Mesoporous molecular sieve catalyst and method for preparing the same

Abstract

The application discloses a kind of mesoporous molecular sieve catalyst and preparation method thereof.The mesoporous molecular sieve catalyst prepared by the application is prepared by SBA-15 mesoporous molecular sieve as carrier, pretreatment, ZrO2 loading, sulfation treatment and ZnO cocatalyst modification step by step, and by adjusting process parameters, the mesoporous molecular sieve catalyst forms stable SO4 2‑ / ZrO2 solid superacid active site, and ZnO and solid acid site produce synergistic catalysis.The mesoporous molecular sieve catalyst obtained by the application has specific surface area of greater than or equal to 180m 2 / g, and the activity retention rate is greater than or equal to 91% under the condition of continuous operation for 500h at 250 DEG C and 5.0MPa, and the conversion rate of hydroxyl methionine polymer is greater than or equal to 93.2%.

Description

Technical Field

[0001] This invention relates to the field of hydroxymethionine polymer alcoholysis technology, and more specifically to a mesoporous molecular sieve catalyst and its preparation method. Background Technology

[0002] The alcoholysis of hydroxymethionine polymers is a crucial step in the preparation of hydroxymethionine isopropyl ester. The reaction efficiency of this step directly determines the yield of hydroxymethionine isopropyl ester, thus affecting the industrial efficiency of the entire production process. Currently, traditional solid acid catalysts (such as zirconium sulfate and Amberlyst-15 ion exchange resin) are mainly used in industrial production to catalyze this alcoholysis reaction. However, these traditional solid acid catalysts generally have inherent defects, specifically: uneven distribution of acidic sites, small specific surface area, and poor water resistance; in the aqueous reaction system of hydroxymethionine polymer alcoholysis, the catalyst is easily affected by water poisoning, leading to rapid decay of catalytic activity, and its continuous operating life is usually less than 200 hours, which is difficult to meet the requirements of continuous industrial production; in addition, the adsorption capacity and catalytic activity of traditional solid acid catalysts for hydroxymethionine polymers are limited, resulting in a conversion rate of hydroxymethionine polymers that is generally less than 85%, which seriously limits the economics of the overall production process and makes it impossible to simultaneously improve product yield and production efficiency.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to address the problems mentioned in the background section by providing a mesoporous molecular sieve catalyst and its preparation method.

[0005] A method for preparing a mesoporous molecular sieve catalyst includes the following steps: S1. The pretreated SBA-15 mesoporous molecular sieve is immersed in a ZrOCl2·8H2O aqueous solution with a concentration of 0.2~0.4mol / L, ultrasonically impregnated for 4~6h, dried at 110~130℃ for 8~12h, and then calcined at 550~650℃ for 4~6h to obtain ZrO2 / SBA-15 intermediate; Furthermore, the specific method for pretreating SBA-15 mesoporous molecular sieve includes calcining the SBA-15 mesoporous molecular sieve at 500~600℃ for 3~5h.

[0006] Furthermore, the solid-liquid volume ratio of the ZrOCl2·8H2O aqueous solution is 8~12:1.

[0007] SBA-15 mesoporous molecular sieves were pretreated by high-temperature calcination to remove template agent residues and adsorbed water, purifying and activating the mesoporous channels. The sieves were then ultrasonically impregnated with a 0.2–0.4 mol / L ZrOCl2·8H2O aqueous solution, utilizing hydroxyl interactions to uniformly adsorb the Zr precursor onto the inner surface of the mesopores. After gradual drying to remove free water and achieve preliminary hydrolysis of Zr species, the zirconium oxychloride precursor was decomposed, dechlorinated, and crystallized to form ZrO2 by high-temperature calcination. Simultaneously, the confinement effect of the SBA-15 mesoporous channels allowed ZrO2 to be loaded onto the inner walls of the channels in a highly dispersed state, ultimately yielding a ZrO2 / SBA-15 intermediate with a complete structure, high specific surface area, and uniformly dispersed active components.

[0008] S2. SO4 is obtained by sulfation of the ZrO2 / SBA-15 intermediate. 2- / ZrO2-SBA-15 precursor; Furthermore, the specific method of S2 includes: The ZrO2 / SBA-15 intermediate was impregnated in a 0.5–1.5 mol / L H2SO4 solution for 2–4 hours, dried at 110–130 °C for 8–12 hours, and then calcined at 500–600 °C for 3–5 hours to obtain SO4. 2- / ZrO2-SBA-15 precursor.

