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Adsorption process of n-alkanes onto BAX-1100 activated carbon: Theoretical estimation of isosteric heat of adsorption and energy distribution of heterogeneous surfaces
Journal of Molecular Liquids ( IF 5.3 ) Pub Date : 2018-01-04 , DOI: 10.1016/j.molliq.2018.01.016
Manel Bergaoui , Asma Nakhli , Shaheen Al-Muhtaseb , Mohamed Khalfaoui

Adsorption of the n-alkane series, C1–C7, on Westvaco BAX-1100 activated carbon were measured over very broad ranges of temperature (293–393 K) and pressure (0.06–4964 Torr), depending on the n-alkane. Different behaviors of experimental adsorption isotherms were observed where various steps were noticed depending on the adsorbate length. A heterogeneous Gauss-monolayer model was developed based on statistical physics approach to evaluate the adsorption energy distribution (AED). Surface heterogeneity was evaluated and confirmed from isosteric heat of adsorption; where the adsorption of longer n-alkanes is energetically more favorable. A new equation was obtained from AED analysis to calculate the isosteric heat of adsorption. A notable difference between the adsorption isosteric heats estimated from AEDs and those obtained from classical Clausius-Clapeyron equation was observed at very low and high capacities. This difference was explained by the fact that, the gas behaves non-ideally at high pressure range. On the other hand, the absolute percentage deviation in adsorbed phase heat capacity was evaluated from the isosteric heat of adsorption predicted from the AED analysis. This percentage deviation increases when increasing the chain length of the alkane.



中文翻译:

BAX-1100活性炭对构烷烃的吸附过程:吸附等规热和异质表面能量分布的理论估计

在Westvaco BAX-1100活性炭上,在很宽的温度范围(293–393 K)和压力(0.06–4964 Torr)范围内,对构烷烃系列C 1 –C 7的吸附进行了测量,具体取决于构烷烃。观察到实验吸附等温线的不同行为,其中根据吸附物的长度注意到各个步骤。基于统计物理方法开发了一种非均质高斯单层模型,以评估吸附能分布(AED)。评价表面异质性,并由等排吸附热确定;其中较长的吸附Ñ-烷烃在能量上更有利。通过AED分析获得了一个新的方程,以计算吸附的等排热。在非常低和很高的容量下,观察到从AEDs估计的吸附等规热与从经典Clausius-Clapeyron方程获得的等温热之间存在显着差异。可以通过以下事实解释这种差异:气体在高压范围内表现不理想。另一方面,根据由AED分析预测的吸附的等排热来评估吸附相热容量的绝对百分比偏差。当增加烷烃的链长时,该百分比偏差增加。

更新日期:2018-01-04
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