Role of CO2 in the Conversion of Toluene as a Tar Surrogate in a Nonthermal Plasma Dielectric Barrier Discharge Reactor

The decomposition of toluene (a model tar compound) in CO2 was investigated at ambient and elevated temperatures in a dielectric barrier discharge (DBD). The effects of reaction parameters, such as the residence time (0.47-4.23 s), plasma power (5-40 w), toluene concentration (20-82 g/Nm(3)), and temperature (20-400 degrees C), were investigated. The DBD was shown to be an effective technique for tar removal. The percentage removal of tar increased with increasing the plasma power and residence time (to as high as 99% at the residence time of 4.23 s). The maximum selectivity to the two major gaseous products, CO and H-2, was 73.5 and 21.9%, respectively. Solid residue formation was also observed inside the reactor. The synergetic effect of the temperature and plasma power was studied. As temperature increased, the decomposition of toluene decreased slightly from 99 to 88% (from ambient to 400 degrees C at 40 w) and the selectivity of CO and H-2 decreased as a result of the increased rate of recombination of CO and O. The selectivity to lower hydrocarbons increased with the temperature.