Selective Conversion of the CaO-Captured CO2 to CH4 by Ni- and Hydrogen-Assisted Calcium Looping Processes in a Batch Reactor

Abstract

Storing and hydrogenating CO2 to CH4 is an efficient solution to alleviate the greenhouse effect and energy shortage. This work demonstrated that the CaO-captured CO2 could be selectively converted to CH4 by Ni- and hydrogen-assisted calcium looping (CaL) processes in a batch reactor. The Ni/CaO composite was first synthesized in one step at room temperature by calcium-induced hydrogenation of Ni-mixed calcium carbonate without the use of any solvent and CO2 emission. The CO2 capture properties over the Ni/CaO composite and the methanation properties of the Ni/CaCO3 composite produced after CO2 capture were then studied in a batch reactor. It was proved that the CO2 capture properties of CaO can be improved, the CaO recovering temperature can be significantly lowered, and valuable CH4 can be selectively produced by Ni- and hydrogen-assisted calcium looping processes at moderate/high temperature. The 68.58% methane yield and 100% methane selectivity were achieved under relatively mild conditions. After five Ni- and hydrogen-assisted CaL processes, the methane yield still reaches 45%. This study offers a novel energy-saving CaL process, which can be utilized for facile and selective conversion of the CaO-captured CO2 to CH4.