Preparation And Performance Of Ag/TS-1 And Au/TS-1 Catalysts

As an important organic chemical raw material,propylene oxide（PO）has received extensive attention from researchers for its green synthesis process.The liquid-phase epoxidation of propylene in the titanium-silicon molecular sieve（TS-1）/H₂O₂ catalytic system and the gas-phase epoxidation of propylene in the Ag（Au）/TS-1/H₂/O₂ catalytic system are currently very promising PO production processes that meet the requirements of green chemistry.Although the former has been industrialized,it still has the problems of small pore size and large mass transfer resistance of TS-1 catalyst;the latter is still in the laboratory research stage,and the development of this type of catalyst and the systematic study of the reaction process are very necessary.This thesis first modified the titanium silicate（TS-1）with tetrapropylammonium hydroxide（TPAOH）as the alkali treatment agent,and studied the effects of TPAOH treatment concentration,time and temperature on TS-1 catalyzed propylene liquid epoxidation and the key factors affecting the reaction were explored.Secondly,silver nitrate（Ag NO₃）was used as the precursor to prepare the supported Ag catalysts,the support under different treatment conditions was investigated,and then the effect of deposition temperature and deposition time in the preparation conditions of the catalyst were studied in detail.Finally,chloroauric acid（HAu Cl₄·3H₂O）was used as the precursor to prepare the supported Au catalysts.The effect of different support treatment conditions on the prepared catalyst and the gas phase epoxidation reaction of propylene was discussed.The influence of reaction temperature and reaction space velocity are investigated,and inspected its stability performance.The main results are as follows:1.TPAOH post-treatment has an important influence on the liquid phase epoxidation of propylene catalyzed by TS-1 molecular sieve.When the concentration of TPAOH is 0.644mol/L,the time is 3 h,and the temperature is 90℃,the reaction effect is the best.The effective utilization rate of hydrogen peroxide and the selectivity of PO were 96.31%and 82.98%,respectively.The results indicated that the enlarged pass transfer channels,improved hydrophobic surfaces,enriched framework titanium,and weaken acid strength of TS-1 catalyst are the major reasons for enhanced conversion and reduced by-products.2.The catalytically active sites of Ag and Au have an important influence on the gas phase epoxidation of propylene.The Ag/TS-1-170 catalyst prepared with TS-1 alkali treated at 170℃after calcination（TS-1-170）as the carrier has the best catalytic performance.When the deposition temperature is 90℃and the deposition time is 4.5 h,the propylene conversion rate is 1.29%,and the PO selectivity is 34.65%.The reaction performance of the catalyst prepared by using Au as the active component is further enhanced.However,comparing the influence of the carrier,it is found that the uncalcined TS-1（TS-1-B）has stronger catalytic performance after being loaded with Au than the calcined TS-1.When the reaction temperature is 200℃and the space velocity is 8000 m L·h^-1·g^-1,the propylene conversion rate and PO selectivity reached 6.00%and 26.28%,respectively.