Preparation method of titanium-silicon molecular sieve with controllable grain size

Abstract

The invention relates to a preparation method of a titanium-silicon molecular sieve with controllable grain size. The method is as follows: the titanium-silicon molecular sieve with the controllable grain size is synthesized in a hydrothermal system by modulating a nano-scale molecular sieve mother solution as a seed crystal, and the range of the grain size is 50-500nm. The titanium-silicon molecular sieve synthesized by the method provided by the invention has the advantages of small grain size, high degree of crystallization, high content of framework titanium, strong hydrophobicity and very high activity against selective oxidation reaction of olefin epoxidation, hydroxylation of aromatic hydrocarbons, ammonia oxidation of ketones and the like. The method is suitable for a classic or cheap system, and the nano-scale titanium-silicon molecular sieve can be synthesized in the cheap system.

Description

technical field [0001] The invention relates to a preparation method of a titanium-silicon molecular sieve with controllable grain size. Background technique [0002] Since the synthesis of titanium-silicon molecular sieve TS-1 was first reported in U.S. Patent 4410501 in 1983, its oxidation system with hydrogen peroxide has shown high activity for olefin epoxidation, aromatic hydrocarbon hydroxylation, and ketone ammoxidation. Moreover, the by-product is water, which belongs to an environmentally friendly process, so it has attracted widespread attention. [0003] The synthesis method of the titanium silicon molecular sieve disclosed by U.S. Patent 4410501 is to adopt ethyl orthosilicate as the silicon source, tetraethyl titanate as the titanium source, and tetrapropyl ammonium hydroxide as the template agent. In a hydrothermal system, crystal It is obtained in 6 to 30 days, and this method is usually called the classical method. [0004] Because tetrapropyl ammonium hydr...

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Problems solved by technology

[0004] Because tetrapropyl ammonium hydroxide is expensive, many researchers use tetrapropyl ammonium bromide instead of tetrapropyl ammonium hydroxide as a template to synthesize titanium silicon molecular sieves. The introduction of TS-1 and the reduction of the alkalinity of the synthetic glue lead to a significant increase in the grain size of the molecular sieve, which greatly reduces the catalytic performance of TS-1. Therefore, if nano-scale (grain size <200nm) TS-1 will play an important role in promoting the synthesis of high-performance and cheap TS-1 molecular sieves

[0005] Chinese patent CN100457622 proposes a titanium-silicon molecular sieve synthesized in an inexpensive system with a grain size of 0.85 μm×0.4 μm×0.15 μm, reducing the grain size of the titanium-silicon molecular sieve synthesized in an inexpensive system to less than 1 μm, but its The synthesis cycle is very long and requires variable temperature crystallization

However, this method has certain limitations. It can only use nanoscale titanium-silicon molecular sieve mother liquor obtained by crystallization at high temperature as the seed crystal, but not other molecular sieve mother liquors. Obtaining Nanoscale Ti-Si Molecular Sieves in an Inexpensive System

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