A catalytic cracking catalyst and its preparation and use

Abstract

A catalytic cracking catalyst and its preparation and use, the catalyst comprising a pseudoboehmite having specific crystal characteristics, a Y-type molecular sieve, a binder and clay; the pseudoboehmite having specific crystal characteristics has a D (130) = 4 nm to 10 nm, D (130) / D (020) = 1.0 to 1.5. The catalytic cracking catalyst has a rich mesopore distribution, in addition to the pore distribution at 3.8 nm, it has a mesopore distribution at a higher pore diameter. The catalyst is used for heavy oil catalytic cracking, and has good diffusion performance for heavy oil macromolecules and reaction intermediates and products, and the catalyst has low coke selectivity.

Description

Technical Field

[0001] This invention relates to a heavy oil catalytic cracking catalyst, its preparation method, and its application. Background Technology

[0002] Catalytic cracking is a heavy oil processing method. Currently used catalytic cracking catalysts typically include molecular sieves and matrix materials. Alumina matrix materials are widely used due to their excellent heavy oil cracking capabilities, and one commonly used alumina matrix material is boehmite. Boehmite, after acidification, exhibits good binding properties and can be used as a binder for catalytic cracking catalysts. It can also form a certain mesoporous structure after catalyst preparation. However, existing catalytic cracking catalysts prepared from boehmite after acidification have a pore size not exceeding 4.5 nm, making it difficult to form pore structures with larger pore sizes. Furthermore, existing catalytic cracking catalysts prepared from boehmite show poor coke selectivity. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a catalytic cracking catalyst containing boehmite with specific crystal characteristics, which results in a low coke yield in catalytic cracking reactions. Another technical problem to be solved by this invention is to provide methods for preparing and applying the aforementioned catalytic cracking catalyst.

[0004] This invention provides a catalytic cracking catalyst, comprising, on a dry basis, 10% to 50% by weight of Y-type molecular sieve, 0 to 40% by weight of other molecular sieves, 10% to 40% by weight of boehmite with specific crystal characteristics (based on alumina), 3% to 20% by weight of binder (based on oxides), and 10% to 80% by weight of clay (based on a dry basis); wherein the boehmite with specific crystal characteristics has a D... (130) =4nm~10nm, D (130) / D (020) =1.0~1.5. Where D (130) The grain size represented by the (130) peak (corresponding to 2θ = 38.3°) in the XRD pattern of pseudoboehmite grains is D. (020) The grain size represented by the (020) peak (corresponding to 2θ = 14.1°) in the XRD pattern of pseudoboehmite grains is indicated.

[0005] According to the present invention, the pseudoboehmite with specific crystal characteristics may have a pore size greater than 4.5 nm and less than 12 nm, for example, 4.5 nm to 9 nm, preferably 4.8 nm to 11 nm, for example, 5 to 10 nm, 5 nm to 9 nm, 6 to 8.5 nm, or 7 to 9 nm. The pore size refers to the diameter.

[0006] The pseudoboehmite with specific crystal characteristics described in this invention has a grain size D. (130) The wavelength range is 4nm to 10nm, preferably 5nm to 8.5nm, for example 5.1nm to 8.5nm, 5.5nm to 8.5nm, or 6nm to 8.2nm.

[0007] According to the present invention, the pseudoboehmite having specific crystal characteristics, the D of the pseudoboehmite (130) / D (020) =1.0 to 1.5, for example, 1.1 to 1.4 or 1.2 to 1.35, preferably 1.1 to 1.3.

[0008] According to the present invention, the crystallinity of the pseudoboehmite having specific crystal characteristics is 85% to 110%, preferably 88% to 108%, for example 90% to 105%, for example 99% to 105%.

[0009] According to the present invention, the pseudoboehmite with specific crystal characteristics has a pore volume of 0.30 cm³. 3 / g~0.58cm 3 / g, preferably 0.31cm 3 / g~0.52cm 3 / g for example 0.33cm 3 / g~0.5cm 3 / g.

[0010] According to the present invention, the pseudoboehmite with specific crystal characteristics has a colloidal index of 90% to 100%, preferably 93% to 99%.

[0011] In one embodiment, the pseudoboehmite having specific crystal characteristics, D (130) For example, 7.8–8.2 nm, D (130) / D (020) The pore size is 1.22–1.29 nm, and the approximate pore size is 7.4–8.5 nm, for example, 7.8–8.5 nm. Under the same conditions, the catalytic cracking catalyst prepared from this pseudoboehmite exhibits higher yields of liquefied petroleum gas and gasoline.

[0012] In the catalytic cracking catalyst provided by the present invention, the content of the pseudoboehmite with specific crystal characteristics, on a dry basis, is 10-40% by weight, preferably 15-35% by weight, for example 20-30% by weight.

[0013] The catalytic cracking catalyst provided by the present invention contains a Y-type molecular sieve, such as one or more of REY, REHY, DASY, SOY, PSRY, HSY, and HRY.

