Study On Catalysts For Chlorinated Volatile Organic Compounds Catalytic Combustion

Chlorinated volatile organic compounds (CVOC) are harmful in accumulation in the environment and lead to the depletion of the stratospheric ozone layer. A combustion process of CVOC leads to the toxic by-products. Thus, the abatement of CVOC emission is highly important. Catalytic combustion has the advantage of being carried out at relatively low temperature, low energy-consumption, and it can destroy the pollutants rather than merely removes them for recycling elsewhere in the biosphere and is widely employed. Therefore, catalysts with excellent activity, high selectivity for product CO₂ and HCl, and good stability have gradually become the focus of investigation on CVOC catalytic combustion.With combination of literature and experiment results, it is concluded that CVOC catalytic process consists of dechlorinative section and oxidative section, and the former is control step. Results showed that, VOx/TiO₂ and WOx/TiO₂ calcined at 500℃exhibited better CVOC catalytic activity, which is attributed to their more strong Br?nsted acid sites than MnOx/CZ and MnOx/γ-Al₂O₃, which is effective in CVOC destruction. However, they have weaker oxidative activity. Thus, the activity of CVOC catalysts depends on its acid property primarily, and the oxidative acitivity secondly.Selectivity test results and TPR results showed that MnOx/CZ and MnOx/γ-Al₂O₃ have higher selectivity for CO₂ and Cl₂ and superior oxidative activity. Stability test results showed that the activity of MnOx/CZ and MnOx/γ-Al₂O₃ became worse with reaction process, due to the formation of Mn-Cl band and then the decrease of active sites on catalysts. The resistance to coke and chloride poisoning of catalysts lies on intensity of the band of metal and chlorine.