Methane adsorption on activated carbon and carbon black
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摘要: 为研究影响碳基吸附剂吸附超临界温度气体的主要因素,选择石墨化热解碳黑BP280和Ajax活性炭,分析超临界温度高压甲烷在其上的吸附平衡。应用容积法,在压力0~20.5MPa、温度253K~313K测定甲烷的吸附平衡数据,并由等量吸附线标绘和亨利定律常数确定等量吸附热。引入通用吸附等温方程,再由方程的Langmuir标绘确定最大吸附容量,进而通过方程的线性化计算吸附平衡态中甲烷分子的作用能。结果表明,甲烷在两种吸附剂上的最大吸附容量均随温度而变化,并都小于液态甲烷的密度;甲烷在碳黑和活性炭上的等量吸附热分别为 11.9kJ/mol~12.5kJ/mol和 17.5kJ/mol~22.5kJ/mol,体现了两种吸附剂不同的表面能量分布;甲烷分子间作用能随吸附量的变化特点反映了超临界温度甲烷以类似于压缩气体状态聚集的特点和吸附剂结构上的差异。碳基吸附剂的比表面积和微孔容积是影响其储存甲烷容量的重要因素。Abstract: Methane adsorption equilibrium on Ajax activated carbon and graphitized thermal carbon black BP280 above the critical temperature were studied experimentally and theoretically. Isotherms of adsorption were volumetrically measured at 253K~313K and 0~20.5MPa and isosteric heats of adsorption were determined by adsorption isosteres and temperature dependence of Henry's Law constant. An approximate model for adsorption equilibrium was developed and the maximum adsorption capacity was further determined by Langmuir plot of the adsorption model. The interaction energy among the adsorbed methane molecules was obtained by linearization of the model and fitting with the adsorption data. The results showed that the isosteric heats of methane adsorption on activated carbon and carbon black are 11.9kJ/mol~12.5kJ/mol and 17.5kJ/mol~22.5kJ/mol, respectively; the isosteric heat of adsorption on carbon black varies evenly with the adsorption amount. The maximum adsorption capacity decreases with the increase of temperature; the density of adsorbates is lower than that of liquid methane. The strength of the interaction energy among the adsorbed methane molecules suggests that the adsorbed phase of the supercritical methane is in a state of compressed gas. The adsorption capacity of supercritical methane on a carbonbase adsorbent is largely determined by its specific surface area and micropore volume.
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Key words:
- methane /
- activated carbon /
- carbon black /
- adsorption
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