[0014] The catalytic cracking catalyst provided by this invention may also contain molecular sieves other than Y-type molecular sieves. Based on the weight of the catalytic cracking catalyst, on a dry basis, the content of the other molecular sieves is, for example, 0-40% by weight, for example, 0-30% by weight or 1-20% by weight. The other molecular sieves are, for example, one or more of MFI-structured zeolites, beta zeolites, and non-zeolite molecular sieves. The MFI-structured zeolites are, for example, one or more of HZSM-5, ZRP, and ZSP; the beta zeolite is, for example, Hβ; and the non-zeolite molecular sieves are, for example, one or more of aluminum phosphate molecular sieves (AIPO molecular sieves) and silica-alumina-phosphorus molecular sieves (SAPO molecular sieves). Preferably, molecular sieves with an MFI structure are preferred, which can further improve the liquefied gas yield.

[0015] The catalytic cracking catalyst provided by this invention contains clay, which is selected from one or more clays used as components of cracking catalysts, such as kaolin, hydrous kaolin (haloysite), montmorillonite, diatomaceous earth, soapstone, rettoitite, sepiolite, attapulgite, hydrotalcite, and bentonite. These clays are well known to those skilled in the art. Preferably, the clay content in the catalytic cracking catalyst provided by this invention is 20-55% by weight, for example, 30-50% by weight, on a dry basis.

[0016] The catalytic cracking catalyst provided by the present invention contains a binder, wherein the binder is an alumina binder, and the content of the alumina binder is 3-20% by weight, for example 5-15% by weight.

[0017] The alumina binder is preferably aluminum sol, and the catalytic cracking catalyst contains 3 to 20% by weight, for example 4 to 10% by weight or 5 to 15% by weight of aluminum sol, based on alumina.

[0018] In one embodiment, the catalytic cracking catalyst provided by the present invention has a pore distribution with a pore size between 3 and 4 nm, for example, 3.5 to 4 nm, and also has a significant pore size distribution between 4.5 and 10 nm, for example, 5 to 9.5 nm or 6.5 to 9 nm, preferably 7.7 to 8.6 nm. Preferably, the catalytic cracking catalyst has a dual-probable pore size distribution, where the probable pore size of the smaller pore is 3.5 to 4 nm, and the probable pore size of the larger pore is between 4.5 and 10 nm, for example, 5 to 9.5 nm or 6.5 to 9 nm, preferably 7.7 to 8.6 nm.

[0019] The catalyst preparation method of this invention generally includes the steps of forming a slurry comprising boehmite with specific crystal characteristics, Y-type molecular sieves, optionally other molecular sieves, a binder, clay, and water; spray drying; and optionally washing and drying. Spray drying, washing, and drying are prior art, and this invention does not have specific requirements for them. Catalytic cracking catalysts can be prepared according to existing methods, such as those disclosed in patents CN1098130A and CN1362472A.

[0020] In a preferred embodiment, the preparation method of the catalytic cracking catalyst includes: slurrying the pseudoboehmite with specific crystal characteristics with water to form a pseudoboehmite slurry, wherein the solid content of the pseudoboehmite slurry is preferably 5-25% by weight; then adding hydrochloric acid, wherein the mass ratio of HCl to the pseudoboehmite with specific crystal characteristics based on alumina is preferably 0.037-0.104, and the concentration of hydrochloric acid can be 10-37% by weight; then mixing with a slurry containing Y-type molecular sieve, optionally other molecular sieves, binder, clay and water to obtain a colloidal slurry, wherein the solid content of the slurry is preferably 20-40% by weight; spray drying, optionally followed by washing and drying.

[0021] The method for preparing a catalytic cracking catalyst provided by the present invention may further include the steps of preparing boehmite with specific crystal characteristics, forming a slurry comprising the boehmite with specific crystal characteristics, Y-type molecular sieve, alumina binder, clay, and water, and spray drying, wherein the method for preparing the boehmite with specific crystal characteristics includes the following steps:

[0022] (1) React sodium aluminate solution with CO2 to generate the first slurry;

[0023] (2) The first slurry is aged under certain conditions to obtain the second slurry;

[0024] (3) The second slurry is filtered, washed and dried to obtain pseudoboehmite with specific crystal characteristics.

[0025] According to the present invention, in the method for preparing the pseudoboehmite with specific crystal characteristics, in step (1), the concentration of the sodium aluminate solution, calculated as Al2O3, is preferably 5-60 g / L. The sodium aluminate solution can be commercially available or prepared according to existing methods. In one embodiment, the preparation method of the sodium aluminate solution includes: reacting aluminum hydroxide and an alkaline solution at a temperature of 90-120°C for 1-4 hours, and diluting to an Al2O3 concentration of 5-60 g / L. The alkaline solution is, for example, a sodium hydroxide solution. The caustic ratio of the sodium aluminate solution is, for example, 1.0-3.2.

