Role of Sr-promoted Ni-based catalysts: A comprehensive study on syngas production via combined steam and dry reforming of methane

초록

The direct conversion of CH4 and CO2 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 Al2O3 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 CH4 and CO2 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 CO2 adsorption and Ni dispersion. However, excessive Sr loading causes the formation of Sr-aluminate phases (SrAl2O4 and SrAl4O7) that negatively affects the catalytic performance. In-situ diffuse reflectance infrared Fourier transform spectroscopy analysis clearly demonstrates improved adsorption of CH4 and CO2 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 CH4 and CO2 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.

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