Response surface methodology for optimization of dry oxidative reforming for hydrogen enrichment of biogas

Abstract

The exploration of domestically available clean and renewable fuel is essential for the attainment of sustainable development goals. The hydrogen (H2)-enriched biogas being renewable and clean can be a highly favorable fuel. In this study, the response surface optimization of dry oxidative reforming using a three-level, three-factor experimental design for hydrogen enrichment of biogas over the nickel-cobalt bimetallic catalyst was investigated. The Box-Behnken design of experimentation was employed to assess the interaction and discrete effect of reforming temperature and ratios of CH4/CO2 and O2/CH4. The effects of CH4/CO2 ratio (1–2) and O2/CH4 ratio (0.3–0.5) on catalytic activity were assessed in the temperature range of 700–800 °C. The conversion of both reactants (CH4 and CO2), yield of products (H2 and CO), and ratio of products (H2/CO ratio) were selected as responses for statistical study. The analysis of variance demonstrated that reforming temperature and O2/CH4 ratio have a statistically considerable impact on the H2 enrichment of biogas by the virtue of higher endothermic nature of the reaction. Experimentally, the maximum H2 enrichment of 44.04% was obtained at 800 °C with 1.5 and 0.5 CH4/CO2 and O2/CH4 ratio, respectively. However, from the statistical model, the optimum H2 enrichment of 36.9% was obtained at 725.68 °C with CH4/CO2 and O2/CH4 ratios of 1.32 and 0.42, respectively. The close agreement between predicted and experimental data shows that the combination of response surface methodology and dry oxidative reforming could be an efficient approach for optimizing the H2 enrichment of biogas and the generation of environment friendly fuel.