[0026] According to the present invention, in the method for preparing the pseudoboehmite with specific crystal characteristics, in step (1), a sodium aluminate solution is brought into contact with CO2 for reaction. The reaction can be carried out by passing a CO2-containing gas through the sodium aluminate solution. The volume concentration of CO2 in the CO2-containing gas is 20-100%, for example, 40-100% by volume.

[0027] According to the present invention, in the method for preparing the pseudoboehmite with specific crystal characteristics, the pH value at the endpoint of the reaction between sodium aluminate solution and CO2 is 8.5 to 10.5.

[0028] According to the present invention, in the method for preparing pseudoboehmite with specific crystal characteristics, in step (1), the reaction starting temperature is preferably 10-35°C, and the reaction ending temperature is preferably 15-55°C.

[0029] According to the present invention, in the method for preparing the pseudoboehmite with specific crystal characteristics, step (1) involves reacting sodium aluminate solution with CO2, wherein the reaction time of the sodium aluminate solution with CO2 is preferably 20 to 70 minutes.

[0030] In one embodiment, the method for preparing the pseudoboehmite with specific crystal characteristics, in step (1), the conditions for the reaction of sodium aluminate solution with CO2 include: an initial reaction temperature of 10–35°C, a reaction time of 20–70 minutes, and an ending reaction temperature of 15–55°C. The pH value at the endpoint of the reaction between sodium aluminate solution and CO2 is 8.5–10.5. Preferably, the reaction of sodium aluminate solution with CO2 involves contacting the sodium aluminate solution with a CO2-containing gas, wherein the volume concentration of CO2 in the CO2-containing gas is 20%–100%.

[0031] In the preparation method of the pseudoboehmite with specific crystal characteristics, step (2) involves aging under certain conditions: first static aging, then aging under stirring, with an aging temperature above 100℃ and not exceeding 185℃.

[0032] In the method for preparing the pseudoboehmite with specific crystal characteristics, step (2) involves aging the first slurry under certain conditions. In one embodiment, the aging temperature is 100–185°C, for example, 120–180°C, preferably 135–180°C. The first slurry can be heated to 100–185°C, for example, 120–180°C, preferably 135–180°C, and then aged at this temperature. Preferably, the time for the first slurry to rise from the reaction endpoint temperature to the aging temperature does not exceed 60 minutes. Preferably, the temperature from the start to the end of aging is constant, meaning that the temperature of static aging and stirring aging is kept constant; for example, the difference between the static aging and stirring aging temperatures preferably does not exceed 2°C.

[0033] Preferably, in step (2), the aging temperature is 135-180°C, which can have a better effect on increasing the total yield of liquefied gas and gasoline.

[0034] In the preparation method of the pseudoboehmite with specific crystal characteristics, the aging pressure in step (2) is preferably 0.2 to 1 MPa.

[0035] In the preparation method of the pseudoboehmite with specific crystal characteristics, in step (2), the stirring speed is controlled at 50-400 r / min. The stirring can be carried out using existing stirring methods. Through stirring, the aging slurry rotates in the aging tank under the action of the stirring paddle.

[0036] In the preparation method of the pseudoboehmite with specific crystal characteristics, the aging time in step (2) is preferably 2 to 10 hours.

[0037] In the preparation method of the pseudoboehmite with specific crystal characteristics, step (2) involves first static aging at a certain temperature, followed by aging under stirring. Static aging means that no stirring is performed during aging, allowing the slurry to remain in a static state, for example, by a static aging method. Preferably, the first slurry is first statically aged at the aging temperature for 1–4 hours, for example, 2–3 hours, and then aged under stirring at the aging temperature for 1–6 hours. The stirring speed is 50–400 r / min, for example, 60–400 r / min.

[0038] In one embodiment of the method for preparing pseudoboehmite with specific crystal characteristics, in step (2), the first slurry is aged under certain conditions, with an aging temperature of 100-185℃ (e.g., 120-180℃) and a pressure of 0.2-1MPa for a constant temperature reaction of 2-10 hours. The first slurry is first allowed to stand for aging for 1-4 hours (e.g., 2-3 hours), and then the aging temperature and pressure are maintained while stirring is applied. The stirring speed is controlled at 50-400 r / min (e.g., 60-400 r / min), and the stirring aging time is 1-6 hours.

[0039] The method for preparing pseudoboehmite with specific crystal characteristics includes step (3), whereby the aged slurry is filtered, washed, and dried to obtain pseudoboehmite with specific crystal characteristics. In one embodiment, the washing conditions are washing with deionized water at 70–100°C until the pH of the wet filter cake is 7–7.5. The drying temperature is preferably 60–98°C, for example, 70–98°C, more preferably 70–95°C, and the drying time is, for example, 2–4 hours.

[0040] According to the catalyst preparation method provided by the present invention, the method for preparing pseudoboehmite with specific crystal characteristics is green and environmentally friendly, low in cost, and easy to implement. It can obtain pseudoboehmite with specific crystal characteristics, which has high crystallinity, large grain size, large pore size, and good colloidal solubility. After colloidal treatment, it can have a large pore size and good wear resistance.

