Carbon dioxide-cofeeding pyrolysis of pine sawdust over nickle-based catalyst for hydrogen production

Highlights: • CO₂ offers a strategic means to maximize the carbon utilization and H₂ production. • CO₂ expedites kinetics of gas phase reaction between CO₂ and volatile pyrolysates. • Ni/SiO₂ catalytically enhances mechanistic roles of CO₂ in pyrolysis. • Exploiting CO₂ in catalytic pyrolysis could prevent coke formation. -- Abstract: This study aimed to determine the synergistic effects of CO₂ on the catalytic pyrolysis of pine sawdust over a Ni-based catalyst (Ni/SiO₂) to establish a sustainable platform for H₂ production. To elucidate the reaction mechanism, the CO₂-cofeeding pyrolysis of pine sawdust was performed. The CO₂-cofeeding pyrolysis of pine sawdust proved that the gas-phase reaction between CO₂ and pyrolysates led to the increase in the amount of generated CO. The CO₂ enhanced thermal cracking and dehydrogenation. These mechanistic features of CO₂ were catalytically enhanced when Ni/SiO₂ was employed as heterogeneous catalyst, which led to an increase in the amounts of generated H₂ and CO. Hence, the CO that was additionally generated during the gas-phase reaction of CO₂ and pyrolysates could be further converted into H₂. In addition, CO₂ could be looped in the CO₂-cofeeding pyrolysis of pine sawdust. Furthermore, exploiting CO₂ as raw material or reactive gas medium in the catalytic pyrolysis process also offered a strategic means for preventing coke formation.