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DE-102014222042-B4 - Titanium silicalite molecular sieve and its synthesis

DE102014222042B4DE 102014222042 B4DE102014222042 B4DE 102014222042B4DE-102014222042-B4

Abstract

Titanium silicalite molecular sieve, wherein the crystal grain of the titanium silicalite molecular sieve has a ratio of (surface Si/Ti ratio) : (mass Si/Ti ratio) of greater than 1.1 and less than 5, where the surface Si/Ti ratio and the mass Si/Ti ratio are molar ratios, wherein the surface Si/Ti ratio is obtained by measuring the Si/Ti ratio of the atomic layer 5 nm or less away from the surface of the crystal grain, and the mass Si/Ti ratio is obtained by measuring a zone that is 20 nm or more away from the surface of the crystal grain; wherein the titanium silicalite molecular sieve has a micropore structure with a pore diameter of less than 1 nm and a mesopore structure with a pore diameter of 2 to 8 nm, wherein the volume of the pores with a pore diameter of 2 to 8 nm is 0.3 to 0.8 ml/g, and the volume of the pores with a pore diameter of less than 1 nm is 0.12 to 0.19 ml/g.

Inventors

  • Min Lin
  • Xingtian Shu
  • Bin Zhu
  • Changjiu XIA
  • Xinxin PENG
  • Chunfeng Shi

Assignees

  • CHINA PETROLEUM AND CHEMICAL CORPORATION
  • RESEARCH INSTITUTE OF PETROLEUM PROCESSING, SINOPEC

Dates

Publication Date
20260513
Application Date
20141029
Priority Date
20131029

Claims (20)

