Deactivation and kinetic studies of unsupported Ni and Ni–Co–Cu alloy catalysts used for hydrogen production by methane decomposition

Abstract

Metallic nickel nano-particles and Ni–Co–Cu alloy particles were prepared primarily as catalysts for the thermal decomposition of methane to produce hydrogen. A series of kinetic experiments were conducted using these two types of catalysts. The effects of methane partial pressure and reaction temperature on the maximal hydrogen formation rate were studied. The reaction order and activation energy were estimated. Based on the TEM micrographs and the deactivation process of catalyst, the widely used empirical model (general power law equation) and a phenomenological model (exponential decay model) were used to simulate the experimental results of Ni catalysts.By quantifying the relationship between the kinetic parameters and the reaction conditions (methane partial pressure and reaction temperature), the transient hydrogen formation rate over the reaction time was derived and validated by comparing with the experimental data. A detailed catalytic deactivation study of Ni and Ni–Co–Cu catalysts was also carried out. Different deactivation mechanisms of pure Ni catalyst and Ni–Co–Cu alloy catalysts were compared and discussed.