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 CO 2 to CH 4 is an efficient solution to alleviate the greenhouse effect and energy shortage. This work demonstrated that the CaO-captured CO 2 could be selectively converted to CH 4 by Ni-and hydrogenassisted 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 CO 2 emission. The CO 2 capture properties over the Ni/CaO composite and the methanation properties of the Ni/CaCO 3 composite produced after CO 2 capture were then studied in a batch reactor. It was proved that the CO 2 capture properties of CaO can be improved, the CaO recovering temperature can be significantly lowered, and valuable CH 4 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 CO 2 to CH 4 .

Low-temperature conversion of CaO-captured CO2 to CH4 over a greenly prepared Ni/CaO/Al2O3 composite under static pressure conditions

“…S2b,† the Ni/CaO composites were greenly prepared by Ca and Ni-induced mechanochemical hydrogenation of CaCO 3 , as reported in our previous work. 35 Then, the Ni/CaO/γ-Al 2 O 3 composites were obtained by ball milling Ni/CaO with γ-Al 2 O 3 at low speed (200 rpm). The obtained solid material was analyzed by XRD.…”

“…It was found that CO 2 can be captured and selectively converted to CH 4 over the Ni/CaO composite through an energy-saving calcium looping (CaL) process at moderate temperatures (450–550 °C) under static pressure conditions. 35 The CO 2 capture capacity and the CH 4 yield for hydrogenating over the 50Ni/2–1CaO composite reach 0.33 mmol g −1 and 68.58%, respectively. This method is fit for small-scale CO 2 conversion.…”