CN109304205B

CN109304205B - Catalytic cracking catalyst for improving coke selectivity and preparation method thereof

Info

Publication number: CN109304205B
Application number: CN201710630437.7A
Authority: CN
Inventors: 高雄厚; 潘志爽; 袁程远; 张海涛; 谭争国; 张忠东; 李雪礼; 段宏昌; 黄校亮; 黄世英; 郑云锋; 孙书红; 陈军
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2017-07-28
Filing date: 2017-07-28
Publication date: 2021-11-02
Anticipated expiration: 2037-07-28
Also published as: CN109304205A

Abstract

The invention provides a catalytic cracking catalyst for improving coke selectivity and a preparation method thereof, wherein the catalyst comprises 15-70wt% of molecular sieve, 15-60wt% of clay, 8-30wt% of pseudoboehmite, 3-20wt% of binder, 0.01-10wt% of phosphorus (calculated by P) and 0.01-5wt% of magnesium (calculated by Mg). The preparation method comprises the following steps: mixing and pulping the molecular sieve, the pore-expanding agent, the clay, the pseudo-boehmite, the phosphorus-containing compound and the binder, and performing spray forming; roasting the formed catalyst microspheres, mixing with a magnesium-containing compound, ammonium salt and water, pulping, adjusting the pH value, heating, stirring, filtering and drying to obtain the catalytic cracking catalyst. The catalyst prepared by the method has more excellent coke selectivity under the conditions of improved conversion rate and reduced heavy oil.

Description

Catalytic cracking catalyst for improving coke selectivity and preparation method thereof

Technical Field

The invention relates to a catalytic cracking catalyst and a preparation method thereof, in particular to a catalytic cracking catalyst for improving coke selectivity and a preparation method thereof.

Background

The Fluid Catalytic Cracking (FCC) technology is an important means for secondary processing of heavy oil due to relatively low investment, strong raw material adaptability and simple operation. With the gradual depletion of high-quality and light crude oil resources and the improvement of coking production capacity in the world, oil refining enterprises blend a large proportion of inferior crude oil, such as residual oil, coking wax oil, deasphalted oil and the like, in a catalytic cracking device for potential excavation and synergism. Due to poor cracking performance of the poor-quality raw oil, the carbon deposit amount on the FCC catalyst is increased, coke is adsorbed on the acid center of the catalyst and is not easy to desorb, and the heavy oil conversion capability and the product distribution of the catalyst are seriously influenced.

High heavy oil conversion and low coke yield are always the goals of catalytic cracker production for the petroleum refining industry. Catalytic cracking catalysts have been adapted to the above-mentioned objectives by modifying the properties of the matrix and molecular sieve.

Patent CN1436835A discloses a catalytic cracking catalyst and a preparation method thereof, wherein the catalyst contains 5-60% of mesoporous alumina, 5-60% of zeolite, 5-40% of binder and 5-85% of clay, the average pore diameter of the mesoporous alumina is not less than 3 nm, and the preparation method of the catalytic cracking catalyst is that the zeolite, the mesoporous alumina, the binder and the clay are uniformly mixed, and then the catalyst is obtained through spraying, roasting, washing and drying. Compared with the conventional catalyst, the heavy oil conversion capability of the catalyst is enhanced, and the selectivity of gasoline and coke is obviously improved.

Patent CN106179458A provides a catalytic cracking catalyst, wherein the catalytic cracking catalyst contains 1-60% of cracking active component, 1-50% of mesoporous active material, 1-70% of clay and 1-70% of binder, based on the total weight of the catalytic cracking catalyst, and the mesoporous active material has a pseudo-boehmite crystal phase structure. The invention increases the content of mesopores in the catalytic cracking catalyst by matching the specific cracking active component, the specific mesoporous active material, the clay and the binder, and is beneficial to the diffusion and cracking of heavy oil macromolecules.

