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CN-117985735-B - Framework heteroatom titanium silicalite molecular sieve with hierarchical pores and preparation method and application thereof

CN117985735BCN 117985735 BCN117985735 BCN 117985735BCN-117985735-B

Abstract

The invention relates to a framework heteroatom titanium silicon molecular sieve with hierarchical pores, a preparation method and application thereof, wherein the framework heteroatom comprises titanium, the framework heteroatom titanium silicon molecular sieve has 29 Si MAS NMR characteristics, wherein the peak area of a spectrum peak at the position of-103+/-1 ppm of the framework heteroatom titanium silicon molecular sieve is marked as Q 3 , the peak area of a spectrum peak at the position of-113+/-1 ppm of the framework heteroatom titanium silicon molecular sieve is marked as Q 4‑1 , the peak area of a spectrum peak at the position of-116+/-1 ppm of the framework heteroatom titanium silicon molecular sieve is marked as Q 4‑2 , X 1 defined as the following formula (1) is any value between 0.02 and 0.35, X 1 ＝Q 3 /Q 4‑1 formula (1), X 2 defined as the following formula (2) is any value between 0.10 and 0.60, and X 2 ＝Q 3 /Q 4‑2 formula (2). The molecular sieve has higher catalytic activity and stability, and obviously improves the cyclohexanone oxime conversion rate and the selectivity of caprolactam.

Inventors

  • ZHANG PENG
  • XIA CHANGJIU
  • PENG XINXIN
  • XING ENHUI
  • ZHANG XIAOXIN
  • 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
20221027

Claims (20)

  1. 1. A framework heteroatom titanium silicalite molecular sieve having hierarchical pores, characterized in that the framework heteroatom titanium silicalite molecular sieve has the following 29 Si MAS NMR characteristics: The peak area of the spectrum peak at the position where the chemical shift of the skeleton heteroatom titanium silicalite molecular sieve is-103+/-1 ppm is recorded as Q 3 ; The peak area of the spectrum peak at the position of the skeleton heteroatom titanium silicalite molecular sieve with the chemical shift of-113+/-1 ppm is recorded as Q 4-1 ; The peak area of the spectrum peak at the position of the skeleton heteroatom titanium silicalite molecular sieve with the chemical shift of-116+/-1 ppm is recorded as Q 4-2 ; X 1 defined by the following formula (1) is any number between 0.02 and 0.35: X 1 =Q 3 /Q 4-1 formula (1); x 2 defined by the following formula (2) is any number between 0.10 and 0.60: X 2 =Q 3 /Q 4-2 formula (2); the framework heteroatom titanium silicalite molecular sieve with the hierarchical pores is prepared by a method comprising the following steps: s1, mixing a titanium source, a silicon source, a first template agent, water, a surfactant and a high molecular polymer to obtain a reaction mixture; s2, sequentially carrying out first hydrothermal crystallization treatment and first roasting treatment on the reaction mixture to obtain a molecular sieve intermediate; s3, mixing the molecular sieve intermediate, the second template agent and water, and then sequentially carrying out second hydrothermal crystallization treatment and second roasting treatment.
  2. 2. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein the value of X 1 is any value between 0.05 and 0.27, and the value of X 2 is any value between 0.15 and 0.45.
  3. 3. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein the molar ratio of silicon atoms to titanium atoms in the framework heteroatom titanium silicalite molecular sieve is (8-120): 1.
  4. 4. The framework heteroatom titanium silicalite molecular sieve according to claim 3, wherein the molar ratio of silicon atoms to titanium atoms in the framework heteroatom titanium silicalite molecular sieve is (10-90): 1.
  5. 5. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein the framework heteroatom titanium silicalite molecular sieve has a configuration selected from one or more of MFI topology, MEL topology, BEA topology and SVR topology.
  6. 6. The framework heteroatom titanium silicalite molecular sieve according to claim 5, wherein the framework heteroatom titanium silicalite molecular sieve has a MFI topology.
  7. 7. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein the framework heteroatom titanium silicalite molecular sieve has a plurality of cavity structures in the crystal, wherein the size of a single cavity structure is 3-50 nm.
  8. 8. The framework heteroatom titanium silicalite molecular sieve according to claim 7, wherein the size of the single cavity structure is 4-40 nm.
  9. 9. The framework heteroatom titanium silicalite molecular sieve according to claim 7, wherein the volume of all the cavity structures is 8-45% of the total volume of the molecular sieve.
  10. 10. The framework heteroatom titanium silicalite molecular sieve according to claim 9, wherein the volume of all the cavity structures is 12-40% of the total volume of the molecular sieve.
  11. 11. The framework heteroatom titanium silicalite molecular sieve according to claim 7, wherein the shape of the cavity structure is selected from one or more of spherical, cubic, ellipsoidal and irregular cubic.
  12. 12. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein the framework heteroatom titanium silicalite molecular sieve comprises molecular sieve particles of single crystallite composition and/or molecular sieve particles of multiple crystallite aggregates.
  13. 13. The framework heteroatom titanium silicalite molecular sieve according to claim 12, wherein the molecular sieve particles have an average particle size of 0.12-0.75 μm, a BET specific surface area of 280-640 m 2 /g, a micropore specific surface area of 240-520 m 2 /g, a total pore volume of 0.18-0.67 cm 3 /g, and a mesopore volume of 0.15-0.48 cm 3 /g.
  14. 14. The framework heteroatom titanium silicalite molecular sieve according to claim 13, wherein the molecular sieve particles have an average particle size of 0.15-0.55 μm, a BET specific surface area of 300-620 m 2 /g, a micropore specific surface area of 270-440 m 2 /g, a total pore volume of 0.22-0.55 cm 3 /g, and a mesopore volume of 0.22-0.39 cm 3 /g.
  15. 15. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of the low temperature nitrogen adsorption of the framework heteroatom titanium silicalite molecular sieve.
  16. 16. The framework heteroatom titanium silicalite molecular sieve according to claim 15, wherein the onset relative pressure (P/P 0 ) of the hysteresis ring is 0.3-0.55.
  17. 17. The framework heteroatom titanium-silicon molecular sieve according to claim 1, wherein in the step S1, the molar ratio of the titanium source to the silicon source to the first template agent to the water to the surfactant is (0.006-0.08): 1 (0.01-3): 1-50): 0.05-0.25, and the weight ratio of SiO 2 to the high molecular polymer is (8-100): 1, calculated as SiO 2 .
  18. 18. The framework heteroatom titanium-silicon molecular sieve according to claim 17, wherein in the step S1, the molar ratio of the titanium source to the first template agent to the water to the surfactant is (0.01-0.06): 1 (0.02-1.8): 10-30): 0.08-0.15, and the weight ratio of the SiO 2 to the high molecular polymer is (10-60): 1, calculated as SiO 2 .
  19. 19. The framework heteroatom titanium silicalite molecular sieve according to claim 1, wherein in step S1, the silicon source is selected from at least one of silicone grease, solid silica gel, white carbon black and silica sol.
  20. 20. The framework heteroatom titanium silicalite molecular sieve according to claim 19, wherein the silicon source is selected from at least one of silicone grease, solid silica gel and white carbon black.

