Modified y-type molecular sieve and preparation method therefor, and hydrocracking catalyst

Abstract

The present invention provides a modified Y-type molecular sieve and a preparation method therefor, and a hydrocracking catalyst. The preparation method comprises: in a liquid-phase system, enabling a first organic matter to react with a Y-type molecular sieve to obtain an intermediate product, wherein the first organic matter comprises one of or a combination of two or more of amidino, benzyl, and a sulfhydryl functional group; and mixing the intermediate product with an immersion solution containing a second organic matter, and then performing thermal treatment in a protective atmosphere to obtain a modified Y-type molecular sieve, wherein the mass ratio of the Y-type molecular sieve to the first organic matter is 3-12.5:1, and the second organic matter can be decomposed and carbonized at 160-200°C. The molecular sieve prepared by the present invention has good catalytic activity.

Description

A modified Y-type molecular sieve and its preparation method, and hydrocracking catalyst Technical Field

[0001] The present invention belongs to the technical field of molecular sieve modification, and in particular relates to a modified Y-type molecular sieve, a preparation method thereof, and a hydrocracking catalyst. Background Art

[0002] Y-type zeolite belongs to the FD-3M space group and has a spinel structure. This structure is composed of tetrahedra and octahedra; it has four sublattices, two of which are adjacent to tetrahedral sublattices, and the other two are adjacent to each other. This synthetic zeolite has a supercage formed by a β cage and a hexagonal prism cage. It is composed of 18 four-membered rings, four six-membered rings, and four twelve-membered rings, resulting in a pore diameter of 0.74 nm and an inner diameter of 1.2 nm. It possesses a rich pore structure and a large number of cracking active sites required for solid acid catalysts.

[0003] During the synthesis of molecular sieves, polycrystalline micron-sized clusters are easily formed. Due to their large crystal size, they result in greater diffusion resistance during the catalytic reaction, which limits the mass transfer effect during the reaction. At the same time, the cracking activity and selectivity of the target product are also restricted. Compared with conventional Y-type molecular sieves, small-grain Y-type molecular sieves have certain advantages in terms of materials. Due to the reduced size of the molecular sieve, the molecular sieve can have a larger specific surface area, and the acidic center is more easily exposed. Therefore, the cracking ability of the molecular sieve-containing catalyst can be significantly improved, and it has better reaction performance.

[0004] There are two main methods for obtaining small-grain Y-type molecular sieves: one is to directly synthesize small-grain molecular sieves, and the other is to process conventional-sized molecular sieves to obtain small-grain molecular sieves.

[0005] CN104843738B discloses a method for synthesizing a small-crystal Y molecular sieve with controllable particle size. The method primarily comprises the following steps: first, preparing a directing agent; then, adding a certain amount of the directing agent to a silica-alumina gel; and then directly placing the gel into a polytetrafluoroethylene-lined autoclave. Crystallization occurs at 80-130°C for a certain period of time, followed by filtration and drying to obtain a small-crystal Y molecular sieve with controllable particle size. However, this method suffers from poor hydrothermal stability and difficulty in solid-liquid separation.

[0006] CN104591212A discloses a method for preparing a small-grain Y-type molecular sieve. The method adopts an acid-base precipitation method to prepare an amorphous silicon-aluminum precursor after preparing a directing agent, and then the amorphous silicon-aluminum precursor is made into a silicon-aluminum gel, and finally a small-grain Y-type molecular sieve is obtained by two-step dynamic crystallization, filtration, washing and drying. However, the molecular sieve preparation path of the method is long, and the change of the silicon-aluminum ratio of the required Y-type molecular sieve has a relatively large impact on the catalyst preparation formula and process, and the scheme flexibility is low.

[0007] CN105712372B discloses a kind of nano-scale small crystal Y type molecular sieve and its preparation method.The method comprises the following steps: first, Y molecular sieve is placed in an appropriate amount of distilled water, and the molecular sieve is dispersed by high-speed stirring and high-frequency ultrasonic instrument; Then, at a certain temperature, ammonium fluorosilicate solution is added dropwise to the slurry to react, and then the solid is separated from the slurry; Finally, the slurry is placed in a closed autoclave and subjected to supercritical carbon dioxide drying treatment, i.e., nano-scale small crystal Y type molecular sieve is obtained. The instrument used in the method is relatively complex, which is not conducive to industrial amplification production, and the processing process involves an alkaline environment. In the process of changing conventional size molecular sieves into nano-scale small crystal molecular sieves, there is a loss of silicon or aluminum in the original molecular sieve, which changes the silicon-aluminum ratio of the original molecular sieve, which is not conducive to the maintenance of the reaction properties of the original molecular sieve.

