Distinct promotion effects of Rh and Ru in Ni/13X granular catalysts for CO2 methanation: A structure–performance study

Ni/13X catalysts promoted with low Rh and Ru loadings were prepared on commercial 13X zeolite granules by low-water dropwise impregnation and evaluated for CO 2 methanation. The preparation procedure preserved the crystalline structure of the zeolite and enabled effective deposition of the active phase without additional shaping. Increasing the Ni loading from 5 to 10 wt% enhanced catalytic performance, while Rh and Ru exhibited distinct loading-dependent effects: 0.3 wt% Rh 2 O 3 was sufficient to achieve near-maximum performance within the investigated Rh loading range, whereas the activity of Ru-promoted catalysts increased progressively with RuO 2 loading. The promoted Ni-based catalysts achieved CO 2 conversions of up to 82.5%, with CH 4 selectivities reaching 86% for Ni–Rh/13X and 85% for Ni–Ru/13X at 450–500 °C. Combined SEM–EDS, H 2 -TPR, CO 2 -TPD, and Raman analyses revealed distinct promoter effects: Rh was associated with a more homogeneous spatial distribution of the Ni-containing phase and a redistribution of basic sites, whereas Ru more strongly enhanced catalyst reducibility. The observed CO formation was consistent with the involvement of the RWGS reaction followed by CO hydrogenation; however, an associative pathway involving the hydrogenation of adsorbed CO 2 -derived species cannot be excluded. Overall, the results demonstrate that low Rh and Ru loadings can effectively modify the physicochemical and catalytic properties of Ni/13X, providing a simple approach to the development of CO 2 methanation catalysts based on commercially available zeolite granules.