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CN-119524909-B - Modified tin-silicon molecular sieve, preparation method and application thereof

CN119524909BCN 119524909 BCN119524909 BCN 119524909BCN-119524909-B

Abstract

The modified tin-silicon molecular sieve is characterized by containing tin, silicon, oxygen and alkali metal elements, wherein the modified tin-silicon molecular sieve is characterized by XPS, the central value of the Sn 3d 5/2 spectral peak binding energy is 487.1 +/-0.4 eV, and the ratio of the spectral peak area of hexacoordinated tin to that of tetracoordinated tin is more than 1:1.

Inventors

  • PENG XINXIN
  • WANG ZHE
  • GAO LIANG
  • XING ENHUI
  • LUO YIBIN
  • SHU XINGTIAN

Assignees

  • 中国石油化工股份有限公司
  • 中石化石油化工科学研究院有限公司

Dates

Publication Date
20260505
Application Date
20230831

Claims (17)

  1. 1. A method for aldol condensation is characterized in that a carbonyl compound with alpha-H and another carbonyl compound undergo carbon-carbon bond coupling reaction in the presence of a catalyst to generate a carbonyl compound with beta-hydroxyl or a carbonyl compound with alpha, beta-unsaturated bonds, the catalyst is a modified tin-silicon molecular sieve, the modified tin-silicon molecular sieve contains tin, silicon, oxygen and alkali metal elements, the alkali metal elements are cesium, the molar ratio of the tin elements to the silicon elements is (0.008-0.015) 1, the molar ratio of the alkali metal elements to the silicon elements in the tin-silicon molecular sieve is (0.008-0.05) 1, the modified tin-silicon molecular sieve is characterized in that the central value of the Sn 3d 5/2 spectral peak binding energy of the modified tin-silicon molecular sieve is 487.1 +/-0.2 eV, the ratio of the spectral peak area of hexacoordinated tin to tetra coordinated tin is greater than 50:1, the acid content under 150 ℃ is less than 10 mu mol/g after infrared acid representation of pyridine, the molar ratio of the alkali metal elements to the silicon elements is (50 mu mol/g), the molar ratio of the alkali metal elements to the silicon elements is less than 180 mu mol/g (52.180 DEG) and the molecular sieve is selected from the group consisting of crystal Q, Q is higher than 52.57 and the molecular sieve has a Q (52.57/48 mol/48) molecular structure of Si (52/48.48).
  2. 2. The method of claim 1, wherein the aldol condensation reaction is carried out on formaldehyde and methyl acetate under the reaction conditions that the molar ratio of methyl acetate to formaldehyde is 1:2-1:1, the molar ratio of methanol to methyl acetate is 1:1-2:1, the reaction temperature is 320-400 ℃, the reaction gauge pressure is 0-1 MPa, the nitrogen flow is 30-100 mL/min, and the reaction liquid hourly space velocity is 0.1-2 h -1 .
  3. 3. The method of claim 1, wherein the aldol condensation reaction is carried out on formaldehyde and methyl propionate under the reaction conditions that the molar ratio of methyl propionate to formaldehyde is 1:2-1:0.2, the molar ratio of methanol to methyl propionate is 1:1-5:1, the reaction temperature is 320-400 ℃, the reaction gauge pressure is 0-1 MPa, the nitrogen flow is 30-100 mL/min, and the reaction liquid hourly space velocity is 0.1-2 h -1 .
  4. 4. The method of claim 1, wherein the modified tin-silicon molecular sieve has a central value of the Sn 3d 5/2 spectral peak binding energy at 487.1 ±0.1eV.
  5. 5. The method of claim 1, wherein the modified tin-silicon molecular sieve has a ratio of hexacoordinated tin to tetracoordinated tin peak areas of greater than 100:1.
  6. 6. The method of claim 1, wherein the molar ratio of the alkali metal element to the silicon element in the modified tin silicon molecular sieve is (0.01-0.03): 1.
  7. 7. The method of claim 1, wherein the modified tin-silicon molecular sieve has an acid content of less than 5 μmol/g at 150 ℃ as characterized by pyridine infrared acidity.
  8. 8. The method of claim 1, wherein the modified tin-silicon molecular sieve is characterized by pyridine infrared acidity and has an acid amount of 0 μmol/g at 150 ℃.
  9. 9. The method of claim 1, wherein the modified tin-silicon molecular sieve has an acid content of less than 160 μmol/g at 50 ℃ as characterized by pyridine infrared acidity.
  10. 10. The method of claim 1, wherein the modified tin-silicon molecular sieve is characterized by an NMR silicon spectrum having a ratio of Q 4 to Q 3 signal peak heights greater than 250:1.
  11. 11. The method of claim 10, wherein the ratio of the peak heights of the Q 4 and Q 3 signals is greater than 300:1.
  12. 12. The method of claim 1, wherein the modified tin-silicon molecular sieve is characterized by NMR silicon spectrum, having no Q 3 signal peak.
  13. 13. The method according to claim 1, wherein the modified tin-silicon molecular sieve is prepared by mixing a tin-silicon molecular sieve as a starting modifying material with a hydroxide or salt of alkali metal cesium, a solvent, and then drying and calcining the mixture to obtain the modified tin-silicon molecular sieve, wherein the mixing is performed under the conditions of 30-70 ℃ and 30-50 KPa for 10-30 min, and wherein the mixing is a grinding method.
  14. 14. The method according to claim 13, wherein the tin-silicon molecular sieve as a starting modifying material is obtained by hydrothermal synthesis.
  15. 15. The method of claim 13, wherein the salt of alkali metal cesium is one or more of a hydrochloride, hypochlorite, chlorite, metachlorate, perchlorate, nitrate, sulfate, bisulfate, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, superphosphate, metaphosphate, phosphite, hypophosphite, carboxylate, pyrophosphate, carboxylate of C 1 -C 20 .
  16. 16. The method according to claim 13, wherein the hydroxide of alkali metal cesium is cesium hydroxide and the salt of alkali metal cesium is selected from one or more of cesium nitrate, cesium carbonate, cesium bicarbonate, and cesium acetate.
  17. 17. The method according to claim 13, wherein the molar ratio of the hydroxide or salt of alkali metal cesium to the solvent calculated as SiO 2 of the tin-silicon molecular sieve as starting modifying material is 1 (0.001-0.1): 0-10.

