Ammonia Methanation of Carbon Dioxide with a Hybrid Catalyst

Abstract

Ammonia methanation is a reaction that synthesizes methane directly from carbon dioxide and ammonia. The Sabatier reaction, which synthesizes methane by hydrogenating carbon dioxide, requires a cooling facility in the reactor due to its large heat value. On the other hand, hydrogen is supposed to be transported as a hydrogen energy carrier such as ammonia, and energy must be injected to produce hydrogen from them. The ammonia methanation reaction, in which these two reactions proceed simultaneously, has a low heat of reaction and can be constructed using an adiabatic reactor. In this study, the ammonia methanation reaction with a hybrid catalyst that combines an ammonia decomposition catalyst and a Sabatier reaction catalyst as powders was investigated. Precipitated iron catalyst modified with alumina and potassium showed good activity for ammonia decomposition. Ammonia methanation reaction was carried out using a hybrid catalyst combining modified precipitated iron catalyst and Ni/CeO2 catalyst, but almost no methane was obtained. This is presumed to be due to the formation of CeFeO3, which is a composite oxide, the shrinkage of the pores of CeO2, and the alteration of Ni. Therefore, in order to reduce the number of contact points between the precipitated iron catalyst and the Ni/CeO2 catalyst, they were formed into particles and mixed to conduct the ammonia methanation reaction. However, although methane was produced, a sufficient yield was not obtained. Ni/Al2O3 catalyst also showed good activity for ammonia decomposition reaction. A hybrid catalyst consisting of Ni/Al2O3 and Ni/CeO2 catalysts was used for the ammonia methanation reaction, and a high methane yield of over 60% was obtained.