Patent CN101767029A discloses a heavy oil cracking catalyst and its application, said catalyst contains Y-type zeolite and modified rectorite, and its preparation method includes: mixing rectorite, an auxiliary agent, water and acid to obtain modified rectorite, then mixing the modified rectorite with Y-type zeolite, pulping, and spray-drying to obtain a catalyst; the auxiliary agent is selected from one or more of La, Co, Zn, Cu and Ti compounds, and the Y-type zeolite comprises modified ultrastable Y-type zeolite with the silicon-aluminum ratio of 6-15, the unit cell constant of 2.440-2.458nm and the proportion of the pore volume of secondary pores with the pore diameter of 80-1000 angstrom in the zeolite to the total secondary pore volume of 30-60%. The catalyst has strong heavy oil conversion capability and good coke selectivity.

In the composition of the FCC catalyst, the Y-type molecular sieve has a decisive influence on the comprehensive reaction performance of the catalyst, so that the modification of the Y-type molecular sieve is one of the most effective means for improving the reaction performance of the catalytic cracking catalyst. In recent years, the acidity of the molecular sieve is regulated and controlled at home and abroad to control the cracking reaction, reduce the condensation reaction of coke precursors and improve the coke selectivity of the catalyst.

EP 39183 pre-exchange NaY molecular sieves with ammonium sulfate to Na in zeolites₂O is 1-5wt%, and then mixed with phosphorus-containing compound, dried and roasted to prepare the phosphorus-containing ultrastable Y-type molecular sieve, so that the cracking activity and gasoline selectivity of the catalyst are improved.

CN1279130A discloses a method for preparing a phosphorus-modified ultrastable Y-type molecular sieve, which comprises the following steps of adding 0.5-5% of phosphorus and 0.5-6% of Na in percentage by weight of oxides₂O, P-NH having a cell constant of 2.460 to 2.475nm₄NaY molecular sieve is put in a roasting furnace in 100 percent steam gasCarrying out hydrothermal roasting for 0.5-4 hours at 450-700 ℃ under an atmosphere; carrying out liquid-phase aluminum extraction and silicon supplement reaction on the roasted product; then filtered and washed. The cracking catalyst containing the molecular sieve has high light oil yield, low coke yield and high heavy oil conversion capacity when being used for hydrocarbon cracking reaction.

CN103506153A discloses a catalytic cracking catalyst for reducing coke yield and producing gasoline, which comprises 10-50% of modified Y-type molecular sieve, no more than 30% of specific Y-type molecular sieve containing rare earth, 10-70% of clay and 10-40% of inorganic oxide binder calculated by oxide on a dry basis; the unit cell constant of the modified Y-type molecular sieve is 2.420-2440nm, and in weight percentage, P is 0.05-6%, RE2O3 is 0.03-10%, alumina is less than 22%, and the concentration of a specific hydroxyl nest is less than 0.35 mmol/g. The catalytic cracking catalyst provided by the invention can reduce green coke and improve the utilization rate of heavy oil.

CN1624079A discloses a hydrocarbon cracking catalyst containing modified faujasite, wherein the modification method of zeolite is that firstly, the faujasite, a phosphorus compound and an ammonium compound are subjected to exchange reaction, the weight ratio of water to zeolite is 2-25, the pH value is 2.0-6.5, the temperature is 10-150 ℃, the exchange time is 0.l-4 hours, then, a rare earth solution is introduced into the exchange slurry, the reaction time is 1-60 minutes, the reaction is further carried out, and the catalyst is obtained by filtering and washing, roasting the phosphorus and rare earth modified zeolite for 0.l-3.5 hours at 250-800 ℃ under water vapor of l-100%. The modified zeolite prepared by the modification method has a unit cell constant of 2.440-2.465 nm, sodium oxide of 2.0-6.5 wt%, phosphorus content of 0.01-3 wt% and rare earth oxide of 0.1-15 wt%. The catalyst containing the molecular sieve has good activity stability, low coke yield, and strong heavy oil cracking capability and heavy metal pollution resistance.