[0041] This invention also provides a catalytic cracking method, comprising the step of contacting heavy oil with the catalytic cracking catalyst provided by this invention under heavy oil FCC conditions. The heavy oil is, for example, one or more of vacuum wax oil, atmospheric residue, vacuum residue, and heavy deasphalted oil. The FCC conditions are the reaction conditions for fluidized bed catalytic cracking of heavy oil; typically, the reaction temperature is 480–530°C, the reaction time is 1–10 seconds, and the catalyst-to-oil ratio is 3–20:1 by weight.

[0042] The catalytic cracking catalyst provided by this invention contains boehmite with specific crystal characteristics, exhibiting significantly larger mesopores (e.g., mesopores with a pore size of 5-10 nm), resulting in better diffusion performance for heavy oil molecules, high accessibility of active centers, and lower coke selectivity. When used in heavy oil catalytic cracking, the catalytic cracking catalyst provided by this invention exhibits lower coke selectivity than existing catalytic cracking catalysts containing conventional boehmite, and preferably, higher gasoline and LPG yields.

[0043] The catalytic cracking catalyst preparation method provided by this invention does not require increasing the amount of other binders and can generate significantly larger mesopores when the catalyst strength is qualified. For example, the catalyst can have more mesopores larger than 5 nm, which significantly improves the pore structure of the catalyst and is conducive to promoting the efficient diffusion of heavy oil macromolecules, reaction intermediates and product molecules in the catalyst. In preferred cases, it can improve the yield of gasoline and liquefied gas. Detailed Implementation

[0044] The following embodiments will further illustrate the present invention, but should not be used to limit the present invention.

[0045] In this application, the crystallinity and grain size D of the sample were measured by X-ray powder diffraction (XRD) using the RIPP 145-90 and RIPP 146-90 standard methods (see *Analytical Methods for Petrochemical Products* (RIPP Test Methods), edited by Yang Cuiding et al., Science Press, 1990). The crystallinity of the sample was calculated based on the peak at 2θ = 38.3° (130 crystal plane). The crystallinity was determined according to the Scherrer formula. Calculate the grain size, where K = 1.075, λ is the wavelength of the Kα1 spectral line of the anodic radiation, β is the full width at half maximum (FWHM) of the specific diffraction peak of the pseudoboehmite, and θ is the Bragg diffraction angle of the diffraction peak. D(130) This indicates the grain size of the sample perpendicular to the (130) crystal plane. β 130 D is the half-maximum width of the diffraction peak of sample (130). (020) This indicates the grain size of the sample perpendicular to the (020) crystal plane. β 020 is the half-peak width of the (020) diffraction peak of the sample.

[0046] In this application, the probabilistic pore size distribution and pore volume of the sample were determined by low-temperature nitrogen static capacity adsorption. Specific surface area and pore volume were calculated using the two-parameter BET formula, and pore size distribution was calculated using the BJH formula. The pore size corresponding to the highest point of the pore size distribution curve is the probabilistic pore size of the sample. An ASAP 2405NV1.01 automated adsorption instrument from Micromeritics (USA) was used, and the sample was at a temperature of 1.33 × 10⁻⁶. -2 The sample was degassed under vacuum at 300℃ for 4 hours, and the adsorption-desorption isotherm was measured at 77.4K using N2 as the adsorption medium.

[0047] In this application, the determination of the colloidal index is as follows: 10 grams of boehmite was weighed, calcined at 600℃ for 3 hours, cooled in a desiccator, and weighed to obtain W0 grams. The dry basis weight a0 = W0 / 10 was obtained. The weight of the boehmite was weighed m1 = 6 / a0 grams. m1 grams of boehmite was placed in a 100 mL polytetrafluoroethylene (PTFE) cup, and deionized water was added to a final volume of 40 grams. The mixture was stirred evenly using a magnetic rotor, and then 20 mL of 0.19 N dilute nitric acid solution was added. The mixture was stirred magnetically for 20 minutes. The entire solution was poured into a centrifuge tube and centrifuged at 1900 rpm for 20 minutes. The upper colloidal solution was poured off, placed in a weighed crucible, dried at 80℃, calcined at 600℃ for 3 hours, cooled in a desiccator, and weighed to obtain m2 grams. The colloidal index DI = (m2 / 6) * 100%.

[0048] The sodium aluminate used in the examples was produced by Shanghai Maclean Biochemical Technology Co., Ltd., with a caustic ratio of 1 and analytical grade.

[0049] Example 1

[0050] A 20g / L sodium aluminate solution was gelled with 40% (v / v) carbon dioxide gas (the remainder being nitrogen), with the final pH value controlled at 9.5. The resulting slurry was transferred to an aging reactor and aged at 135℃ and 0.35MPa for 3 hours. While maintaining this temperature and pressure, stirring was started and the stirring rate was kept at 150 r / min for another hour. After aging, the resulting slurry was separated into solid and liquid components and washed continuously with deionized water at 85℃ for half an hour until the pH of the wet filter cake reached 7.1, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 80℃ for 3 hours and then pulverized to obtain boehmite powder SP1, the physicochemical properties of which are shown in Table 1.

