One-step preparation of multi-level pore high silicon-aluminum ratio Y-type molecular sieve

Abstract

The present invention belongs to the technical field of molecular sieve synthesis, and specifically relates to a one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve. The steps of the present invention are as follows: HY type molecular sieve fine powder is loaded into a roasting furnace, and the furnace temperature is raised to a certain temperature; an organic acid solution is passed into a roasting furnace, and at a certain mass space velocity, a Y-type molecular sieve with a multi-level pore structure is finally prepared after hydrothermal roasting for a period of time; the prepared Y-type molecular sieve has a molar ratio of skeleton silicon oxide to aluminum oxide of 25-60, a relative crystallinity of 60-90%, a unit cell constant of 2.425-2.440nm, and an average pore size of between 2-5nm. The present invention solves the problem of multiple exchange washing and multiple hydrothermal roasting in conventional production, reduces energy consumption and pollution, improves efficiency, and hydrothermally roasts the HY molecular sieve in a gas phase organic acid atmosphere, which can dredge the pores, and by adjusting the pore structure, the performance of the molecular sieve can be optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve synthesis, and in particular relates to a one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve. Background Art

[0002] Y-type molecular sieve is particularly important in the development of petrochemical catalysts due to its excellent pore structure and suitable surface acidity. As crude oil becomes increasingly heavy, improving the accessibility of catalyst active centers and the catalytic conversion ability of macromolecules has become a research focus.

[0003] Due to its mesoporous or macroporous structure, the multi-level pore Y-type molecular sieve has the advantages of improving the mass transfer of macromolecular substances and enhancing the accessibility of catalytic active centers. At the same time, the rich multi-level pore structure helps to reduce the pore blockage caused by carbon deposition or coking, and prolong the service life of the catalyst. The high silicon-aluminum ratio Y-type molecular sieve exhibits better thermal stability and hydrothermal stability, which is conducive to maintaining the crystallinity and catalytic stability of the molecular sieve. The multi-level pore high silicon-aluminum ratio Y-type molecular sieve is designed to improve its performance in catalysis, adsorption and separation.

[0004] In practical applications, molecular sieves with multi-level pore structures can adjust the crystallinity, silicon-aluminum ratio and specific surface area of ​​Y-type molecular sieves by adjusting the synthesis conditions, using different templates or post-treatment methods, thereby optimizing their performance. Molecular sieves with multi-level pore structures can be made by direct synthesis, post-treatment or high-temperature hydrothermal methods. Among them, the direct synthesis method directly synthesizes molecular sieves with multi-level pore structures by controlling the synthesis conditions. The direct synthesis method can reduce the post-treatment steps, but some specific syntheses require expensive templates or precursors, thereby increasing costs. The post-treatment method is to introduce mesoporous or macroporous structures on the basis of existing Y-type molecular sieves through specific chemical or physical methods. The modification process involves multiple exchanges, hydrothermal roasting and acid treatment, which makes the entire process complicated, resulting in reduced production efficiency, and the reaction produces a large amount of wastewater and waste, which seriously pollutes the environment. The high-temperature hydrothermal method will cause the generated Al(OH) x The pores are blocked, reducing the catalytic performance and reaction selectivity. The vacancies that are not replenished in time after dealumination will cause defects in the crystal structure, resulting in a significant reduction in crystallinity.

[0005] In patent CN 112209400 A, NaY molecular sieve is contacted with rare earth salt solution or a mixed solution of rare earth salt solution and ammonium salt, filtered, washed, dried and pressurized hydrothermal calcined to finally obtain two mesopore pore size distributions of 2-3nm and 3-4nm, a unit cell constant in the range of 2.440-2.470nm, and a relative crystallinity in the range of 30-60%. However, the modified Y-type molecular sieve lacks pore size diversity and low crystallinity, which affects its performance.

[0006] Patent CN112206810A discloses a method for preparing a rare earth Y-type molecular sieve, which is obtained by contacting a NaY molecular sieve with a rare earth salt solution or a mixed solution of a rare earth salt solution and an ammonium salt, filtering, washing, and drying. The rare earth NaY molecular sieve is hydrothermally calcined in an atmosphere where external pressure is applied and an aqueous solution containing an acidic substance or an alkaline substance is added externally, and then filtered, washed, and dried to obtain a rare earth Y-type molecular sieve. This invention can improve the hydrothermal stability of the molecular sieve, adjust the acid content, and improve the catalytic activity after the introduction of rare earth.

[0007] In patent CN 110203945 A, the Y-type molecular sieve is first treated in an alkaline buffer solution, filtered and washed, and then treated in an acidic buffer solution. After treatment, it is filtered, washed, dried, and calcined to finally obtain a Y-type molecular sieve with a high silicon-aluminum ratio and high crystallinity. However, the complicated process results in low efficiency and low yield of finished products. At the same time, multiple acid washing and alkali washing also bring many environmental problems to production.

