The Study On The Catalyst Of Direct Oxidation Ethane To Ethylene Oxide

Ethylene oxide as derivatives of ethylene industury is an important organic chemical products and wildely used as organic synthetic intermediate. In the industrial process ethylene oxide is obtained through epoxidation of ethylene which is obtained through steam cracking of ethane or naphtha. Generally, the preparation temperature of ethylene by high temperature cracking of ethane is above 900℃, but the preparation temperature of ethylene oxide by direct oxidation of ethylene is between 200℃and 300℃. The great temperature difference makes it impossible to synthesize ethylene oxide by direct oxidation of ethane.Nanoscaled nickel oxide can greatly reduce the reaction temperature of oxidation dehydrogenation of ethane. In this paper we firstly investigate low-temperature oxidation of ethane to ethylene using nanosized nickel oxide as catalyst in order to reduce the reaction temperature. The result indicated that under 350℃the catalyst prepared in optimum conditions showed better catalystic performance and the yield of ethylene can reach 25 %. On this basis we studied the "one step with two stage" on nanosized nickel oxide and Ag with ethane flowing through them orderly under the same temprature. It's found that ethylene oxide can be directly prepared by ethane.The catalyst was prepared by different method and Ag-Ni-O catalyst prepared by homogeneous precipitation method shows better behavior with ethane conversion of 21.0 % and ethylene oxide selectivity of 6.1 %. We also optimized the preparation condition of catalyst, disscussed the effect of promoter on catalytic performance, investigated the effects of reaction conditions such as space velocity, the ratio of reaction gas.This paper also discussed the mechanism of the one-step reaction over Ag-Ni-O catalyst. The results of TPR and XPS indicated that there is an interaction between Ni and Ag in the catalyst, and it is the surface species of Ni that activate ethane. Since the surface active species were reduced and separated by the doping of Ag, the activity of Ag-Ni-0 catalyst reduced compared with pure NiO. The product of ethylene oxide was obtained by the oxygen intercalation reaction between the intermediate and electrophilic oxygen species on the surface of Ag.