二氧化碳固態捕捉劑：製備、操作條件、選擇性與可重複使用性之研究

Abstract

本研究探討中孔碳材、固體胺材、鹽批覆負載型鎂基材與負載型鈣基材四種捕捉劑之製備與二氧化碳捕獲能力評估。 中孔碳材捕捉劑製備方式為採軟模板法合成具中孔結構碳材，再分別以不同處理程序調控碳材表面含氧官能基形式，探討不同含氧官能基形式對捕獲表現影響。表面以可釋出氫離子的含氧官能基為主的捕捉劑0 °C、10 °C、20 °C及常壓環境下捕獲量分別為2.49 mmole/g、2.09 mmole/g、1.71 mmole/g，而表面以不可釋出氫離子的含氧官能基為主的捕捉劑0 °C、10 °C、20 °C及常壓環境下捕獲量分別為2.60 mmole/g、2.25 mmole/g、1.90 mmole/g。以理想溶液理論模擬氮氣/二氧化碳或甲烷/二氧化碳之二元混合氣體中分離二氧化碳效率之結果顯示，表面以可釋出氫離子的含氧官能基為主的捕捉劑較適合在低於室溫環境下工作，而表面以不可釋出氫離子的含氧官能基為主的捕捉劑較適合在接近室溫環境下工作。 固體胺材捕捉劑製備方式為以軟模板法合成具中孔結構的碳材為載體，先以高溫氨氣處理表面，再將四乙烯戊胺引入至載體中。增加高溫氨氣處理步驟有助於提升胺基分子在載體中的負載量與分散程度，捕獲量在35 °C、50 °C、70 °C、85 °C及常壓環境下分別為1.41 mmole/g、1.17 mmole/g、0.89 mmole/g、0.76 mmole/g，經20次重複使用後捕獲量幾乎無任何損失。結合靜態化學吸附法與原位紅外光譜法可分別量化固體胺捕捉劑對二氧化碳的物理吸附量與化學吸附量，並可進一步去計算胺基使用效率，與文獻不同的是本研究計算的結果較能反映出胺基以化學機制捕獲的參與程度。 鹽批覆負載型鎂基材捕捉劑製備方式為以連續式氣膠噴霧自組裝技術快速將氧化鎂分散至中孔微米球載體中。鎂鈦莫耳比2的捕捉劑在300 °C及常壓環境下捕獲量為0.26 mmole/g，高出商業氧化鎂近一倍表現，而亞硝酸鈉促進劑引入後捕獲量獲得顯著提升，當引入量來到45 wt%時，捕獲量來到1.30 mmole/g，由於孔道空間有限，因燒結現象導致粒徑增長的幅度受到抑制，使捕捉劑具有較佳的可重複使用特性，經6次重複使用後的捕獲量與第1次捕獲量相比損失約11%。 負載型鈣基材在鈣鈦莫耳比3的條件下，在600 °C及常壓環境下捕獲量在5分鐘內即可達到7.00 mmole/g之飽和容量，在700 °C氮氣流通的再生環境下，經20次重複使用後的捕獲量幾乎無任何損失，而在920 °C二氧化碳流通的再生環境下，經5次重複使用後的捕獲量損失幅度僅約32%，且此後趨於穩定，至第11次重複使用捕獲量不再有損失現象。700 °C氮氣流通的條件下產生的物種以氫氧化鈣為主，而920 °C二氧化碳流通的再生條件下產生的物種以氧化鈣為主。 總結本研究探討之四種捕捉劑，對二氧化碳捕獲皆具優秀的選擇性與多次重複使用特性，在燃燒化石燃料電廠與工業上移除二氧化碳具應用潛力。

The preparation and CO2 capture performance of mesoporous carbon sorbent, solid amine sorbent, salt promoted supported Mg-beaed sorbent and supported Ca-based sorbent were discussed in this work. The mesoporous carbon sorbent was obtained via soft-template method following by different treatment process to adjust surface oxygen functional groups type. The capture capacities of sorbent with acidic oxygen functional groups at 0 oC, 10 oC, 20 oC were 2.49 mmole/g, 2.09 mmole/g, 1.71 mmole/g, while sorbent with non-acidic oxygen functional groups show 2.60 mmole/g, 2.25 mmole/g, 1.90 mmole/g. In CO2/N2 or CO2/CH4 binary gas mixture case, the ideal adsorbed solution theory simulation results show that sorbent with acidic oxygen functional groups is suggested to work at low temperature, whereas sorbent with non-acidic oxygen functional groups is suggested to work at near room temperature. The solid amine sorbent was obtained by loading tetraethylenepentamine into NH3-treated mesoporous carbon support. The NH3-treated step can help support retain more amine molecules with better distribution. The capture capacities at 35 oC, 50 oC, 70 oC, 85 oC were 1.41 mmole/g, 1.17 mmole/g, 0.89 mmole/g, 0.76 mmole/g. The capacity was unchanged after 20 cycles use. Quantification of physisorption and chemisorption can be done though in situ infrared technology assisted static chemisorption method. The result can futhur calculate amine efficiency, which reflects the degree that amines capture CO2 via chemical mechanism. The salt promoted supported Mg-beaed sorbent was obtained via aerosol-assisted self-assembly method following by salt impregnation. At 300 oC, the Mg/Ti mole ratio 2 show 0.26 mmole/g capture capacity, almost twice higher than commercial MgO. The capture capacity futhur increased to 1.30 mmole/g as 45 wt% NaNO2 loading. Due to restricted space in nanochannel, particle size growth caused by sintering was mitigated. Therefore the sorbent show better multicycle stability. The capture capacity loss about 11% at 6th use compared to 1st use. The supported Cg-beaed sorbent was obtained via aerosol-assisted self-assembly method. At 600 oC, the Ca/Ti mole ratio 3 show 7.00 mmole/g capture capacity in 5 minutes. Under 700 oC and N2 atmosphere regeneration condition, the capture capacity was almost unchanged after 20 cycle use. As regeneration condition came to 920 oC and CO2 atmosphere, the capture capacity only loss about 32% after 5 cycle use, and then became uncganged. After the former regeneration condition, the Ca species was mainly in Ca(OH)2 form, while in CaO form after the latter regeneration condition. In summary, these four sorbents discussed in this work possess high selectivity to CO2 and good muiticycle stability. The four sorbents have great potential application in fossil fuel power plant or industry CO2 removal.