[0051] 714.5 g of alumina sol with an alumina content of 21 wt% was added to 1565.5 g of decationized water. Stirring was started, and 2763 g of kaolin with a solid content of 76 wt% was added and dispersed for 60 minutes to obtain a well-dispersed kaolin slurry. 2049 g of SP1 pseudoboehmite with an alumina content of 61 wt% was added to 8146 g of decationized water. While stirring, 210 ml of 36% hydrochloric acid was added, and after acidification for 60 minutes, the well-dispersed kaolin slurry was added. Then, finely ground molecular sieves (HSY-12 and ZSP-3 molecular sieves, with a dry basis weight ratio of HSY-12 to ZSP-3 molecular sieves of 14:1; both products of Sinopec Catalyst Qilu Branch; HSY-12 molecular sieve had a Re2O3 content of 11.6 wt%, a crystallinity of 50.3%, and Na2O content of 11.6 wt%, with a Na2O content of 50.3% and a Na2O content of 14.6 wt%) were added. The content is 0.9 wt%, Si / Al molar ratio is 2.5, and the grinding particle size is d(0.5) = 2.6, d(0.9) = 6.6); ZSP-3 molecular sieve: Fe2O3 content 1.7 wt%, P2O5 content 3.9 wt%, crystallinity 78%, Na2O content 0.05 wt%, Si / Al molar ratio is 25, and the grinding particle size is d(0.5) = 3.9, d(0.9) = 7.8 (the same molecular sieve was used in all examples and comparative examples). 1500 g (on a dry basis) was stirred evenly, spray-dried and washed, and dried to obtain the catalyst, denoted as SC1. The obtained SC1 catalyst contains, on a dry basis, 30 wt% molecular sieve, 42 wt% kaolin, 25 wt% SP1 pseudoboehmite, and 3 wt% alumina sol.

[0052] Example 2

[0053] A sodium aluminate solution with a concentration of 45 g Al2O3 / L was reacted with 60% carbon dioxide gas (60% CO2, the remainder being nitrogen) to achieve a final pH of 10.3. The resulting slurry was transferred to an aging reactor and aged at 180℃ and 1.0 MPa for 2.5 h. Then, while maintaining the temperature and pressure at 180℃ and 1.0 MPa, stirring was started and maintained at a stirring rate of 450 r / min for 1 h. After aging, the resulting slurry was separated into solid and liquid components and continuously washed with 95℃ deionized water for half an hour until the pH of the wet filter cake reached 7.3, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 90℃ for 4 h and pulverized to obtain boehmite powder SP2, the physicochemical properties of which are shown in Table 1.

[0054] Referring to the preparation method of Example 1, HSY-12 molecular sieve, ZSP-3 molecular sieve, kaolin, water, SP2 boehmite binder, and alumina sol were prepared into a slurry using conventional methods for preparing catalytic cracking catalysts, and then spray-dried to prepare microsphere catalysts. The prepared catalytic cracking catalyst is designated as SC2. On a dry basis, the obtained SC2 catalyst contains 30% by weight of molecular sieves (HSY-12 and ZSP-3 molecular sieves), 42% by weight of kaolin, 25% by weight of SP2 boehmite, and 3% by weight of alumina sol.

[0055] Example 3

[0056] A sodium aluminate solution with a concentration of 8 g Al₂O₃ / L was reacted with carbon dioxide gas (35% CO₂, the remainder being nitrogen) at a volume fraction of 35%, with the final pH value controlled at 9.3. The resulting slurry was transferred to an aging reactor and aged at 120℃ and 0.2 MPa for 4 hours. Then, while maintaining the temperature and pressure at 120℃ and 0.2 MPa, stirring was started and maintained at a stirring rate of 100 r / min for 2.5 hours. After aging, the resulting slurry was separated into solid and liquid components. The slurry was continuously washed with deionized water at 75℃ for half an hour until the pH of the wet filter cake reached 7.1, yielding a boehmite wet filter cake with impurities removed. The wet filter cake was dried at 75℃ for 4 hours and pulverized to obtain boehmite powder SP3, the physicochemical properties of which are shown in Table 1.

[0057] Following the method in Example 1, SP3 was used to replace SP1 to prepare the catalyst, resulting in SC3.

[0058] Example 4

[0059] A sodium aluminate solution with a concentration of 15 g Al2O3 / L was reacted with 50% (volume fraction) carbon dioxide gas (50% CO2, the remainder being nitrogen), and the final pH value was controlled to be 9.7. The resulting slurry was transferred to an aging reactor and aged at 150℃ and 0.48 MPa for 5 hours. Then, while maintaining the temperature and pressure at 150℃ and 0.48 MPa, stirring was started and the stirring rate was kept at 250 r / min for 4 hours. After aging, the resulting slurry was separated into solid and liquid components and washed continuously with 80℃ deionized water for half an hour until the pH value of the wet filter cake reached 7.3, obtaining a purified boehmite wet filter cake. The wet filter cake was dried at 85℃ for 4 hours and pulverized to obtain boehmite powder SP4, the physicochemical properties of which are shown in Table 1.

