CaO/TiO2中孔洞微米球之合成、改質及其對二氧化碳捕集能力之研究

Synthesis and modification of mesoporous CaO/TiO2 microsphere for CO2 capture

陳品臻(Ping-Jhen Chen)

指導教授 ： 劉雅瑄

國立臺灣大學/理學院/地質科學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702891

摘要

能耐高溫之鈣基吸附劑已被視為有潛力之碳捕捉技術之一，且具有再生簡單、高溫下穩定、成本低等優點。本研究利用氣膠自組裝系統(aerosol-assisted self-assembly system, AASA system) 合成中孔洞材料(mesoporous material)作為載體，分別為摻雜鈣之二氧化鈦微米球(Ca-TiO2)及純二氧化鈦微米球(TiO2)，接下來利用含浸法改質載體以期提升材料之二氧化碳吸附容量。從X光繞射分析(XRD) 可以發現Ca-TiO2有鈦酸鈣(CaTiO3)之特徵峰。在穿透式電子顯微鏡(TEM)下，可觀察到微米球呈現規則圓球狀，且結構內部具孔洞。經由BET分析之比表面積可以發現TiO2及Ca-TiO2之比表面積分別為45.01 m2/g及39.44 m2/g。
本研究使用含浸法改質材料，並使用不同變因，找出迴圈吸脫附二氧化碳表現最佳的材料。所採取的變因分別為載體（Ca-TiO2及TiO2）、溶劑（99.5%酒精及去離子水）以及鈣前驅物（醋酸鈣及硝酸鈣）。於XRD分析中可發現改質後之材料皆出現鈦酸鈣特徵峰以及氫氧化鈣或氧化鈣特徵峰，顯示改質能使載體和鈣反應形成鈦酸鈣，而鈣化合物形式以氫氧化鈣或氧化鈣為主。另外，以酒精製得之材料的二氧化碳吸附量較以去離子水製得之材料約高出0.07 g-CO2/g-CaO，對於吸附劑之衰減趨勢影響不大。
相較於溶劑的影響，鈣前驅物的不同則對吸附劑的二氧化碳吸脫附表現影響較大。以醋酸鈣製得之材料的比表面積較大（最大有50.09 m2/g），故與二氧化碳之反應較為迅速，初期碳化轉換率皆大於80%，由於含浸改質上去之鈣的顆粒聚集現象較為明顯，故其衰減速率仍快，衰減速率約60%左右。另外，以硝酸鈣製得之材料的衰減現象則不明顯，僅於最後數個迴圈有約5%的衰減，但由於其比表面積較低（最大僅10.26 m2/g），故碳化轉換率較低，皆低於60%。

關鍵字

碳化／煅燒迴圈 ； 燒結 ； 氣膠自組裝系統 ； 中孔 ； 含浸法

並列摘要

Because of high thermal stability than other techniques, calcium-based adsorbent has been regarded as one of the most potential carbon capture technology. In this research, supports of mesoporous microspheres were synthesized from aerosol-assisted self-assembly system (AASA system), which are pure titanium dioxide(TiO2) and titanium dioxide with calcium(Ca-TiO2, Ca/Ti=0.3). In order to enhance CO2 adsorption capacity of materials, supports were modified through impregnation method. From X-ray Powder Diffraction (XRD), Ca-TiO2 synthesized through AASA system possesses crystalline CaTiO3 phase. Besides XRD, Transmission Electron Microscope (TEM) revealed that TiO2 and Ca-TiO2 are all microspheres with ordered mesopores. Brunauer–Emmett–Teller (BET) analysis was used to identify the surface area and pore size of adsorbent and the results showed that the specific surface areas of pure TiO2 and Ca-TiO2 are 45.01 m2/g and 39.44 m2/g, respectively.
Different variables of modification, which were support (TiO2 and Ca-TiO2), solvent (99.5% ethanol and DI water) and calcium precursor (calcium acetate and calcium nitrate), were discussed in this research. After modification, the peak of CaTiO3, Ca(OH)2 and CaO can be observed from XRD. The CO2 adsorption capacity of materials made through ethanol is higher than materials made through DI water about 7 g-CO2/g-CaO. The influence of different solvents on decay is not obvious.
The specific surface area of materials which made from calcium acetate monohydrate is bigger, and the maximal value is 50.09 m2/g. Bigger specific surface area results in bigger area of contact between CO2 and materials as well as higher molar conversion (about 80~90%). However, because of apparent aggregation calcium particles on support, the decay rate is still fast (about 60%). The surface area of these serial materials which were made from calcium nitrate is small, and the maximal value is only 10.26 m2/g, so the area of contact between CO2 and materials is also smaller which results in lower molar conversion (less than 60%). Because of evenly distributed CaO particles, there is almost no decay can be observed.

並列關鍵字

carbonation/calcination cycles ； sintering ； AASA system ； mesopores ； impregnation method

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