以不同催化方式從痲瘋樹油脂製備生質柴油的研究

Abstract

近年來由於石油短缺、高油價以及環境的議題，生質柴油已經更加的引人注目。在眾多生產生質柴油的原料當中，痲瘋樹種子油生產生物柴油的潛力是眾所皆知的，酯交換是一種能將三甘酸油脂轉換成生質柴油的技術。然而，甲醇毒化現象和質傳阻力阻礙了酯交換反應進一步的適用性。本篇研究調查痲瘋樹油以不同催化方式和技術對於酯交換效率的影響，同時，動力學參數以及各個脂肪酸組成在酯交換過程中的變化也加以估計。反應在裝有痲瘋樹油的旋轉燒瓶中進行，加熱燒瓶到反應溫度和設定攪拌速率為300轉，當醇和催化劑添加至燒瓶時，反應即開始。結果顯示在40oC酵素酯交換的過程中，將甲醇從批次式添加改變成連續式的添加可使脂肪酸甲酯的轉化率從37.73 上升至63.91以及將活化能從54.9 kJ/mole 減少至 23.0 kJ/mole，但對於乙醇並沒有顯著的影響。此外，透過40 W超聲波的輔助，脂肪酸甲酯的轉化率可以從37.73提高到56.23%，而透過 50 W微波的輔助整個反應時間可以縮短大約3個小時。最後但也是很重要的，痲瘋樹油中以棕櫚酸甲酯的轉化率最快，而亞油酸的雙鍵對於酯交換的效率造成了負面的影響。此外，透過微波轉酯化可以提高長鏈不飽和脂肪酸的轉酯率。

Biodiesel has been getting attractive recently due to the scarcity of petroleum, environmental issues and high oil prices. Among several feedstocks for biodiesel production, the potential of Jatropha curcas oil (JCO) for biodiesel production is well recognized. Transesterification is a techonology to transfer triglycerides into biodiesel. However, intoxication by methanol and mass transfer resistance hamper further applicability of transesterification. This study investigated the impact of different catalytic approaches and technologies on transesterification efficiency for jatropha oil; meanwhile, kinetic constants and variation of each constituent of fatty acid were also estimated during transesterification. Reactions were carried out in spin flasks filled with jatropha oils, and heated to the reaction temperature with stirring rate at 300 rpm. The reactions started when the alcohols and catalysts were added to the flasks. The result showed the conversions of fatty acid methyl ester (FAME) were from 37.73 to 63.91% and reduction of the activation energy from 54.9 kJ/mole to 23.0 kJ/mole changing from stepwise methanol addition to continuous addition at 40oC during lipase transesterification, but no significant effect for ethanol. In addition, the conversion of FAME was improved from 37.73 to 56.23% through 40 W ultrasound assisted, and the whole reaction time was shortened about 3 hours by 50 W microwave assisted. The last but not the least, faster palmitic acid methyl ester conversion of jatropha oil was found while the negative impact of double bonds of linoleic acid on transesterification efficiency. In addition, Microwave assisted process could improve the conversion of the constitute with longer fatty acid chain and unsaturated fatty acid.