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 method comprises the following steps: reacting an organic matter with a Y-type molecular sieve in a liquid phase system to obtain an intermediate product A; wherein the mass ratio of the Y-type molecular sieve to the organic matter is (3-12.5): 1; wherein the organic matter contains one or a combination of more than two of amidino, benzyl and sulfydryl functional groups; carrying out heat treatment on the intermediate product A in a protective atmosphere to obtain an intermediate product B; and carrying out chemical treatment on the intermediate product B in an acidic or alkaline liquid phase system, and then roasting to obtain the modified Y-type molecular sieve. The molecular sieve prepared by the preparation method has good catalytic activity.

Description

Technical Field

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

[0002] Hydrocracking technology plays a very important role in the process of converting heavy and inferior distillate oils into clean fuels and high-quality chemical raw materials. Hydrocracking catalysts containing molecular sieves are favored by the industry due to their better activity selectivity and long-cycle service life. The Y-type molecular sieve has a supercage surrounded by β-cages and hexagonal prismatic cages, which is composed 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. Due to its rich pore structure, it has a large number of cracking active centers required for solid acid catalysts. Since the directly synthesized Y-type molecular sieve has a silica-alumina ratio of only 2-5, the low-silica-alumina Y-type molecular sieve that only removes sodium ions through ammonium exchange has limited hydrothermal stability. The high-silica-alumina Y-type molecular sieve obtained by modification can have good hydrothermal stability and acid stability. Currently, the modification methods of Y-type molecular sieves used in the hydrocracking technology field mainly include acid-base processes and high-temperature steam heat treatment processes for adjusting the pore structure and acid distribution through dealumination treatment. In recent years, the process of first performing acid treatment and then alkali treatment or alkaline salt treatment on Y molecular sieves can greatly increase the secondary pore volume of the molecular sieve and improve the diffusion ability of reaction products in the molecular sieve. Adjusting the pore structure and acid distribution of the molecular sieve through modification technology is an important research direction. However, in some reaction systems, on the one hand, it is necessary to retain a certain amount of regular microporous structure in the molecular sieve structure, and on the other hand, it is necessary to have a certain amount of connected tunnel structures on the surface of the molecular sieve to facilitate the distribution of active metal atoms. This poses higher requirements for the modification process of the molecular sieve. Especially in the current situation where environmental protection requirements are becoming increasingly strict, using an environmentally friendly treatment process is of practical significance.

[0003] Currently, there is still room for optimization in the modification process of Y-type molecular sieves. It is necessary to provide a Y-type molecular sieve for hydrocracking catalysis that is safe, environmentally friendly, and has high catalytic activity. Summary of the Invention

[0004] In order to solve the above problems in the prior art, the object of the present invention is to provide a modified Y-type molecular sieve and a preparation method thereof. The preparation method is safe and harmless, and the obtained molecular sieve has a tunnel structure on its surface, and the molecular sieve has good catalytic activity.

[0005] To achieve the above object, according to one aspect, the present invention provides a preparation method of a modified Y-type molecular sieve, which includes:

[0006] In a liquid phase system, an organic compound reacts with a Y-type molecular sieve to obtain an intermediate product A; wherein, the mass ratio of the Y-type molecular sieve to the organic compound is 3 to 12.5:1; wherein, the organic compound contains one or a combination of two or more of amidino, benzyl, and mercapto functional groups;

[0007] Under a protective atmosphere, the intermediate product A is heat-treated to obtain an intermediate product B;

[0008] The intermediate product B is chemically treated in an acidic or basic liquid phase system and then calcined to obtain the modified Y-type molecular sieve.

[0009] The method of the present invention first adsorbs a certain amount of organic compound onto the surface of the Y-type molecular sieve through a chemical reaction for the first step of modification; secondly, heat treatment is carried out under a protective atmosphere. In this process, the organic compound decomposes and loses weight, releasing water vapor, and H and O elements are removed. The remaining C element can coat the surface of the molecular sieve, which is beneficial for protecting the microporous structure in the molecular sieve; then, the chemical treatment mainly affects the mesoporous properties of the Y-type molecular sieve. The chemical treatment of the present invention can achieve directional regulation of the mesoporous channel structure of the molecular sieve and enhance the connectivity of the channel structure; on the outer surface of the molecular sieve, the framework structure on the outer surface of the molecular sieve can be directionally damaged, thereby generating a certain pit structure. The generation of this pit structure is beneficial in the preparation of the catalyst, enabling the near-spherical non-supported active phase to fall into the pits, thereby enhancing the binding degree between the non-supported active phase and the Y-type molecular sieve, achieving the purpose of enhancing the activity and selectivity of the non-supported catalyst.

