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

Abstract

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.