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Indexed by:Journal Papers

Date of Publication:2015-08-01

Journal:JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

Included Journals:SCIE、EI、Scopus

Volume:404

Page Number:98-105

ISSN No.:1381-1169

Key Words:Ag/MCM-41; HCHO; O-2 pretreatment; Particle size; Ag2O

Abstract: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.