Modified Y-type molecular sieve, preparation method thereof and hydrocracking catalyst

Abstract

The invention provides a modified Y-type molecular sieve, a preparation method thereof and a hydrocracking catalyst. The preparation method comprises the following steps: reacting a first organic matter with a Y-type molecular sieve in a liquid phase system to obtain an intermediate product; the first organic matter has one or a combination of more than two of amidino, benzyl and sulfydryl functional groups; mixing the intermediate product with an impregnation liquid containing a second organic matter, and then carrying out heat 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; wherein the second organic matter can be decomposed and carbonized at 160-200 DEG C. The molecular sieve prepared by the method has good catalytic activity.

Description

Technical Field

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

[0002] The Y-type molecular sieve belongs to the FD-3M space group and has a spinel-type structure. This structure is composed of tetrahedrons and octahedrons; it has four sublattices, where two octahedral sublattices are adjacent to the tetrahedral sublattice, and the other two octahedral sublattices are adjacent to each other. This molecular sieve is an artificially synthesized molecular sieve, having a supercage surrounded by β cages and hexagonal prism cages, consisting of 18 four-membered rings, 4 six-membered rings, and 4 twelve-membered rings, forming a structural pore orifice diameter of 0.74 nm and an inner diameter of 1.2 nm; it has a rich pore structure and a large number of cracking active centers required for solid acid catalysts.

[0003] During the synthesis process of the molecular sieve, polycrystalline micron-sized clusters are easily formed. Due to its relatively large grain size, the diffusion resistance is large during the catalytic reaction process, which limits the mass transfer effect during the reaction process. At the same time, the cracking activity and the selectivity of the target product will also be restricted. Compared with conventional Y-type molecular sieves, small-grain Y-type molecular sieves have certain advantages in terms of materials. Since the size of the molecular sieve is reduced, the molecular sieve can have a larger specific surface area, and at the same time, the acidic centers are 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 mainly two methods to obtain 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 small-grain Y molecular sieves with controllable particle size. This method mainly includes the following steps: First, a guiding agent is prepared, and then a certain amount of the guiding agent is added to the silica-alumina gel, and it is directly loaded into an autoclave with a polytetrafluoroethylene liner, and crystallized at 80-130 °C for a certain time. After filtration and drying, small-grain Y molecular sieves with controllable particle size can be obtained. However, this synthesis method has problems of poor hydrothermal stability and difficult solid-liquid separation.

[0006] CN104591212A discloses a method for preparing small-grain Y-type molecular sieves. After preparing the guiding agent, this method uses an acid-base precipitation method to prepare an amorphous silica-alumina precursor, and then the amorphous silica-alumina precursor is made into a silica-alumina gel. Finally, through two-step dynamic crystallization, and then through filtration, washing, and drying, small-grain Y-type molecular sieves are obtained. However, this method has a relatively long molecular sieve preparation path, and the change in the silica-alumina ratio of the required Y-type molecular sieve has a relatively large impact on the catalyst preparation formula and process, and the flexibility of the scheme is relatively low.

[0007] CN105712372B discloses a nano-sized small-crystalline Y-type molecular sieve and a preparation method thereof. The method comprises the following steps: First, place the Y-type molecular sieve into an appropriate amount of distilled water, and disperse the molecular sieve by using high-speed stirring and a high-frequency ultrasonic instrument; then, at a certain temperature, dropwise add an ammonium fluorosilicate solution to the slurry for reaction, and then separate the solid from the slurry; finally, place the slurry in a sealed high-pressure reaction kettle for supercritical carbon dioxide drying treatment, and thus obtain the nano-sized small-crystalline Y-type molecular sieve. The instruments used in this method are relatively complex, which is not conducive to industrial scale-up production, and the treatment process involves an alkaline environment. During the process of changing the conventional-sized molecular sieve into a nano-sized small-crystalline molecular sieve, there is a loss of silicon or aluminum in the original molecular sieve, changing the silicon-aluminum ratio of the original molecular sieve, which is not conducive to maintaining the reaction properties of the original molecular sieve. Summary of the Invention

[0008] In order to solve the above problems in the prior art, the object of the present invention is to provide a preparation method of a modified Y-type molecular sieve. The preparation method of the present invention performs heat treatment on the Y-type molecular sieve modified by a first organic matter and a second organic matter in sequence, and obtains a small-crystalline Y-type molecular sieve. The modified Y-type molecular sieve has good hydrocracking catalytic activity.

