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

The aerobic biodegradation and catalytic oxidation of vapor-phase 2-propano l (IPA) were investigated. The catalytic oxidation of IPA was carried out o ver zinc, copper, and chromium oxide catalysts prepared via a sol-gel techn ique in a fixed-bed reactor operated at atmospheric pressure and in the tem perature range of 25-165 degreesC. The activity of the catalysts was measur ed by means of the light-off temperature (defined as 50% conversion of IPA) . The light-off temperatures of zinc oxide, copper oxide, and chromium oxid e are 90, 100, and 110 degreesC, respectively. The results indicate that, a t relatively low temperature (40-100 degreesC), IPA was partially oxidized, which resulted in acetone formation. The maximum acetone selectivity varie d between 30 and 97% at ca. 100 degreesC, depending on the types of catalys t. 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) w as demonstrated by this biofiltration system. A slip feed experiment, using acetone, was investigated in order to assess the substrate specificity per formance. The results show that the biofilter can deal with an alteration i n feed composition and display no major reduction in the elimination perfor mance. This paper shows that the concentration and compound distribution fr om the exit of a catalytic partial oxidation process are consistent with th e inlet conditions of a gas-phase biofilter containing a solvent-tolerant m icrobial consortium. This points the way toward a potential integrated biof iltration-catalytic combustion system for the overall enhanced pollution ab atement performance.