Catalytic technology assisted with ionization/ozonization phase for the abatement of volatile organic compounds

The catalytic combustion process of air-mixtures containing volatile organic compounds (VOCs)! associated with an ionization/ozonization reactor (IOCC technique, ionization-ozonization-catalytic-combustion) has been utilized for the abatement of two very toxic industrial VOCs: acrylonitrile (ACN) and vinyl chloride (VCM). The pre-catalytic effects (electric discharge plus the action of ozone), the conventional and IOCC combustion tests were studied. Two different catalysts were used: oxide catalyst, copper-chromite (Cu-Cr), and Pt metal catalyst (0.5 wt.% Pt/gamma-Al2O3). The abatement of ACN was markedly influenced by the pre-catalytic effects. Starting from 3 kV, an increasing abatement of ACN was observed with the voltage applied to the ionization reactor at any initial ACN concentration (500-1500 ppm). The ACN catalytic combustion, performed by the IOCC technique, led to 91 and 98% yield of CO2 on Cu-Cr and Pt catalysts, respectively, at 260 degrees C. Complete absence of hazardous intermediates, such as hydrogen cyanide, was observed. The Cu-Cr catalyst, at 300 degrees C, was able to abate 57 and 23% of VCM at 10000 and 20000h(-1), respectively. IOCC combustion led to improved conversion. At 200 degrees C and 3300 h(-1), 98% and only 49% of VCM abatement operating according to IOCC and classical combustion was obtained, respectively. The IOCC combustion runs, performed at different initial VCM concentrations (585 and 1170 ppm). indicated a superior abatement when low VCM concentration was fed, at a given catalyst temperature and contact time. This indicated a marked influence of the pre-catalytic effects on the abatement. (C) 2000 Elsevier Science B.V. All rights reserved.