[0008] Summary of the Invention

[0009] To address the aforementioned problems in the prior art, the present invention provides a method for preparing a modified Y-type molecular sieve. The method comprises heat-treating a Y-type molecular sieve modified with a first organic compound and then a second organic compound to produce a small-grain Y-type molecular sieve. This modified Y-type molecular sieve exhibits excellent hydrocracking catalytic activity.

[0010] In order to achieve the above object, according to one aspect of the present invention, a method for preparing a modified Y-type molecular sieve is provided, which comprises:

[0011] In a liquid phase system, a first organic compound reacts with a Y-type molecular sieve to obtain an intermediate product; the first organic compound has one or a combination of two or more of an amidine, a benzyl, or a thiol functional group;

[0012] mixing the intermediate product with an impregnation solution containing a second organic compound, and then heat-treating the mixture in a protective atmosphere to obtain the modified Y-type molecular sieve;

[0013] Wherein, the mass ratio of the Y-type molecular sieve to the first organic matter is 3-12.5:1;

[0014] The second organic matter can be decomposed and carbonized at 160-200°C.

[0015] In the first step of the reaction, the present invention causes the Y-type molecular sieve to adsorb a certain amount of the first organic matter, forming an intermediate product. In the second step of the reaction, the present invention causes the intermediate product to be impregnated with a second organic matter that is easily decomposed and carbonized at low temperatures. After heat treatment and carbonization, the second organic matter can preferentially form a dense carbon film on the surface of the molecular sieve. The carbon film can coat the Y-type molecular sieve. Furthermore, during the heat treatment, the first organic matter decomposes and releases water vapor. The water vapor is trapped in the aforementioned dense carbon film and cannot overflow in time, so a small-scale explosion occurs.

[0016] Because Y-type molecular sieve is composed of tetrahedron and octahedron, in the molecular sieve preparation process, it is very easy to generate polycrystalline micron-sized clusters. There are defect sites between multiple crystals in the cluster, specifically nanoscale voids. During the small-scale explosion of the intermediate product caused by the heat treatment of the present invention, it is very easy to destroy the defect sites in the cluster, thereby forming a Y-type molecular sieve material with smaller particles. Therefore, the molecular sieve obtained by the heat treatment method of the present invention can significantly increase the specific surface area of ​​the material, enrich the molecular sieve pore properties, effectively increase the exposure of the molecular sieve acid sites, and then achieve the purpose of improving catalyst performance.

[0017] In some preferred embodiments of the present invention, the solvent in the liquid phase system is water. Further preferably, the solid-liquid mass ratio is 1:5-10. Preferably, the solid-liquid mass ratio is 1:10.

[0018] In some preferred embodiments of the present invention, the mass ratio of the Y-type molecular sieve to the first organic compound is 5-10:1. Furthermore, preferably, the mass percentage of the first organic compound in the intermediate product is not less than 8 wt %. This ratio is conducive to achieving the beneficial effects of modifying the first organic compound.

[0019] In some preferred embodiments of the present invention, the protective atmosphere includes nitrogen atmosphere, argon atmosphere, helium atmosphere, etc.

[0020] In some preferred embodiments of the present invention, the second organic matter includes one or a combination of two or more of glucose, fructose, and sucrose.

[0021] In some preferred embodiments of the present invention, the heat treatment comprises a low temperature stage and a high temperature stage performed sequentially;

[0022] Preferably, the temperature of the low temperature stage is 160-200°C and the time is 2-5h;

[0023] Preferably, the temperature of the high temperature stage is 200-350° C., and the time is 2-5 hours.

[0024] More preferably, the low temperature stage lasts for 2-3 hours.

[0025] More preferably, the temperature of the high temperature stage is 240-280°C.

