Characteristics and Application of 1. Titanium Silicalite Molecular Sieve

Titanium silicalite molecular sieve (TS-1) in1983yearTaramassoFirst reported,MFItopology,TiThe atoms enter the zeolite framework with a four-coordination structure and isomorphous substitution of partSiThe atoms give it a unique catalytic oxidation activity. Up to now, the successful creation of titanium silicalite molecular sieves with MFI structure represented by TS-1 has opened up a new direction of liquid phase selective oxidation of hydrocarbons based on hydrogen peroxide oxidant. In the key steps of caprolactam production, cyclohexanone ammoxidation process (Ammoximation) and propylene direct epoxidation process to propylene oxide (HPPO) have been applied in large-scale industrialization, and the clean production of bulk oxygen (nitrogen) containing chemicals has been realized, milestone achievements have been made in the field of molecular sieve catalysis. In addition, titanium silicalite molecular sieves are expected to replace the original high energy consumption and high pollution chemical processes in the hydroxylation of phenol, one-step ethylene glycol and oxidative desulfurization reactions, and thus play an important role in reducing waste emissions and realizing green low-carbon chemical synthesis and production.

Titanium silicon molecular sieve is characterized by the skeleton is electrically neutral, no ion charge compensation is required, and the pore channel preferentially adsorbs non-polar or low-polarity organic molecules and presents hydrophobicity, so hydrogen peroxide (H2O2) The solution is used as an oxidant to selectively catalyze the oxidation of organic matter in an aqueous solution system. taking the epoxidation of olefins as an example,Tiactive site.H2O2formTi-OOHand continue to bond with the solvent molecule to form a five-membered ring transition state structure, and thenTiOxygen in atomic proximity donates electrons to the olefin and ultimately forms the epoxidation product.

However, dueTS-1limitation of the pore size of micropores (straight channels5.6 A, the sine channel is5.4 A), the size of organic molecules that can effectively catalyze oxidation is generally smaller than xylene, and organic molecules of larger size cannot enter the pores to contact active sites, thus limiting the formation of large-size reaction intermediates and products or effective diffusion in microporous pores, affecting the catalytic reaction path and even causing catalyst deactivation. Accordingly, a variety of structures of microporous and mesoporous titanium silicon materials have been developed to solve this problem, suchTi-MWW(MWW），Ti-Beta.(BEA），Ti-MORandTi-MCM-41However, these molecular sieves also have low crystallinity,TiInsufficient site activity and low hydrophobicity.

Advantages of 2. national porcelain molecular sieve

1. High conversion rate

National porcelainTS-1It has an ordered microporous structure, as well as an interconnected mesoporous structure, and its mesoporous size can be adjusted, while having a regularTS-1molecular sieve unique catalytic selective oxidation performance, good thermal/Hydrothermal stability and excellent diffusion performance, showing good application prospects in the field of catalytic oxidation. Through the control of hydrothermal synthesis, the channel system can effectively improve the utilization efficiency of the active center of the framework titanium and shorten the diffusion path of the reactant, and the titanium species and its distribution in the molecular sieve can be adjusted by post-treatment, and the catalytic activity and stability of the molecular sieve can be significantly improved.

In the synthesis of vinyl sulfate, the temperature35℃, reaction time5h,TS-1Addition in3%under the conditions,DTDThe highest yield can be96%.

2. High recovery rate and high application times

The solid-liquid separation of ultrafine particles, especially the efficient separation of solid-liquid heterogeneous systems, is extremely difficult, and regular separation methods, such as filtration and centrifugal separation, are difficult to apply to industrial production. regularTS-1The average particle size is small (mostly in28-500 NM), the separation of catalyst and product in the reaction is a thorny problem. regular methods are adopted200nmAperture below inorganic ceramic membrane separation technology. Due to the high investment cost of inorganic ceramic membranes (single set of investment in100More than 10,000 yuan), the membrane tube replacement cost is high (the cost of a single membrane tube is in.1000yuan), often prohibitive.

In this regard, the National porcelain TS-1 on the basis of ensuring catalytic activity, large grains (≥5um) products. Customers use metal sintered precision filters during use (a single set of investment is less5Ten thousand yuan) can effectively filter, recycle molecular sieve, will apply the number of times from 15 about times, promoted 30 more than once.

RegularTS-1                                                                National porcelainTS-1

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