CN101537366A reports a modified molecular sieve capable of improving coking performance, which is characterized in that the molecular sieve is obtained by a preparation method of a NaY molecular sieve through twice roasting, (1) the NaY molecular sieve is treated by phosphorus-containing ammonium solution exchange, and the treatment conditions are as follows: the temperature of the system is 40-100 ℃, the solution treatment time is 0.5-3 hours, the pH is 3.0-6.0, the weight ratio of the phosphorus-containing exchange solution to the molecular sieve is 3-20, and the weight ratio of P/molecular sieve is 0.05-6.0%Filtering and washing after exchanging; (2) carrying out hydrothermal treatment at the temperature of 450-750 ℃ and roasting for 0.5-4 hours under 1-100% of water vapor; (3) with elements containing RE³⁺The ammonium solution exchange treatment of the sample after the first roasting is carried out, and the treatment conditions are as follows: the temperature of the system is 40-100 ℃, the solution treatment time is 0.5-3 hours, the pH value is 3.0-8.5, and the RE is contained³⁺The weight ratio of the exchange solution to the molecular sieve is 3-20, and RE is₂O₃The weight ratio of the molecular sieve/the molecular sieve is preferably 0.05-6.5%, and the mixture is filtered and washed after exchange; (4) and performing the second hydrothermal treatment under the same conditions as the conditions (2) in the first hydrothermal treatment. The molecular sieve has larger mesopore volume and larger macropore volume and good stability, and the heavy oil cracking capability is further improved while the coke yield of the catalyst is reduced.

CN102019195A discloses a catalytic cracking catalyst containing a modified Y molecular sieve, which contains 2-45 wt% of the modified Y molecular sieve, wherein the modified Y molecular sieve is obtained by carrying out exchange reaction on a Y-type molecular sieve and a rare earth solution, the weight ratio of water to the molecular sieve is 2-30, the pH value is 2.5-7.0, the temperature is 0-100 ℃, the exchange time is 0.1-3.5 hours, then a precursor of phosphorus is introduced into the exchange slurry, the reaction time is 1-70 minutes, and after filtering and washing, a filter cake is roasted for 0.5-6 hours at 180-650 ℃ under 5-100% of water vapor; the molecular sieve has a unit cell constant of 2.450-2.479 nm, sodium oxide of 2.0-6.0 wt%, phosphorus of 0.01-2.5 wt%, and rare earth oxide of 11-23 wt%. The catalyst containing the modified molecular sieve has strong heavy oil conversion capability and good coke selectivity.

Patent CN101284243A discloses a cracking catalyst comprising a rare earth ultrastable Y-type molecular sieve and a matrix, said matrix comprising a silica binder, said rare earth ultrastable Y-type molecular sieve being obtained by a process comprising the steps of: mixing the ultrastable Y-type zeolite and acid solution with equivalent concentration of 0.01N-2N according to the liquid-solid weight ratio of 4-20 at the temperature of 20-100 ℃, stirring for 10-300 min, washing, filtering, adding rare earth salt solution for rare earth ion exchange, washing, filtering and drying after exchange. The catalyst of the invention is used for heavy oil catalytic cracking, and has high conversion rate, high gasoline yield and low coke yield.

It can be seen from the above patents that the heavy oil conversion capability and coke selectivity of the catalyst can be improved by increasing the proportion of mesopores and macropores of the matrix material and increasing the diffusion rate of oil gas molecules, but the improvement range is limited; the modification of the molecular sieve is to introduce a single phosphorus element or a single magnesium element for modification. When the molecular sieve is modified by phosphorus-containing solution, phosphate is hydrolyzed to generate phosphoric acid, and the phosphoric acid cannot enter the small holes of the molecular sieve to react with the strong acid center in the pore channel due to the influence of the size and the space configuration of the phosphoric acid molecule [ Shenshihong, Panhuiwang, Xuchunsheng and the like ]. 86-99 ], the coke selectivity of the acid centers in the channels cannot be improved; the magnesium ions have small radius and can migrate into the pores of the molecular sieve. However, due to the diffusion resistance of the pore channels, the magnesium ions inevitably cover the outer surface of the molecular sieve and the acid centers in the large pore channels in the process of migrating to the pore channels, so that the acid content of the molecular sieve is reduced, and finally the heavy oil conversion capability is lost. Thus, the above patents do not address the contradiction between small pore coke selectivity and heavy oil conversion simultaneously.

Disclosure of Invention

The invention aims to provide a catalytic cracking catalyst with low coke yield and strong heavy oil conversion capability and a preparation method thereof.

