Bi-reforming of methane on Ni/SBA-15 catalyst for syngas production: Influence of feed composition

Bi-reforming of methane (BRM) was evaluated for Ni catalyst dispersed on SBA-15 support prepared by hydrothermal technique. BRM reactions were conducted under atmospheric condition with varying reactant partial pressure in the range of 10–45 kPa and 1073 K in fixed-bed reactor. The ordered hexagonal mesoporous SBA-15 support possessing large specific surface area of 669.5 m² g⁻¹ was well preserved with NiO addition during incipient wetness impregnation. Additionally, NiO species with mean crystallite dimension of 14.5 nm were randomly distributed over SBA-15 support surface and inside its mesoporous channels. Thus, these particles were reduced at various temperatures depending on different degrees of metal-support interaction. At stoichiometric condition and 1073 K, CH₄ and CO₂ conversions were about 61.6% and 58.9%, respectively whilst H₂/CO ratio of 2.14 slightly superior to theoretical value for BRM would suggest the predominance of methane steam reforming. H₂ and CO yields were significantly enhanced with increasing CO₂/(CH₄ + H₂O) ratio due to growing CO₂ gasification rate of partially dehydrogenated species from CH₄ decomposition. Additionally, a considerable decline of H₂ to CO ratio from 2.14 to 1.83 was detected with reducing H₂O/(CH₄ + CO₂) ratio due to dominant reverse water-gas shift side reaction at H₂O-deficient feedstock. Interestingly, 10%Ni/SBA-15 catalyst was resistant to graphitic carbon formation in the co-occurrence of H₂O and CO₂ oxidizing agents and the mesoporous catalyst structure was still maintained after BRM. A strong correlation between formation of carbonaceous species and catalytic activity was observed.