Selective CO oxidation on a Ru/Al2O3 catalyst in the surface ignition regime: 1. Fine purification of hydrogen-containing gases

Abstract

Selective CO oxidation in a mixture simulating the methanol steam reforming product with an air admixture was studied over Ru/Al2O3 catalysts in a quasi-adiabatic reactor. On-line monitoring of the gas temperature in the catalyst bed and of the residual CO concentration at different reaction conditions made it possible to observe the ignition and quenching of the catalyst surface, including transitional regimes. A sharp decrease in the residual CO concentration takes place when the reaction passes to the ignition regime. The evolution of the temperature distribution in the catalyst bed in the ignition regime and the specific features of the steady-state and transitional regimes are considered, including the effect of the sample history. In selective CO oxidation and in H2 oxidation in the absence of CO, the catalyst is deactivated slowly because of ruthenium oxidation. In both reactions, the deactivated catalyst can be reactivated by short-term treatment with hydrogen. A 0.1% Ru/Al2O3 catalyst is suggested. In the surface ignition regime, this catalyst can reduce the residual CO concentration from 0.8 vol % to 10–15 ppm at O2/CO = 1 even in the presence of H2O and CO2 (up to ∼20 vol %) at a volumetric flow rate of ∼100 1 (g Cat)−1 h−1, which is one magnitude higher than the flow rates reported for this process in the literature.