The invention provides a preparation method of a catalytic cracking catalyst for improving coke selectivity, which comprises the steps of mixing and pulping a molecular sieve, a pore-expanding agent, clay, pseudo-boehmite, a phosphorus-containing compound and a binder, wherein the addition amount of the pore-expanding agent accounts for 0.1-2% of catalyst slurry (dry basis), and the addition amount (calculated by P) of the phosphorus-containing compound accounts for 0.01-10% of the catalyst slurry (dry basis), and carrying out spray forming; roasting the formed catalyst microspheres at the temperature of 300-600 ℃ for 60-180min, mixing the catalyst microsphere particles, a magnesium-containing compound, an ammonium salt and water, pulping, and adding the magnesium-containing compound (calculated by Mg) in a weight ratio: catalyst particles (dry basis): ammonium salt: deionized water 0.001-0.05: 1: 0.01-0.1: 2-5, adjusting the pH value to 2.5-5.5, heating to 50-110 ℃, and stirring for 15-60 min; filtering and drying to obtain the catalytic cracking catalyst.

The molecular sieve is one or more of NaY, NaX modified molecular sieves, such as REY, REX, REHY, USY and REUSY, and various Y-type molecular sieves, X-type molecular sieves, ZSM-type molecular sieves and beta molecular sieves with high silica-alumina ratio.

The pore-expanding agent is one or more of activated carbon, carbon nano tubes, starch, cane sugar, flour, polyethylene glycol and polystyrene, and preferably the activated carbon and the polystyrene.

The clay of the invention is various clays which can be used as catalyst components, such as kaolin, bentonite, sepiolite, halloysite, montmorillonite and the like.

The pseudoboehmite of the invention can be one of boehmite, gibbsite and bayer stone or the combination thereof, and is preferably boehmite.

The phosphorus-containing compound is selected from one or more of orthophosphoric acid, phosphorous acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, aluminum phosphate and pyrophosphoric acid.

The binder is one or a mixture of silicon-aluminum gel, silicon-aluminum composite sol, aluminum sol, basic aluminum chloride and silica sol.

In the method provided by the invention, in the preparation step of the catalyst microsphere particles, rare earth can be added into the mixed pulping slurry to improve the reaction performance.

The rare earth is selected from one or the combination of La, Ce, Pr and Nd.

The magnesium-containing compound is selected from one or more of magnesium chloride, magnesium nitrate, magnesium hydroxychloride and magnesium sulfate, and preferably magnesium chloride.

In the method provided by the invention, the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium oxalate and ammonium phosphate.

The methods provided by the present invention can be implemented by conventional methods, and specific methods thereof are described in detail in patents CN98117896.0, CN02103907.0 and CN200610112685.4, which are incorporated herein by reference.

The invention provides a catalytic cracking catalyst for improving coke selectivity, which comprises a molecular sieve, clay, pseudo-boehmite, a phosphorus-containing compound, a magnesium-containing compound and a binder. The catalyst comprises 15-70wt% of molecular sieve, 15-60wt% of clay, 8-30wt% of pseudo-boehmite, 3-20wt% of binder, 0.01-10wt% of phosphorus-containing compound (calculated as P) and 0.01-5wt% of magnesium-containing compound (calculated as Mg) based on the mass of a dry base of the catalyst. The catalyst may also contain 0-8wt% of a rare earth metal oxide.