[0009] The ZrO2 / SBA-15 intermediate was impregnated in a sulfuric acid solution. The sulfuric acid interacted with the hydroxyl groups on the ZrO2 surface to form surface sulfate species. After drying to remove free water, the intermediate was calcined at a suitable temperature. The surface sulfate species underwent dehydration condensation to form bidentate chelate sulfate ions, which induced the formation of a highly active tetragonal phase in ZrO2 and constructed SO42-. 2- The ZrO2-type solid superacid center is maintained, while the SBA-15 mesoporous channel structure is preserved, ultimately yielding SO4 with high specific surface area, strong acidity, and uniformly dispersed active sites. 2- / ZrO2-SBA-15 precursor.

[0010] S3, SO4 2- The ZrO2-SBA-15 precursor was ultrasonically impregnated in a Zn(NO3)2·6H2O aqueous solution with a concentration of 0.05~0.15mol / L for 3~5h, dried at 110~130℃ for 8~12h, and then calcined at 450~550℃ for 3~5h to obtain a mesoporous molecular sieve catalyst.

[0011] Furthermore, in S3, the ultrasonic power of ultrasonic impregnation is 200~300W and the ultrasonic time is 30~60min.

[0012] SO4 2-The ZrO2-SBA-15 precursor was immersed in an aqueous solution of zinc nitrate and ultrasonically impregnated at 200-300 W. Ultrasonic cavitation was used to enhance mass transfer, allowing the Zn... 2+ ⁺ Uniformly adsorbed and dispersed in the carrier pores and surface; after drying to remove moisture, calcined at a suitable temperature, the zinc nitrate precursor thermally decomposes to form a highly dispersed ZnO active component; ZnO and SO4 2- The ZrO2 solid acid sites generate interfacial synergistic effects, which, while retaining the SBA-15 mesoporous structure and high specific surface area, construct a multifunctional mesoporous molecular sieve catalyst that combines strong acid sites and metal oxide active sites.

[0013] As having the same inventive concept as the above-described technical solutions, this invention also claims protection for a mesoporous molecular sieve catalyst, prepared by any of the preparation methods described above, comprising a support and a supported component, wherein the support is an SBA-15 mesoporous molecular sieve, and the supported component includes SO4. 2- / ZrO2 solid acid and ZnO.

[0014] Furthermore, the SO4 2- The loading of ZrO2 is 28-32%, and the loading of ZnO is 0.5-1.5%.

[0015] Furthermore, the specific surface area of ​​the mesoporous molecular sieve catalyst is ≥180 m². 2 / g, pore size of 3~5nm and acidic site density ≥0.95mmol / g.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Using SBA-15 mesoporous molecular sieve as a support, and pretreating the SBA-15 mesoporous molecular sieve to remove residual template agent and physically adsorbed water from the SBA-15 synthesis process, the mesoporous channels were purified and activated, ensuring the regularity and integrity of the support channels. At the same time, the subsequent drying and calcination temperatures were controlled within the range that would not damage the SBA-15 mesoporous structure, so that the final prepared mesoporous molecular sieve catalyst still maintains a high specific surface area. The ordered mesoporous structure can reduce the diffusion resistance between reactants and products, allowing the supported active components to be fully exposed, and significantly improving the catalytic reaction efficiency. 2. By loading SO4 2- / ZrO2 forms solid superacid sites with strong acidity, suitable acid content, and good thermal stability, which can improve the activity and selectivity of acid catalytic reactions; then, by introducing ZnO active components to form a synergistic catalytic effect with solid acid sites, it can not only regulate surface acidity, but also provide multifunctional active centers for oxidation / dehydrogenation, etc. 3. Through ultrasonic stepwise impregnation, ZrO2, sulfate and Zn components are highly dispersed and not prone to agglomeration, and do not block the mesoporous channels, resulting in strong structural stability of the mesoporous molecular sieve catalyst. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The materials and instruments used in the following embodiments are all commercially available.