[0060] Following the method of Example 1, SP4 was used to replace SP1 to prepare the catalyst, resulting in SC4.

[0061] Example 5

[0062] A sodium aluminate solution with a concentration of 55 g Al2O3 / L was reacted with 90% carbon dioxide gas (90% CO2, the remainder being nitrogen) to achieve a final pH of 10.0. The resulting slurry was transferred to an aging reactor and aged at 160℃ and 0.62 MPa for 7 hours. Then, while maintaining the temperature and pressure at 160℃ and 0.62 MPa, stirring was started and maintained at a stirring rate of 350 r / min for 5 hours. After aging, the resulting slurry was separated into solid and liquid components. The slurry was continuously washed with deionized water at 90℃ for half an hour until the pH of the wet filter cake reached 7.4, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 95℃ for 4 hours and then pulverized to obtain boehmite powder SP5. Its physicochemical properties are shown in Table 1.

[0063] Following the method of Example 1, SP5 was used to replace SP1 to prepare the catalyst, resulting in SC5.

[0064] Comparative Example 1

[0065] A sodium aluminate solution with a concentration of 20 g Al2O3 / L was reacted with carbon dioxide gas at a volume fraction of 40% to form a gel, with the final pH value controlled at 9.5. The resulting slurry was transferred to an aging reactor and aged at 90°C for 3 hours. After aging, the slurry was separated into solid and liquid components, and washed continuously with deionized water at 78°C for half an hour to obtain a filter cake with impurities removed. The filter cake was dried at 90°C for 3 hours and then pulverized to obtain boehmite powder DP1. Its physicochemical properties are shown in Table 1.

[0066] Molecular sieve (same as the molecular sieve used in Example 1), kaolin, water, DP1 boehmite binder, and alumina sol were slurried using conventional methods for preparing catalytic cracking catalysts, and then spray-dried to prepare microsphere catalysts. The prepared catalytic cracking catalyst is designated DC1 (refer to the preparation method in Example 1). On a dry basis, the obtained DC1 catalyst contains 30% by weight of molecular sieve, 42% by weight of kaolin, 25% by weight of DP1 boehmite, and 3% by weight of alumina sol.

[0067] Comparative Example 2

[0068] A 20 g / L sodium aluminate solution was reacted with 40% (v / v) carbon dioxide gas to form a gel, with the final pH value controlled at 9.5. The resulting slurry was transferred to an aging reactor and aged at 135 °C and 0.35 MPa for 3.5 h. After aging, the slurry was separated into solid and liquid components, and continuously washed with deionized water at 80 °C for half an hour to obtain a boehmite wet filter cake with impurities removed. The wet filter cake was dried at 80 °C for 3 h and pulverized to obtain boehmite powder DP2, the physicochemical properties of which are shown in Table 1.

[0069] Molecular sieves, kaolin, water, DP2 boehmite binder, and alumina sol were mixed and slurry-formed according to conventional methods for preparing catalytic cracking catalysts. The resulting slurry was then spray-dried to prepare microsphere catalysts, denoted as DC2 (refer to the preparation method in Example 1). The DC2 catalyst, on a dry basis, contained 30% by weight of molecular sieve, 42% by weight of kaolin, 25% by weight of DP2 boehmite, and 3% by weight of alumina sol.

[0070] Comparative Example 3

[0071] Using a high-purity sodium aluminate solution with an Al2O3 content of 45 g / L as raw material, a gelation reaction was initiated by introducing 40% CO2, with the flow rate controlled at 3.0 m³ / h. 3 The reaction time was controlled at 40 minutes, with Al2O3 residue controlled at 5 g / L, and the final temperature controlled at 35℃. After the reaction, the slurry was separated and washed, and the filter cake was washed with high-purity water at 85℃ until the pH value of the filter cake was 7.0. The filter cake obtained above was added to high-purity water and stirred, and then urea with a concentration of 8 g / L was added. After stirring for 50 minutes, the slurry was transferred to a high-pressure reactor, and the reactor temperature was controlled at 150℃ and the pressure at 0.6 MPa. It was allowed to stand for 3 hours for aging. After aging, it was continuously washed with deionized water at 85℃ for half an hour, filtered, and dried at 90℃. The final product, pseudoboehmite DP3, was obtained by pulverization, and its physicochemical properties are shown in Table 1.

