Effect of the preparation method on the performance of CuO–MnO x–CeO 2 catalysts for selective oxidation of CO in H 2-rich streams

Abstract

Selective oxidation of CO in H 2-rich streams is performed over a series of CuO–MnO x –CeO 2 catalysts prepared by hydrothermal (CuMC-HY), co-precipitation (CuMC-CP), impregnation (CuMC-IM) and citrate sol–gel (CuMC-SG) methods. The catalysts are characterized by N 2 adsorption/desorption, XRD, SEM, HR-TEM, TPR and XPS techniques. The results show that the catalyst prepared by a hydrothermal method exhibits the best catalytic activity, especially at low temperatures. The temperature of 50% CO conversion ( T 50) is only 74 °C and the temperature window of CO conversions up to 99.0% is about 40 °C wide, from 110 to 140 °C. Moreover, the temperature window is still maintained 20 °C wide even at lower temperatures when there are 15% CO 2 and 7.5% H 2O in the reaction gas. The superior catalytic performance of CuMC-HY is attributed to the formation of Mn–Cu–Ce–O solid solution, the unique pore structure and the existence of more Cu + and Mn 4+ species as well as oxygen vacancies. The sequence of catalytic activity is as follows: CuMC-HY > CuMC-SG > CuMC-IM > CuMC-CP. The worst catalytic activity, obtained from the catalyst prepared by the co-precipitation method, is possibly related to the existence of independent CuO x and MnO x oxides, which weakly interact with ceria in the catalyst.