According to the invention, the pore-expanding agent is introduced in the catalyst pulping process, so that the pore channel structure of the catalyst is favorably improved, meanwhile, the phosphorus-containing compound is added into the catalyst slurry, and the phosphorus-containing compound is firstly used for reacting with the molecular sieve in the slurry and the strong acid center on the surface of the active matrix, so that the acid strength of the catalyst is weakened, the number of the weak acid centers is increased, the contact probability of oil gas molecules and the acid centers on the surface of the catalyst is improved, the catalytic activity of the outer surface of the catalyst is improved, the acid strength of the outer surface is weakened, the adsorption capacity of the acid centers on the surface of the catalyst on the oil gas molecules is reduced, the secondary reaction is inhibited, and the formation of coke is reduced; then adding a magnesium compound for modification in the water washing process, wherein the strong acid on the outer surface of the catalyst and in the large pore channel is weakened by phosphorus, so that the adsorption effect on magnesium is weakened, the diffusion of magnesium ions is accelerated, the magnesium ions are easier to migrate into the small pores of the catalyst to modulate the strong acid centers of the magnesium ions, the contact probability of oil gas molecules outside the pores and the acid centers in the pore channels, which are influenced by the strong adsorption of the oil gas molecules in the pore channels of the catalyst, is reduced, the catalytic activity in the pore channels of the catalyst is improved, and the utilization rate of the active centers in the pore channels of the catalyst is improved; by the synergistic action of phosphorus and magnesium, acid centers inside and outside the pore channels of the catalyst can be fully utilized, and the catalytic activity and coke selectivity of the catalyst are obviously improved.

Detailed Description

The following examples further illustrate the features of the present invention, but the scope of the present invention is not limited by these examples.

Evaluation methods used in (A) examples

Evaluation of catalytic cracking reaction selectivity: the catalyst cracking reaction selectivity evaluation was performed in a small Fixed Fluidized Bed (FFB) unit. The catalyst is treated for 10 hours at 800 ℃ under the condition of 100 percent of water vapor in advance. The reaction raw material is raw oil of a Lanzhou petrochemical catalytic device, the specific properties are shown in table 1, the reaction temperature is 500-535 ℃, and the airspeed is 12-15 h^-1The solvent-oil ratio is 5.

TABLE 1 Properties of the stock oils

(II) production area and specification of raw materials used in examples

Kaolin: china kaolin company, kaolinite 86 wt%.

Halloysite: guangxi Nanning Sizheng mining Co., Ltd., halloysite 95 wt%.

Aluminum sol: catalyst works of Lanzhou petrochemical Co., Ltd., Al₂O₃The content was 24.56% by weight, and the Al/Cl molar ratio was 1.24.

USY zeolite, REHY zeolite, REY zeolite, DASY, ZSM-5 and all-clay catalysts are all produced by Lanzhou petrochemical company catalyst factories.

The balancing agent was obtained from a refinery of petrochemical company, Lanzhou.

Pseudo-boehmite: 75.4 wt% of alumina, produced by Shandong alumina works.

Hydrochloric acid and nitric acid: and (4) industrial products.

Ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium carbonate, ammonium bicarbonate, ammonia water: and (4) industrial products.

Silica sol: SiO produced by the institute of chemical and physical university of Chinese academy of sciences₂The content was 27.0 wt%, and the pH was adjusted to 2.5 with hydrochloric acid.

Diammonium hydrogen phosphate, magnesium chloride, ammonium phosphate, magnesium nitrate, phosphoric acid, magnesium sulfate, activated carbon, polystyrene: pure analysis, and is produced in Beijing chemical plants.

Example 1

Preparing catalyst microspheres: 660g of pseudo-boehmite, 991g of kaolin, 216g of alumina sol, 990g of USY molecular sieve, 2431g of deionized water, 2.1 g of activated carbon and 3g of diammonium hydrogen phosphate (calculated by phosphorus) are homogenized and spray-molded to prepare the catalyst microsphere CB-1.

307 g of catalyst microsphere CB-1 is roasted at 450 ℃ for 90 minutes, is pulped by 1516 g of deionized water, is added with 2.1 g of magnesium chloride (calculated by magnesium) and 10g of ammonium chloride for mixing and pulping, is adjusted to have a pH value of 3.9, is heated to 85 ℃, is stirred for 40 minutes, is filtered and is dried for 45 minutes at 120 ℃ to obtain the patent catalyst C1.

Example 2

Preparing catalyst microspheres: 0.3 g of phosphoric acid (calculated by phosphorus), 570g of pseudo-boehmite, 503g of kaolin, 225g of alumina sol, 810g of gREY molecular sieve, 80g of ZSM-5, 28g of polystyrene, 5175g of deionized water and 67mL of hydrochloric acid are mixed, homogenized and spray-molded to prepare the catalyst microsphere CB-2.