[0018] In a first aspect, embodiments of the present invention provide a method for preparing a mesoporous molecular sieve catalyst, comprising the following steps: S1. The pretreated SBA-15 mesoporous molecular sieve is immersed in a ZrOCl2·8H2O aqueous solution with a concentration of 0.2~0.4mol / L, ultrasonically impregnated for 4~6h, dried at 110~130℃ for 8~12h, and then calcined at 550~650℃ for 4~6h to obtain ZrO2 / SBA-15 intermediate; Furthermore, the specific method for pretreating SBA-15 mesoporous molecular sieve includes calcining the SBA-15 mesoporous molecular sieve at 500~600℃ for 3~5h.

[0019] Furthermore, the solid-liquid volume ratio of the ZrOCl2·8H2O aqueous solution is 8~12:1.

[0020] S2. SO4 is obtained by sulfation of the ZrO2 / SBA-15 intermediate. 2- / ZrO2-SBA-15 precursor; Furthermore, the specific method of S2 includes: The ZrO2 / SBA-15 intermediate was impregnated in a 0.5–1.5 mol / L H2SO4 solution for 2–4 hours, dried at 110–130 °C for 8–12 hours, and then calcined at 500–600 °C for 3–5 hours to obtain SO4. 2- / ZrO2-SBA-15 precursor.

[0021] S3, SO4 2- The ZrO2-SBA-15 precursor was ultrasonically impregnated in a Zn(NO3)2·6H2O aqueous solution with a concentration of 0.05~0.15mol / L for 3~5h, dried at 110~130℃ for 8~12h, and then calcined at 450~550℃ for 3~5h to obtain a mesoporous molecular sieve catalyst.

[0022] Furthermore, in S3, the ultrasonic power of ultrasonic impregnation is 200~300W and the ultrasonic time is 30~60min.

[0023] Secondly, embodiments of the present invention provide a mesoporous molecular sieve catalyst, prepared using the method described above. The mesoporous molecular sieve catalyst comprises a support and a supported component; the support is SBA-15 mesoporous molecular sieve, and the supported component includes SO4. 2- / ZrO2 solid acid and ZnO.

[0024] Furthermore, the SO4 2- The loading of ZrO2 is 28-32%, and the loading of ZnO is 0.5-1.5%.

[0025] Furthermore, the specific surface area of ​​the mesoporous molecular sieve catalyst is ≥180 m². 2 / g, pore size of 3~5nm and acidic site density ≥0.95mmol / g.

[0026] Thirdly, embodiments of the present invention provide an application of a mesoporous molecular sieve catalyst in the alcoholysis of hydroxymethionine polymers.

[0027] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0028] Example 1 This embodiment provides a method for preparing a mesoporous molecular sieve catalyst, including the following steps: 1) Carrier pretreatment: Take 100g of SBA-15 mesoporous molecular sieve, calcine it at 550℃ for 4h, and cool it to room temperature for later use. 2) Loading of active components: Prepare 1000 mL of 0.3 mol / L ZrOCl2·8H2O aqueous solution, add the pretreated SBA-15 support, sonicate for 5 h, dry at 120 ℃ for 10 h, and then calcine at 600 ℃ for 5 h to obtain ZrO2 / SBA-15 intermediate. 3) Sulphation treatment: Prepare 800 mL of 1.0 mol / L H2SO4 solution, add ZrO2 / SBA-15 intermediate, impregnate for 3 h, dry at 120℃ for 10 h, and then calcine at 550℃ for 4 h to obtain SO4. 2- / ZrO2-SBA-15 precursor; 4) Catalyst modification: Prepare 600 mL of 0.1 mol / L Zn(NO3)2·6H2O aqueous solution, add the precursor, ultrasonically impregnate for 4 h (ultrasonic power 250 W, ultrasonic time 45 min), dry at 120 ℃ for 10 h, and then calcine at 500 ℃ for 4 h to obtain mesoporous molecular sieve catalyst.

[0029] Performance test results: The specific surface area of ​​the mesoporous molecular sieve catalyst is 192 m². 2 / g, with a pore size of 4.2nm, an acidic site density of 0.98mmol / g, and a mechanical strength of 105N / cm; after continuous operation at 250℃ and 5.0MPa for 500h, the activity retention rate was 92% and the hydroxymethionine polymer conversion rate was 93.5%.

