Morphology-dependent properties of Co3O4/CeO2 catalysts for low temperature dibromomethane (CH2Br2) oxidation.

Brominated hydrocarbons are a typical pollutant in purified terephthalic acid (PTA) exhaust gas, which is harmful for human health and the environment once released to the atmosphere. In this study, three Co 3 O 4 /CeO 2 catalysts with different CeO 2 morphologies (rod, plate, and cube) were prepared and were used for low temperature dibromomethane (CH 2 Br 2 ) oxidation, which was used as the model compound for brominated hydrocarbons. The experimental results showed that Co 3 O 4 /CeO 2 -rod achieved significantly higher catalytic activity, with a T-90 of approximately 312 °C for CH 2 Br 2 oxidation and higher selectivity to CO 2 than Co 3 O 4 /CeO 2 -plate and Co 3 O 4 /CeO 2 -cube. All of the Co 3 O 4 /CeO 2 catalysts investigated were stable for at least 30 h at 500 ppm CH 2 Br 2 and 10% O 2 at a GHSV of 75,000 mL/(g·h) −1 , and the final products were CO x , Br 2 , and HBr, without the formation of other Br-containing organic byproducts. The higher catalytic activity of Co 3 O 4 /CeO 2 -rod was attributed to the high content of Co 3+ , more surface-adsorbed oxygen, and more oxygen vacancies in their exposed {1 0 0} and {1 1 0} planes. In addition, Co 3 O 4 had a stronger interaction with CeO 2 -rod, making it superior for CH 2 Br 2 oxidation. Moreover, on the basis of the analysis of products and in situ DRIFTS studies, a credible reaction mechanism for CH 2 Br 2 oxidation over Co 3 O 4 /CeO 2 catalysts was proposed. [ABSTRACT FROM AUTHOR]