307 g of catalyst microsphere CB-2 is roasted at 600 ℃ for 60 minutes, is pulped by 620 g of deionized water, is added with 15 g of magnesium nitrate (calculated by magnesium) and 3g of ammonium nitrate for mixing and pulping, is adjusted to have a pH value of 2.5, is heated to 55 ℃, is stirred for 60 minutes, is filtered and is dried for 60 minutes at 80 ℃, and the patent catalyst C2 is obtained.

Example 3

Preparing catalyst microspheres: 1095g of pseudo-boehmite, 728g of kaolin, 1.5 g of ammonium phosphate (calculated by phosphorus), 300 g of phosphoric acid (calculated by phosphorus), 365g of halloysite, 1082g of alumina sol, 26 g of polystyrene, 353g of a Zey molecular sieve, 358g of a gREY molecular sieve, 352g of a DASY molecular sieve, 31g of ZSM-5 and 5375g of deionized water are mixed, homogenized and spray-molded to prepare the catalyst microsphere CB-3.

Roasting 303 g of catalyst microsphere CB-3 at 300 ℃ for 180 minutes, pulping with 1200 g of deionized water, adding 30g of ammonium chloride, 0.2 g of magnesium sulfate (calculated as magnesium) and 0.1 g of magnesium chloride (calculated as magnesium), mixing and pulping, adjusting the pH value to 3.4, heating to 110 ℃, stirring for 15 minutes, filtering, and drying at 150 ℃ for 30 minutes to obtain the patent catalyst C3.

Example 4

Preparing catalyst microspheres: 776g of pseudo-boehmite, 1368g of kaolin, 1005g of alumina sol, 89 g of ammonium phosphate (calculated by phosphorus), 275g of silica sol, 857g of DASY molecular sieve, 102mL of rare earth solution, 15 g of polystyrene, 2g of activated carbon, 4270g of deionized water and 71mL of hydrochloric acid are mixed, homogenized and spray-molded to prepare the catalyst microsphere CB-4.

303 g of catalyst microsphere CB-4 is taken and roasted at 500 ℃ for 70 minutes, after 1100 g of deionized water is used for pulping, 3g of magnesium sulfate (calculated by magnesium), 30g of ammonium chloride and 10g of ammonium sulfate are added for mixing and pulping, the pH value is adjusted to 5.5, the temperature is increased to 80 ℃, the stirring is carried out for 35 minutes, the filtration is carried out, and the drying is carried out at 95 ℃ for 45 minutes, thus obtaining the catalyst C4.

Comparative example 1

Prepared according to the method provided by patent CN 1436835A: 1056 g of mesoporous alumina, 898 g of rare earth ultrastable Y (dry basis), 872 g of kaolin, 560 g of halloysite, 976 g of alumina sol and 3257 g of deionized water are fully mixed, stirred for 2 hours, and then spray-dried and formed. The resulting microspheres were calcined at 450 ℃ for 0.5 hour. Removing 1000 g of roasted microspheres, adding 10 kg of deionized water and 0.225 kg of ammonium chloride, stirring and washing at 75 ℃ for 20 minutes, filtering, adding ammonium phosphate (to ensure that the phosphorus content of the catalyst is 1.0 percent by weight) and 10 kg of deionized water, stirring and washing at 75 ℃ for 10 minutes, filtering and drying to obtain the modified catalyst D1.

Comparative example 2

Preparing catalyst microspheres: 660g of pseudo-boehmite, 991g of kaolin, 216g of alumina sol, 990g of USY molecular sieve, 2431g of deionized water, 2.1 g of activated carbon, 3g of diammonium hydrogen phosphate (calculated as phosphorus) and 2.1 g of magnesium chloride (calculated as magnesium) are mixed, homogenized and spray-molded to prepare the catalyst microsphere DB-2.

307 g of catalyst microsphere DB-1 is roasted at 450 ℃ for 90 minutes, 1516 g of deionized water is used for pulping, 10g of ammonium chloride is added for mixing and pulping, the pH value is adjusted to 3.9, the temperature is raised to 85 ℃, the stirring is carried out for 40 minutes, the filtration is carried out, and the drying at 120 ℃ is carried out for 45 minutes to obtain the modified catalyst D2.

