(661v) Utilization of CO2-Rich Residues for Syngas Production: Strategies for Catalyst Design

Compared to a Reverse Water Gas Shift (RWGS) process carried out under ideal conditions, the valorization of CO₂-rich residues involve additional challenges. Indeed, for an ideal RWGS reaction unit, the CO₂ methanation reaction and the constitution of carbon deposits via Boudouard reaction are the main side reactions to take into consideration. For CO₂-rich residues derived from biomass treatment and heavy metal industries, the presence of CH₄ and CO species (among others) constitute an, although often disregarded, much complex panorama where side reactions like CO methanation, dry reforming of methane, the forward Water Gas Shift reaction and the decomposition of CO and CH₄ resulting in carbon deposits, are occurring to some extent within the catalytic reactor. This work aimed at designing advanced catalytic systems capable of converting the CO₂/CO/CH₄ feedstocks into syngas mixtures. Thus, with the RWGS reaction considered as the major process, this work focusses on the side reactions involving CO/CH₄ species. In this context, a series Cu-MnO_x/Al₂O₃ spinel derived catalysts were optimized for syngas production in presence of CO and CH₄ fractions. Once the optimal active phase was determined, the optimal Cu contents and the impact of the support nature (Al₂O₃, SiO₂-Al₂O₃ and CeO₂-Al₂O₃) was evaluated for the valorization of realistic CO₂-rich feedstocks. Remarkably, the obtained outcomes underline operative strategies for developing catalytic systems with advanced implementation potential. For that aim, the catalyst design should present, along with an active and selective phase for RWGS reaction, superior cooking resistances, activities towards methane reforming and low tendencies towards the forward WGS reaction. Further developments should tackle difficult tasks like improving the RWGS reaction rate while inhibiting the forwards WGS reaction as well as improving the CH₄ conversion to CO without affecting the process selectivity. Strategies towards advancing catalytic systems capable of operating under variable conditions also arise as appealing routes.