The Study Of Propylene Epoxidation Over Modified Micro TS-1 Catalysts

In this article, the micro TS-1 was modified by tetrapropylammonium hydroxide (TPAOH) in 100 ml autoclave at optimizing modification conditions. The effect of catalysts, solvent, reaction temperature, the concentration of hydrogen peroxide solution, reaction time, the amount of ammonia on the catalytic properties of propylene epoxidation was investigated over Batch reactor. Then catalysts were modified in 5 M3 synthetic clave over optimal modification conditions, then extruded catalysts was prepared by extruders. Then the reaction conditions such as temperature, weight hourly space velocity of propylene, hydrogen peroxide solution concentration and the concentration of ammonia are optimized on fixed bed reactor use methanol solvent. The long time catalytic properties of fresh catalyst, laboratory in situ regeneration catalyst were studied respectively, and then a 500 h experiment was studied over the 100 t/a medium-sized test device. At last, the micro TS-1 was modified with magnesium acetate by the impregnation method, the catalytic performance with methanol as solvent was studied. Explore micro TS-1 subsequent modification and improve the catalytic performance use methanol solvent methods.The study found that as follows:(1) Treated with TPAOH solution can increase the number of mesoporous and reduce the acidic content, improve its activity and stability, decrease the acetaldehyde generation; using methanol solvent can also reduce the amount of acetaldehyde; low reaction temperature, can control the generation acetaldehyde;(2) Use extruded TS-1 as catalyst, methanol as solvent in fixed bed, the orthogonal test was studied. The best reaction conditions are as follows:temperature 40℃, concentration of ammonia 0.4 mmol/L, weight hourly space velocity of propylene 0.6 h-1, hydrogen peroxide solution concentration 1.2 mol/L, At this reaction condition, the long time catalytic properties of fresh catalyst, laboratory in situ regeneration catalyst were studied respectively,1800h long running experiments results show that the catalyst has good activity and selectivity and stability. A 500 h long running experiments over 100 t/a medium-sized test device,XH2O2 amd SPO are can achieve 97%; (3) The micro TS-1 was modified with MgO by the impregnation method. The catalytic performance for propylene epoxidation reaction with methanol as solvent was studied. The results show that an obvious decrease of the catalyst acidity w as observed either modified by MgO, reduce the byproduct generate rate. Under the optimal reaction condition CH2O2=1-0 mol/L, mTS-1=0.4 g, T=60℃, t=60 min, PC3H6=0.6 MPa, the hydrogen peroxide conversion was 99.5%, propylene epoxide selectivity was 96.67%,propylene epoxide selectivity and propylene epoxide yield was higher than that over unmodified microns TS-1, propylene epoxide selectivity increase 8.8%,propylene epoxide yield increase 12.44%. Reusability test shows that MgO modified micro TS-1 have good stability, after reuse twice, catalytic performance are maintained at high levels.