[0008] Patent CN113003585A discloses a method for preparing a meso-micro hierarchical pore structure Y-type molecular sieve. The method comprises the following steps: (1) mixing and slurrying NaY molecular sieve with deionized water, adjusting the pH of the slurry system to a range of 3-6 with dilute hydrochloric acid, adding polycarboxylic acid and boron-containing compounds, heating to 60-90°C and stirring the reaction for 0.5-5h, adding water glass solution, stirring the reaction for 5-30 minutes, then filtering, washing, drying and performing high-temperature water vapor ultrastabilization treatment; (2) mixing and slurrying the molecular sieve obtained in (1) with deionized water, adding sodium alkyl sulfonate, stirring the reaction for 0.5-3h at 50-85°C, then filtering, washing, drying and calcining to obtain the meso-micro hierarchical pore structure Y-type molecular sieve. The prepared sample not only has a significantly higher mesoporous specific surface area and mesoporous pore volume, but also has a significantly higher crystallinity. However, this method uses organic matter in the preparation process, which is not conducive to industrial production.

[0009] Patent CN 118145666 A discloses a method for preparing a multi-level pore Y-type molecular sieve, in which a silicon source, an aluminum source, an alkali source, a carbonate and a Y-type molecular sieve structure directing agent are mixed to form a gel, and a multi-level pore Y-type molecular sieve is obtained through hydrothermal crystallization, separation, washing, drying, calcination and other steps. The biggest problem of this method is that the aging time is too long and the production efficiency is low. Summary of the invention

[0010] The purpose of the present invention is to provide a one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve, which solves the problems of multiple exchange water washing and multiple hydrothermal roasting in conventional production, reduces energy consumption and pollution, and improves efficiency. The HY molecular sieve is hydrothermally roasted in a gas phase organic acid atmosphere, which can effectively dredge the pores, and by adjusting the pore structure, the performance of the molecular sieve can be optimized to meet different industrial application requirements.

[0011] The one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve according to the present invention comprises the following steps:

[0012] (1) Load HY molecular sieve fine powder into the calcining furnace and raise the furnace temperature to a certain temperature;

[0013] (2) The organic acid solution is introduced into a calcination furnace, and after hydrothermal calcination for a period of time at a certain mass space velocity, a Y-type molecular sieve with a multi-level pore structure is finally prepared; the molar ratio of framework silicon oxide to aluminum oxide in the prepared Y-type molecular sieve is 25-60, the relative crystallinity is 60-90%, the unit cell constant is 2.425-2.440nm, and the average pore size is between 2-5nm.

[0014] The molar ratio of silicon oxide to aluminum oxide in the HY type molecular sieve is 6-10, the relative crystallinity is ≥90%, and the unit cell constant is 2.447-2.462nm.

[0015] In step (1), the furnace temperature is raised to a temperature of 260-450°C; preferably 350-450°C.

[0016] In step (2), the organic acid solution is a mixed solution of one or more of acetic acid, propionic acid, and malonic acid.

[0017] In step (2), the pH value of the organic acid solution is 2.5-5.7, and the preferred pH value of the organic acid solution is 3-5.

[0018] In step (2), the mass space velocity of the organic acid solution is 0.5-5h -1 , preferably 0.8-2h -1 .

[0019] In step (2), the hydrothermal roasting temperature is 260-450°C; preferably, the hydrothermal roasting temperature is 350-450°C.

[0020] In step (2), the hydrothermal calcination time is 0.5-6 h; the preferred calcination time is 1-4 h.

[0021] The present invention adopts one-step hydrothermal roasting.

[0022] The specific technical solutions of the present invention are as follows:

[0023] (1) Prepare HY molecular sieve as raw material, wherein the molar ratio of silicon oxide to aluminum oxide in the HY molecular sieve is 6-10, the relative crystallinity is ≥90%, and the unit cell constant is 2.447-2.462nm.

[0024] (2) Load HY molecular sieve fine powder as the initial raw material into the roasting furnace, raise the furnace temperature to 260-450℃, pass the organic acid solution into the furnace, and the solution will vaporize at high temperature to form a gas phase organic acid environment in the furnace. -1 The Y-type molecular sieve with a multi-level pore structure is finally prepared by hydrothermal calcination at 260-450°C for 0.5-6h at a mass space velocity of .

[0025] The invention adjusts the pH value of an organic acid solution and controls the mass space velocity of the organic acid solution, the time and temperature of roasting to finally prepare a Y-type molecular sieve with a multi-level pore structure; after roasting, the product Y-type molecular sieve with a multi-level pore structure is obtained after the temperature is lowered to room temperature.

