Preparation Of TS-1Zeolite Supported Nano Au Catalysts And Their Performance For Gas-phase Epoxidation Of Propylene

Propylene oxide is an important organic chemical intermediate and it is an important reaction in the chemical industry to produce propylene oxide by the selective oxidation of propylene. The industrial production of propylene oxide mainly includes chlorohydrin process and organic hydroperoxide process, etc. These traditional production methods are of high-consumption, high-pollution thus does not meets with the destination of green chemistry and cleaner production. The direct propylene epoxidation with molecular oxygen is one of the most challenging subjects in catalysis field.In this thesis, using TS-1zeolite as support and urea as precipitator, we synthesized the supported nano gold catalysts using the deposition-precipitation method and they were examined in the direct propylene epoxidation with molecular oxygen. The effects of catalyst preparation parameters were carefully investigated on the catalytic performance, with respect to the treatment of the support TS-1zeolite, urea/Au molar ratio, Au loading, catalyst calcination temperature and H2-reduction conditions. Optimization of the reaction conditions were also carried out.The best catalyst is the one with1wt%Au loading onto the TS-1zeolite without organic template removal, being obtained by deposition-precipitation using urea/Au molar ratio of100at90℃for4.5h followed by a calcination at300℃and subsequent H2-reduction at250℃for1h. At150℃and a gas hourly space velocity (GHSV) of12000mL·h-1g-1, propylene conversion of8.0％can be obtained with the PO selectivity of81.5%, using a feedstock of C3H6:O2:H2:N2=1:3:9:12. Note that the Au catalysts obtained using TS-1zeolite with removal of the organic template are not active for the titled reaction.It has been found that the organic template in the TS-1zeolite plays a crucial role in highly dispersion of Au onto the support surface. Gold loading amount on the TS-1cannot be affected by either organic template removal or not, and the TS-1zeolite framework preserved very well after gold deposition-precipitation. TEM measurements indicate that the presence of organic template in the TS-1facilitated uniform and high dispersion of gold (Au particle size is about5nm on the best catalyst of1%Au/TS-1); in contrast, gold cannot be highly and uniformly dispersed onto the TS-1without organic template.