[0072] Molecular sieves, kaolin, water, DP3 boehmite binder, and alumina sol were mixed and slurry-formed according to conventional methods for preparing catalytic cracking catalysts. The resulting slurry was then spray-dried to prepare microsphere catalysts, denoted as DC3 (refer to the preparation method in Example 1). The DC3 catalyst, on a dry basis, contained 30% by weight of molecular sieve, 42% by weight of kaolin, 25% by weight of DP3 boehmite, and 3% by weight of alumina sol.

[0073] Comparative Example 4

[0074] A sodium aluminate solution with a concentration of 45 g Al2O3 / L was reacted with 60% carbon dioxide gas (60% CO2, the remainder being nitrogen) to achieve a final pH of 10.3. The resulting slurry was transferred to an aging reactor and aged at 180℃ and 1.0 MPa with a stirring rate of 450 r / min for 3.5 h. After aging, the slurry was separated into solid and liquid components and continuously washed with deionized water at 95℃ for half an hour until the pH of the wet filter cake reached 7.3, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 90℃ for 4 h and then pulverized to obtain boehmite powder DP4. Its physicochemical properties are shown in Table 1.

[0075] The catalyst DC4 was prepared using DP4 instead of SP1, following the method of Example 1.

[0076] Examples 6-10

[0077] Examples 6-10 illustrate the catalytic cracking performance of the pseudoboehmite provided by the present invention.

[0078] Catalysts SC1–SC5 were aged at 800℃ for 17 hours using 100% steam. Their catalytic cracking performance was evaluated in a small fixed fluidized bed reactor (ACE). Cracking gas and product oil were collected and analyzed by gas chromatography. The catalyst loading was 9 g, the reaction temperature was 500℃, and the weight hourly space velocity (WHSV) was 16 h⁻¹. －1 The properties of the feedstock oil in the ACE experiment are shown in Table 3, and the evaluation results are shown in Table 4.

[0079] Comparative Examples 5-8

[0080] Comparative Examples 5-8 illustrate the reaction performance of the catalytic cracking catalysts prepared from boehmite in Comparative Examples 1-3.

[0081] After the DC1 to DC4 catalysts were aged at 800℃ for 17 hours with 100% steam, their catalytic cracking performance was evaluated in a small fixed fluidized bed reactor (ACE). The properties of the feedstock oil in the ACE experiment are shown in Table 3, and the evaluation results are listed in Table 4.

[0082] Table 1

[0083]

[0084] *Acidification conditions: Acid-to-aluminum ratio (concentration 36 wt% HCl:Al2O3 mass ratio) is 0.2, solid content of acidified mixture is 10 wt%; calcination temperature is 550℃, calcination time is 2h.

[0085] Table 2

[0086] Instance number Sample number Catalysts can have pore sizes of several nm Wear Index Example 1 SC1 3.8，7.2 2.0 Example 2 SC2 3.8，7.7 2.1 Example 3 SC3 3.8，4.8 1.5 Example 4 SC4 3.8，7.0 2.3 Example 5 SC5 3.8，8.6 2.5 Comparative Example 1 DC1 3.8 1.6 Comparative Example 2 DC2 3.8 1.6 Comparative Example 3 DC3 3.8，4.3 2.4

[0087] As shown in Table 1, the pseudoboehmite provided by this invention has a relatively large grain size and D... (130) / D (020) The catalytic cracking catalyst provided by this invention exhibits a large mesopore distribution, with mesopores present not only at 3.8 nm but also at higher pore sizes. Furthermore, the mesopore size remains relatively large even after calcination following gelation. Table 2 shows that the catalyst has a large mesopore distribution, with mesopores present at various pore sizes beyond 3.8 nm. In contrast, conventional boehmite-based catalysts only exhibit mesopores at 3.8 nm.

[0088] Table 3

[0089]

[0090] Table 4

[0091]

[0092] As shown in Table 4, the catalytic cracking catalyst provided by this invention exhibits significantly lower coke selectivity and higher gasoline and LPG yields. This is especially true for the D-type boehmite with the specific characteristics described above. (130) When the value is 7.8 to 8.2 and D (130) / D (020) At values ​​above 1.2, significantly higher gasoline and LPG yields can be achieved.

Claims

1. A catalytic cracking catalyst comprising, on a dry basis, 10% to 50% by weight of Y-type molecular sieve, 0% to 40% by weight of other molecular sieves on a dry basis, 10% to 40% by weight of boehmite with specific crystal characteristics on alumina, 3% to 20% by weight of binder on an oxide basis, and 10% to 80% by weight of clay on a dry basis; wherein the boehmite with specific crystal characteristics, D... （130） / D （020） =1~1.5, D （130） =4nm~10nm, where D （130） The grain size represented by the (130) peak in the XRD pattern of pseudoboehmite grains, corresponding to the crystal plane represented by 2θ=38.3°, is D. （020） The XRD pattern of the pseudoboehmite grains indicates the grain size corresponding to the crystal plane represented by the (020) peak at 2θ=14.1°. The pseudoboehmite with specific crystal characteristics has a pore volume of 0.3 cm³. 3 / g~0.58cm 3 / g, wherein the pseudoboehmite with specific crystal characteristics has a pore size greater than 4.5 nm and not exceeding 12 nm.

