Direct Gas-phase Epoxidation Of Propene To Propylene Oxide Over Ag/TS-1 Catalyst

Since environmental problems have been severe nowadays, a lot of efforts have been made to develop an alternative direct epoxidation processes for the production of propene oxide (PO). PO production using oxygen is now the most promising process, and also one of the top tough projects, which is suffering from low conversion or low PO selectivity. It’s important to figure out the factors which are affecting the PO production on gas-phase propene epoxidation.Therefore, this work is focus on support and promoter effort on Ag/TS-1 for gas-phase epoxidation, also a new preparing Ag/TS-1 catalyst approach is investigated. The major parts include:(1) Alkali precipitator KOH, NaOH, K2CO3 and Na2CO3 are used to prepare Ag/TS-1 catalyst by deposition-precipitation (DP) method. KOH shows good ability on controlling Ag dispersity and size distribution. It was found that K+ is good promoter for Ag/TS-1 catalyst. The catalyst maintains activity above 1%, and selectivity above 90% in at least 600 min.(2) In order to observe Ti species on propene epoxidation, different Ti and alkali sources are used to prepare a serial of micro TS-1. The results show that tetrahedral Ti sites are active for PO formation, non-framework TiOx results in by-reaction of propene, leading to deactivation of catalyst. Anatase also could be beneficial for propene epoxidation.(3) Plasma sputtering process is found to be useful approach for preparing Ag/TS-1, which can produce different size Ag embedding onto TS-1. Compared with DP method, the plasma sputtering made Ag/TS-1 catalyst has more by-products. The propene conversion is 0.5-1.6%, and propene oxide selectivity is 76-95%.(4) Ag size and thermal effect are also discussed in this paper. The results indicate that PO selectivity was not sensetive to Ag particle size. In an Ag size range of 8-40 nm, All Ag/TS-1 catalysts show propene oxide selectivity above 90%. Ag-Ti balance is important on catalyst activity for PO production. Thermal effect severely affects PO selectivity and the life of catalyst.