The Influence of Lanthanide on NiO-MgO-SiO2 Catalysts for Syngas Production via Propane Steam Reforming

Abstract

In this study, 15 wt. % NiO-MgO-SiO2 catalysts modified by La2O3 promoter were prepared through a co-precipitation route and employed for syngas production via propane steam reforming. Various techniques including X-Ray diffraction, BET, TPR, CO2-TPD, CO-chemisorption, TPO, and Scanning electron microscopy were utilized to characterize the final samples. The results indicated that the incorporation of La2O3 enhanced the metal-support interaction providing less reducible Ni species. In comparison with the La-free catalyst, the promoted ones possessed higher metal dispersion and smaller Ni particles. Nonetheless, excessive amounts of La covering the active sites negatively decreased the Ni dispersion and corresponding surface area. In addition, upon the introduction of La2O3 the strength and amount of strong basic sites enhanced owing to the preferential adsorption of CO2 on La2O3. The evaluation of the catalytic performance disclosed that despite the improved metal dispersion, the promoted catalysts possessed lower propane conversion and hydrogen yield than the un-promoted one. It might be attributed to the decrease in the acidic sites which contributed to CHx decomposition. Nevertheless, the highest activity was achieved with 3 wt. % La2O3 loading which was induced by highly dispersed metallic Ni and more accessible active sites for adsorption and dissociation. It was also confirmed that, the existence of La2O3 improved the resistance against coke formation owning to the formation of well-dispersed Ni species and acceleration of gasification reaction through the La2O2CO3.