Controlling structure of CeO$_{2}$-based precious metal catalysts for hydrocarbon upgrading or reforming

Abstract

Hydrocarbon upgrading or reforming reactions are essential catalytic processes for the production of valuable product or hydrogen gas in the chemical industry. However, these reactions have been limited because hydrocarbons are converted inefficiently due to high temperature conditions or poor catalyst durability. In this dissertation, efficient hydrocarbon conversion processes were studied by controlling the structure of cerium oxide (CeO$_{2}$)-based precious catalysts. First, CeO$_{2}$-based palladium (Pd) catalyst was developed that continuously converts methane to ethane below low temperature of 400 °C. Highly oxidized PdO was the active site for low-temperature methane coupling. Pd doping in ceria lattice improved the oxygen activation properties of the catalyst, resulting in better ethane production rate. In order to maximize the ethane yield, zeolite was physically mixed with the catalyst to reduce the water poisoning effect during the reaction. Second, CeO$_{2}$-based rhodium (Rh) catalyst exhibiting high durability in the propane steam reforming reaction was developed. Ex-solution method was used to prepare a ceria based Rh catalyst with high surface area. The structure of Rh nanoparticles strongly anchored to the support showed high stability in long-term propane steam reforming. After reaction, high sintering and coking resistance of Rh exsolution catalyst was confirmed through various characterizations. This study will provide a platform for the optimal catalyst structure that can be applied to the efficient hydrocarbons conversion.