Ambient temperature NO oxidation over Cr-based amorphous mixed oxide catalysts: effects from the second oxide components

Abstract

Three series of Cr-based mixed oxides (Cr–Co, Cr–Fe, and Cr–Ni oxides) with high specific surface areas and amorphous textures were synthesized using a novel sol–gel method. These mixed oxides, in comparison to their pure metal oxide (CrO_x, Co₃O₄, FeO_x and NiO) counterparts, display enhanced performance for catalytic oxidation of low-concentration NO at room temperature. The best performing catalysts achieve 100% NO conversion for ∼30 h of operation at a high space velocity of 45 000 ml g⁻¹ h⁻¹. The amorphous structure was found to be critical for these catalysts to maintain high activity and durability. Control of the Cr/M (M = Co, Fe and Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature was key to the synthesis of these highly active catalysts.