[0009] In order to achieve the above object, according to one aspect of the present invention, there is provided a preparation method of a modified Y-type molecular sieve, which comprises:

[0010] In a liquid phase system, react a first organic matter with a Y-type molecular sieve to obtain an intermediate product; the first organic matter has one or a combination of two or more of amidino, benzyl, and mercapto functional groups;

[0011] Mix the intermediate product with an impregnating solution containing a second organic matter, and then perform heat treatment in a protective atmosphere to obtain the modified Y-type molecular sieve;

[0012] wherein, the mass ratio of the Y-type molecular sieve to the first organic matter is 3-12.5:1;

[0013] wherein, the second organic matter can be decomposed and carbonized at 160-200 °C.

[0014] In the reaction of the first step, the present invention enables the Y-type molecular sieve to adsorb a certain amount of the first organic matter to form an intermediate product. In the reaction of the second step, the present invention impregnates the intermediate product with the second organic matter that is prone to decompose and carbonize at low temperature, and after the heat treatment and carbonization of the second organic matter, a dense carbon film can be preferentially formed on the surface of the molecular sieve. The carbon film can coat the Y-type molecular sieve. Further, in the heat treatment, the first organic matter decomposes to release water vapor, and the water vapor is trapped in the aforementioned dense carbon film and cannot overflow in time, so a small-scale explosion will occur.

[0015] Since the Y-type molecular sieve is composed of tetrahedrons and octahedrons, polycrystalline micron-sized clusters are very likely to be generated during the preparation of the molecular sieve. 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 damage the defect sites in the cluster, thereby forming a smaller particle size Y-type molecular sieve material. 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 pore properties of the molecular sieve, effectively increase the exposure of the acidic sites of the molecular sieve, and further achieve the purpose of improving the performance of the catalyst.

[0016] In some preferred embodiments of the present invention, in the liquid phase system, the solvent is water. Further preferably, the solid-liquid mass ratio is 1:5 to 10. Preferably, the solid-liquid mass ratio is 1:10.

[0017] In some preferred embodiments of the present invention, the mass ratio of the Y-type molecular sieve to the first organic matter is 5 to 10:1; further preferably, in the intermediate product, the mass percentage of the first organic matter is not less than 8 wt%. Reacting according to this ratio is more conducive to achieving the beneficial effects brought by the modification of the first organic matter.

[0018] In some preferred embodiments of the present invention, the protective atmosphere includes nitrogen atmosphere, argon atmosphere, helium atmosphere, etc.

[0019] 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.

[0020] In some preferred embodiments of the present invention, the heat treatment includes a low-temperature stage and a high-temperature stage carried out in sequence;

[0021] Preferably, the temperature of the low-temperature stage is 160 to 200 °C, and the time is 2 to 5 h;

[0022] Preferably, the temperature of the high-temperature stage is 200 to 350 °C, and the time is 2 to 5 h.

[0023] Further preferably, the time of the low-temperature stage is 2 to 3 h.

[0024] Further preferably, the temperature of the high-temperature stage is 240 to 280 °C.

[0025] In the low-temperature stage, carbonization of the second organic matter occurred, resulting in weight loss. The main component released during the weight loss process is water. In the high-temperature stage, decomposition of the first organic matter occurred, resulting in weight loss. The main component released during the weight loss process is water.

[0026] In some preferred embodiments of the present invention, the temperature difference between the low-temperature stage and the high-temperature stage is not less than 40 °C. Setting such a temperature difference preferably can better ensure the stepwise reaction of the two substances. If the temperatures are closer, the possibility of the two substances reacting simultaneously is greater.

[0027] In some preferred embodiments of the present invention, in the impregnating solution, the mass concentration of the second organic matter is 1 to 8%. If it is lower than this range, the effect is not good.

