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论文类型：期刊论文

发表时间：2015-08-01

发表刊物：JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

收录刊物：SCIE、EI、Scopus

卷号：404

页面范围：98-105

ISSN号：1381-1169

关键字：Ag/MCM-41; HCHO; O-2 pretreatment; Particle size; Ag2O

摘要：The effect of oxygen pretreatment on HCHO catalytic oxidation of Ag/MCM-41 catalysts has been investigated from 500 degrees C to 800 degrees C in this paper. The highest HCHO surface reaction activity is achieved on the silver sample pretreated at 700 degrees C. The state and the dispersion of silver species on the support are strongly related to the pretreatment temperature. The increase of the O-2 pretreatment temperature for Ag/MCM-41 catalysts results in the diffusion of Ag2O clusters from outside to inside of the channels. And the amount of Ag2O clusters inside the channels becomes maximum at 600 degrees C. Interestingly, it is found that the smaller metallic Ag nanoparticles coexist with large particles when the catalyst is pretreated at 700 degrees C. It is suggested that Ag2O clusters inside of MCM-41 pores improves the HCHO adsorption capacity and accelerates the formation of HCHO adsorption intermediates, particularly dioxymethylene(DOM) ad-species. And the formed meallic silver particles with smaller size at 700 degrees C plays an essential effect on the formation of formate intermediate and the enhancement of surface reaction activity. It is also concluded that CO2 formation rate from formate is higher than that from DOM species in HCHO oxidation. The decrease of HCHO surface reaction activity after oxygen pretreatment at 800 degrees C may be due to the decrease of the Ag2O clusters inside MCM-41 pores and the aggregation of metallic Ag nanoparticles. (C) 2015 Elsevier B.V. All rights reserved.