[0026] During the low temperature stage, the second organic matter carbonizes, resulting in weight loss, with water being the main component released during the weight loss process. During the high temperature stage, the first organic matter decomposes, resulting in weight loss, with water being the main component released during the weight loss process.

[0027] In some preferred embodiments of the present invention, the temperature difference between the low-temperature stage and the high-temperature stage is no less than 40°C. Such a temperature difference is preferably set to better ensure that the two substances react step by step. The closer the temperatures are, the greater the possibility that the two substances will react simultaneously.

[0028] In some preferred embodiments of the present invention, the mass concentration of the second organic matter in the impregnation solution is 1-8%. If the concentration is lower than this range, the effect is not good.

[0029] In some preferred embodiments of the present invention, the intermediate product is mixed with the impregnation solution containing the second organic compound by equal volume impregnation. Preferably, equal volume impregnation is adopted, which can better allow the impregnation solution to be completely absorbed into the molecular sieve and avoid excessive residue.

[0030] In some preferred embodiments of the present invention, the reaction temperature of the first organic compound and the Y-type molecular sieve is 20-50°C and the reaction time is 0.5-3 hours. More preferably, the reaction temperature is 20-45°C.

[0031] In some preferred embodiments of the present invention, after the reaction of the first organic compound with the Y-type molecular sieve, the slurry is filtered, washed, and dried. In the preparation method of the present invention, the solid-liquid separation, washing, and drying methods can be conventional in the art.

[0032] In some preferred embodiments of the present invention, the first organic compound is one or a combination of two or more of arginine, phenylalanine, methionine, and 4-hydroxybenzamidine hydrochloride.

[0033] According to another aspect of the present invention, a modified Y-type molecular sieve obtained according to the above preparation method is provided, which has small crystals.

[0034] In the preparation method of the present invention, there is no additional limitation on the Y-type molecular sieve used as a raw material. After the modification of the present invention, the silicon-aluminum ratio in the Y-type molecular sieve does not change.

[0035] According to another aspect of the present invention, a hydrocracking catalyst is provided, wherein the raw material thereof comprises the modified Y-type molecular sieve described above. The method for preparing the hydrocracking catalyst from the modified Y-type molecular sieve of the present invention can be conventional in the art.

[0036] The present invention also provides a hydrocracking process, which is carried out using the hydrocracking catalyst provided by the present invention.

[0037] Compared with the prior art, the molecular sieve synthesized by the present invention has the following beneficial effects: the modified Y-type molecular sieve prepared by the method of the present invention has smaller crystals and has good performance when used in the field of hydrocatalytic cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 shows a mass spectrum of the intermediate product Y-C1 with a molecular mass of 18 under programmed temperature conditions according to Example 1 of the present invention.

[0039] FIG2 shows UV-visible spectra of an initial aqueous solution of the intermediate product Y-C1 prepared according to Example 1 of the present invention and a solution of Y-C1 after washing.

[0040] FIG3 shows a SEM image of the modified Y-type molecular sieve Y-A1 according to Example 1 of the present invention.

[0041] FIG4 shows a SEM image of the comparative Y-type molecular sieve Y-B1 according to Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0042] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0043] Example 1

[0044] Weigh 10 g of Y molecular sieve and add it to 50 g of water, stir evenly, then add 0.8 g of phenylalanine, and keep the temperature at 45 ° C for 3 hours. Then, filter and wash the slurry, and dry the solid material at 80 ° C to obtain the intermediate product Y-C1.

[0045] After preparing an 8% sucrose solution, the intermediate product Y-C1 was impregnated with an equal volume of the solution and then dried. The resulting solid was maintained at 160°C in a nitrogen atmosphere for 2 hours, then heated to 200°C for 5 hours to obtain the modified Y-type molecular sieve Y-A1.

[0046] The intermediate product Y-C1 was characterized using thermogravimetric-infrared chromatography-mass spectrometry (TG-IR) to characterize its molecular sieve properties, focusing on the release of water molecules under programmed temperature. Therefore, the release curve of a molecule with a molecular mass of 18 was measured as a function of temperature.

[0047] As shown in Figure 1, as the temperature increases, water is released preferentially around 100°C. This temperature is close to the boiling point of water, indicating that the water released at this temperature is water from the air adsorbed by the intermediate product. Subsequently, water is released between 200°C and 350°C. When the intermediate product is treated at this temperature, the color of the molecular sieve changes to brown, indicating that this portion of water released is water released by the decomposition of the second organic compound involved in the modification. This demonstrates that the intermediate product has the ability to release gas when heat treated at 200°C to 350°C.

