Synthesis gas production by combined Steam and Dry Reforming of clean biogas

Ni-based catalyst promoted with Rh or Cu were prepared from hydrotalcite-like precursors by two different synthesis methods (co-precipitation and via surfactant-assisted-templating route) and employed in Dry Reforming (DR) and combined Steam/Dry Reforming (S/DR) of clean biogas (CB, an equimolar mixture of CH4 and CO2) to produce a synthesis gas suitable for Fischer-Tropsch or methanol synthesis. The catalyst before and after reaction were deeply characterized by porosimetric analyses, XRD, Raman, TG, H2-TPR, CO2-TPD, TEM and SEM techniques. The DR results showed that the addition of a small amount of Rh increased the CO2 conversion and significantly decreased the carbon formation. The addition of steam to the reactant feed to perform the combined S/DR reaction promoted the catalyst activity further improving its resistance to carbon deposition. XRD and TPR analyses showed that increasing the amount of Mg in the catalytic formulation, it was possible to improve the active phase stability through the formation of MgO-NiO solid solution by calcination. The extensive formation of a Ni-Rh alloy on the catalyst surface, increased the catalyst reducibility improving the dispersion of the active sites and avoided sintering phenomena during reaction. Although the substitution of Rh with Cu to form the Ni-Cu alloy did not increased the catalyst performances, a further improvement was obtained by enhancing the textural and morphological properties of the catalyst using a surfactant in the synthesis, allowing to decrease the Rh content in the catalyst formulation. The feasibility of the H2 production from CB, integrating the process with a Water Gas Shift unit (S/DR-WGS) was also investigated. Using a Medium Temperature Shift (MTS) reactor and a Zr-promoted Cu/Zn/Al catalyst, good H2 yields were obtained, producing a H2-rich syngas suitable for many downstream applications.