Das, S.; Ashok, J.; Bian, Z.; Dewangan, N.; Wai, M. H.; Du, Y. H.; Borgna, A.; Hidajat, K.; Kawi, S., Silica-Ceria sandwiched Ni core-shell catalyst for low temperature dry reforming of biogas : coke resistance and mechanistic insights. Applied Catalysis B: Environmental 2018, 230, 220-236.
In this paper, a novel sandwiched core–shell structured Ni-SiO2@CeO2 catalyst, with nickel nanoparticles encapsulated between silica and ceria, was developed and applied for dry reforming of biogas (CH4 / CO2 = 3/2) under low temperature conditions to test its coke inhibition properties. Ni-phyllosilicate was used as the Ni precursor in order to produce highly dispersed Ni nanoparticles on SiO2. Cerium oxide was chosen as the shell due to its high redox potential and oxygen storage capacity, that can reduce coke formation under severe dry reforming conditions. The core shell Ni-SiO2@CeO2 catalyst showed excellent coke inhibition property under low temperature (600 °C) reforming of biogas, with no coke detected after a 72 h catalytic run. Under the same conditions, Ni-SiO2 catalyst deactivated within 22 h due to heavy coke formation and reactor blockage, while Ni-CeO2 catalyst showed very low activity. The higher activity of the core–shell catalyst is attributed to its higher Ni dispersion and reducibility. TEM and XRD results show that the core–shell catalyst shows higher resistance to Ni particle sintering and agglomeration during the reaction than the Ni-SiO2 and Ni-CeO2 catalysts. In-situ DRIFTS on the Ni-SiO2@CeO2 catalyst indicate a change in the reaction mechanism from a mono-functional pathway on the Ni-SiO2 catalysts to a bi-functional route on the Ni-SiO2@CeO2 catalyst with active participation of oxygen species from CeO2 in carbon gasification. The confinement effect of the sandwich structure and the bifunctional mechanism of dry reforming are the primary reasons for the excellent coke resistance of the Ni-SiO2@CeO2 catalyst.
This work was supported by National University of Singapore, National Research Foundation (NRF), Prime Minister's Office, Singapore and National Environment Agency under the Waste-to-Energy Competitive Research Program (WTE CRP 1501 103) and Advanced Manufacturing and Engineering Individual Research Grant (AME IRG) of Agency for Science, Technology and Research (A*STAR) (R-279-000-509-305).