Novel vapor-phase biofiltration and catalytic combustion of volatile organic compounds

The aerobic biodegradation and catalytic oxidation of vapor-phase 2-propanol (IPA) were investigated. The catalytic oxidation of IPA was carried out over zinc, copper, and chromium oxide catalysts prepared via a sol-gel technique in a fixed-bed reactor operated at atmospheric pressure and in the temperature range of 25-165°C. The activity of the catalysts was measured by means of the light-off temperature (defined as 50% conversion of IPA). The light-off temperatures of zinc oxide, copper oxide, and chromium oxide are 90, 100, and 110 °C, respectively. The results indicate that, at relatively low temperature (40-100 °C), IPA was partially oxidized, which resulted in acetone formation. The maximum acetone selectivity varied between 30 and 97% at ca. 100 °C, depending on the types of catalyst. For the biodegradation study, enriched solvent-tolerant bacterial cells were immobilized onto porous glass cylinders within a biofilter. Successful biofiltration of high solvent vapor concentrations of up to 34 g m^-3 was achieved. An average IPA elimination capacity of up to 280 g m^-3 h^-1 was demonstrated by this biofiltration system. A slip feed experiment, using acetone, was investigated in order to assess the substrate specificity performance. The results show that the biofilter can deal with an alteration in feed composition and display no major reduction in the elimination performance. This paper shows that the concentration and compound distribution from the exit of a catalytic partial oxidation process are consistent with the inlet conditions of a gas-phase biofilter containing a solvent-tolerant microbial consortium. This points the way toward a potential integrated biofiltration-catalytic combustion system for the overall enhanced pollution abatement performance.