[0028] In some preferred embodiments of the present invention, the method of mixing the intermediate product with the impregnating solution containing the second organic matter is equal-volume impregnation. Equal-volume impregnation is preferably adopted, which can better enable the impregnating solution to be completely absorbed into the molecular sieve and avoid excessive residue.

[0029] In some preferred embodiments of the present invention, the temperature of the reaction of the first organic matter with the Y-type molecular sieve is 20 to 50 °C, and the time is 0.5 to 3 h. Further preferably, the reaction temperature is 20 to 45 °C.

[0030] In some preferred embodiments of the present invention, after the reaction of the first organic matter with the Y-type molecular sieve, the slurry is filtered, washed, and dried. In the preparation method of the present invention, the methods of solid-liquid separation, washing, and drying can be conventional in the art.

[0031] In some preferred embodiments of the present invention, the first organic matter is one or a combination of two or more of arginine, phenylalanine, methionine, and 4-hydroxybenzimidine hydrochloride.

[0032] According to another aspect of the present invention, there is provided a modified Y-type molecular sieve obtained by the above preparation method, which has small crystal grains.

[0033] In the preparation method of the present invention, there is no additional limitation on the Y-type molecular sieve as a raw material. After the modification of the present invention, the silicon-aluminum ratio in the Y-type molecular sieve will not change.

[0034] According to another aspect of the present invention, a hydrocracking catalyst is provided, the raw material of which includes the above-mentioned modified Y-type molecular sieve. The method for preparing the hydrocracking catalyst from the modified Y-type molecular sieve of the present invention can be conventional in the technical field.

[0035] Compared with the prior art, the molecular sieve synthesized in the present invention has the following beneficial effects: the modified Y-type molecular sieve prepared by the method of the present invention has smaller crystal grains and has good performance when used in the field of hydrocatalytic cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The mass spectrometry diagram of intermediate Y-C1 according to Example 1 of the present invention with a molecular mass of 18 under the condition of temperature programmed heating is shown.

[0037] Figure 2 The ultraviolet-visible spectra of the initial aqueous solution of intermediate Y-C1 and the solution after washing Y-C1 according to Example 1 of the present invention are shown.

[0038] Figure 3 The SEM image of the modified Y-type molecular sieve Y-A1 according to Example 1 of the present invention is shown.

[0039] Figure 4 The SEM image of the comparative Y-type molecular sieve Y-B1 according to Comparative Example 1 of the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention will be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0041] Example 1

[0042] Weigh 10 g of Y molecular sieve, add it to 50 g of water, stir evenly, then add 0.8 g of phenylalanine, keep it at a constant temperature of 45 °C for 3 h, then filter, wash the slurry, and dry the solid substance at 80 °C to obtain intermediate Y-C1.

[0043] After preparing a sucrose solution with a mass concentration of 8%, equal-volume impregnation of intermediate Y-C1 is carried out, and then it is dried. The obtained solid is in N 2 In an environment, it is kept at 160 °C for 2 hours, and then the temperature is raised to 200 °C and kept for 5 hours to obtain the modified Y-type molecular sieve Y-A1.

[0044] The intermediate product Y-C1 was characterized for the performance of molecular sieve by using a thermogravimetry-infrared chromatography-mass spectrometry (TG-IR-GC-MS) instrument, with a focus on the release of water molecules under the condition of programmed temperature rise. Therefore, the release curve of molecules with a molecular mass of 18 detected by the instrument was monitored as a function of temperature.

[0045] It can be seen from Figure 1 that as the temperature increases, water release preferentially occurs around 100 °C. This temperature is close to the boiling point of water, indicating that the water released at this temperature is the water in the air adsorbed by the intermediate product. Subsequently, water release occurs in the range of 200 - 350 °C. When the intermediate product is treated at this temperature, the color of the molecular sieve turns brown, indicating that the water released in this part is from the decomposition of the second organic substance participating in the modification, which proves that the intermediate product has the ability to release gases during heat treatment at 200 - 350 °C.

[0046] The ultraviolet-visible spectroscopy was used to characterize that washing the intermediate product Y-C1 with water does not cause a change in its organic content.

