Dehydrochlorination of 1,2-dichloroethane over Ba-modified Al2O3 catalysts

Abstract

Bimodal mesoporous alumina (Al₂O₃) was prepared using polyethyleneglycol (PEG 20 000) and cetyl trimethyl ammonium bromide as a template. The incorporation of Ba with various loadings was carried out by incipient wetness. Characterization was performed by XRD, N₂ sorption isotherms, and pyridine FTIR. Ba can be highly dispersed on Al₂O₃ covering the strong acid sites of Al₂O₃. In the catalytic dehydrochlorination of 1,2-dichloroethane (1,2-DCE), the Ba/Al₂O₃ catalysts present a high activity, of which Al₂O₃ is most active with 95% conversion at 325 °C, related to the more Lewis acidic Al³⁺ sites in a tetrahedral environment. 1,2-DCE adsorbs dissociatively on Lewis acid–base pair sites, forming chlorinated ethoxy species, which are supposed to be intermediate species for vinyl chloride (VC) production. At a temperature higher than 400 °C, the dehydrochlorination of VC occurs on the strong acid sites of Al₂O₃. Ba can promote greatly the selectivity for VC through a decrease in the strong acid sites. A high stable activity for dehydrochlorination and high selectivity for VC can be obtained over Ba/Al₂O₃ in the presence of oxygen.