Low temperature reductive pretreatment of Au/Fe2O3 catalysts, TPR/TPO studies and behaviour in the water-gas shift reaction

The Au/Fe2O3 catalyst is prepared by a deposition-precipitation method and reduced using different organic/inorganic precursors before the measurement for low temperature water-gas shift reaction (WGSR). Addition of 2,6-dimethylpyridine to the water-gas mixture decreases the WGS activity suggesting the involvement of surface hydroxyl groups in the WGS reaction. Temperature programmed reduction (TPR) analysis revealed reduction signals due to oxidic-gold species and changes in TPR profiles were seen after treatment with organic/inorganic reducing agents. Catalysts were treated with different reducing agents and some of them were characterized by BET-surface area, TEM analysis and TPR/TPO studies. An HF treated Au/Fe2O3 sample showed lower activity compared to the catalyst made by conventional methods. A microwave irradiated sample showed lower WGSR activity compared to a conventionally heated catalyst. Based on the experimental observations and from TPR2 analysis of the microwave irradiated sample, it is concluded that An is redispersed after TPR1 and with the subsequent exposure to oxygen during TPO analysis. TEM analysis revealed that the average particle size of fresh 3 wt.% Au/Fe2O3 catalyst is ca. 15 nm. which is increased to 32 nm in the spent catalyst form. (C) 2003 Elsevier B.V. All rights reserved.