Catalytic dry reforming of methane over high surface area ceria

Abstract

High surface area ceria (CeO2 (HSA)), synthesized by a surfactant-assisted approach, was found to have useful dry reforming activity for H2 and CO production under solid oxide fuel cells (SOFCs) conditions. The catalyst provides significantly higher reforming reactivity and excellent resistance toward carbon deposition compared to Ni/Al2O3 and conventional low surface area ceria (CeO2 (LSA)) under dry reforming conditions. These enhancements are due to the high redox property of CeO2 (HSA). During the dry reforming process, the redox reactions between the gaseous components in the system and the lattice oxygen (Ox) take place on ceria surface. Among these reactions, the rapid redox reactions of carbon compounds such as CH4, and CO with lattice oxygen (CH4+Ox→CO+H2+Ox−1 and CO+Ox=CO2+Ox−1) can prevent the formation of carbon species from the methane decomposition and Boudard reactions even at low inlet carbon dioxide concentration.In particular, the dry reforming rate over CeO2 (HSA) is proportional to the methane partial pressure and the operating temperature. Carbon dioxide presents weak positive impact on the methane conversion, whereas both carbon monoxide and hydrogen inhibit the reforming rate. The activation energies and reforming rates under the same methane concentration for CeO2 toward the dry reforming are almost equal to the steam reforming as previously reported [1–4]. This result suggests the similar reaction mechanisms for both the steam reforming and the dry reforming over CeO2; i.e., the dry reforming rate is governed by the slow reaction of adsorbed methane, or surface hydrocarbon species, with oxygen in CeO2, and a rapid gas–solid reaction between CO2 and CeO2 to replenish the oxygen.