A kind of titanium silicon molecular sieve and its preparation method and application

Abstract

The invention relates to a titanium silicate molecular sieve and a preparation method thereof and a purpose thereof. According to the preparation method, a free radical initiator is introduced into areaction raw material to enable .OH free radical to be generated in the reaction process; and therefore, effects of shortening time needed by hydrothermal crystallization and enhancing the degree of crystallinity of the titanium silicate molecular sieve are achieved. In the titanium silicate molecular sieve prepared by the preparation method, the content of titanium silicate molecular sieve crystals of MFI structures is larger than or equal to 85%, and the content of amorphous SiO2 structures is less than or equal to 15%; and through ultraviolet-visible light spectral analysis, the conditionsthat a titanium silicate molecular sieve framework is rich in isolated sexadentate titanium species, and the weight percentage of the titanium in the titanium silicate molecular sieve reaches 0.15-4%are confirmed.

Description

technical field [0001] The invention relates to the field of material preparation, in particular to a titanium-silicon molecular sieve and its preparation method and application. Background technique [0002] Since the United States Patent (U.S. Patent No. 4410501) reported the synthesis and application of titanium-silicon molecular sieve TS-1 in 1983, microporous titanium-silicon molecular sieve TS-1 has attracted extensive attention of researchers. The unique structural characteristics of titanium-silicon molecular sieve TS-1 have special selective catalytic oxidation performance, which is suitable for selective oxidation reactions of hydrocarbon organic matter, such as propylene epoxidation, phenol hydroxylation, etc. One of the milestones in the field. [0003] In recent years, researchers have done a lot of research work on eliminating the formation of anatase, improving the repeatability and stability of the molecular sieve preparation process, and adjusting the size ...

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Problems solved by technology

[0004] CN102627292A discloses a preparation method of TS-1 molecular sieve, the method is: first prepare the mixed solution of silicon source and titanium source, the mixed solution of organic base and water, and then pass the prepared two mixed solutions through co-current feeding The method is continuously added to the reactor to form a hydrolysis mixed solution, and the hydrolysis mixed solution is also continuously discharged, and finally the discharged hydrolysis mixed solution is subjected to conventional steps such as alcohol removal and hydrothermal crystallization to obtain a TS-1 molecular sieve product. The defect of scheme is that the crystallinity of the obtained titanium silicon molecular sieve is lower

[0005] CN103818924A discloses a method for preparing a titanium-silicon molecular sieve. After mixing silicon source, template agent, water and titanium source, adding seed crystals, crystallization is carried out after obtaining sol, and molecular sieve can be obtained after filtering, washing and drying, wherein , the seed crystal is prepared by a classical hydrothermal synthesis method, and the preparation process needs to add a seed crystal, which makes the operation of the preparation process complicated and not suitable for industrial applications

[0006] CN106829996A discloses a method for preparing a titanium-silicon molecular sieve rich in isolated four-coordinated titanium species, comprising the following steps: (1) mixing a template agent, water, and an alkali source to obtain an alkaline mixed solution I, and the template agent is Tetrapropylammonium bromide; (2) part of the mixed solution I is mixed with the silicon source to obtain the mixed solution II; (3) the remaining mixed solution I is mixed with the alcohol solution III containing the titanium source to obtain the mixed solution IV; (4 ) mixing mixed solution IV with mixed solution II to obtain mixed solution A; (5) aging and removing alcohol from mixed solution A to obtain mixture B; The mixture B is crystallized, washed, and dried by a hydrothermal method to obtain a titanium-silicon molecular sieve TS-1. The crystallization time required for the preparation method is relatively long, which increases the preparation cost

[0007] The above-mentioned documents provide some methods for preparing titanium-silicon molecular sieves, but there are still some defects in the preparation process, such as complex operation, the need to introduce crystal seeds, long hydrothermal crystallization time, and low crystallinity of the obtained product. It needs to introduce crystal seeds, and the time required for hydrothermal crystallization is short, and the preparation method with high crystallinity of the obtained product is still of great significance

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