用于吸附分离CO_2的活性炭研究

Research on Activated Carbon for Separating CO_2 by Adsorption

以无烟煤为原料、NH4NO3和K2CO3混合物为添加剂制备了变压吸附分离CO2用活性炭.将煤粉、添加剂和煤焦油经过充分混合后挤压成条状,在600℃及无氧的条件下炭化30 min,然后用水蒸气在900℃下活化一定时间得到活性炭.测定了活性炭的比表面积、微孔孔容、碘吸附值、四氯化碳吸附值、CO2吸附量、堆积密度等指标.结果表明,添加剂用量以2%～3%为宜,活化前对炭化料进行酸洗有利于提高活性炭的综合性能.实验的最佳结果出现在烧失率45%～50%或四氯化碳吸附值45%～55%左右,这时,活性炭的CO2吸附量和堆积密度分别达到70mL/g和600 g/L左右.此外,CO2吸附量与微孔孔容之间呈正相关关系,而与比表面积、碘吸附值、四氯化碳吸附值等指标之间则没有很好的相关性.采用本方法制备出的活性炭已经成功应用于变压吸附法提纯氢气的工业装置,氢气的纯度达到99.999%.

Activated carbons used in separating CO2 were prepared by using anthracite as the feed coal and mixture of NH4NO3 and K2CO3(1 : 1) as additive. The feed anthracite, additive and tar binder were Mixed and kneaded into a paste; Then the paste was extruded and carbonized at 600 C for 30 min; At last, it was activated at 900℃ in steam flow for a certain time to prepare the activated carbon. The iodine number, hardness, apparent density, carbon tetrachloride adsorption, specific surface area, pore size distribution, and CO2 adsorption of the activated carbons were determined. The results show that the additive of 2%-3% is appropriate and the acid washing before activation is beneficial to the performance of the activated carbon. When the burnoff is in the range of 45%-50% or the carbon tetrachloride adsorption in 45%-55%, the CO2 adsorption and bulk density are about 70 mL/g and 600 g/L respectively. It is found that the micro pore volume is closely related with CO2 adsorption, but other parameters such as iodine number, carbon tetrachloride adsorption and specific surface area are not so closely related. The activated carbon prepared by this method has been successfully used in industrial equipment for hydrogen purification, with the hydrogen purity being more than 99. 999%.