Modify Ts-1 By The Secondary-crystallization Method And Study On Its Catalytic Performance For Epoxidation Of Allyl Chloride

Epichlorohydrin (ECH) is an important organic industrial chemicals. There are two ways for the production of epichlorohydrin: high temperature chlorination of chloropropene and allyl alcohol method. But all these two methods have environmental harassment that large numbers of wastewater and waste residue are produced. The exploitation of new cleanly technics with high efficiency is more important. TS-1 is a new kind of zeolite catalyst developed in 1980s. It can activate in the low temperature system when aqueous hydrogen peroxide as the oxide. The TS-1 have been attracted more attention for its moderate reaction conditions, high selectivity and non-poluting process. But the expensive production cost and harsh synthesised conditions limit its large-scale industrial applications. At the same time, the grain of the TS-1 that made from organic titanium-silicon materials is too small to separate from the reaction system, and the catalytic activity will be limited while loading the grain of the TS-1 to some carriers. These problems are in need of further researchs.Titanium silicate molecular sieves TS-1 was synthesized using inorganic titanium and silicon as titanium source and silicon source respectively in this paper. TS-1 grains suited for separating from the liquid phase was obtained in this method, the inorganic TS-1 is cheaper than organic TS-1 at the same time. But the catalytic activity of the inorganic TS-1 was lower than the organic TS-1. So that Secondary-crystallization method was proposed and used to modify the inorganic TS-1. To study the catalytic performance of modified TS-1 by the Secondary-crystallization, the epoxidation of allyl chloride was used as the probe-reaction. aqueous thermal conditions of the Secondary-crystallization as follow have been investigated: the temperate, the synthesised time, the pH value of the solution, the anion and cation in the solution. The secondary-crystallizated TS-1 samples attained in the optimized condition were used to catalyse the epoxidation of allyl chloride. reaction conditions which affect the reaction results as follow have been investigated: reaction temperature (T), reaction time (t), amount of catalyst, the molar ratio of reactants (n(ALC)/n(H₂O₂)) and amount of solvent (methanol). at last, the recycle and regeneration of the secondary-crystallizated TS-1 were studied in this paper.The experiment results showed that the optimum conditions of the secondary-crystallization were as follow: T=170℃, pH=12, ammonia diluted by water as aqueous thermal solution, time>24h. modified under this condition the catalytic activity of the inorganic TS-1 is the same as the organic TS-1. From the SEM, XRD, IR and N₂ adsorption of TS-1, we can say that the improve of the catalytic activity of inorganic TS-1 after the secondary-crystallization is because of the Ti entered into the framework again. The experiments showed that the optimum reaction conditions of the epoxidation of allyl chloride were as follow: T=30℃,t=40min, amount of TS-1=2.96%(the quality percentage of TS-1 relative to the whole materiel), n((ALC)/n(H₂O₂)=1.2, n(CH₃OH) / n(ALC) =5.2, in these conditions, the conversion of H₂O₂ (X_H2O2) reached higher than99%, the effective utilization of H₂O₂ (U_H2O2) could be higher than97%, while the yield of the product (Y_ECH) could achieve above to 96%. As to the research about the recycle and regeneration of the secondary-crystallizated TS-1, bake TS-1 can make it regenerated, but the catalytic activity is a few lower than the fresh TS-1, the selectivity to the ECH of regenerated TS-1 is the same as the fresh TS-1,so the lower part of catalytic activity can make up by increasing the quality of TS-1.