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Effect Of Impregnation Method And Precipitation Method On The Performance Of Ag-based Catalysts Doped With CeO2or Fe For One-step Synthesis Of Indole

Posted on:2015-03-25Degree:MasterType:Thesis
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:2181330431988044Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Indole, a very important fine chemical, is widely used in the fields of medicine, agriculture, industry. The synthesis of indole from aniline and ethylene glycol (EG) is one of the most promising routes from an industrial point of view because it is not only convenient in operation and cheap in price but also green environmental-protection.In this paper, the influence of CeO2and Fe promoter on the activity, selectivity and stability of silver-based catalysts prepared by impregnation was studied and the catalytic performance of silver-based catalysts prepared by precipitation was investigated. The catalysts was characterized by methods of X-ray powder diffraction (XRD), temperature programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD) and thermogravimetric (TG-DTA), etc.The results indicated that for silver-based catalysts prepared by impregnation, CeO2promoter and Fe promoter can improve the catalytic activity, selectivity and stability significantly and adding two promoters, in which CeO2first, then Fe exhibited more efficiency. Over the catalyst of Ag/SiO2-ZnO-CeO2-Fe, the yield of indole can be up to84%at the sixth hour when the content of CeO2was0.040mmol/g and the content of Fe was0.050mmol/g. The characterizations indicated CeO2and Fe promoter can not only disperse active component of silver and inhibit the sintering of the silver particles to some extent, but also increase the amount of weak acid sites of catalyst.The Ag/SiO2-ZnO catalyst prepared by precipitation exhibited high activity and selectivity, as well as good stability when the weight ratio of SiO2and ZnO was12:1. The yield of indole was90%at the first hour of the reaction, and the yield can sill reach86%at the sixth hour. XRD and NH3-TPD results indicated that active component of silver on the catalyst was highly dispersed and there were a number of weak acid sites. The activity and selectivity of Ag/SiO2-ZnO-CeO2and Ag/SiO2-ZnO-Fe catalyst which prepared by precipitation was low because the dispersion of silver was poor and there were a lot of middle-strong acid sites.
Keywords/Search Tags:Indole, Ag/SiO2-ZnO catalyst, CeO2promoter, Fe promoter, Ethylene glycol, Aniline
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