[0026] In the multi-level pore high silicon-aluminum ratio Y-type molecular sieve described in the present invention, the molar ratio of silicon oxide to aluminum oxide in the molecular sieve framework is between 25-60, the relative crystallinity is 60-90%, the unit cell constant is 2.425-2.440nm, the average pore size is between 2-5nm, and the average pore size can be adjusted.

[0027] The pore structure of the present invention can be adjusted as required.

[0028] Compared with the direct synthesis method, the one-step hydrothermal preparation method of the present invention can produce mesoporous channels and reduce production costs without using expensive templates; compared with the traditional post-treatment method, it reduces the sewage treatment pressure caused by multiple exchange water washings and reduces costs.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention is calcined in a gas phase organic acid atmosphere, which effectively removes the framework aluminum, dredges the pores, increases the pore diversity, and can change the acid distribution and improve the catalytic effect.

[0031] 2. Compared with conventional production processes, it solves the problems of multiple exchanges and multiple water washings, simplifies the process flow and improves production efficiency.

[0032] 3. The present invention can generate mesoporous channels and reduce production costs without using expensive templates, and can also reduce the pressure of sewage treatment caused by multiple exchanges and multiple water washings, greatly reduce sewage generation, and reduce production costs.

[0033] 4. Compared with the mesoporous Y molecular sieve prepared by the existing process, the multi-level pore Y molecular sieve synthesized in the present invention has a rich pore structure and a large total specific surface area, and has unique advantages in catalytic activity and selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Acid distribution diagram of Examples 1-4 and Comparative Examples 1-2.

[0035] Figure 2 Pore ​​size distribution diagram of Examples 1-4. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the embodiments.

[0037] Example 1

[0038] 300g HY molecular sieve fine powder was put into the roasting furnace, and the temperature of the roasting furnace was raised from room temperature to 260℃. The pH value of the mixed solution of acetic acid and propionic acid was adjusted to 5.7, and the mixture was heated to 260℃ at a mass space velocity of 5h. -1 The mixed acid solution was injected into a calcination furnace and calcined at a constant temperature of 260°C for 0.5 h. After the calcination was completed, it was naturally cooled to room temperature to obtain the modified Y-type molecular sieve. The skeleton silicon-aluminum ratio, relative crystallinity, specific surface area and pore structure of the sample were tested.

[0039] The silicon to aluminum molar ratio of HY molecular sieve fine powder is 6.

[0040] The molar ratio of acetic acid to propionic acid is 2:1.

[0041] Example 2

[0042] 300g HY molecular sieve fine powder was put into the roasting furnace, and the temperature of the roasting furnace was raised from room temperature to 350℃. The pH value of the mixed solution of acetic acid and malonic acid was adjusted to 5.7, and the mixture was heated to 2.5h at a mass space velocity of 1.5h. -1 The mixed acid solution was injected into a calcination furnace and calcined at 350°C for 2 h. After the calcination, it was naturally cooled to room temperature to obtain the modified Y-type molecular sieve. The skeleton silicon-aluminum ratio, relative crystallinity, specific surface area and pore structure of the sample were tested.

[0043] The silicon to aluminum molar ratio of HY molecular sieve fine powder is 8.

[0044] The molar ratio of acetic acid to malonic acid is 2:1.

[0045] Example 3

[0046] Take 300g HY molecular sieve fine powder and put it into the roasting furnace. The temperature of the roasting furnace is raised from room temperature to 400℃. The pH value of the acetic acid solution is adjusted to 3.5. -1The acetic acid solution was injected into the calcination furnace and calcined at 400°C for 4 hours. After the calcination, it was naturally cooled to room temperature to obtain the modified Y-type molecular sieve. The skeleton silicon-aluminum ratio, relative crystallinity, specific surface area and pore structure of the sample were tested.

[0047] The silicon to aluminum molar ratio of HY molecular sieve fine powder is 8.

[0048] Example 4

[0049] Take 300g HY molecular sieve fine powder and put it into the roasting furnace. The roasting furnace is heated from room temperature to 450℃. The pH of the acetic acid solution is adjusted to 2.5 and the mass space velocity is 0.8h -1 The acetic acid solution was injected into the calcination furnace and calcined at a constant temperature for 6 hours. After calcination at 450°C, it was naturally cooled to room temperature to obtain the modified Y-type molecular sieve. The skeleton silicon-aluminum ratio, relative crystallinity, specific surface area and pore structure of the sample were tested.

[0050] The silicon to aluminum molar ratio of HY molecular sieve fine powder is 10.

