生質柴油非勻相催化轉酯製程之探討

Abstract

生質柴油又稱生物柴油，是以未加工過或者使用過之植物油或動物性脂肪作為原料，採用混合稀釋、微細乳化、熱解或轉酯化反應等方法所產製之生質燃料，具生物可分解性、無毒、燃燒後污染性低等優點，不僅可以單獨使用，也可與石化柴油混合使用，是一項具有潛力之潔淨替代燃料。 轉酯化反應是指以適當比例混合油脂與醇類，在加入與反應物同相之酸性催化劑、鹼性催化劑、脂解酶或非勻相之固體催化劑，或超臨界狀態下，反應、產製出另外一種酯類的過程，也是產製生質柴油最常用之方法。其中，採用非勻相催化劑者，具有可簡化產物分離與純化程序，減少廢水產出等優點，是一種對環境較友善且經濟上可行之方法。 本研究採用共沉澱法製備不同煅燒溫度、不同Mg/Al 莫爾比之非勻相催化劑－水滑石，在溫度60℃下，對甲醇與黃豆油催化轉酯成生質柴油，並探討其對轉酯率的影響研究結果顯示，以Mg/Al 莫耳比為3、煅燒溫度為550℃製程之水滑石催化能力最高，轉酯最佳條件為溫度60°C、時間8 小時、醇油莫耳比15:1、催化劑劑量5%，且可以85~95%的再生率重複使用水滑石達三次以上。

Biodiesel is a kind of clean and renewable energy which can be used directly or mixed with fossil diesel as fuel on vehicles. It can be extracted from recycled vegetable oil or animal fat by using blending, diluting, microemulsion, pyrolysis, or transesterification method. Transesterification means that appropriate amount of alcohols and fat are mixed in supercritical condition with various kind of catalyst to produce esters. It is a common process in producing biodiesel. By using all kinds of catalyst, heterogeneous catalyst is relatively environment-friendly and makes a simple process. In this study, soybean oil is mixed with methanol under 60℃ with hydrotalcite as catalyst to investigate the effect of Mg/Al molar ratio and calcination temperature to the conversion. As result, hydrotalcite made at 550℃ and Mg/Al ratio in 3 has the best conversion. Optimal condition of transesterification is at 60℃, 8hrs, Methanol/Oil=15, catalyst of 5%.