Description

Framework heteroatom titanium silicalite molecular sieve with hierarchical pores and preparation method and application thereof Technical Field The disclosure relates to the field of preparation of titanium-silicon molecular sieves, in particular to a skeleton heteroatom titanium-silicon molecular sieve with hierarchical pores, and a preparation method and application thereof. Background Epsilon-caprolactam (epsilon-Caprolactam, CPL for short) is an important monomer for synthesizing nylon-6, is widely used for producing engineering plastics, nylon-6 fibers, industrial cord fabrics and other important downstream products, and can also be used in the fields of coating, medicines, fine chemicals and the like. The global consumption of caprolactam increased from 527 ten thousand tons in 2015 to 640 ten thousand tons in 2019 with an average rate of 4.9%. China is the largest caprolactam consumer world, and the consumption of caprolactam is about 52.7% of the total consumption. The cyclohexanone oxime gas phase Beckmann rearrangement process based on molecular sieve catalysts is highly valued in academia and industry. Compared with the traditional liquid phase method, the process avoids the use of ammonia gas and fuming sulfuric acid from the source, has the atomic utilization rate of 100 percent, and is an environment-friendly caprolactam green production process. The pure silicon molecular sieve with the MFI topological structure shows excellent catalytic performance, and the industrial experiment of cyclohexanone oxime gas-phase Beckmann rearrangement is carried out by adopting the pure silicon molecular sieve in succession by Japanese Sumitomo and China petrochemical industry in the beginning of the century. However, the gas-phase Beckmann rearrangement has two problems of poor selectivity of the product CPL and short single-pass life of the catalyst, which affect technical economy and continuous stability of operation, and cause extremely slow progress in subsequent large-scale industrial scale-up and commercial popularization. The MFI structure has small micropore size, and the micropore size is close to the molecular size of reactants and products, so that guest molecules in the pore canal of the molecular sieve limit domain diffuse slowly, and the residence time in the crystal is obviously prolonged, thereby aggravating the by-product generation and the blocking of the pore canal by carbon deposition substances. In addition, because the silicon hydroxyl active center of the pure silicon molecule is unstable, the silicon hydroxyl active center is easily deactivated by heated and alkaline byproducts, so that a new active center needs to be introduced to enhance the deactivation resistance of the catalyst. Baojun Li (RSC adv.,2013,3,20811-20815) adds S-1 and TS-1 molecular sieves as seed crystals during crystallization of the molecular sieves, and synthesizes titanium-silicon molecular sieves with different particle sizes for the cyclohexanone oxime gas phase beckmann rearrangement reaction, the conversion rate of the molecular sieves is reduced to 95% at 6h, the selectivity is stabilized at 86%, and the reaction effect is not ideal. Ferdi Sch uth et al (Microporous and Mesoporous Materials,2009,117,228-232) added 1, 7-dichloro-octamethyl-tetraoxy-silylating agent during the synthesis of titanium silicalite to perform pore-forming to obtain a titanium silicalite molecular sieve with multi-stage pores, which was reacted for 30 hours with a caprolactam yield of 1.6mmol CPL g -1cat h-1. Therefore, when the titanium-silicon molecular sieve synthesized by the existing preparation process is used for the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, the caprolactam selectivity and the catalyst life improving effect are not ideal, and a certain gap is reserved between the selectivity and the catalyst life improving effect and the industrial production requirement. Disclosure of Invention The invention aims to provide a skeleton heteroatom titanium-silicon molecular sieve with hierarchical pores, a preparation method and application thereof, wherein the molecular sieve has higher catalytic activation and stability, and the cyclohexanone oxime conversion rate and the caprolactam selectivity are obviously improved. To achieve the above object, a first aspect of the present disclosure provides a skeletal heteroatom titanium silicalite molecular sieve having hierarchical pores, the skeletal heteroatom titanium silicalite molecular sieve having 29 Si MAS NMR characteristics, wherein a peak area of a spectral peak at a position of-103+ -1 ppm of the skeletal heteroatom titanium silicalite molecular sieve is denoted as Q 3, a peak area of a spectral peak at a position of-113+ -1 ppm of the skeletal heteroatom titanium silicalite molecular sieve is denoted as Q 4-1, a peak area of a spectral peak at a position of-116+ -1 ppm of the skeletal heteroatom titanium silicalite molecular sieve is denoted as Q 4-2