  1. Titanium silicalite molecular sieve, wherein the crystal grain of the titanium silicalite molecular sieve has a surface Si/Ti ratio : mass Si/Ti ratio of greater than 1.1 and less than 5, where the surface Si/Ti ratio and the mass Si/Ti ratio are molar ratios, where the surface Si/Ti ratio is obtained by measuring the Si/Ti ratio of the atomic layer 5 nm or less from the surface of the crystal grain, and the mass Si/Ti ratio is obtained by measuring a zone 20 nm or more from the surface of the crystal grain; wherein the titanium silicalite molecular sieve has a micropore structure with a pore diameter of less than 1 nm and a mesopore structure with a pore diameter of 2 to 8 nm, wherein the volume of the pores with a pore diameter of 2 to 8 nm is 0.3 to 0.8 ml/g, and the volume of the pores with a pore diameter of less than 1 nm is 0.12 to 0.19 ml/g.
  2. Titanium silicalite molecular sieve according to Claim 1 , where the ratio of (surface Si/Ti ratio): (mass Si/Ti ratio) (1,2-4):1 is.
  3. Titanium silicalite molecular sieve according to Claim 1 , wherein the titanium silicalite molecular sieve has a Ti/Si molar ratio of (0.005-0.03):1, preferably (0.01-0.025):1.
  4. Titanium silicalite molecular sieve according to Claim 1 , wherein the titanium silicalite molecular sieve is a TS-1 molecular sieve, TS-2 molecular sieve or a Ti-β molecular sieve.
  5. Titanium silicalite molecular sieve according to Claim 1 , wherein the crystal grain of the titanium silicalite molecular sieve has a hollow structure with a radial length of 5 to 300 nm for the cavity region of the hollow grain, the adsorption capacity of benzene, measured for the molecular sieve sample under the conditions of 25 °C, P/P0 = 0.10 and 1 hour adsorption time is at least 70 mg/g, and there is a hysteresis loop between the adsorption isotherm and the desorption isotherm for the low-temperature nitrogen adsorption by the molecular sieve.
  6. Titanium silicalite molecular sieve according to Claim 1 , wherein within a depth of 10 nm from the surface of the titanium silicalite molecular sieve to the interior of the titanium silicalite molecular sieve, in a direction from the surface to the interior, the Si/Ti ratio, per atom, gradually decreases “in a pattern of a quadratic function curve with a downward opening”.
  7. Method for the synthesis of the titanium silicalite molecular sieve according to Claim 1 , comprising the following steps: (1) a titanium source, a template agent, an organic silicon source, water and an optional inorganic ammonium source are mixed and subjected to hydrolysis and removal of alcohols; wherein the time for hydrolysis and removal of alcohols is at least 10 minutes with stirring; the temperature for hydrolysis and removal of alcohols is 50-95 °C, wherein the organic silicon source is an organic silicate having a general formula Si(OR 1 ) 4 , wherein R 1 is a linear or branched C 1-6 alkyl; wherein the titanium source is an organic titanium source and/or an inorganic titanium source; wherein the template agent contains a quaternary ammonium base, and optionally an amine and a quaternary ammonium salt, wherein the molar ratio of the quaternary ammonium base to the amine is 1: (0-10) and the molar ratio of the quaternary ammonium base to the quaternary ammonium salt is 1: (0-10); or wherein the template agent contains a quaternary ammonium salt and a quaternary ammonium base, wherein the molar ratio of the quaternary ammonium salt to the total silicon source is (0.04-0.55):1, the molar ratio of the quaternary ammonium base to the quaternary ammonium salt is (0.04-0.45):1 and the molar ratio of the inorganic ammonium source (as NH4 + ) to the titanium source (as TiO2 ) is (0-0.5):1; or wherein the template agent comprises a quaternary ammonium base and/or a quaternary ammonium salt, an optional amine, and a long-chain alkylammonium compound, wherein the molar ratio of the quaternary ammonium base and the quaternary ammonium salt to the total silicon source is (0.04–0.45):1, and the molar ratio of the long-chain alkylammonium compound to the total silicon source is (0.04–0.45): 1 ; wherein the long-chain alkylammonium compound has the formula R₅NH₃X or R₅N ( R₆ ) ₃X , wherein R₅ is a C₁₂₁₈ alkyl, R₆ is a C₁₆₁₆ alkyl, wherein three R₆ in R₅N ( R₆ ) ₃X may or may not be identical; X is a monovalent anion; wherein the inorganic ammonium source is an inorganic ammonium salt and/or aqueous ammonia; (2) the product obtained in step (1) is aged by standing at 15 to 50 °C for 1 to 60 hours; (3) the aged product obtained in step (2) and a solid silicon source are homogeneously mixed, then subjected to crystallization in a closed reaction vessel and the titanium silicalite molecular sieve is collected; wherein the solid silicon source is a silica particle or powder of high purity, wherein, on a dry basis and by weight, the solid silicon source has a SiO2 content of more than 99.99% and a total atomic content of Fe, Al and Na of less than 10 ppm, wherein the ‘total silicon source’ consists of the combination of the organic silicon source and the inorganic silicon source.