[0047] As Figure 2 shown, at the initial stage of preparation, 0.8 g of phenylalanine dissolved in 50 g of water showed an obvious ultraviolet-visible absorption spectrum. After adding the intermediate product Y-C1 to 50 g of water, stirring, filtering, and taking the washed solution, it did not show a significant ultraviolet-visible absorption spectrum, indicating that the second organic substance for modification has undergone a chemical reaction with the molecular sieve to form a stable amino acid-Y type molecular sieve structure.

[0048] Example 2

[0049] 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-hydroxybenzimidine hydrochloride, and keep the temperature at 50 °C for reaction for 0.5 h. Then filter and wash the slurry, and dry the solid at 90 °C to obtain the intermediate product Y-C2.

[0050] After preparing a fructose solution with a mass concentration of 1%, perform equal-volume impregnation on Y-C2, and then dry it. The obtained solid is kept at 180 °C for 5 hours in an Ar environment, and then heated to 240 °C and kept for 2 hours to obtain the modified Y type molecular sieve Y-A2.

[0051] Example 3

[0052] 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 reaction for 2 h. Then filter and wash the slurry, and dry the solid at 100 °C to obtain the intermediate product Y-C3.

[0053] After preparing a mixed solution of fructose with a mass concentration of 1% and glucose with a mass concentration of 2%, perform a 1.2-fold volume impregnation on Y-C3, and then dry it. The obtained solid is maintained at 200 °C for 3 hours in a He environment, and then heated to 280 °C and maintained for 4 hours to obtain the modified Y-type molecular sieve Y-A3.

[0054] Example 4

[0055] Weigh 10 g of Y-type molecular sieve, 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 it at a constant temperature of 40 °C for 2.5 h. Then filter and wash the slurry, and dry the solid substance at 110 °C to obtain the intermediate product Y-C4.

[0056] After preparing a mixed solution of fructose with a mass concentration of 1%, glucose with a mass concentration of 2%, and sucrose with a mass concentration of 3%, perform an equal-volume impregnation on Y-C4, and then dry it. The obtained solid is in N 2 environment, maintained at 200 °C for 4 hours, and then heated to 350 °C and maintained for 2 hours to obtain the modified Y-type molecular sieve Y-A4.

[0057] Comparative Example 1

[0058] Weigh 10 g of Y-type molecular sieve, prepare a sucrose solution with a mass concentration of 8%, perform an equal-volume impregnation on the molecular sieve, and then dry it. The obtained solid is in N 2 environment, maintained at 160 °C for 2 hours, and then heated to 200 °C and maintained for 5 hours to obtain the comparative Y-type molecular sieve Y-B1.

[0059] Comparative Example 2

[0060] Weigh 10 g of Y-type molecular sieve, add it to 50 g of water, stir evenly, then add 0.8 g of phenylalanine, and keep it at a constant temperature of 45 °C for 3 h. Then filter and wash the slurry, and dry the solid substance at 80 °C to obtain the intermediate product.

[0061] The intermediate product is in N 2 environment, maintained at 160 °C for 2 hours, and then heated to 200 °C and maintained for 5 hours to obtain the small crystal Y-type molecular sieve Y-B2.

[0062] The SEM characterization pictures of Y-A1 and Y-B1 are respectively as Figure 3 and Figure 4 shown. It is clearly shown in the figure that the size of the molecular sieve prepared by the present invention has been significantly reduced, which proves that the technology of the present invention for preparing small crystal Y-type molecular sieve is effective.

[0063] Perform physical adsorption characterization on the molecular sieves Y-A1, Y-A2, Y-A3, Y-A4, Y-B1, and Y-B2. The characterization results are shown in Table 1.

[0064] As can be seen from the data in Table 1, compared with the comparative technology, the Y zeolite prepared by the present invention has the advantages of larger pore volume and higher specific surface area. The average pore diameter of the modified Y zeolite obtained in the present invention is relatively low, because the cracking process mainly occurs at the defect sites between multiple crystals, specifically the mesoporous channels. The reduction of the average pore diameter of the zeolite proves that the cracking process mainly occurs in the mesoporous channels between multiple crystals in the zeolite clusters, which proves the effectiveness of the method for preparing small crystal zeolites in the present invention.

