Dry reforming of model biomass pyrolysis products to syngas by dielectric barrier discharge plasma

Biomass is frequently used to produce CO and H₂ together with undesirable by-products containing CO₂ and liquid tar by pyrolysis and gasification. This leads to decreased energy efficiency and increased maintenance costs. This study investigated the reforming of biogas and tar, respectively, using non-thermal plasma featuring dielectric barrier discharge (DBD). The gas surrogates studied were CH₄ and CO₂, and toluene was used as a substitute for tar. During reforming of biogas, CO or H₂ was added to the CH₄ and CO₂ to investigate their effects on CH₄ and CO₂ conversion. Both the discharge power and gas components influenced the conversion of CH₄ and CO₂. The conversion efficiency of CH₄ and CO₂ and the selectivity of H₂ and CO both increased with the discharge power while reforming the mixture of CH₄ and CO₂. The maximum conversion efficiency of CH₄ and CO₂ and selectivity of CO and H₂ were obtained with a CH₄:CO₂ ratio of 1:2. During reforming of toluene, the conversion efficiency of toluene reached a maximum value of 90% and the production yields of H₂, CO, and CO₂ reached respective maximums of 0.79, 2.24, and 1.51 mol/mol-toluene at a discharge power of 90 W and temperature of 300 °C. Higher temperatures of 400-500 °C did not favour toluene destruction due to the thermal breakdown of the quartz dielectric and the rapid decrease in the discharging intensity. In addition, reaction mechanism for reforming of both biogas and toluene was proposed to improve our understanding of the reforming process in DBD plasma.