Moderate-temperature chemical looping splitting of CO2 and H2O for syngas generation

Abstract

Moderate-temperature chemical looping processes circumvent challenges including the sintering of oxygen carrier (redox catalyst) materials and the deterioration of the reactor at elevated temperatures (800–1000 °C). While the activation of hydrocarbons and oxygen releasing from metal oxides are difficult at lower temperatures, leading to slow redox kinetics in chemical looping. Herein, we proposed a moderate-temperature (500–700 °C) chemical looping scheme composed of methane partial oxidation and splitting of CO2 and H2O for syngas generation. By virtue of the methane activation of highly dispersed nano-metallic Ni on CeZrO2 solid solution, CO2 activation over the oxygen vacancies-enriched Ni-CeZrO2-δ interface and the high recyclability of the material redox process, syngas with an ideal H2/CO molar ratio is produced by alternative selective oxidation of methane using lattice oxygen and conversion of CO2 and H2O using oxygen vacancies over Ni-CeZrO2 redox catalyst at 650 °C. Lattice oxygen/oxygen vacancies in 3wt.%Ni/CeZrO2 catalyst dominate the redox process for methane/H2O-CO2 conversion, and deposited carbon from methane crack at a deep reduction condition will transfer to the oxidation step to increase syngas production via gasification. The proposed chemical looping scheme provides an efficient strategy for the CO2 and methane conversion at moderate-temperature condition, which will extremely expand the application of redox catalysts in chemical looping reforming processes.