[0010] It should be noted that only under the protection of a protective atmosphere can the above-mentioned C element coat the surface of the molecular sieve.

[0011] In some preferred embodiments of the present invention, in the liquid phase system, the solvent is water. Preferably, the solid-liquid mass ratio is 1:5 to 10.

[0012] In some preferred embodiments of the present invention, the protective atmosphere is an atmosphere composed of gases such as nitrogen, argon, and helium.

[0013] In some preferred embodiments of the present invention, in the chemical treatment, the pH of the liquid phase system is ≤1 or ≥13. In actual operation, an acid or a base is added to the liquid phase system to achieve the pH range. Among them, the acid can be an organic acid and / or an inorganic acid, such as oxalic acid, citric acid, dilute hydrochloric acid, and dilute nitric acid, and the base can be a common base in industry, such as sodium hydroxide and ammonia water.

[0014] In some preferred embodiments of the present invention, the temperature of the chemical treatment is 35 to 60 °C and the time is 0.5 to 4 h.

[0015] In some preferred embodiments of the present invention, the temperature for reacting the organic matter with the Y-type molecular sieve is 20 to 50 °C, and the time is 1 to 3 h.

[0016] In some preferred embodiments of the present invention, the temperature of the calcination is 450 to 560 °C, and the time is 3 to 6 h.

[0017] In some preferred embodiments of the present invention, the mass ratio of the Y-type molecular sieve to the organic matter is 5 to 10:1.

[0018] In some preferred embodiments of the present invention, the organic matter is one or a combination of two or more of arginine, phenylalanine, methionine, ethylamidine hydrochloride, benzamidine hydrochloride, and 3-(formamidothio)-1-propanesulfonic acid.

[0019] More preferably, the organic matter is one or a combination of two or more of arginine, phenylalanine, and methionine.

[0020] In some preferred embodiments of the present invention, the temperature of the heat treatment is 210 to 240 °C, and the time is 0.1 to 1 h.

[0021] 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 a tunnel structure on its surface. In the preparation of the catalyst, the generation of this tunnel structure is conducive to the near-spherical non-supported active phase falling into the tunnels, thereby enhancing the binding degree between the non-supported active phase and the Y-type molecular sieve, and achieving the purpose of enhancing the activity and selectivity of the non-supported catalyst.

[0022] According to another aspect of the present invention, there is provided a hydrocracking catalyst, the raw material of which includes the above-mentioned modified Y-type molecular sieve.

[0023] In some embodiments of the present invention, preferably, the hydrocracking catalyst further includes a non-supported active phase, alumina, and optionally amorphous silica-alumina. Through mixing, shaping, drying, and calcination, a non-supported hydrocracking catalyst is obtained.

[0024] Compared with the prior art, the molecular sieve synthesized in the present invention has the following beneficial effects: The hydrocracking catalyst prepared from the modified Y-type molecular sieve of the present invention has a higher conversion rate, which means that the molecular sieve synthesized by the present invention has higher performance. Description of the Drawings

[0025] Figure 1 Shows the ultraviolet-visible spectra of the aqueous solution at the initial stage of preparing the Y-A1 molecular sieve in Example 1 and the solution after washing the Y-A1.

[0026] Figure 2 The mass spectrometry diagram with a molecular mass of 18 under the condition of temperature rise of Y-A2 molecular sieve in Example 2 is shown.

[0027] Figure 3 The SEM image of Y3 molecular sieve in Example 3 is shown.

[0028] Figure 4 The SEM image of unmodified Y-type molecular sieve is shown. Detailed implementation manners

[0029] For a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0030] Example 1

[0031] Weigh 10 g of Y molecular sieve and add it to 80 g of deionized water, stir evenly, then add 0.3 g of methionine and 0.5 g of acetamidine hydrochloride, and carry out the reaction at 22 °C for 3 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain the intermediate product A, denoted as Y-A1.

[0032] Heat-treat the Y-A1 molecular sieve at 210 °C under a nitrogen atmosphere for 0.5 h to obtain Y-B1. Then, take 9 g of Y-B1 and add it to 90 g of deionized water, stir evenly; then add 10.3 g of citric acid, with the pH less than 1, and raise the temperature to 60 °C for constant temperature. After reacting for 2 h, filter and wash the slurry, dry it at 120 °C for 3 h, and calcine it at 470 °C for 4 h to obtain the modified Y-type molecular sieve, denoted as Y1.