  8. Procedure according to Claim 7 , wherein the titanium source is one or more of tetraalkyl titanate (Ti(alkoxy) 4 ), TiCl 4 , Ti(SO 4 ) 2 and hydrolysates thereof, wherein the alkyl group in the tetraalkyl titanate contains 1 to 6 carbon atoms.
  9. Procedure according to Claim 7 , wherein the molar ratio of the titanium source (as TiO2 ) to the total silicon source (as SiO2 ) is (0.005-0.05):1; the molar ratio of the template agent to the total silicon source (as SiO2 ) is (0.05-0.6):1; the molar ratio of water to the total silicon source (as SiO2 ) is (5-100):1; the molar ratio of the optional inorganic ammonium source (as NH4 + ) to the titanium source (as TiO2 ) is (0-5):1; the weight ratio of the aged product (as SiO2 ) to the solid silicon source (as SiO2 ) is 1:(0.1-10).
  10. Procedure according to Claim 7 , wherein in step (3) the crystallization temperature is 110 to 200 °C, the crystallization pressure is an autogenous pressure and the crystallization time is 2 hours to 20 days.
  11. Procedure according to Claim 7 , wherein the template agent is selected from the group consisting of: • the quaternary ammonium base and the long-chain alkylammonium compound; • the quaternary ammonium salt, the amine and optionally the long-chain alkylammonium compound; • the quaternary ammonium salt and the long-chain alkylammonium compound.
  12. Procedure according to Claim 7 , wherein the titanium silicalite molecular sieve is a TS-1 molecular sieve, wherein the template agent is one or more of tetrapropylammonium hydroxide, tetrapropylammonium chloride and tetrapropylammonium bromide, and optionally with an amine and/or a long-chain alkylammonium compound; or the titanium silicalite molecular sieve is a TS-2 molecular sieve, wherein the template agent is one or more of tetrapropylammonium hydroxide, tetrapropylammonium chloride and tetrapropylammonium bromide, and optionally with an amine and/or a long-chain alkylammonium compound; or the titanium silicalite molecular sieve is a Ti-β molecular sieve, wherein the template agent is one or more of tetrapropylammonium hydroxide, tetrapropylammonium chloride and tetrapropylammonium bromide, and optionally with an amine and/or a long-chain alkylammonium compound.
  13. Procedure according to Claim 7 , wherein the process comprises a further step: (4) the titanium silicalite molecular sieve obtained in step (3) is subjected to crystallization in a solution of an organic base and then the titanium silicalite molecular sieve is collected; wherein in step (4) the organic base is a quaternary ammonium base and/or an amine, wherein the quaternary ammonium base is preferably one or more of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and tetraethylammonium hydroxide; wherein the amine is one or more of an aliphatic amine, aromatic amine and amino alcohol; wherein the aliphatic amine has a general formula R 3 (NH 2 ) n , wherein R 3 is a C 1-4 alkyl or C 1-4 alkylene, n is 1 or 2; wherein the aliphatic amine is preferably one or more of ethylamine, n-butylamine, butylenediamine and hexamethylenediamine; the amino alcohol has a general formula (HOR 4 ) m NH (3-m) wherein R 4 is C 1-4 alkyl, m is 1, 2 or 3; wherein the amino alcohol is preferably one or more of monoethanolamine, diethanolamine and triethanolamine; the aromatic amine is an amine with an aromatic substituent, wherein the aromatic amine preferably one or more of aniline, aminotoluene and p-phenylenediamine; wherein in step (4) the crystallization temperature is 100 to 200 °C; the crystallization time is 0.1 to 10 days; the molar ratio of the titanium silicalite molecular sieve to the organic base is 1:(0.02-0.5) and the molar ratio of the titanium silicalite molecular sieve to water is 1:(2-50).
  14. Procedure according to Claim 7 , wherein the solid silicon source is white soot with a specific surface area of 50 to 400 m² /g.
  15. Procedure according to Claim 7 , wherein the molar ratio of the titanium source (as TiO 2 ) to the total silicon source (as SiO 2 ) = (0.005-0.040):1 is.
  16. Procedure according to Claim 7 , wherein the molar ratio of the template medium to the total silicon source (as SiO 2 ) = (0.05-0.30):1 is.
  17. Procedure according to Claim 7 , wherein the molar ratio of water to the total silicon source (as SiO2 ) is (5-50):1.
  18. Procedure according to Claim 7 , wherein the molar ratio of the inorganic ammonium source (as NH 4 + ) to the titanium source (as TiO 2 ) is (0.01-4):1.
  19. Procedure according to Claim 7 , wherein the molar ratio of the inorganic ammonium source (as NH 4 + ) to the total silicon source (as SiO 2 ) is (0.01-0.07):1.
  20. Procedure according to Claim 7 , wherein the weight ratio of the aged product (as SiO 2 ) to the total silicon source (as SiO 2 ) is 1:(2-8).

