Determination of optimum combination for CuO/CeO5 oxygen carriers in the production of syngas using chemical looping

Abstract

Synthesis gas is a gaseous fuel that is composed of carbon II oxide (CO) and hydrogen (H₂) which can be produced from various fuel either in gaseous, liquid or solid form with the gaseous fuel being the most predominant. There are various conventional means of producing syngas among which is chemical looping where metal oxides called oxygen carriers are used for transferring both material and energy between two or more reactors thereby interloping both exothermic and endothermic reactions in a cyclic form. CuO is one of the oxides with oxygen uncoupling characteristics, so it is very reactive and can be used to modify other metal oxides such as CeO₂. It has been shown that CuO/CeO₂ is a good material for production of syngas but their optimum combination has not been reported. This study therefore wishes to determine the optimum combination of CuO and CeO₂ to form a composite of CuO/CeO₂ oxygen carrier that gives the best desirability in terms of reactivity, selectivity and stability in the production of syngas. This is done by using liquefied petroleum gas (LPG) as fuel at a temperature of 800^oC. The oxygen carrier material was synthesized using coprecipitation method and then used in a fixed bed reactor for the study. Response surface methodology (RSM) in Design expert 6.0.6 was used for the optimization. It was discovered that 10% CuO composition was found to be the optimum value in term of reactivity, syngas selectivity as well as stability of the material, with desirability of 84.9%. The reactivity obtained for that combination was found to be 67.67% while the CO selectivity, H₂ selectivity and degradation are found to be 84.28%, 91.11% and 3.56% respectively.