Effect of preparation modes on the properties of cobalt-containing honeycomb monolithic catalysts modified by rare-earth metal oxides

Abstract

Two series of supported Co-containing catalysts modified with La and Ce oxides were synthesized by solution combustion with different amounts of glycine. Their properties were compared with characteristics of unmodified Co catalyst and modified catalysts synthesized by impregnation in an excess of solution without glycine. XRD, TEM, UV–vis DRS and differential dissolution were employed to investigate the phase and chemical composition, morphology and localization of catalytically active particles in the support matrix. Their redox and catalytic properties were characterized using H2-TPR and kinetic experiments on the oxidation of butane. Specific surface area, particle size, chemical composition of the active component and its localization as well as the reducibility by hydrogen were shown to depend on the synthesis mode and amount of fuel additive (glycine). A higher catalytic activity of the samples obtained by solution combustion synthesis as compared to those synthesized by impregnation is caused by the enrichment of subsurface layers of the support with Co(II,III) cations in the composition of simple (Co3O4) and mixed (CoAl2O4) nanosized oxides, by an increase in specific surface area and a decrease in the particle size of the active component and promotor. It was shown that the amount of glycine has a stronger effect on the properties of the catalyst than its modification with lanthanum or cerium oxides.