Abstract:

A series of Cr₂O₃ catalysts was prepared by a precipitation method and tested for the gas phase dehydrochlorination of 1,1,2-trichloroethane(TCE) to synthesize cis-1,2-dichloroethylene(cis-DCE). X-ray diffraction(XRD), hydrogen temperature-programmed reduction(H₂-TPR), ammonia temperature-programmed desorption(NH₃-TPD) and X-ray photoelectron spectroscopy(XPS) were used to study the dehydrochlorination of TCE on Cr₂O₃ catalyst and its reaction mechanism. It is found that the conversion ratio of TCE on the catalysts decreases with the increase of the calcination temperature, while the selectivity to cis-DCE first increases and then decreases. The best performance is obtained on the catalyst calcined at 400 ℃, with a TCE conversion ratio of 70.8% and a cis-DCE selectivity of 90.0%. In addition, the areal specific reaction rate also first increases and then decreases with the increase of the calcination temperature, with the highest value being obtained on the catalysts calcined at 400 ℃(0.801×10^-2 μmol/(s·m²). The catalytic behaviors of the catalysts are well related to their surface Cr₂O₃ species. Turnover frequencies(TOFs) calculated based on the surface acidity and the highest value being obtained on the catalysts calcined at 400 ℃(2.82×10^-5 s^-1) show that the oxidation states of the surface Cr species are important for the reaction and the Cr species with an average valence of 3.2 are appropriate for the reaction.

Key words: Cr₂O₃ catalysts, 1,1,2-trichloroethane, dehydrochlorination, cis-1,2-dichloroethylene, surface Cr₂O₃ species