[0065] Table 1

[0066] Molecular sieve <![CDATA[Pore volume (cm 3 / g)]]> Average pore diameter (nm) <![CDATA[Specific surface area (m 2 / g)]]> Y-A1 0.53 5.39 867.8 Y-A2 0.55 5.37 869.2 Y-A3 0.61 5.33 872.4 Y-A4 0.57 5.35 871.0 Y-B1 0.45 5.89 855.6 Y-B2 0.47 5.85 860.9

[0067] The Y-A1, Y-A2, Y-A3, Y-A4, Y-B1, and Y-B2 zeolites were subjected to NH 3 -TPD characterization, and the characterization results are shown in Table 2. As can be seen from the data in Table 2, compared with the comparative technology, the present invention has a higher NH 3 adsorption amount, which means there are more acidic sites. Using the method of the present invention to prepare zeolites can make the acidic sites of the zeolites more fully exposed.

[0068] Table 2

[0069] Molecular sieve <![CDATA[Adsorption capacity (cm 3 / g)]]> Y-A1 36.4 Y-A2 36.8 Y-A3 37.1 Y-A4 35.9 Y-B1 33.1 Y-B2 33.5

[0070] Weigh 3 g of Y-A1, Y-A2, Y-A3, Y-A4, Y-B1, and Y-B2 zeolites respectively, mix them evenly with 70 g of alumina, 30 g of non-supported active phase, and 2 g of phthalic anhydride powder, carry out wet mixing with nitric acid aqueous solution, and then extrude into pellets. After the formed products are dried at 120 °C for 4 h and calcined at 500 °C for 3 h, the hydrocracking catalysts CAT-A1, CAT-A2, CAT-A3, CAT-A4, CAT-B1, and CAT-B2 are obtained respectively. Using the prepared catalysts with straight-run diesel as the raw material, under the conditions of 350 °C, 6.5 MPa, hydrogen-oil ratio of 1000, and space velocity of 3.5 h -1 , carry out the catalyst evaluation experiment, and the test results are shown in Table 3 below. Among them, the conversion rate is the mass fraction of the fraction product with a boiling point less than 180 °C in all products.

[0071] Table 3

[0072] Catalyst Conversion rate CAT-A1 35.2％ CAT-A2 34.3％ CAT-A3 36.1％ CAT-A4 35.8％ CAT-B1 24.8％ CAT-B2 25.2％

[0073] As can be seen from the evaluation results of each catalyst in Table 3, compared with the comparative technology, the hydrocracking catalyst prepared from the small crystal zeolite synthesized by the present invention has a higher conversion rate, which means that the zeolite synthesized by the technical solution of the present invention has higher performance.

[0074] 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 can make various corresponding changes and modifications according to the present invention. However, these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a modified Y-type molecular sieve, characterized in that, it includes: In a liquid phase system, reacting a first organic substance with a Y-type molecular sieve to obtain an intermediate product; The first organic substance has one or a combination of two or more of amidino, benzyl, and mercapto functional groups; Mixing the intermediate product with an impregnating solution containing a second organic substance, and then performing heat treatment 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 substance is 3 to 12.5:1; Wherein, the second organic substance can be decomposed and carbonized at 160 to 200 °C.

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

3. The preparation method according to claim 1, characterized in that, The heat treatment includes a low-temperature stage and a high-temperature stage carried out in sequence.

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

5. The preparation method according to claim 3, characterized in that, The temperature of the high-temperature stage is 200 to 350 °C, and the time is 2 to 5 h.

6. The preparation method according to claim 3, characterized in that, 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, characterized in that, In the impregnating solution, the mass concentration of the second organic substance is 1 to 8%.

8. The preparation method according to claim 1, characterized in that, The method of mixing the intermediate product with the impregnating solution containing the second organic substance is equal-volume impregnation.

9. The preparation method according to claim 1, characterized in that, The temperature of the reaction of the first organic substance with the Y-type molecular sieve is 20 to 50 °C, and the time is 0.5 to 3 h.

10. The preparation method according to claim 1, characterized in that, The first organic substance is one or a combination of two or more of arginine, phenylalanine, methionine, and 4-hydroxybenzimidine 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, characterized in that, Its raw material contains the modified Y-type molecular sieve according to claim 11.

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