Characterization of CrO x/Al 2O 3 catalysts for dichloromethane oxidation

Abstract

Chlorinated volatile organic compounds (CVOCs) are hazardous and potent environmental pollutants. Catalytic combustion has been regarded as one of the most promising technologies to eliminate CVOCs emissions. CH 2Cl 2 is difficult to be oxidized among CVOCs. A catalyst with high activity for CVOCs oxidation is desirable. In this paper, CrO x /Al 2O 3 catalysts with different Cr contents were prepared using a deposition–precipitation method and tested for CH 2Cl 2 oxidation. The highest activity was obtained over the catalyst with 18% Cr content, with a complete oxidation of CH 2Cl 2 at 350 °C. Characterization results indicated that both high oxidation state Cr species (Cr(VI) species) and crystalline Cr 2O 3 existed in the CrO x /Al 2O 3 catalysts, and the average valence of Cr species in the catalysts decreased with Cr content. It was found that the reaction rate for CH 2Cl 2 oxidation increased with increasing average valence of Cr, which indicated that high oxidation state Cr species were probably the active phase for the reaction.