Four series of Cr-based mixed oxides (Cr-Zr, 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 (CrOx, ZrO2, Co3O4, FeOx and NiO) counterparts, displayed enhanced performance for catalytic oxidation of low-concentration NO at room temperature. Over best performing catalysts, 100% NO conversion could be maintained up to 30 h of operation at a high space velocity of 45,000 ml g-1 h-1. An amorphous structure was found to be critical for these catalysts to maintain high activity and durability. Cr/M (M=Zr, Co, Fe and Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature were important criteria for the synthesis of such amorphous structures. X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR) analyses and hydrogen temperature-programmed reduction (H2-TPR) also indicated an electronic effect from the second oxides. That is, second oxides addition induced an increase in surface concentrations of Cr6+. Rapid deactivation of a pre-reduced catalyst, coupled with the fact that a deactivated catalyst contained lower concentrations of surface Cr6+, provided rather strong evidence for a Mars-van Krevelen NO oxidation mechanism.

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

253rd National Meeting (2017)

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