製備ZIF-78晶體及其於二氧化碳/環氧丙烷之環加成反應之應用

現今全球暖化日益嚴重，要如何降低大氣中二氧化碳之排放可說是當務之急，目前主要著重的減碳技術為碳捕捉和封存 (Carbon capture and storage，CCS)，然而封存技術一直存有安全性疑慮的問題，因此二氧化碳再利用是一值得大力推動的途徑。以二氧化碳為原料進行聚合反應生產高分子材料為二氧化碳再利用的重點之一，主要以合成環碳酸酯類為主要大宗，利用二氧化碳與環氧化物合成環狀碳酸酯的反應中，催化劑扮演著舉足輕重的角色，咪唑類配位沸石 (zeolitic imidazolate frameworks，ZIFs) 為近幾年蓬勃發展之有機-無機複合式的多孔洞材料，其具有高比表面積、高化學性且易分離等優點，非常適合應用於催化反應使用上。在過去研究曾指出，ZIF-78粒子具有最好的二氧化碳吸附能力，原因在於製備ZIF-78粒子的咪唑類配位子具有硝基 (-NO2) 官能基，而硝基與二氧化碳之間會產生強烈相互作用力，在具有良好的二氧化碳吸附能力情況下，推測將有利於二氧化碳環加成反應之應用。因此，本研究將利用水熱法製備出ZIF-78粒子，並將其與環氧丙烷及二氧化碳進行環加成反應合成碳酸丙烯酯，探討各項反應參數 (反應壓力、反應溫度、反應時間) 對環加成反應之影響。由實驗結果顯示，反應溫度150℃、反應壓力為10kg/cm2、反應時間為15h的條件下有著50.7 ％的碳酸丙烯酯產率，且反應過程中無須加入共催化劑以及溶劑以提升催化效果，由此可證明ZIF-78粒子有著良好的催化效果。最後與本實驗室過去成熟發展的ZIF-7粒子進行環加成反應比較，由結果顯示，當反應壓力為10kg/cm2、反應溫度150℃、反應時間6h條件下，ZIF-78粒子的催化效果高於ZIF-7粒子，推測主要原因在於過去研究曾指出，ZIF-78具有最好的二氧化碳吸附能力，ZIF-78的咪唑類配位子具有硝基存在，而硝基與二氧化碳之間會產生強烈相互作用力，此外ZIF-78粒子的孔洞大小比ZIF-7粒子來的大，亦有利於二氧化碳分子進入孔洞內進行反應。

關鍵字

咪唑類配位沸石；二氧化碳再利用；環加成反應；環氧丙烷；碳酸丙烯酯

並列摘要

CO2 is the primary greenhouse gas which causes global warming in recent decade. How to reduce carbon dioxide emissions to the atmosphere is urgent priority, as it were. Carbon capture and storage (CCS) is the most indicated technology to decrease CO2 emission. However, sequestration technology there has been the problem of security concerns, hence it is worthwhile to promote CO2 recovery technology. The cyclic carbonate is main research target to synthesis from CO2 and epoxide. Catalyst plays an important role in Cycloaddition reaction. Zeolitic imidazolate frameworks (ZIFs) is a novel kind of porous crystalline materials with excellent properties, like large surface areas, high Chemical stability. It is suitable for use on the catalytic reaction. ZIF-78 crystals have the best CO2 adsorption capacity in the previous literatures. The presence of nitro groups of ZIF-78 causes a strong interaction with CO2 molecules. Under the premise of great CO2 adsorption capacity, ZIF-78 will facilitate the application of cycloaddition reaction. In this study, we synthesized ZIF-78 through hydrothermal method, and use to cycloaddition reaction of CO2 and propylene oxide. We would investigate the effect of reaction parameters (pressure, temperature, reaction time) on the cycloaddition efficiency. According to the results, the propylene carbonate yield was up to 50.7 ％when reaction conditions (P=10kg/cm2,T=150℃, time=15h). No cocatalysts or solvents were required during the reaction. At least, we try to compare the cycloaddition efficiency with ZIF-78 and ZIF-7 which was matured development in our laboratory. According to the results, the Catalytic effect of ZIF-78 was better than ZIF-7. The reason ZIF-78 was better is that the ZIF-78 crystals has the best CO2 adsorption capacity and the pore size was bigger than ZIF-7.

並列關鍵字

Zeolitic imidazolate frameworks ； CO2 recovery ； cycloaddition ； propylene oxide ； propylene carbonate

參考文獻

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製備ZIF-78晶體及其於二氧化碳/環氧丙烷之環加成反應之應用

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