[0030] Example 2 This embodiment provides a method for preparing a mesoporous molecular sieve catalyst, including the following steps: 1) Carrier pretreatment: Take 100g of SBA-15 mesoporous molecular sieve, calcine it at 520℃ for 3.5h, and cool it to room temperature for later use; 2) Loading of active components: Prepare 900 mL of 0.25 mol / L ZrOCl2·8H2O aqueous solution, add the pretreated SBA-15 support, sonicate for 4.5 h, dry at 115 ℃ for 9 h, and then calcine at 580 ℃ for 4.5 h to obtain ZrO2 / SBA-15 intermediate; 3) Sulphation treatment: Prepare 700 mL of 0.8 mol / L H2SO4 solution, add ZrO2 / SBA-15 intermediate, impregnate for 2.5 h, dry at 115 °C for 9 h, and then calcine at 520 °C for 3.5 h to obtain SO4. 2- / ZrO2-SBA-15 precursor; 4) Catalyst modification: Prepare 500 mL of 0.08 mol / L Zn(NO3)2·6H2O aqueous solution, add the precursor, ultrasonically impregnate for 3.5 h (ultrasonic power 220 W, ultrasonic time 35 min), dry at 115 ℃ for 9 h, and then calcine at 480 ℃ for 3.5 h to obtain mesoporous molecular sieve catalyst.

[0031] Performance test results: The specific surface area of ​​the mesoporous molecular sieve catalyst is 185 m². 2 / g, with a pore size of 3.8nm, an acidic site density of 0.96mmol / g, and a mechanical strength of 102N / cm; after continuous operation at 250℃ and 5.0MPa for 500h, the activity retention rate was 91% and the hydroxymethionine polymer conversion rate was 93.2%.

[0032] Example 3 This embodiment provides a method for preparing a mesoporous molecular sieve catalyst, including the following steps: 1) Carrier pretreatment: Take 100g of SBA-15 mesoporous molecular sieve, calcine it at 580℃ for 4.5h, and cool it to room temperature for later use; 2) Loading of active components: Prepare 1100 mL of 0.35 mol / L ZrOCl2·8H2O aqueous solution, add the pretreated SBA-15 support, sonicate for 5.5 h, dry at 125 ℃ for 11 h, and then calcine at 620 ℃ for 5.5 h to obtain ZrO2 / SBA-15 intermediate. 3) Sulphation treatment: Prepare 900 mL of 1.2 mol / L H2SO4 solution, add ZrO2 / SBA-15 intermediate, impregnate for 3.5 h, dry at 125 °C for 11 h, and then calcine at 580 °C for 4.5 h to obtain SO4. 2- / ZrO2-SBA-15 precursor; 4) Catalyst modification: Prepare 700 mL of 0.12 mol / L Zn(NO3)2·6H2O aqueous solution, add the precursor, ultrasonically impregnate for 4.5 h (ultrasonic power 280 W, ultrasonic time 55 min), dry at 125 ℃ for 11 h, and then calcine at 520 ℃ for 4.5 h to obtain mesoporous molecular sieve catalyst.

[0033] Performance test results: The specific surface area of ​​the mesoporous molecular sieve catalyst is 198 m². 2 / g, with a pore size of 4.5nm, an acidic site density of 1.02mmol / g, and a mechanical strength of 108N / cm; after continuous operation at 250℃ and 5.0MPa for 500h, the activity retention rate was 93% and the hydroxymethionine polymer conversion rate was 94.0%.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example lacks the ZnO co-catalyst, while the rest is the same as Example 1.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example does not involve ultrasonic impregnation, but is otherwise the same as Example 1.

[0036] Comparative Example 3 The difference between this comparative example and Example 1 is that the concentration of the sulfuric acid solution in this comparative example is 0.3 mol / L and the volume is 800 mL during the sulfation treatment, while the rest is the same as in Example 1.

[0037] Comparative Example 4 The difference between this comparative example and Example 1 is that this comparative example does not pretreat the SBA-15 mesoporous molecular sieve, while the rest is the same as Example 1.

[0038] The following is a comparative analysis of Examples 1-3 and Comparative Examples 1-4. The detection results of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1: Table 1. Detection results of Examples 1-3 and Comparative Examples 1-4 As shown in Table 1, Example 1 and Comparative Example 1, the absence of ZnO cocatalyst in Comparative Example 1 prevents the formation of a synergistic effect between solid acid sites and metal oxide sites, resulting in a significant decrease in the stability and catalytic conversion rate of the mesoporous molecular sieve catalyst. This demonstrates that the introduction of ZnO is crucial for improving the performance of the mesoporous molecular sieve catalyst.

