Activated coke preparation by physical activation of coal and biomass co-carbonized chars

Abstract

Activated cokes have been prepared with a two-step process: co-carbonization of bituminous coal and poplar bark biomass in nitrogen at moderate temperatures, followed by physical activation of the char residues with CO2 and steam at higher temperatures. The microstructures, pore distributions and surface chemical characteristics of the generated chars were examined by Scanning Electron Microscopy (SEM), N2 adsorption, and Fourier Transform Infrared Spectroscopy (FTIR). This study assessed the effects of the mixing ratio of bituminous and biomass feedstocks, the carbonization temperature, as well as the type and mole fraction of activation agents on the pore structure of the produced activated cokes. It was found that char obtained by co-carbonization of coal and biomass at a ratio of 2:1, at 600 °C for 30 min, had the highest micropore surface area at 200 m2/g. Subsequent activation of this char, at 800 °C for 90 min, with 40 % CO2 and 10 % steam resulted in a threefold increase of micropore surface area (607 m2/g). Steam enhanced pore broadening and, thus, it promoted the formation of mesoporous structure, while CO2 promoted additional development of microporous structure. As a result, activated coke with extensive and multimodal pore size distribution was produced.