Hydrodechlorination of DDT and chloroalkanes over carbon-supported Ni–Mo catalyst

Abstract

Catalytic hydrodechlorination (HDC) is an efficient method for the elimination of chlorinated compounds from organic wastes. HDC allows for the recovery of parent hydrocarbons. Herein, we studied the dechlorination of chlorododecane (CDD), dichlorocyclohexane (DCH) and dichlorodiphenyltrichloroethane (DDT) over a sulfided Ni–Mo/C catalyst in a flow reactor. The Ni–Mo/C catalyst was prepared by the incipient wetness method using a granular activated carbon support. In contrast to alumina, which is a commonly used support for commercial catalysts, the carbon support is resistant to decomposition by HCl formed during the HDC reaction. The composition of the tested catalyst was 5 wt.% NiO and 15 wt.% MoO 3, and it was characterized by well developed both the micro- and mesoporosity ( V mic = 0.559 cm 3 g −1, V mes = 0.430 cm 3 g −1). The level of conversion of CDD, DCH, and DDT was directly related to reaction temperatures in the HDC process; the total chlorine removal was achieved at 200 °C. The tested catalyst was determined to have good thermal stability in the HDC process at 170 °C for 100 h. This corresponded to conversions of 85–72% for CDD and 81–79% for DCH. For CDD the hydrogen pressure affected the ratio of dodecane to dodecene in the reaction products.