CO₂ Reforming of Biomass Gasification Tar over Ni-Fe-Based Catalysts in a DBD Plasma Reactor

The removal of tar and CO₂ represents a critical challenge in the production of biomass gasification syngas, necessitating the development of advanced catalytic systems. In this study, plasma-enhanced catalytic CO₂ reforming was employed to remove biomass tar, with toluene selected as a model compound for biomass tar. Supported Ni_x-Fe_y/Al₂O₃ catalysts, with varying Ni/Fe molar ratios (3:1, 2:1, 1:1, 1:2, and 1:3), were synthesized for the CO₂ reforming of toluene in dielectric barrier discharge (DBD) non-thermal plasma reactors. The experiments were conducted at 250 °C and ambient pressure. The effects of various Ni/Fe molar ratios, discharge powers, and CO₂ concentrations on DBD plasma-catalytic CO₂ reforming of toluene to synthesis gas were analyzed. The results indicate that CO and H₂ are the primary gaseous products of toluene decomposition, with the selectivity for these gaseous products increasing with the discharge power. Increasing discharge power leads to a higher selectivity for CO and H₂ production. A CO₂/C₇H₈ ratio of 1.5 was found to effectively enhance the catalytic performance of the system, leading to the highest toluene conversion and syngas selectivity. The selectivity of the Ni_x-Fe_y/Al₂O₃ catalysts for H₂ and CO follows the following order: Ni₃-Fe₁/Al₂O₃ > Ni₂-Fe₁/Al₂O₃ > Ni₁-Fe₁/Al₂O₃ > Ni₁-Fe₂/Al₂O₃ > Ni₁-Fe₃/Al₂O₃. Notably, the Ni₃-Fe₁/Al₂O₃ catalyst exhibits a high CO₂ adsorption capacity due to its strong basicity, demonstrating significant potential for both tar conversion and carbon resistance.