Effect of oxygen-containing functional groups on methane adsorption by activated carbon

Abstract

Natural gas has been applied as a fuel for vehicle because it is cheaper and cleaner burning than other fuels. In the vehicle, natural gas is ordinarily reserved by compressing and storing under high pressure at room temperature but this method has several limitations (e.g. low energy density, high weight of tank). Therefore, a porous material with high specific surface area (e.g. activated carbon) is suggested to eliminate the limitations of natural gas storage by compression, natural gas is adsorbed at relatively low pressure and room temperature. The adsorption capacity of activated carbons is related with their physical and chemical surface properties. In this study, bituminous activated carbon was modified by different methods to produce different quantity of oxygen-containing functional groups on activated carbon surface (1) by acid solution or (2) by alkali solution, for studying the relation between oxygen-containing functional groups and the adsorption capacity of methane on activated carbon surface. The physical properties of the activated carbon were Elucidated by using Brunauer-Emmett-Teller (BET) surface analysis. Boehm titration technique and Fourier Transform Infrared Spectroscopy (FTIR) were applied for qualitative and quantitative analyses of oxygen-containing functional groups. The results confirmed the presence of oxygen-containing functional groups on the activated carbon surface consisting of phenolic group, lactone group and carboxylic group. The oxygen-containing functional groups on the surface of activated carbon play an important role on the methane adsorption but the methane adsorption also depends on other surface properties of activated carbon.