[0048] UV-visible spectroscopy was used to characterize that the water-washed intermediate product Y-C1 would not cause any change in its organic matter content.

[0049] As shown in Figure 2, at the initial stage of preparation, 0.8 g of phenylalanine dissolved in 50 g of water exhibited an obvious UV-visible absorption spectrum. When the intermediate product Y-C1 was added to 50 g of water, stirred, and filtered, the solution after washing did not have a significant UV-visible absorption spectrum, indicating that the modified second organic matter had chemically reacted with the molecular sieve to form a stable amino acid-Y type molecular sieve structure.

[0050] Example 2

[0051] Weigh 10 g of Y molecular sieve and add it to 100 g of water, stir evenly, then add 0.2 g of methionine and 0.8 g of 4-hydroxybenzamidine hydrochloride and keep the temperature at 50 ° C for 0.5 h. Then filter and wash the slurry, and dry the solid material at 90 ° C to obtain the intermediate product Y-C2.

[0052] After preparing a 1% fructose solution, Y-C2 was impregnated with an equal volume of the solution and then dried. The resulting solid was kept at 180°C in an Ar atmosphere for 5 hours, then heated to 240°C for 2 hours to obtain the modified Y-type molecular sieve Y-A2.

[0053] Example 3

[0054] Weigh 10 g of Y molecular sieve and add it to 80 g of water, stir evenly, then add 2 g of arginine and keep the temperature at 20°C for 2 hours. Then filter and wash the slurry, and dry the solid material at 100°C to obtain the intermediate product Y-C3.

[0055] A mixed solution of 1% fructose and 2% glucose was prepared, and then impregnated with 1.2 times the volume of Y-C3, followed by drying. The resulting solid was maintained at 200°C in a He environment for 3 hours, then heated to 280°C for 4 hours to obtain the modified Y-type molecular sieve Y-A3.

[0056] Example 4

[0057] Weigh 10 g of Y molecular sieve and add it to 90 g of water, stir evenly, then add 2 g of arginine, 1 g of phenylalanine, and 0.3 g of methionine and keep the temperature at 40 ° C for 2.5 hours. Then filter and wash the slurry, and dry the solid material at 110 ° C to obtain the intermediate product Y-C4.

[0058] A mixed solution of 1% fructose, 2% glucose, and 3% sucrose was prepared, and then an equal volume of Y-C4 was impregnated and dried. The resulting solid was maintained at 200°C in a nitrogen atmosphere for 4 hours, then heated to 350°C for 2 hours to obtain the modified Y-type molecular sieve Y-A4.

[0059] Comparative Example 1

[0060] Weigh 10g of Y molecular sieve and prepare an 8% sucrose solution. The sieve is then impregnated with an equal volume of sucrose solution and dried. The resulting solid is held at 160°C in a nitrogen atmosphere for 2 hours, then heated to 200°C for 5 hours to obtain comparative Y molecular sieve Y-B1.

[0061] Comparative Example 2

[0062] Weigh 10g of Y molecular sieve and add it to 50g of water, stir evenly, then add 0.8g of phenylalanine, and keep the temperature at 45°C for 3h. Then filter and wash the slurry, and dry the solid matter at 80°C to obtain an intermediate product.

[0063] The intermediate product was kept at 160°C for 2 hours in a N2 environment, and then heated to 200°C and kept for 5 hours to obtain a small-grain Y-type molecular sieve Y-B2.

[0064] The SEM characterization images of Y-A1 and Y-B1 are shown in Figures 3 and 4, respectively. The figures clearly show that the size of the molecular sieve prepared by the present invention is significantly reduced, which proves that the technology of the present invention is effective in preparing small-grain Y-type molecular sieves.

[0065] The Y-A1, Y-A2, Y-A3, Y-A4, Y-B1 and Y-B2 molecular sieves were subjected to physical adsorption characterization, and the characterization results are shown in Table 1.

