PHOTOCATALYTIC DESTRUCTION OF VOCS IN THE GAS-PHASE USING TITANIUM-DIOXIDE

The gas-phase photocatalytic destruction of 17 VOCs over illuminated t itanium dioxide was investigated using a plug flow reactor with the fo llowing experimental conditions: 200 ml min(-1) flow rate, 23% relativ e humidity, 21% oxygen and an organic compound concentration range of 400-600 ppmv. At steady state, high conversion yields were obtained fo r trichloroethylene (99.9%), isooctane (98.9%), acetone (98.5%), metha nol (97.9%), methyl ethyl ketone (97.1%), t-butyl methyl ether (96.1%) , dimethoxymethane (93.9%), methylene chloride (90.4%), methyl isoprop yl ketone (88.5%), isopropanol (79.7%), chloroform (69.5%) and tetrach loroethylene (66.6%). However, the photodegradation of isopropylbenzen e (30.3%), methyl chloroform (20.5%) and pyridine (15.8%) was not so e fficient. Carbon tetrachloride photoreduction was investigated in the presence of methanol as an electron donor. It was observed that the pr esence of methanol results in higher degradation rates. No reaction by products were detected for all VOCs tested under the experimental set- up and conditions described. Also, long-term conversion was obtained f or all tested compounds. Catalyst deactivation was detected with tolue ne only, but the activity was restored by illuminating the catalyst in the presence of hydrogen peroxide. The capacity of the process to des troy different classes of volatile organic compounds present in the at mosphere was demonstrated. (C) 1997 Elsevier Science B.V.