Tungsten carbide preparation using carbon from palm kernel shells and its catalytic hydrodehalogenation of dichlorodifluoromethane

Abstract

The importance of activated carbon as an adsorbent, catalyst and catalyst support has increased in industrial and environmental applications due to its special features; a very high surface area absorbency, inertness, and porosity. The surface structure and porosity of an activated carbon largely depended on the starting materials and the activation method used. In this study, activated carbons were prepared from palm kernel shell by chemical activation using zinc chloride, ZnCl2 under both nitrogen flow and vacuum condition. The effects of impregnation ratio (ZnCl2 to palm kernel shell) and activation condition on the surface properties of carbons were carefully studied in order to optimize these parameters. All the prepared activated carbons were characterized using FTIR, single point BET surface area, nitrogen adsorption analysis, FESEM-EDX and Thermogravimetry analysis. The selected activated carbons were used as a carbon source as well as catalyst support in the preparation of tungsten carbide, WC. The catalyst was prepared via sublimation technique where the metal precursor tungsten hexacarbonyl and activated carbon were milled together and heat-treated at 700ºC and 950ºC under helium flow. Two sets of WC catalysts with 6% and 15% tungsten content were prepared. The heat-treated catalysts were characterized by XRD, single point BET surface area and FESEM-EDX. The performance of the optimal prepared WC catalyst was tested on dichlorodifluoromethane, CFC-12 in hydrodehalogenation reaction. The results show that the impregnation ratio and the activation conditions had significant effect on the properties of activated carbon prepared. The activated carbon prepared with ZnCl2 impregnation ratio of 1:1 under nitrogen gas flow (AC- 1Z-N) showed the highest surface area, 878 m2g-1 with micropore volume of 0.36 cm3g-1. The catalyst with 15% tungsten content supported on AC-1Z-N showed the highest formation of tungsten carbide and found to be very active in the dehalogenation reaction of CFC-12.