LaNiO3 as a precursor of Ni/La2O3 for reverse water-gas shift in DBD plasma: Effect of calcination temperature

Abstract

Reverse water–gas shift (RWGS) is considered as a promising reaction to convert CO2 into CO, which together with H2, can be used for the synthesis of Fisher-Tropsch chemicals. In this study, a hybrid dielectric barrier discharge (DBD) plasma-catalysis system was developed for RWGS at room temperature. LaNiO3 perovskite catalysts calcined at 600, 700, 800 and 900 °C (denoted as LNO-600, LNO-700, LNO-800 and LNO-900) were synthesized and tested for RWGS in DBD plasma reactor. Different methods including XRD, N2 adsorption-desorption, H2-TPR, TEM, CO2-TPD, O2-TPD, XPS, XANES, EXAFS and TG-DTA were employed for the characterization of fresh, reduced and spent catalysts. The results showed that a fully crystallized LaNiO3 perovskite structure could be formed only at temperatures of >800 °C, and lower calcination temperatures resulted in the presence of NiO and amorphous La2O3. Ni was extracted from the LaNiO3 perovskite structure to form Ni supported on La2O3 support (Ni/La2O3) after reduction for all catalysts. The CO2 conversion did not show obvious difference over different catalysts. However, the maximum CO selectivity and the minimum CH4 selectivity were achieved over LNO-600. The higher catalytic activity of LNO-600 should be attributed to its higher Ni dispersion, smaller Ni particle size and stronger metal-support interaction. It should be noted LNO-800 showed the highest coke resistance ability, due to the highest ratio of surface adsorption oxygen and largest oxygen storage capacity evidenced by the XPS and O2-TPD results. In addition, the effect of H2/CO2 ratio on the performance of RWGS was studied and a H2/CO2 ratio of 2:1 was confirmed to be the optimum for the simultaneous achievement of higher CO2 conversion and CO selectivity.