Effect of coal type on the physical properties and CO2 adsorption performance of activated coke prepared by a single-step method

Activated coke is considered to be one of the promising CO2 adsorbents. It could be prepared using coals by a single-step method, but the physical properties and CO2 adsorption performance of the prepared activated coke were significantly different when different ranks of coals were used as the raw materials. In this study, a single-step rapid pyrolysis activation method based on entrained-flow bed was proposed to prepare powdered activated coke (PAC) for CO2 adsorption. Six typical coals covering lignite, bituminous coal and anthracite were selected as raw material to prepare PACs by the proposed method. The pore structure, surface morphologies and surface functional groups of the prepared PACs were characterized and the yields were calculated. The CO2 adsorption capacities and adsorption selectivity for CO2/N-2 were determined. Results show that the PAC prepared from lignite had the maximum specific surface area of 479 m(2)/g, the most abundant oxygen-containing functional groups and the highest CO2 adsorption capacity of 3.35 mmol/g at 0 degrees C and 1.2 bar. The physical properties and CO2 adsorption performance of PACs prepared using bituminous coals were greatly affected by the caking property. The PACs prepared using non-caking/weak-caking bituminous coals, such as Zhundong coal and Jinjie coal had good physical properties and CO2 adsorption performance, while those prepared using strong-caking coals had poor physical properties and CO2 adsorption performance. The yields were higher than those of PACs prepared from lignite. The PAC prepared using anthracite had the similar physical properties and CO2 adsorption performance to PAC prepared using medium-caking bituminous coal, but the yield of 72.17% was the most. It could provide references and basic support for the selection of coal for rapid preparation of coal-based adsorbents related to CO2 adsorption by the single-step method.