Microwave assisted tungsten carbide from waste kernel shell for remediation of chlorodifluoromethane

Abstract

The production of activated carbon production has been utilized from local waste palm kernel shell by chemical activation using phosphoric acid (H3PO4), a strong dehydrating agent. In this study, the effect of different acid concentration ranging from 10% to 50% was studied to establish the optimal condition to produce high surface area activated carbon. The activated carbon preparation includes soaking and dehydration of palm kernel shell in H3PO4 at 120 ºC and activation at 500 ºC. The activated carbon prepared was characterized by Nitrogen Adsorption analysis, FTIR, FESEM and TGA. The highest surface area of activated carbon prepared was used as the carbon source and selected as support in tungsten carbide (WC) synthesis. In this study, the WC catalyst was prepared via solid-state reaction using modified microwave oven and this method is named as Microwave-Assisted Method using two different precursors, tungsten metal and tungstic acid for comparison. Two sets of samples for each precursor were prepared with 6% and 15% tungsten respectively. Catalyst with high crystalinity structure was used to study the catalytic activity by hydrodehalogenation (HDH) reaction of Chlorodifluromethane (HCFC-22). Characterization results showed that acid concentration is an important factor for pore development and porosity of the activated carbon produced. The highest BET surface area was achieved when the palm kernel shell soaked in 50% phosphoric acid (AC50) with surface area of 1227 m2g-1. Meanwhile, catalyst with 6% tungsten (WC-M2) prepared from tungstic acid precursor produced better crystalinity of tungsten carbide (WC) than when tungsten powder was used as precursor. This catalyst is also found to be reactive to hydrodehalogenation of HCFC-22 with 84% conversion.