Coking resistant Ru supported on Sm-substituted CaZrO3 catalyst for dry reforming of methane: The effect of Ru loading on catalytic activity

Abstract

Dry reforming of methane has industrially appealing advantages over other routes towards syngas production: CH4 and CO2 DRM conversion simultaneously tackles two main greenhouse gases to obtain a H2/CO ratio close to unity, ideal for long-chain hydrocarbons production via Fischer-Tropsch method. Designing high-performing and stable catalysts is pivotal for long-lasting operation. Ni-supported systems are by far the most used, owing to their outstanding activity and cost-effectiveness. Nevertheless, Ni promotes carbon deposition which results in severe deactivation. Supported noble metals combine high performance to coking resistance but this comes at a high cost. Here, the effects on DRM activity of low (≤3.0 wt%) ruthenium strategical loading onto a calcium zirconate perovskite oxide were investigated. In the CaZrO3, Zr substrate was partially substituted with samarium (CaZr0.85Sm0.15O3-δ, CZSm) to increase the extent of oxygen vacancies, favoring reactants adsorption on a highly basic surface. Ru was added during the perovskite synthesis to obtain RxCZSm (x = 0.5, 1.5, 3.0 wt% Ru). Structural and textural analyses revealed partial Ru inclusion in the oxide lattice leading to a net surface area increase (>50%). Different DRM activity depending on Ru oxidation state, substrate NPs coverage and reaction temperature was observed. R0.5CZSm displayed higher CH4 conversion (97.6 %) at 850 °C, while R3.0CZSm outperformed the lower Ru-loaded compounds at 550 °C, showing an H2/CO ratio of 0.77. Durability tests revealed high stability of all RxCZSm catalysts, with no carbon deposition. Low Ru loading on a tailored oxide substrate is an effective alternative for active and durable DRM catalysts