Characterization of CrOx/Al2O3 catalysts for dichloromethane oxidation

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. CH2Cl2 is difficult to be oxidized among CVOCs. A catalyst with high activity for CVOCs oxidation is desirable. In this paper, CrOx/Al2O3 catalysts with different Cr contents were prepared using a deposition–precipitation method and tested for CH2Cl2 oxidation. The highest activity was obtained over the catalyst with 18% Cr content, with a complete oxidation of CH2Cl2 at 350 °C. Characterization results indicated that both high oxidation state Cr species (Cr(VI) species) and crystalline Cr2O3 existed in the CrOx/Al2O3 catalysts, and the average valence of Cr species in the catalysts decreased with Cr content. It was found that the reaction rate for CH2Cl2 oxidation increased with increasing average valence of Cr, which indicated that high oxidation state Cr species were probably the active phase for the reaction.

Figure optionsDownload high-quality image (122 K)Download as PowerPoint slideHighlights
► The average valence of Cr species in the catalysts decreased with Cr content.
► The reaction rate for CH2Cl2 oxidation increased with increasing average valence of Cr species.
► The enhanced reactivity of the catalysts was due to high oxidation state Cr species.