Comparative example 3

Preparing catalyst microspheres: 660g of pseudo-boehmite, 991g of kaolin, 216g of alumina sol, 990g of USY molecular sieve, 2431g of deionized water, 2.1 g of magnesium chloride (calculated by magnesium) and 2.1 g of activated carbon are mixed, homogenized and spray-molded to prepare the catalyst microsphere DB-3.

307 g of catalyst microsphere DB-3 is roasted at 450 ℃ for 90 minutes, is pulped by 1516 g of deionized water, is added with 3g of diammonium hydrogen phosphate (calculated by phosphorus) and 10g of ammonium chloride for mixing and pulping, is adjusted to have a pH value of 3.9, is heated to 85 ℃, is stirred for 40 minutes, is filtered and is dried for 45 minutes at 120 ℃, and the modified catalyst D3 is obtained.

Example 5

Preparing catalyst microspheres: 660g of pseudo-boehmite, 1467g of kaolin, 968g of aluminum sol, 11 g of ammonium phosphate (calculated by phosphorus), 7.7 g of polystyrene, 777g of DASY molecular sieve, 3g of activated carbon, 71mL of rare earth solution, 3500g of deionized water and 40mL of hydrochloric acid are mixed, homogenized and spray-molded to prepare the catalyst microsphere CB-5.

Roasting 303 g of catalyst microsphere CB-5 at 550 ℃ for 67 minutes, pulping with 877 g of deionized water, adding 21 g of magnesium sulfate (calculated as magnesium) and 11 g of ammonium nitrate, mixing and pulping, adjusting the pH value to 4.7, heating to 75 ℃, stirring for 55 minutes, filtering, and drying at 95 ℃ for 100 minutes to obtain the catalyst C5.

Example 6

Preparing catalyst microspheres: 1.1 g of phosphoric acid (calculated by phosphorus), 971g of pseudo-boehmite, 800g of kaolin, 350g of alumina sol, 16g of polystyrene, 932g of a molecular sieve, 4500g of deionized water and 19mL of hydrochloric acid are mixed, homogenized and spray-molded to prepare the catalyst microsphere CB-6.

307 g of catalyst microspheres CB-6 are roasted at 475 ℃ for 45 minutes, 1305 g of deionized water is used for pulping, 22 g of magnesium nitrate (calculated by magnesium) and 11 g of ammonium chloride are added for mixing and pulping, the pH value is adjusted to 3.7, the temperature is increased to 65 ℃, the stirring is carried out for 70 minutes, the filtration is carried out, and the drying is carried out at 75 ℃ for 80 minutes to obtain the patent catalyst C6.

The results of evaluating the reaction properties of the catalysts prepared in examples 1 to 6 and comparative examples 1 to 3 are shown in Table 2.

TABLE 2 catalyst fixed bed evaluation results

Catalyst and process for preparing same	C1	C2	C3	C4	C5	C6	D1	D2	D3
										Dry gas	3.48	3.55	3.46	3.33	3.43	3	3.51	3.49	3.33
Liquefied gas	13.7	13.84	13.53	14.77	13.87	13.26	13.73	13.86	12.4
										Gasoline (gasoline)	41.9	42.57	41.52	40.5	42.78	43.39	40	40.48	38.11
Diesel oil	28.79	27.88	29.15	29.07	27.88	29.23	29.19	29.11	27.03
										Heavy oil	4.98	4.93	5.31	5.52	4.87	4.46	5.84	6.02	12.11
Coke	7.15	7.23	7.03	6.81	7.17	6.66	7.73	7.04	7.02
										Conversion rate	66.23	67.19	65.54	65.41	67.25	66.31	64.97	64.87	60.86
Total liquid yield	84.39	84.29	84.2	84.34	84.53	85.88	82.92	83.45	77.54

From the fixed bed evaluation results, it is understood that the catalyst prepared by the method of the present invention has excellent heavy oil conversion ability and good coke selectivity. The catalysts of comparative examples D2 and D3, which were modified, had reduced heavy oil conversion ability due to the fact that when phosphorus and magnesium were introduced simultaneously or after magnesium was introduced first during the catalyst modification, magnesium ions had a small radius and low diffusion resistance and reacted preferentially with the acid sites of the catalyst to cover a portion of the acid sites, resulting in a decrease in the total acid content of the catalyst and a decrease in the cracking performance of the catalyst. The catalyst prepared by the method of the present invention has more excellent coke selectivity with increased conversion and decreased heavy oil, compared to the catalyst of comparative example 1 (D1).

