Synergistic effects between Mn and Co species in CO2 hydrogenation over xCo/MnO catalysts

Abstract

CO2 hydrogenation technology has great potential for mitigating the greenhouse effect and creating a green economy. The development of catalysts plays a key role in the progress of CO2 hydrogenation technology. In this study, the xCo/MnO catalysts for CO2 hydrogenation reaction were prepared by the impregnation method using MnOx as the catalyst support. And the effects of the Co loading on the CO2 hydrogenation performances of the prepared xCo/MnO catalysts were investigated. The active Co0 species on the xCo/MnO catalysts surface are the main active centers for the CO2 hydrogenation reaction, and the medium basic sites on the xCo/MnO catalysts are the main CO2 adsorption sites. The MnOx support possesses a large number of medium basic sites, which can enhance the CO2 molecules adsorption ability of the xCo/MnO catalysts. An effective regulation of the basic and hydrogenation active site numbers on the xCo/MnO catalysts surface can be achieved by changing the Co loading amount, which in turn can affect the CO2 molecules adsorption, activation and hydrogenation abilities of the xCo/MnO catalysts. Moreover, the Mn1-yCoyO solid solution was found to be formed in the prepared xCo/MnO catalysts, which is conducive to the dispersion of metal Co nanoparticles on the MnO surface and the generation of oxygen-deficient sites. The CO2 desorption amount on the 12Co/MnO catalyst reached 1.76 mmol/g, which provided the catalyst with strong CO2 adsorption and activation abilities, enabling it to exhibit great CO2 hydrogenation performance. Under the conditions of atmosphere and 420 °C, the CO2 conversion and CH4 selectivity on the prepared 12Co/MnO catalyst reached 57.5 % and 78.8 %, separately. Furthermore, the CO2 conversion was able to consistently remain at the initial 57.5 %, and the CH4 selectivity was maintained above 70.0 % in the 10 times CO2 hydrogenation cycle tests on the 12Co/MnO catalyst. Our study highlights the potential of using MnOx as catalyst support in the CO2 hydrogenation reaction, and the findings will provide convenient for the future studies.