Enhanced methane dry reforming using Ni-Co bimetallic catalysts supported on lanthanum-zirconia

Monometallic (Ni and Co) and bimetallic (Ni-Co) catalysts supported on lanthanum-zirconia (LaZr) were synthesized with different ratios of 1.25Ni-3.75Co, 2.5Ni-2.5Co, 3.75Ni-1.25Co and 4.25Ni-0.75Co and evaluated for the dry reforming of methane (DRM) process. The total metal loading was adjusted to 5 wt% in all catalysts. The catalysts evaluation was performed at a stoichiometric CH₄/CO₂ feed ratio of 1, in a fixed-bed stainless steel reactor at 750 °C under atmospheric pressure. This work evaluates the effect of Ni/Co ratio on catalytic performance, CO₂ desorption behaviour and carbon accumulation. The catalysts were characterized by techniques: H₂-temperature-programmed reduction (H₂-TPR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), transmission electron microscopy (TEM) to monitor the textural, structural, and surface characteristics change with varying the chemical composition and link these characteristics with the catalytic efficiency. The 4.25Ni-0.75Co-LaZr catalyst showed the highest initial activity, achieving CH₄ and CO₂ conversions of 82.07 and 82.74%, respectively, together with the highest H₂ yield of 78.81% under the investigated conditions, with CH₄ conversion reaching 75.16% after 360 min. CO₂-TPD showed composition-dependent desorption behaviour, with more pronounced high-temperature features for Co-rich catalysts. TGA indicated moderately lower carbon deposition for 4.25Ni-0.75Co-LaZr than for 5Ni-LaZr (34.7 versus 41.9 wt%), while Raman spectra indicated differences in the structural disorder of the carbon. These findings highlight the potential of Ni-Co/LaZr catalysts for syngas production and demonstrate the influence of Ni/Co ratio on catalytic performance and carbon accumulation during DRM.