多孔性奈米碳纖維對二氧化碳的吸附效能研究

Adsorption of Carbon Dioxide on Porous Carbon Nanofibers

江右君(Yu-Chun Chiang) ； 李岳融(Yueh-Jung Lee) ； 王挺翰(Ting-Han Wang) ； 楊家驊(Chia-Hua Yang) ； 洪正倫(Cheng-Lun Hung)

《燃燒季刊》 110期 (2020/08) Pp. 5-18

https://doi.org/10.30041/CQ.202008_(110).0001

摘要

本研究將Polyacrylonitrile（PAN）和poly（methyl methacrylate）（PMMA）混合，利用靜電紡絲技術開發多孔性奈米碳纖維，所添加的PMMA在高溫碳化後會熱解揮發，可作為造孔劑。經由靜電紡絲、穩定化、碳化和活化等階段，以合成多孔活化奈米碳纖維，探討其材料特性，並評估對CO_2的吸附效能。研究發現，所合成的奈米碳纖維平均直徑介於420～730 nm，纖維表面和斷面均可清楚觀察到孔洞結構。氮氣等溫吸附－脫附曲線中具有明顯的hysteresis loop，型態與PAN和PMMA比值有關。將PMMA掺雜至PAN漿料中，不僅可產生中孔隙範圍之孔洞，還有助於超微孔的生成。當PMMA含量高時，因PMMA的熱解揮發，使碳化和活化過程纖維內部暴露的面積增加，可能間接導致N原子的額外損失。在0oC、101.3 kPa下，樣本對CO_2的平衡吸附量可達4.14 mmole/g；與SSA、Smi、Vt、Vmi、和pyridonic N有關。但在0 oC、15 kPa下，三樣本對CO_2的平衡吸附量則與median pore width和Smi/SSA有較大的關連性。為了可同時滿足Langmuir-type和Freundlich-type的行為，本研究採用Sips方程式（即Langmuir-Freundlich方程式）針對吸附數據加以擬合，三參數的Sips方程式可用以描述CO_2等溫吸附數據，所涉及之參數也能反應出吸附效能。

關鍵字

奈米碳纖維 ； 靜電紡絲 ； 多孔性 ； 二氧化碳 ； 吸附

並列摘要

The objective of this study was to investigate the properties and the CO_2 adsorption performance of porous carbon nanofibers prepared by electrospinning, stabilization, carbonization, and activation processes using the mixture of polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA), where PAN was used as the carbon precursor and PMMA was the pore generator. Results showed that the average fiber diameters ranged from 420 to 730 nm, and the pore features could be observed on the surface and the cross-sections. The hysteresis loop existed in the N2 adsorption-desorption isotherm and its loop pattern was related to the ratio of PMMA to PAN. It believed that the introduction of PMMA into the PAN electrospun ink not only generated mesopores but also promoted the development of ultrmicropores. The decomposition of PMMA would make much more interior surface areas of carbon nanofibers to expose during the carbonization and the activation processes, which could lead to the loss of nitrogen atoms. The CO_2 adsorption capacity achieved 4.14 mmole/g at 0 oC and 101.3 kPa, which was highly related to the value of SSA, Smi, Vt, Vmi and pyridonic N. But the CO_2 adsorption capacity at 0 oC and 15 kPa was associated with the median pore width and the ratio of Smi/SSA. The Sips model fitted the CO_2 adsorption data well, and the results showed that the parameters in the Sips equation were responsible for the CO_2 adsorption performance.

並列關鍵字

Carbon nanofibers ； electrospinning ； porosity ； carbon dioxide ； adsorption