Ru4 + ion in CeO2 (Ce0.95Ru0.05O $_{\bf 2-\boldsymbol\delta})$ : A non-deactivating, non-platinum catalyst for water gas shift reaction

Abstract

Hydrogen is a clean energy carrier and highest energy density fuel. Water gas shift (WGS) reaction is an important reaction to generate hydrogen from steam reforming of CO. A new WGS catalyst, Ce1 − xRuxO2 − δ (0 ≤ x ≤ 0.1) was prepared by hydrothermal method using melamine as a complexing agent. The Catalyst does not require any pre-treatment. Among the several compositions prepared and tested, Ce0.95Ru0.05O2 − δ (5% Ru4 + ion substituted in CeO2) showed very high WGS activity in terms of high conversion rate (20.5 μmol.g − 1.s − 1 at 275°C) and low activation energy (12.1 kcal/mol). Over 99% conversion of CO to CO2 by H2O is observed with 100% H2 selectivity at ≥ 275°C. In presence of externally fed CO2 and H2 also, complete conversion of CO to CO2 was observed with 100% H2 selectivity in the temperature range of 305–385°C. Catalyst does not deactivate in long duration on/off WGS reaction cycle due to absence of surface carbon and carbonate formation and sintering of Ru. Due to highly acidic nature of Ru4 + ion, surface carbonate formation is also inhibited. Sintering of noble metal (Ru) is avoided in this catalyst because Ru remains in Ru4 + ionic state in the Ce1 − xRuxO2 − δ catalyst. A novel Ru ion substituted CeO2, Ce0.95Ru0.05O2-δ, synthesized by hydrothermal method showed, nearly 100% CO conversion in the WGS reaction with conversion rate 20.5 μ mol.g-1.s-1 at 275°C and activation energy 12.1 kcal/mol.