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for preparing catalytic cracking catalyst for improving coke selectivity is characterized by comprising the steps of mixing and pulping a molecular sieve, a pore-expanding agent, clay, pseudo-boehmite, a phosphorus-containing compound and a binder, wherein the addition amount of the pore-expanding agent accounts for 0.1-2% of dry-based catalyst slurry, the addition amount of the phosphorus-containing compound accounts for 0.01-10% of the dry-based catalyst slurry by P, and performing spray forming; roasting the formed catalyst microspheres at the temperature of 300-600 ℃ for 60-180min, mixing and pulping the catalyst microsphere particles, the magnesium-containing compound, the ammonium salt and water, and adding the magnesium-containing compound in a weight ratio of Mg: dry-based catalyst particles: ammonium salt: deionized water =0.001-0.05: 1: 0.01-0.1: 2-5, adjusting the pH value to 2.5-5.5, heating to 50-110 ℃, and stirring for 15-60 min; filtering and drying to obtain the catalytic cracking catalyst.

2. The preparation method according to claim 1, wherein the molecular sieve is selected from one or more of REY, REX, REHY, USY, REUSY and various Y-type molecular sieves with high silica-alumina ratio, X-type molecular sieves, ZSM-type molecular sieves and beta-type molecular sieves.

3. The preparation method of claim 1, wherein the pore-expanding agent is one or more of activated carbon, carbon nanotubes, starch, sucrose, flour, polyethylene glycol and polystyrene.

4. The production method according to claim 1 or 3, wherein the pore-expanding agent is activated carbon and polystyrene.

5. The preparation method according to claim 1, wherein the clay is one or more of kaolin, bentonite, sepiolite, halloysite and montmorillonite.

6. The method of claim 1, wherein the pseudoboehmite is one of boehmite, bayerite, or a combination thereof.

7. The method according to claim 1 or 6, wherein the pseudoboehmite is boehmite.

8. The method according to claim 1, wherein the phosphorus-containing compound is one or more selected from orthophosphoric acid, phosphorous acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, aluminum phosphate and pyrophosphoric acid.

9. The preparation method according to claim 1, wherein the binder is one of a silicon-aluminum gel, a silicon-aluminum composite sol, an aluminum sol, basic aluminum chloride and a silicon sol or a mixture thereof.

10. The method according to claim 1, wherein in the step of preparing the catalyst microsphere particles, rare earth is added to the mixed and beaten slurry.

11. The method according to claim 10, wherein the rare earth is selected from one of La, Ce, Pr, Nd, or a combination thereof.

12. The preparation method according to claim 1, wherein the magnesium-containing compound is one or more selected from the group consisting of magnesium chloride, magnesium nitrate, magnesium hydroxychloride and magnesium sulfate.

13. The method according to claim 1 or 12, wherein the magnesium-containing compound is magnesium chloride.

14. The method according to claim 1, wherein the ammonium salt is one or more selected from the group consisting of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium oxalate and ammonium phosphate.

15. A catalytic cracking catalyst for improving coke selectivity prepared by the preparation method of claim 1, wherein the catalytic cracking catalyst comprises molecular sieve, clay, pseudoboehmite, a phosphorus-containing compound, a magnesium-containing compound and a binder, and the catalyst comprises the following components, by mass, 15-70% of the molecular sieve, 15-60% of the clay, 8-30% of the pseudoboehmite, 3-20% of the binder, 0.01-10% of the phosphorus-containing compound in terms of P, and 0.01-5% of the magnesium-containing compound in terms of Mg on a dry basis.

16. The catalyst of claim 15 wherein the rare earth metal oxide is included in the catalyst in an amount of 0 to 8 wt%.