活性碳纖維布之KOH活化的孔隙特性及其對二氧化碳之吸附效能

Process Porosity of KOH-activated carbon fibers and their adsorption capacity for carbon dioxide

江右君(Yu-Chun Chiang) ； 張祐銓(Yu-Chuan Chang)

《燃燒季刊》 98期 (2017/08) Pp. 4-17

https://doi.org/10.30041/CQ.201708_(98).0002

摘要

本研究將商用活性碳纖維布予以表面KOH活化，利用3^(3-1)部份因子設計之方法，可在較少的試驗次數下，探討影響比表面積、孔體積(特別是微孔、超微孔)的主要實驗參數，並評估對CO_2之吸附效能和選擇性。研究發現，對於比表面積和孔體積，反應溫度是影響程度最大的因子。KOH比例會影響孔隙體積的分佈，KOH: ACFs = 4:1時，微孔比例較高；KOH: ACFs = 6:1時，則是中孔比例會提升。反應時間增加時，比表面積和孔體積會先增後減，主要係因微孔出現擴孔現象。最高的CO_2吸附量是出現在超微孔體積最大的樣本，而非比表面積和孔體積最大的樣本。大孔體積較大者，N_2的吸附量也會提高。因此欲提高CO_2選擇性，應提高吸附劑之超微孔體積，且儘量減少大孔體積。

關鍵字

活性碳纖維 ； 活化 ； 實驗設計 ； 二氧化碳 ； 吸附

並列摘要

This study attempted to modify the surface of activated carbon fibers (ACFs) by potassium hydroxide (KOH) activation. The 3^(3-1) fractional factorial design was used to find the main effects on specific surface area and pore volume (especially for micropore and ultramicropore) and discuss their adsorption capacities of carbon dioxide (CO_2) and selectivity under limited number of test. Results showed that the reaction temperature was the main factor for specific surface area and pore volume of the samples. The KOH ratio would control the pore size distribution, where the highest microporosity occurred at KOH: ACFs = 4: 1 but the larger mesoporosity happened at KOH: ACFs = 6: 1. When reaction time increased, the specific surface area and total pore volume increased first and then followed decrease. It could be ascribed to the enlargement of micropores when the time much extended. The maximum CO_2 uptake was observed on the samples with the largest ultramicropore volume, rather than on the samples with the largest specific surface area or total pore volume. The N_2 uptakes increased when the samples had a larger macropore volume. Thus, that increasing the ultramicropore volume and decreasing the macropore volume was believed to improve the CO_2 selectivity.

並列關鍵字

Activated carbon fibers ； Activation ； Experimental design ； Carbon dioxide ； Adsorption