Highly selective gas-phase synthesis of 1,1-dichloroethylene from 1,1,2-trichloroethane over supported amine catalysts

The manufacture of 1,1-dichloroethylene(1,1-DCE) usually employs liquid phase method to perform the dehydrochlorination of 1,1,2-trichloroethane(TCE), where large amounts of high-concentration salty wastewater is produced inevitably. It has been a long-term goal to achieve the gas phase synthesis of 1,1-DCE via supported catalysts. In this work, the gas-phase synthesis of 1,1-DCE from TCE was studied in the presence of pentaethylenehexamine( PEHA) supported on silica. High and stable selectivity to 1,1-DCE(up to 98%) was obtained, which could be ascribed to the relatively strong basicity of PEHA according to a proposed E2 mechanism. The formation of PEHA chloride from the HCl generated in situ was detected and was considered to be the main reason for the deactivation of PEHA catalyst.