[0066] As can be seen from the data in Table 1, the Y molecular sieve prepared by the present invention has the advantages of larger pore volume and higher specific surface area compared with the comparative technology. The average pore size of the modified Y-type molecular sieve obtained by the present invention is relatively low. The reason is that the explosion process mainly occurs in the defect sites between multiple crystals, specifically the mesoporous channels. The reduction in the average pore size of the molecular sieve proves that the explosion process mainly occurs in the mesoporous channels between multiple crystals in the molecular sieve cluster, proving the effectiveness of the method of the present invention in preparing small-grain molecular sieves.

[0067] Table 1

[0068] The Y-A1, Y-A2, Y-A3, Y-A4, Y-B1, and Y-B2 molecular sieves were characterized by NH3-TPD, and the characterization results are shown in Table 2. As can be seen from the data in Table 2, the present invention has a higher NH3 adsorption capacity than the comparative technology, which means that there are more acidic centers. The molecular sieve prepared by the method of the present invention can more fully expose the acidic sites of the molecular sieve.

[0069] Table 2

[0070] 3g of Y-A1, Y-A2, Y-A3, Y-A4, Y-B1 and Y-B2 molecular sieves were weighed respectively and evenly mixed with 70g of alumina, 30g of non-supported active phase and 2g of sesbania powder. The mixture was wet mixed with aqueous nitric acid solution and then extruded into strips. The shaped products were dried at 120°C for 4h and calcined at 500°C for 3h to obtain hydrocracking catalysts CAT-A1, CAT-A2, CAT-A3, CAT-A4, CAT-B1 and CAT-B2 respectively. The prepared catalysts were prepared using straight-run diesel as raw material at 350°C, 6.5MPa, hydrogen-to-oil ratio of 1000 and space velocity of 3.5h. -1 Catalyst evaluation experiments were carried out under the conditions of , and the test results are shown in Table 3. The conversion rate is the mass fraction of the fraction below 180 ° C in the total products.

[0071] Table 3

[0072] It can be seen from the evaluation results of each catalyst in Table 3 that the hydrocracking catalyst prepared by using the small-particle molecular sieve synthesized by the present invention has a higher conversion rate than that of the comparative technology, which means that the molecular sieve synthesized by using the technical solution of the present invention has higher performance.

[0073] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a modified Y-type molecular sieve, wherein: include: In a liquid phase system, a first organic compound is reacted with a Y-type molecular sieve to obtain an intermediate product; The first organic compound has one or a combination of two or more of amidine, benzyl, and thiol functional groups; The intermediate product is mixed with an impregnation solution containing a second organic compound, and then heat-treated in a protective atmosphere to obtain the modified Y-type molecular sieve; Wherein, the mass ratio of the Y-type molecular sieve to the first organic matter is 3-12.5:1; The second organic matter can be decomposed and carbonized at 160-200°C.

2. The preparation method according to claim 1, wherein The second organic matter includes one or a combination of two or more of glucose, fructose and sucrose.

3. The preparation method according to claim 1, wherein The heat treatment comprises a low temperature stage and a high temperature stage which are performed sequentially.

4. The preparation method according to claim 3, wherein The temperature of the low temperature stage is 160-200° C. and the time is 2-5 hours.

5. The preparation method according to claim 3, wherein: The temperature of the high temperature stage is 200-350° C. and the time is 2-5 hours.

6. The preparation method according to claim 3, wherein: The temperature difference between the low temperature stage and the high temperature stage is not less than 40°C.

7. The preparation method according to claim 1, wherein In the impregnation solution, the mass concentration of the second organic matter is 1-8%.

8. The preparation method according to claim 1, wherein The method of mixing the intermediate product with the impregnation solution containing the second organic matter is equal volume impregnation.

9. The preparation method according to claim 1, wherein The temperature for the reaction between the first organic matter and the Y-type molecular sieve is 20-50° C. and the time is 0.5-3 h.

10. The preparation method according to claim 1, wherein: The first organic matter is one or a combination of two or more of arginine, phenylalanine, methionine, and 4-hydroxybenzamidine hydrochloride.

11. A modified Y-type molecular sieve obtained by the preparation method according to any one of claims 1 to 10.

12. A hydrocracking catalyst, wherein: The raw material comprises the modified Y-type molecular sieve described in claim 11.

13. A hydrocracking process, which is carried out using the hydrocracking catalyst according to claim 12.

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