[0051] Comparative Example 1

[0052] Add 1200 mL of water to 300 g of HY molecular sieve fine powder, add 60 g of ammonium sulfate, heat to 70 ° C, stir for 60 min, filter, wash with 3000 mL of water, dry and grind, and then hydrothermally roast the material, raise the room temperature to 400 ° C, and the mass space velocity is 1 h -1 The material was calcined at a constant temperature for 1 hour. After calcination, the material was exchanged for the second time, 1200 mL of water was added, 60 g of ammonium sulfate was added, the temperature was raised to 70 ° C, stirred for 60 minutes, filtered, washed with 3000 mL of water, and then dried and ground. The material was hydrothermally calcined for the second time, the room temperature was raised to 400 ° C, and the air velocity was 1h -1 The mixture was calcined at a constant temperature for 1 hour. After calcination, the material was exchanged for the third time, 1200 mL of water was added, 60 g of oxalic acid was added, the temperature was raised to 70 ° C, stirred for 60 min, filtered, washed with 3000 mL of water, and then dried and ground. The material was hydrothermally calcined for the third time, the room temperature was raised to 550 ° C, and the mass space velocity was 1 h -1 The material was calcined at a constant temperature for 1 hour. After calcination, the material was exchanged for the fourth time and 1200 mL of water was added. Then 30 g of oxalic acid was added, the temperature was raised to 70°C, stirred for 60 minutes, filtered, washed with 3000 mL of water, dried and ground, and calcined at 600°C in a muffle furnace for two hours to obtain the finished material. The sample was tested for the skeleton silicon-aluminum ratio, relative crystallinity, specific surface area and pore structure.

[0053] The silicon-aluminum ratio of HY molecular sieve fine powder is 8.

[0054] Comparative Example 2

[0055] Take 300g HY molecular sieve fine powder and add HY molecular sieve into NH 3·H 2 O-NH 4 Cl buffer system, sealed and stirred at 25°C for 300 minutes, then filtered, washed with deionized water of 1 times the mass of the buffer system to obtain a filter cake; the filter cake was added to an acetic acid-ammonium acetate buffer system with a pH value of 3.5 at a mass ratio of 1:15, sealed and stirred at 55°C for 720 minutes, then filtered, washed with deionized water of 1 times the mass of the buffer system, and finally dried at 100°C for 12 hours, and calcined at 500°C for 6 hours to obtain a modified Y-type molecular sieve. The sample was measured for the framework silicon-aluminum ratio, relative crystallinity, specific surface area and pore structure.

[0056] Among them, Y-type molecular sieve and NH 3 ·H 2 O-NH 4 The mass ratio of Cl buffer system is 1:12.

[0057] The silicon-aluminum ratio of HY molecular sieve fine powder is 8.

[0058] The samples of Examples 1-4 and Comparative Examples 1-2 were tested, and the acid distribution diagrams of Examples 1-4 and Comparative Examples 1-2 were as follows: Figure 1 , the pore size distribution of Examples 1-4 is Figure 2 .

[0059] Depend on Figure 1 It is found that the acid strength of the HY molecular sieve prepared by the one-step calcination method of the present invention becomes higher after modification, while the weak acid content is reduced and the strong acid content is increased; in the comparative example, only the overall acid content is reduced, and there is no change in the strong and weak acids.

[0060] The silicon-to-aluminum ratio, relative crystallinity, total specific surface area, mesopore diameter, mesopore volume, average pore diameter and average mesopore volume of the samples of Examples 1-4 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1.

[0061]

[0062] From Table 1 and Figure 2 It can be seen from the results in that, compared with the mesoporous Y molecular sieve prepared by the existing process, the multi-level pore Y molecular sieve synthesized in the present invention has a rich pore structure and a larger total specific surface area.

Claims

1. A one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve, characterized in that: Here are the steps: (1) Load HY molecular sieve fine powder into the calcining furnace and raise the furnace temperature to a certain temperature; (2) introducing an organic acid solution into a calcining furnace, and hydrothermally calcining the solution for a period of time at a certain mass space velocity to finally prepare a Y-type molecular sieve having a multi-level pore structure; the prepared Y-type molecular sieve has a molar ratio of framework silicon oxide to aluminum oxide of 25-60, a relative crystallinity of 60-90%, a unit cell constant of 2.425-2.440 nm, and an average pore size of 2-5 nm; In step (1), the furnace temperature is raised to a temperature of 260-450°C; In step (2), the hydrothermal calcination temperature is 260-450°C; In step (2), the hydrothermal roasting time is 0.5-6h; In step (2), the pH value of the organic acid solution is 2.5-5.

7.

2. The one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve according to claim 1, characterized in that: The molar ratio of silicon oxide to aluminum oxide in the HY type molecular sieve is 6-10.

3. The one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve according to claim 1, characterized in that: The organic acid solution is a mixed solution of one or more of acetic acid, propionic acid and malonic acid.

4. The one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve according to claim 1, characterized in that: The mass space velocity of the organic acid solution is 0.5-5h -1 .

5. The one-step method for preparing a multi-level pore high silicon-aluminum ratio Y-type molecular sieve according to claim 4, characterized in that: The mass space velocity of the organic acid solution is 0.8-2h -1 .

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