深共熔離子液體在二氧化碳捕獲的應用

Application of the Deep Eutectic Solvent in CO2 Capture

蘇紋正(Wen-Cheng Su)

指導教授 ： 汪上曉

國立清華大學/工學院/化學工程學系/博士(2009年)

摘要

二氧化碳捕獲之重要性在於降低人為所產生的二氧化碳排放與溫室效應。利用醇胺水溶液作吸收與汽提之操作為從燃燒後煙道氣回收二氧化碳的重要技術之一。然而此一製程的能源消耗仍然很高，本研究為探索利用新型溶劑與製程的改善來降低二氧化碳捕獲的能耗之可行性。
首先我們量測了二氧化碳於不同水含量下之深共熔離子液體 “ Reline ” 的溶解度，證明水可以扮演著反溶劑的角色去除Reline 中的二氧化碳。然而由於二氧化碳於Reline中的溶解量過低，造成反溶劑脫除法顯得不具競爭力。
接著我們也量測了二氧化碳於不同水含量下之氨基酸鹽 “ [Choline][Pro] ” 溶液中的負載。 高水含量會促使碳酸氫根離子的產生，增加二氧化碳的負載。此時水扮演共溶劑的角色而並非反溶劑；因此我們提出一個不需熱能再生的二氧化碳汽提步驟：使用含氯離子交換樹脂將 [Choline][Pro]轉換成其之前驅物氯化膽鹼與脯氨酸，進而將已溶解的二氧化碳汽提出來；然後用含氫氧離子交換樹脂將氯化膽鹼與脯氨酸混合物再生成[Choline][Pro]。
最後我們發展了對不同二氧化碳吸收劑之能源消耗簡易估算法。藉由此方法可以發現，因為[Choline][Pro]之聚乙烯溶液具備高二氧化碳吸收量及溶劑揮發損失可忽略，故有機會成為低能耗的替代二氧化碳溶劑。然而其高黏度導致實際應用有困難。
基於上述研究結果，未來發展新型二氧化碳溶劑與與創新吸收製程可能有兩個方向。其中之一為將新型吸收劑如氨基酸鹽溶於低黏度不具揮發性之溶劑中進行二氧化碳捕獲；此外也可將以離子交換輔助，不須耗費熱能的溶劑再生法應用於其他氨基酸鹽水溶液。

關鍵字

二氧化碳捕獲 ； 深共熔離子液體 ； 離子交換

並列摘要

Carbon dioxide capture and sequestration is becoming an important means for reducing anthropogenic carbon dioxide emission and global warming. One of the most developed technologies for carbon dioxide capture from post-combustion flue gas is the absorption/stripping process utilizing aqueous alkanolamine solutions. However, this process is still energy intensive. This work explores the feasibility of reducing energy consumption using alternative solvents and process configurations.
Firstly, we measured the solubilities of carbon dioxide in the deep eutectic solvent, Reline with different water contents. Water can act as an anti-solvent to strip carbon dioxide from Reline. However, a concentration swing process based on anti-solvent effect is non-competitive due to the low carbon dioxide capacity in Reline.
The carbon dioxide loadings in the amino acid salt, [Choline][Pro], with different water contents were measured. High water content results in the formation of bicarbonate ion and increase carbon dioxide loadings. Water acts as a co-solvent rather than anti-solvent. A thermal energy free stripping process was proposed by using ion exchange resin. Chloride form resin was used to convert saturated [Choline][Pro] solution to choline chloride and L-proline, driving out dissolved carbon dioxide. Hydroxide form resin was used to regenerate [Choline][Pro] from the mixture of choline chloride and L-proline.
Finally, a simplified method to evaluate the energy consumption of different carbon dioxide absorbents was developed. It was found that [Choline][Pro] in PEG200 solution is the energy-efficient alternative absorbent because of its high capacity and negligible solvent vaporization loss. However, high viscosity of the solution becomes the bottleneck of its application.
Based on results of this study, two directions for developing new solvent systems and processes are proposed. One way is to dissolve innovative amino acid salts in non-viscous solvent of low volatility. Alternatively, the thermal energy free stripping process can be applied to aqueous solutions of amino acid salts.

並列關鍵字

CO2 Capture ； Deep Eutectic Solvent ； Ion Exchange

參考文獻

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