Description

TECHNICAL AREA This invention relates to a titanium silicalite molecular sieve and its synthesis. BACKGROUND The titanium silicalite molecular sieve (sometimes also called Ti-Si molecular sieve) is a novel heteroatom-containing molecular sieve developed in the 1980s. TS-1 with an MFI structure, TS-2 with a MEL structure, MCM-22 with an MWW structure, and TS-48 with larger pores were synthesized. In the currently known direct hydrothermal synthesis of the Ti-Si molecular sieve, the organic silicon source and/or the inorganic silicon source are generally used. Organic silicon sources, such as the organic silicate TEOS, are expensive, and the molecular sieve produced from them has a lower content of the active component. Increasing the solid fraction of the crystallization product during molecular sieve synthesis is difficult. Additionally, a large amount of ethanol is evaporated during sieve production. Collecting and reusing this evaporated ethanol is challenging. To reduce costs, inorganic silicon sources are used to partially or completely replace organic silicon sources. However, the Ti-Si molecular sieve produced from inorganic silicon sources has lower activity. Furthermore, the Ti-Si molecular sieve obtained using quaternary ammonium salt as a template agent also exhibits lower activity. Finally, the Ti-Si molecular sieve produced by the known method has a higher micropore volume and a lower mesopore volume. State of the art: The patent specification US 4 410 501 A discloses a synthetic crystalline porous material made of silicon and titanium oxides, a method for its production and its use. The published unexamined patent application CN 1 260 241 A concerns a manufacturing process for a Ti-Si molecular sieve (TS-1). The publication of the patent application US 2008 / 0 118 431 A1 discloses a crystalline titanium silicate composition in which an atomic surface Si/Ti ratio is at least 1.75 times an atomic internal Si/Ti ratio. SUMMARY OF THE INVENTION To solve the problem of the titanium silicalite molecular sieve according to the prior art, this invention shall provide a new titanium silicalite molecular sieve and its synthesis method. This invention discloses a method for synthesizing a titanium silicalite molecular sieve, comprising the following steps: (1) A titanium source, a template agent, an organic silicon source, water, and an optional inorganic ammonium source are mixed and subjected to hydrolysis and removal of alcohols; wherein the time for hydrolysis and removal of alcohols is at least 10 minutes with stirring; the temperature for hydrolysis and removal of alcohols is 50-95 °C; wherein the organic silicon source is an organic silicate having a general formula Si( OR₂ ) ₄ , wherein R₁ is a linear or branched C₁ -₆ alkyl; wherein the titanium source is an organic titanium source and/or an inorganic titanium source; wherein the template agent contains a quaternary ammonium base, and optionally an amine and a quaternary ammonium salt, wherein the molar ratio of the quaternary ammonium base to the amine is 1:(0-10) and the molar ratio of the quaternary ammonium base to the quaternary ammonium salt is 1:(0-10); or wherein the template agent contains a quaternary ammonium salt and a quaternary ammonium base, wherein the molar ratio of the quaternary ammonium salt to the total silicon source is (0.04-0.55):1, the molar ratio of the quaternary ammonium base to the quaternary ammonium salt is (0.04-0.45):1, and the molar ratio of the inorganic ammonium source (as NH4 + ) to the titanium source (as TiO₂ ) (0-0.5):1; or wherein the template agent contains a quaternary ammonium base and/or a quaternary ammonium salt, an optional amine, and a long-chain alkylammonium compound, wherein the molar ratio of the quaternary ammonium base and the quaternary ammonium salt to the total silicon source is (0.04-0.45):1, and the molar ratio of the long-chain alkylammonium compound to the total silicon source is (0.04-0.45):1; wherein the long-chain alkylammonium compound has a formula R₅NH₃X or R₅N (R₆ ) ₃X , wherein R₅ is a C₁₂-₁₈ alkyl, R₆ is a C₁₆- alkyl, wherein three R₆ in R₅N ( R₆ ) ₃X may or may not be identical; X is a monovalent anion; wherein the inorganic ammonium source is an inorganic ammonium salt and/or aqueous ammonia; (2) the product obtained in step (1) is aged by standing at 15 to 50 °C for 1 to 60 hours; (3) The aged product obtained in step (2) and a solid silicon source are homogeneously mixed, then subjected to crystallization in a closed reaction vessel, and the titanium silicalite molecular sieve is collected; wherein the solid silicon source is a silica particle or powder of high purity, wherein, on a dry basis and by weight, the solid silicon source has a SiO₂ content of more than 99.99% and a total atomic content of Fe, Al, and Na of less than 10 ppm, wherein the “total silicon source” consists of the combination of the organic silicon source and the inorganic silicon source. Preferred em