Role of catalyst support over PdO-NiO catalysts on catalyst activity and stability for oxy-CO2 reforming of methane

摘要

PdO-NiO catalysts over several commercial metal oxides were synthesized using incipient wet impregnation method. The activities of PdO-NiO catalysts for syngas production via oxy-CO2 reforming of methane were investigated at temperatures ranging from 500 °C to 800°C in a fixed-bed continuous-flow reactor. The PdO-NiO/Y2O3 and PdO-NiO/Al2O3 catalysts show very high CH4 and CO2 conversions due to the formation of metal-support compound on these catalysts. On the PdO-NiO/Y2O3 catalyst, Pd interacts with Y2O3 support to form Pd_xO_yY_z compound while Ni interacts with A12O3 support to form NiAl2O4 spinel compound on the PdO-NiO/Al2O3 catalyst. However, the amount of deposited carbon on the spent PdO-NiO/Y2O3 catalyst is much lower than the one on the PdO-NiO/Al2O3 catalyst due to the presence of surface β-oxygen species and ability of Y2O3 to form oxycarbonate species, resulting in stable catalytic performance without noticeable deactivation during reaction. The surface β-oxygen species are found to promote cracking of C-H bond in CH4 while the oxycarbonate species can oxidize the deposited carbon, respectively, hence leading to the stability of the PdO-NiO/Y2O3 catalyst.