Influence of reduction conditions on the structure-activity relationships of NaNO3-promoted Ni/MgO dual function materials for integrated CO2 capture and methanation

Abstract

Integrated CO 2 capture and utilization (ICCU) represents an innovative concept and technique for reducing industrial carbon emissions. Ni-MgO dual function materials (DFMs) promoted by alkali metal salt (AMS) for integrated CO 2 capture and methanation (ICCU-M) is gaining increasing interest. The in-situ methanation performance depends heavily on the high-temperature NiO reduction process, while this might adversely affect CO 2 adsorption due to loss of AMS . Herein, we investigated the effects of H 2 concentration and reduction temperature on structure–activity relationships of AMS-promoted Ni-MgO DFMs for ICCU-M. The increase in H 2 concentration and reduction temperature favors NiO reduction to metallic Ni 0 and boosts oxygen vacancy concentration in the DFMs. Both CO 2 uptakes and CH 4 yield increase with the elevating H 2 concentration, and CH 4 yield also increases with the increasing reduction temperature, considering the increased metallic Ni 0 content and oxygen vacancy concentration. CO 2 uptakes of the DFMs decline with the increase in reduction temperature, due to the obvious loss in AMS . The bulk diffusion kinetics in CO 2 adsorption stage will be improved under higher H 2 concentration and reduction temperature, while the chemisorption kinetics will be weakened at elevating reduction temperature. The methanation kinetics will be enhanced when the DFMs are reduced under higher H 2 concentration and temperature. The AMS-NM-100-450 DFMs reduced in 100 %H 2 and 450 °C exhibit good ICCU-M performance with high CO 2 adsorption capacity and CH 4 yield of 6.46 mmol CO 2 /g and 0.85 mmol CH 4 /g. The results in this work enlighten that the ICCU-M performance of AMS promoted Ni-MgO DFMs can be tuned by regulating the operating parameters for catalyst reduction.

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