[0039] As shown in Table 1, Example 1 and Comparative Example 2, Comparative Example 2 did not undergo ultrasonic impregnation, and the active component could not penetrate evenly into the mesoporous channels of SBA-15, which easily led to agglomeration, resulting in a decrease in specific surface area and acidic site density, and a reduction in catalytic performance and stability. This proves that ultrasonic impregnation is crucial for the uniform dispersion of the active component.

[0040] As can be seen from Table 1, Example 1, and Comparative Example 3, the concentration of sulfation treatment and the calcination temperature in Comparative Example 3 deviate from the parameter range defined in this invention, and thus cannot form stable chelated SO4. 2- The presence of superacidic sites in ZrO2 solids results in insufficient acidity, leading to a decrease in catalytic performance and demonstrating the rationality of the sulfation parameters defined in this invention.

[0041] As shown in Table 1, Example 1 and Comparative Example 4, Comparative Example 4 did not undergo carrier pretreatment. The residual template agent and adsorbed water in the SBA-15 channels blocked the channels and could not effectively activate the carrier surface, resulting in uneven loading of active components, a decrease in specific surface area, and a significant reduction in catalytic performance and stability, thus proving the necessity of the carrier pretreatment step.

Claims

1. A method for preparing a mesoporous molecular sieve catalyst, characterized in that, Includes the following steps: S1. The pretreated SBA-15 mesoporous molecular sieve is immersed in a ZrOCl2·8H2O aqueous solution with a concentration of 0.2~0.4mol / L, ultrasonically impregnated for 4~6h, dried at 110~130℃ for 8~12h, and then calcined at 550~650℃ for 4~6h to obtain ZrO2 / SBA-15 intermediate; S2. SO4 is obtained by sulfation of the ZrO2 / SBA-15 intermediate. 2- / ZrO2-SBA-15 precursor; S3, SO4 2- The ZrO2-SBA-15 precursor was ultrasonically impregnated in a Zn(NO3)2·6H2O aqueous solution with a concentration of 0.05~0.15mol / L for 3~5h, dried at 110~130℃ for 8~12h, and then calcined at 450~550℃ for 3~5h to obtain a mesoporous molecular sieve catalyst.

2. The method for preparing the mesoporous molecular sieve catalyst according to claim 1, characterized in that, The specific method for pretreatment of SBA-15 mesoporous molecular sieve includes calcining the SBA-15 mesoporous molecular sieve at 500~600℃ for 3~5h.

3. The method for preparing the mesoporous molecular sieve catalyst according to claim 1, characterized in that, The specific method of S2 includes: The ZrO2 / SBA-15 intermediate was impregnated in a 0.5–1.5 mol / L H2SO4 solution for 2–4 hours, dried at 110–130 °C for 8–12 hours, and then calcined at 500–600 °C for 3–5 hours to obtain SO4. 2- / ZrO2-SBA-15 precursor.

4. The method for preparing the mesoporous molecular sieve catalyst according to claim 1, characterized in that, The solid-liquid volume ratio of the ZrOCl2·8H2O aqueous solution is 8~12:

1.

5. The method for preparing the mesoporous molecular sieve catalyst according to claim 1, characterized in that, The ultrasonic power of ultrasonic impregnation in S3 is 200~300W and the ultrasonic time is 30~60min.

6. A mesoporous molecular sieve catalyst, prepared by any one of the preparation methods described in claims 1 to 5, characterized in that, It includes a support and a supported component. The support is SBA-15 mesoporous molecular sieve, and the supported component includes SO4. 2- / ZrO2 solid acid and ZnO.

7. The mesoporous molecular sieve catalyst according to claim 6, characterized in that, The SO4 2- The loading of ZrO2 is 28-32%, and the loading of ZnO is 0.5-1.5%.

8. The mesoporous molecular sieve catalyst according to claim 6, characterized in that, The specific surface area of ​​the mesoporous molecular sieve catalyst is ≥180 m². 2 / g, pore size of 3~5nm and acidic site density ≥0.95mmol / g.

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