Effect of Ru on the activity of Co3O4 catalysts for chlorinated aromatics oxidation

Ru/Co3O4 catalysts with a Ru content of 0-2 wt% were prepared by wet impregnation, and used in the catalytic combustion of chlorinated aromatic VOCs. Characterization by XRD, HRTEM, EXAFS, XPS, and H-2-TPR showed that Co3O4 existed in the form of a spinel structure. Some Ru species entered the octahedral sites of Co3O4 to form Ru-O-Co, which significantly increased the surface oxygen, while the formation of RuOx clusters or nanoparticles on the surface promoted the reducibility of Co3O4. In the oxidation of chlorinated aromatics, Ru species can retard the negative effect of Cl species on the activity of Co3O4 catalysts through modification in the chemical environments of surface oxygen and Cl species. The Ru/Co3O4 catalysts presented good activity and selectivity, with a rate (R-Ru) of 9.4-9.8 mol m(-2) min(-1) under 1000 ppm 1,2-dichlorobenzene at 30000 ml g(-1) h(-1). The R-Ru in wet feed over 2.0% Ru/Co3O4 was increased by almost 100%, through the increase in availability of active surface oxygen from RuOx. A highly stable activity could be maintained for at least 50 h. In situ FT-IR showed that 1,2-DCB adsorbs on the Co3+/Co2+ sites of Ru/Co3O4 catalysts, and the formation of partial oxidation products involve the surface oxygen. For the Co3O4 catalyst, surface active oxygen is almost not available during 1,2-DCB oxidation.