Effect of Calcination Temperature of Support on Catalytic Performance of RuO₂/TiO₂ for HCl Oxidation

RuO₂/TiO₂-C (C=450, 550, 650 and 750℃)catalysts were prepared using wet impregnation with metatitanic acidas as precursor, which were calcined at different temperature. Based on the characterizations from various techniques, including XRD, N₂ adsorption-desorption analysis, HRTEM and H₂-TPR, the physical and chemical properties of the catalysts were revealed. The performance of catalysts for gas-phase HCl catalytic oxidation to Cl₂ were also investigated. The results showed that the calcination temperature of the support had effects on the structure of catalysts and the activity of HCl oxidation. RuO₂ was loaded on the support calcinated at lower temperature(≤650℃), while the match-degree between RuO₂ and TiO₂ increased with the elevated support calcination temperature. This promoted the dispersion of RuO₂ on the support, and the best catalytic performance over RuO₂/TiO₂-650 was observed. Further increase of the TiO₂ calcination temperature led to a seriously decline of the activity of RuO₂/TiO₂-750. The inhibition of HCl oxidation was related to the agglomeration of the support and its too strong interaction with the active sites which was mainly caused by the high calcination temperature. In addition, we found that the decrease of average particle size of RuO₂ could enhance the active of HCl oxidation. Kinetic studies showed that the partial pressure of oxygen was significantly effected HCl oxidation over catalyst which meant the dissocative dsorption of oxygen is the rate-determining step of the reaction.