The direct conversion of CH 4 and CO 2 into syngas garners significant attention as a promising strategy for greenhouse gas utilization. However, the development of highly active and stable catalysts remains a significant challenge. Here, Ni-based catalysts supported on Al 2 O 3 and promoted with alkaline–earth metals (Ca, Mg, Sr, and Ba) are prepared via an impregnation method and systematically characterized using various analytical techniques. The catalytic performance is evaluated in the combined steam and dry reforming of methane. Among the investigated promoters, Sr notably enhances CH 4 and CO 2 adsorption capacities and improves the reducibility of Ni active sites. The catalyst containing 9 wt% Sr exhibits the smallest Ni particle size and the highest catalytic activity. Sr doping modifies surface basicity, oxygen vacancies, and metal–support interactions, thereby enhancing CO 2 adsorption and Ni dispersion. However, excessive Sr loading causes the formation of Sr–aluminate phases (SrAl 2 O 4 and SrAl 4 O 7 ) that negatively affects the catalytic performance. In-situ diffuse reflectance infrared Fourier transform spectroscopy analysis clearly demonstrates improved adsorption of CH 4 and CO 2 and formation of carbonate species, providing insight into the surface reaction mechanism. Kinetic studies reveal that the lower apparent activation energy is attributed to enhanced surface reactivity. Long-term stability tests demonstrate steady CH 4 and CO 2 conversions over 500-h without detectable carbon deposition. Overall, Sr incorporation stabilizes Ni particles, suppresses sintering, and preserves active surface area, thereby markedly improving the catalytic performance. • Ca, Mg, Sr, Ba were added to Ni/Al 2 O 3 for combined steam and dry reforming of CH 4 . • Sr enhanced adsorption of CH 4 and CO 2 and improved reducibility of Ni active sites. • Ni-9Sr/Al 2 O 3 exhibited the highest activity, achieving 94 % CH 4 and 66 % CO 2 conversion. • Effect of Sr promoter was due to Ni dispersion, oxygen vacancies, and basicity. • The overall reaction mechanism was also comprehensively evaluated.
Park et al. (Wed,) studied this question.