2. The catalytic cracking catalyst according to claim 1, characterized in that, The pseudoboehmite with specific crystal characteristics has a colloidal index of 90%~100%; the other molecular sieves are one or more of MFI structure zeolites, Beta zeolites, and non-zeolite molecular sieves.

3. The catalytic cracking catalyst according to claim 2, characterized in that, The pseudoboehmite with specific crystal characteristics has a pore size of 5 nm to 10 nm and a crystallinity of 85% to 110%.

4. The catalytic cracking catalyst according to claim 2, characterized in that, The D of the pseudoboehmite with specific crystal characteristics （130） / D （020） It is 1.1~1.

3.

5. The catalytic cracking catalyst according to claim 1, characterized in that, The Y-type molecular sieve is one or more of REY, REHY, DASY, SOY, PSRY, HSY, and HRY; the other molecular sieves are one or more of HZSM-5, ZRP, and ZSP.

6. The catalytic cracking catalyst according to any one of claims 1 to 5, characterized in that, The aforementioned pseudoboehmite with specific crystal characteristics, D （130） The wavelength is 6.5~8.2nm, D （130） / D （020） The pore size is 1.22~1.29, and the approximate pore size is 7.4~8.5 nm.

7. The catalytic cracking catalyst according to claim 6, characterized in that, The aforementioned pseudoboehmite with specific crystal characteristics, D （130） The wavelength range is 7.8~8.2nm, and the pore size is 7.8~8.5nm.

8. The catalytic cracking catalyst according to any one of claims 1 to 5, characterized in that, The catalytic cracking catalyst has a pore size of 3.5~4 nm and 4.5~10 nm.

9. A method for preparing a catalytic cracking catalyst, comprising the steps of preparing boehmite with specific crystal characteristics, forming a slurry comprising the boehmite with specific crystal characteristics, a Y-type molecular sieve, optionally other molecular sieves, a binder, clay and water, and spray drying; in, The preparation method of the pseudoboehmite with the specific crystal characteristics mentioned above includes the following steps: (1) The sodium aluminate solution is reacted with CO2 to generate a first slurry; the conditions for the reaction of the sodium aluminate solution with CO2 include an initial reaction temperature of 10~35℃ and an endpoint pH value of 8.5~10.

5. (2) The first slurry is aged under certain conditions to form the second slurry; the aging under certain conditions is: first static aging, then aging under stirring, the aging temperature is above 100℃ and not exceeding 185℃; the static aging time is 1~4h, and the aging time under stirring is 1~6h. (3) The second slurry is filtered, washed and dried to obtain pseudoboehmite with specific crystal characteristics.

10. The method according to claim 9, characterized in that, In step (1), the Al2O3 concentration of the sodium aluminate solution is 5~60 g / L.

11. The method according to claim 9 or 10, characterized in that, In step (1), the conditions for the reaction between the sodium aluminate solution and CO2 include passing CO2 gas with a concentration of 20% to 100% by volume into the sodium aluminate solution for the reaction, and the reaction endpoint temperature being 15 to 55°C.

12. The method according to claim 9, characterized in that, The aging pressure is 0.2~1 MPa, and the aging time is 2~10 h; the static aging time in step (2) is 2~3 h.

13. The method according to claim 12, characterized in that, The aging temperature is 135~180℃, and the aging is constant temperature aging.

14. The method according to claim 12, characterized in that, The stirring speed for the aging process is 50~400 r / min.

15. The method according to claim 9, characterized in that, The washing conditions in step (3) are: washing with deionized water at 70~100℃ until the pH value of the wet filter cake is 7~7.5; the drying in step (3) is at a temperature of 70~98℃.

16. The method according to claim 9, characterized in that, The preparation method of the catalytic cracking catalyst includes: slurrying boehmite with specific crystal characteristics with water to form a boehmite slurry; adding hydrochloric acid, HCl, and boehmite with specific crystal characteristics in a mass ratio of 0.037 to 0.104 (calculated as alumina); then mixing the mixture with a slurry containing Y-type molecular sieve, optional other molecular sieves, binder, clay, and water to obtain a colloidal slurry; spray drying; and optionally washing and drying.

17. The method according to claim 16, characterized in that, The pseudo-boehmite slurry has a solid content of 5-25% by weight, a hydrochloric acid concentration of 10-37% by weight, and a colloidal slurry solid content of 20-40% by weight.

18. A catalytic cracking method, comprising the step of contacting heavy oil with a catalytic cracking catalyst under FCC conditions, characterized in that, The catalytic cracking catalyst is the catalytic cracking catalyst according to any one of claims 1 to 8 or the catalytic cracking catalyst obtained according to any one of claims 9 to 17; the FCC conditions include: a reaction temperature of 480 to 530°C, a reaction time of 1 to 10 seconds, and a catalyst-to-oil ratio of 3 to 20:1 by weight.

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