Reactions of toluene and oxygen in an electrical discharge

The chemical reactions of toluene and oxygen in a 50 Hz ac discharge have been studied in a capacitive coupled discharge reactor. The variables investigated were partial pressure of the reactants, reactor pressure, reactor temperature, reactant ratios, applied reactor voltage, discharge current,capacitive current, breakdown voltage, and the phase shift. The thermal reaction was negligible at temperatures below 300 °C. The major products of the reaction between toluene and oxygen were benzaldehyde, o-cresol, benzene, m+p-cresol, phenol and benzyl alcohol. The reaction was controlled by the electric field and the total reactor pressure. The threshold energy for the chemical reaction was found to be about 10 eV. The reaction was found to be of first order with respect to oxygen. The effect of the electric field was correlated by the parameter E/N. The selectivity of benzene was mainly determined by the ratio of toluene to oxygen. Cresol, benzaldehyde, benzyl alcohol and phenol were mainly controlled by the parameter E/N and the partial pressure of oxygen and were all first order with respect to oxygen. A rate expression for bimolecular reactions in cold plasmas was derived and found to agree well with the experimental results. A model was proposed to explain some unusual features of the discharge current and a circuit for measuring the discharge current was described. The energy yield obtained was about 1 kWhr per mole toluene.