Hydrogen production via chemical looping reforming on NiO/CeO₂

Abstract

This work focuses on the production of hydrogen from methane via the chemical looping reforming process, where NiO was used as the oxygen storing species. The study involved simulation of this process using a simulation package, Aspen Plus and laboratory experiments. The simulation work considered a conventional chemical looping process and a sorption enhanced chemical looping process, with the aim of finding appropriate operating conditions for the production of high purity hydrogen gas with low energy process requirements. The experimental work involved the loading of NiO on two different supports, CeO₂ and Al₂O₃, used in conventional chemical looping and sorption enhanced chemical looping operated under both combined combustion as well as reforming processes. Experiments were conducted in a fixed-bed reactor operating at 1 bar and 600°C. NiO was used as a solid oxygen carrier which in this process is reduced by methane and subsequently oxidized by air in a cyclic process. In the chemical looping combustion experiments, methane was fed as a reactant at a rate of 2x10⁶ mol/s (3 cm³(NTP)/min), and in the chemical looping reforming experiments, methane was fed at a rate of 2x10-⁶ mol/s (3 cm³(NTP)/min) and steam at a rate of 4x10-⁶ mol/s (6 cm³(NTP)/min). The results show a higher production rate of hydrogen with NiO/CeO₂ than for NiO/Al₂O₃. This result is explained by the higher oxygen storage capacity of CeO₂ which promotes the partial oxidation of methane. In addition, a higher hydrogen gas purity and a higher methane conversion were observed in the presence of CaO.