and modifications made within the scope of the patent application of the invention should fall within the scope of the invention.