Ni catalysts supported on calcium aluminate (Ni/CA) with loadings of 5–30 wt% were synthesized and evaluated in the dry reforming of methane (DRM). The catalysts were characterized by X-ray diffraction (XRD), thermogravimetry (TGA/DTA), N 2 physisorption (BET), temperature-programmed reduction (H 2 -TPR), CO 2 and H 2 desorption (CO 2 - and H 2 -TPD, respectively), and oxidation (TPO), complemented by post-reaction field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). XRD revealed the formation of Ni–Al layered double hydroxide precursors, which decomposed upon calcination into mayenite, NiO, and Ni–Al–O and Ni–Ca–Al–O mixed oxides. Subsequent reduction produced metallic Ni 0 , whose crystallite size increased with Ni loading. Ni impregnation regenerated porosity, with Ni10 showing the highest surface area, while higher loadings led to agglomeration and partial pore blocking. H 2 -TPR and H 2 -TPD indicated that intermediate Ni contents (10–20 wt%) offered the best balance between reducibility, dispersion, and metallic accessibility. In contrast, Ni5 suffered from insufficient Ni, while Ni30 exhibited poor dispersion and larger initial crystallites. Catalytic performance followed these trends: Ni10 and Ni20 achieved the highest conversions (CH 4 ≈ 40–43% and CO 2 ≈ 95% at 700 °C) and higher H 2 selectivity, while Ni5 and Ni30 were less active. In fixed-temperature tests at 700 °C for 8 h, Ni20 maintained the highest activity but accumulated carbon mainly as nanotubes (∼98%), while Ni30 exhibited the lowest overall sintering and carbon deposition. Altogether, Ni20 exhibited the highest catalytic activity, while Ni30 provided the greatest structural robustness and resistance to deactivation. These findings confirm calcium-aluminate-supported Ni catalysts as an effective and versatile system for H 2 production by DRM. Activity and stability can be finely modulated through Ni loading. • Ni catalysts supported on calcium aluminate formed Ni–Al LDH precursors and calcium aluminate phases after calcination. • Intermediate Ni loading (10–20 wt%) maximized Ni reducibility and metallic accessibility on calcium aluminate support. • Catalysts with 10–20 wt% Ni showed the highest CH 4 (≈40–43%) and CO 2 (≈95%) conversions at 700 °C. • Catalysts with 20 wt% Ni achieved the highest activity but accumulated more carbon during DRM, mainly nanotubes. • Catalysts with 30 wt% Ni exhibited the lowest carbon formation rate and the highest resistance to sintering.
Wenzel et al. (Mon,) studied this question.