Ni-Co bimetallic catalyst for hydrogen production in sewage treatment plants: Biogas reforming and tars removal

Abstract

A Ni–Co bimetallic catalyst supported on lanthana promoted alumina was prepared by excess volume solution method. The catalyst was characterised by XRD, N2 adsorption isotherms, XRF, TPO, SEM and XPS. The catalyst was tested in a simulated biogas stream with a CH4:CO2 1:1, usually presented after anaerobic digestion in sewage treatment plants, and in a simulated air gasification stream containing toluene as a tar model compound. The catalyst was submitted to catalytic activity vs. temperature tests in order to determine the optimum temperature to maximize conversion and selectivity in both processes. At 700 °C, equilibrium conversion in the case of biogas conversion was achieved, and total toluene and methane conversion in gasification stream was reached, maximizing hydrogen production with the lack of complex tar by-products formation. Long-term reaction experiments up to 100 h demonstrated the stability of catalyst performance. Post-reaction characterisation of catalytic samples by SEM-EDX and XPS revealed the lack of coke deposits on the catalyst, responsible of catalyst deactivation in the most of catalytic systems reported in the literature. At the light of the results obtained, the catalyst developed could be applied to produce renewable hydrogen from anaerobic digestion units of sewage plants, through the energy valorisation of biogas stream and sludge gasification.