[0033] Use ultraviolet-visible spectroscopy to characterize the ability of washed Y-A1 not to cause changes in its organic matter content. As Figure 1 shown, at the initial stage of preparation, there is an obvious ultraviolet-visible absorption spectrum when 0.3 g of methionine and 0.5 g of acetamidine hydrochloride are dissolved in 80 g of water; add Y-A1 to 80 g of water, stir and then filter to take the washed solution, which does not have a significant ultraviolet-visible absorption spectrum, indicating that the structure of the organic matter-modified Y molecular sieve is stable and the modified organic matter cannot be eluted by washing with water.

[0034] Example 2

[0035] Weigh 10 g of Y molecular sieve and add it to 100 g of deionized water, stir evenly, then add 2 g of arginine, and carry out the reaction at 30 °C for 2 h. Then, filter and wash the formed slurry, and dry it at 120 °C for 3 h to obtain the intermediate product A, denoted as Y-A2.

[0036] The Y-A2 molecular sieve was heat-treated at 230 °C under a nitrogen atmosphere for 0.1 h to obtain Y-B2. Then, 9 g of Y-B2 was added to 90 g of deionized water and stirred evenly; 1.88 g of hydrochloric acid (mass concentration 36%) was added, the pH was less than 1, and the temperature was raised to 50 °C for constant temperature. After reacting for 2 h, the slurry was filtered, washed, dried at 120 °C for 3 h, and calcined at 500 °C for 5 h to obtain a modified Y-type molecular sieve, denoted as Y2.

[0037] The performance of the Y-A2 molecular sieve was characterized using a thermogravimetry-infrared-chromatography-mass spectrometry instrument, with a focus on the release of water molecules under programmed temperature conditions. Therefore, the release curve of molecules with a molecular mass of 18 detected in the combined instrument as a function of temperature is as Figure 2 shown. As can be seen from Figure 2 this, there is water release in the range of 200 - 350 °C. By observing the change in the color of the molecular sieve, it can be seen that its color changes from white to brown. This indicates that the water released during the heat treatment process is released from the carbonization and dehydration of organic matter, rather than the crystal water or adsorbed water in the molecular sieve framework.

[0038] Example 3

[0039] Weigh 10 g of Y molecular sieve and add it to 50 g of deionized water, stir evenly, then add 1.7 g of phenylalanine and 1.3 g of benzamidine hydrochloride, and react at 45 °C for 2 h. After that, the formed slurry was filtered, washed, and dried at 120 °C for 3 h to obtain an intermediate product A, denoted as Y-A3.

[0040] The Y-A3 molecular sieve was heat-treated at 240 °C under a nitrogen atmosphere for 1 h to obtain Y-B3. Then, 9 g of Y-B3 was added to 90 g of deionized water and stirred evenly; 1.8 g of sodium hydroxide was added, the pH was greater than 13 and less than 14, and the temperature was raised to 40 °C for constant temperature. After reacting for 2 h, the slurry was filtered, washed, dried at 120 °C for 3 h, and calcined at 550 °C for 3 h to obtain a modified Y-type molecular sieve, denoted as Y3.

[0041] Scanning electron microscopy was used to characterize that a pit structure was formed on the outer surface of the molecular sieve before and after modification. The scanning electron micrographs of Y3 molecular sieve and Y molecular sieve are respectively as Figure 3 and Figure 4As shown, it can be clearly recognized that for the molecular sieve obtained by the modification of the present invention, compared with the unmodified Y-type molecular sieve, a certain pit structure is generated on the surface. For the non-supported active phase commonly used in the hydrocracking system, since its particle size is generally concentrated between 18 and 30 nm, when the modified Y-type molecular sieve of the present invention is combined with it for the preparation of a hydrocracking catalyst, it is beneficial for the non-supported active phase to be embedded in the surface pit structure of the molecular sieve, thereby enhancing the synergistic effect between the solid acid center and the metal active center and improving the catalytic reaction activity of the catalyst.

[0042] Comparative Example 1

[0043] Weigh 9 g of Y molecular sieve and add it to 90 g of deionized water, stir evenly, then add 10.3 g of citric acid, with the pH less than 1, and raise the temperature to 60 °C for reaction for 2 h. Then, filter and wash the slurry, dry it at 120 °C for 3 h, and calcine it at 470 °C for 4 h to obtain the conventional modified D1 molecular sieve.

[0044] Comparative Example 2

[0045] Weigh 9 g of Y molecular sieve and add it to 90 g of deionized water, stir evenly, then add 1.8 g of sodium hydroxide, with the pH greater than 13 and less than 14, and raise the temperature to 50 °C for reaction for 2 h. Then, filter and wash the slurry, dry it at 120 °C for 3 h, and calcine it at 550 °C for 3 h to obtain the conventional modified D2 molecular sieve.

[0046] The physical adsorption characterization results of Y, Y-B1, Y-B2, Y-B3, Y1, Y2, Y3, D1, and D2 molecular sieves are shown in Table 1.

