以體積測定法研究VOCs之吸附平衡並與重量測定法比較

Volumetric Measurement of the Adsorption Equilibrium of VOCs and Compared with the Gravimetric Measurement

黃秀株(Show-Chu Huang)

指導教授 ： 鍾財王

中原大學/工學院/化學工程學系/碩士(2006年)

https://doi.org/10.6840/cycu200600307

摘要

本研究選用活性碳作為吸附劑，及九種揮發性有機物(正己烷、環己烷、1-己烯、2-甲基戊烷、3-甲基戊烷、2,2-二甲基丁烷、丙酮、丁酮、戊酮)作為吸附質，並利用自製體積測定法吸附平衡量測設備進行實驗與計算求得九種揮發性有機物在活性碳上的吸附等溫線，主要探討不同吸附質之物理化學性質對其在活性碳上的吸附行為之影響，及溫度對揮發性有機物吸附行為之影響，且嘗試與本實驗室重量法數據比較，實驗後利用Toth吸附等溫式進行回歸建立模式，以及根據熱力學理論結合Toth吸附等溫式求得吸附熱，進而瞭解其吸附機制。
由實驗結果可知，吸附行為及其機制是很複雜的，不同組合情況的吸附作用，其影響吸附量差異的因素也不同，綜合實驗結果顯示，非極性或弱極性的吸附質、立體障礙較小的吸附質及分子量較小的吸附質較易於被活性碳吸附，而極性氣體分子在高壓的情況下有助於被吸附，此外，低溫是有利於吸附的。由Toth等溫吸附式進行等溫吸附平衡數據之回歸結果顯示，Toth等溫吸附式適於描述本研究之實驗結果，也說明了本實驗數據與理論計算數據有極佳的相關性。根據吸附熱結果顯示，對於活性碳吸附，在零覆蓋率下的等量吸附熱和吸附質之極性大小成反比，此外，本研究所有VOCs之等量吸附熱皆隨覆蓋率的增加而降低，說明了本研究所用之活性碳表面是非均相的。

關鍵字

吸附熱 ； 吸附 ； 吸附平衡等溫曲線 ； 活性碳 ； 體積測定法 ； 揮發性有機氣體

並列摘要

The objective of this study was to investigate the adsorption isotherm of nine volatile organic compounds (n-hexane, cyclohexane, 1-hexene, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, acetone, 2-butanone, 2-pentanone) adsorbed by activated carbon by the equipment of volumetric adsorption. This study focused on the effects of the physical and chemical properties of different volatile organic compounds and temperature on the behavior of adsorption. And the results of this study were compared with the results of gravimetric adsorption. Toth model was used to fit experimental data. The isosteric heat of adsorption was calculated by the combination of Clausius-clapeyron equation and Toth model. The results from the adsorption equilibrium data reveal the interaction between the adsorbent and the adsorbate.
Results from the study indicated that the interaction between adsorbents and adsorbates was complex. The adsorption interaction between adsorbents and adsorbates would affected by different factor. And results from the study indicated the nonpolar or weak polar adsorbate, adsorbate with little steric barrier and adsorbate with little molecular weight was adsorbed more easily by active carbon. The polar adsorbate was adsorbed more easily in high pressure. And low temperature was good for adsorption. The experimental data was fitted well by Toth model. The isosteric heat of adsorption at zero coverage was inverse proportioned to polarity of adsorbate. The isosteric heat of adsorption for all adsorbates investigated decreases with increasing loading. It implies that the surface of activated carbon is energetically heterogeneous.

並列關鍵字

adsorption isotherm ； adsorption ； volumetric measurement ； activated carbon ； volatile organic compounds ； heat of adsorption

參考文獻

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