Description

Modified tin-silicon molecular sieve, preparation method and application thereof Technical Field The invention belongs to the technical field of molecular sieves, and particularly relates to a tin-silicon molecular sieve, a method for modifying the molecular sieve and application of the molecular sieve as a catalyst. Background Methyl Methacrylate (MMA) is an important organic chemical raw material, is mainly used for producing polymethyl methacrylate and acrylic resin materials, and is also widely used for producing other resins, plastics, coatings, adhesives, lubricants, sizing agents, polishing agents, printing and dyeing aids, insulating filling materials and the like. The methyl methacrylate is prepared by directly aldolising methyl propionate and formaldehyde without using extremely toxic raw materials, the raw materials are low in price and wide in source, and the method is an important production method of methyl methacrylate in the future. The most effective aldol condensation catalysts for methyl propionate and formaldehyde at present are known to be supported catalysts having silica as the main carrier and cesium as the main active component. The supported catalyst has low activity, the raw materials cannot be fully converted, and the catalyst takes amorphous silicon dioxide as a carrier, so that the specific surface area gradually decreases and the strength gradually decreases along with the extension of time in a reaction system. CN103551148B discloses a water-resistant catalyst for aldol condensation, the main active component comprises one or more of oxides or salts of Cs, the active auxiliary agent is one or more of oxides or salts of Sb, nb, ag, al, zr, and the carrier comprises SiO 2 and a carrier auxiliary agent. CN112675830a discloses an aldol condensation catalyst, which uses foam porous silicon dioxide as a carrier to load metal elements, so that the catalyst has excellent water resistance, anti-carbon property and long-period activity stability, and is suitable for industrial application of methyl propionate and formaldehyde to prepare methyl methacrylate through aldol condensation. The catalyst adopted in the aldol condensation reaction studied in the prior literature is an alkaline catalyst with amorphous silicon dioxide loaded with alkali metal, and the catalyst has the advantages of poor carrier stability, single active center, low activity and low selectivity, and cannot meet the requirement of industrial mass production. Disclosure of Invention The object of the present invention is to provide a catalytic material which is different from the prior art and is suitable for aldol condensation reactions, and to provide a process for its preparation and its use in aldol condensation reactions. In order to achieve one of the above purposes, the first aspect of the present invention provides a modified tin-silicon molecular sieve, which is characterized by comprising tin, silicon, oxygen and alkali metal elements, wherein the modified tin-silicon molecular sieve is characterized by XPS, the central value of the Sn 3d 5/2 spectral peak binding energy is 487.1 + -0.4 eV, and the ratio of the spectral peak area of hexacoordinated tin to tetra coordinated tin is greater than 1:1. In order to achieve the second object of the present invention, a second aspect of the present invention provides a method for producing a modified tin-silicon molecular sieve, characterized in that a tin-silicon molecular sieve as a starting modifying material is mixed with an alkali metal hydroxide or salt, and a solvent, and then dried and calcined to obtain a modified titanium-silicon molecular sieve. In order to achieve the third object of the present invention, a third aspect of the present invention provides a catalyst containing a modified tin-silicon molecular sieve, which is characterized by comprising the modified tin-silicon molecular sieve provided in the first aspect of the present invention or comprising the modified tin-silicon molecular sieve prepared by the method provided in the second aspect of the present invention, wherein the weight ratio of the modified tin-silicon molecular sieve to the catalyst containing the modified tin-silicon molecular sieve is preferably 5% -100%. In order to achieve the fourth object of the present invention, a fourth aspect of the present invention provides a method for aldol condensation, which comprises the step of subjecting a carbonyl-containing compound having α -H to a carbon-carbon bond coupling reaction with another carbonyl-containing compound under aldol condensation reaction conditions in the presence of a catalyst comprising a modified tin-silicon molecular sieve to produce a carbonyl-containing compound having β -hydroxy group or a carbonyl-containing compound having α, β -unsaturated bond. The modified tin-silicon molecular sieve of the invention takes alkali metal and tin as main active components, the alkali metal provides an alkaline active center,