Intensified micro-mixing effects on evolution of oxygen vacancies of CeO2-based catalysts for improved CO oxidation

Abstract

The oxygen vacancies in CeO2-based catalysts play a vital role in the oxidation reactions due to the repeatable Ce4+/Ce3+ redox cycles. However, the influence of micro-mixing efficiency during co-precipitation reaction on the oxygen vacancy concentration in CeO2-based catalysts was scarce. In this work, a rotating packed bed (RPB) reactor was employed to intensify the micro-mixing of reactants before crystal nucleation, aiming to increase the oxygen vacancy concentration of CeO2-based catalysts. The MOx-CeO2 (M = Cu, Co, Fe) catalysts prepared in the RPB reactor featured more M-O-Ce species and 1.3 – 1.4 times concentration of oxygen vacancy compared to those prepared in a stirred tank reactor (STR). The RPB-CuO-CeO2 catalyst showed an elevated reaction rate of CO (6.70 × 10-4 mol gcat-1 s-1) at 90 °C and remained unchanged after 8 cycles in CO oxidation. This work demonstrates a feasible “nonchemical” strategy to prepare the high-activity solid solution catalysts with increased oxygen vacancies.