Low temperature water-gas shift reaction on cerium containing mordenites prepared by different methods

Cerium containing mordenites catalysts were prepared by impregnation (CeM imp), solid-state ion exchange (CeM ss) and in situ incorporation during synthesis (CeM in). The structure of the samples has been investigated by X-ray diffraction, FT-IR, N 2 adsorption, thermal analyses (TG and DTA) and pyridine-FT-IR. Water-gas shift reaction (WGSR) was carried out over various catalysts and the catalytic reaction was monitored using in situ FT-IR. The results obtained showed the presence of cerium silicate phase in case of CeM in sample as evidenced by XRD and FT-IR spectroscopy. In case of CeM imp and CeM ss, a separate CeO 2 phase was observed in a highly dispersed state in the former than in the latter, which measured the highest specific surface area. FT-IR results of pyridine adsorption indicate the presence of acid–base site pairs on the surface of CeM imp and CeM ss samples where only Lewis acidity was found on CeM in, reflecting the presence of Ce 3+ with Si 4+ cations at tetrahedral lattice sites in mordenite. CeM imp showed the highest catalytic activity followed by CeM ss. It has been shown that reduction by H 2 carried out at 500 °C was responsible for activating different carbonyls attached to Ce 3+; such as Ce 3+–CO and Ce 3+–(CO) 2 which decomposed into CO 2 ads . The role of basicity, Ce dispersion and surface texture of reduced Ce–mordenites on their catalytic activity in CO oxidation by H 2O was evaluated and discussed.