[0047] Among them, the total specific surface area is calculated by the BET method. In order to make the BET equation hold, when the range of p / p 0 is within 0.01 - 0.30 and not less than 3 points, and the C value satisfying the BET equation is greater than 0, the BET specific surface area is obtained.

[0048] The characterization of the mesoporous and microporous specific surface areas is based on the BET specific surface area and calculated by the t-Plot method.

[0049] From the data in Table 1, it can be seen that the microporous specific surface areas of Y-B1, Y-B2, and Y-B3 molecular sieves are significantly lower than that of the Y molecular sieve, while the mesoporous specific surface areas are not much different, indicating that the carbonization method of the present invention can block and protect the microporous structure. The mesoporous specific surface areas of Y1, Y2, and Y3 molecular sieves are expanded to a certain extent, indicating that the method of the present invention can achieve directional regulation of the mesoporous channel structure of the molecular sieve and enhance the connectivity of the channel structure.

[0050] In the comparison of the micropore specific surface area, it can be seen that there is little difference between Y1, Y2, Y3 and Y zeolite. However, there is a significant decrease in the micropore specific surface area of D1 and D2 zeolites, indicating that the method of the present invention can play a protective role in the micropore structure of Y zeolite during chemical modification.

[0051] Table 1

[0052]

[0053] Weigh 5 g of Y1, Y2, Y3, D1, and D2 zeolites, 55 g of alumina, 25 g of amorphous silica-alumina, 15 g of non-supported active phase metal, and 1.5 g of phthalic anhydride powder respectively, mix them evenly, and carry out wet mixing with nitric acid aqueous solution. Then extrude them into pellets. After the formed products are dried at 120 °C for 4 h and calcined at 450 °C for 3 h, hydrocracking catalysts CAT-Y1, CAT-Y2, CAT-Y3, CAT-D1, and CAT-D2 are obtained respectively. Using the prepared catalysts with straight-run diesel as the raw material, carry out catalyst evaluation experiments under the conditions of 345 °C, 6.0 MPa, hydrogen-oil ratio of 850, and space velocity of 2.5 h -1 . The test results are shown in Table 2 below. Among them, the conversion rate is the mass fraction of the fraction product with a boiling point lower than 180 °C in all products. From the evaluation results of each catalyst in Table 2, it can be seen that compared with the comparative technology, the hydrocracking catalysts prepared using the zeolite synthesized by the present technology have a higher conversion rate, indicating that the zeolite synthesized by the present technology has higher performance.

[0054] Table 2

[0055] catalyst conversion rate CAT-Y1 43.5％ CAT-Y2 45.7％ CAT-Y3 39.6％ CAT-D1 33.9％ CAT-D2 35.8％

[0056] 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 deformations according to the present invention. However, these corresponding changes and deformations 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, an organic substance reacts with a Y-type molecular sieve to obtain an intermediate product A; wherein, the mass ratio of the Y-type molecular sieve to the organic substance is 3 to 12.5:1; wherein, the organic substance contains one or a combination of two or more of amidino, benzyl, and mercapto functional groups; Under a protective atmosphere, the intermediate product A is heat-treated to obtain an intermediate product B; The intermediate product B is chemically treated in an acidic or alkaline liquid phase system and then calcined to obtain the modified Y-type molecular sieve.

2. The preparation method according to claim 1, characterized in that, In the chemical treatment, the pH of the liquid phase system is ≤1 or ≥13.

3. The preparation method according to claim 1, characterized in that, The temperature of the chemical treatment is 35 to 60 °C, and the time is 0.5 to 4 h.

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

5. The preparation method according to claim 1, characterized in that, The temperature of the calcination is 450 to 560 °C, and the time is 3 to 6 h.

6. The preparation method according to claim 1, characterized in that, The mass ratio of the Y-type molecular sieve to the organic substance is 5 to 10:

1.

7. The preparation method according to claim 1, characterized in that, The organic substance is one or a combination of two or more of arginine, phenylalanine, methionine, ethylamidine hydrochloride, benzamidine hydrochloride, and 3-(amidinosulfanyl)-1-propanesulfonic acid.

8. The preparation method according to claim 7, characterized in that, The organic substance is one or a combination of two or more of arginine, phenylalanine, and methionine.

9. The preparation method according to claim 1, characterized in that, The temperature of the heat treatment is 210 to 240 °C, and the time is 0.1 to 1 h.

10. A modified Y-type molecular sieve obtained by the preparation method according to any one of claims 1 to 9.

11. A hydrocracking catalyst, characterized in that, Its raw material contains the modified Y-type molecular sieve according to claim 10.

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