VOC Decomposition System Based upon Heater-Integrated Catalyst Units Using NiO or Cr_{2}O_{3}

We have previously shown that oxide semiconductors (TiO2, NiO, Cr2O3, etc.) exhibit remarkable catalytic effects when heated at high temperatures of about 350–500 C and that the effect has been interpreted in terms of the formation of a large number of highly oxidative holes caused by thermal excitation of semiconductors. This prompted us to utilize this technology for complete removal of volatile organic compounds (VOCs). In the present investigation, we aim at constructing a compact device for practical implementation composed of four-stacked ‘‘heater/ honeycomb’’ units. Each unit comprises a spiral Ni-Cr heater as well as a honeycomb plate coated with powdered NiO or Cr2O3. Decomposition experiment was carried out in the range from room temperature to 500 C, using 10000 ppm toluene as the VOC at a flow rate of 10 l/min. As a result, the toluene decomposition was found to begin at about 100 C and was completed (i.e., 0 ppm) at about 300 C, showing an excellent decomposition characteristic in both NiO and Cr2O3. [doi:10.2320/matertrans.M2010105]