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

Reverse water-gas shift (RWGS) is considered as a promising reaction to convert CO2 into CO, which together with H-2, 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 degrees 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, N-2 adsorptiondesorption, H-2-TPR, TEM, CO2-TPD, O-2-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 degrees 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 O-2-TPD results. In addition, the effect of H-2/CO2 ratio on the performance of RWGS was studied and a H-2/CO2 ratio of 2:1 was confirmed to be the optimum for the simultaneous achievement of higher CO2 conversion and CO selectivity.