本研究探討以自由脂肪酸產製生質柴油之新穎兩階段程序,第一階段以自由脂肪酸為原料,在無添加觸媒的情況下與甘油進行高溫酯化反應,此反應可降低原料油裡的酸價,以便後續進行轉酯化反應產製生質柴油。最適酯化反應操作條件為醇酸莫耳比0.9、反應溫度250 oC、及反應時間1.5小時,可得脂肪酸轉化率為99.08%。第二階段以氫氧化鉀為觸媒,將酯化後脂肪酸與甲醇進行轉酯化反應,最適轉酯化反應條件為醇油莫耳比3、觸媒劑量1%w/w、反應溫度60 oC、及反應時間1小時,所生成脂肪酸甲基酯產率為97.0%。在本研究兩階段生質柴油產製程序中,粗甘油的回收率約為50%,已測試回收粗甘油可重複利用於酯化反應,且對反應無明顯不良影響。將本系統所產製的自由脂肪酸生質柴油進行油品性質分析,所得自由脂肪酸生質柴油的冷濾點為-15 oC、密度883 kg/m3、碘價118.66 g I2/100 g、動黏度4.93 mm2/s、及氧化穩定性0.32小時。
The objective of this study is to produce biodiesel from free fatty acids (FFAs) using a two-step process. In the first step, the FFAs are esterified with glycerol to produce glycerides. The reaction can reduce the acid value of FFAs before transesterification reaction. The conversion of FFAs was 99.08% under the optimal esterification conditions including the molar ratio of glycerol to FFAs of 9:10, reaction temperature of 250 oC, and reaction time of 1.5 h. The second step was the transesterification of the glycerides with methanol with potassium hydroxide as the catalyst. In the study, the recommended conditions for the trnsesterification of glycerides were molar ratio of methanol to oil of 3:1, catalyst loading of 1%w/w, reaction temperature of 60 oC, and reaction time of 1 h to obtain the yield of fatty acid methyl ester (FAMEs) as 97.0%. The recovery percentage of crude glycerol in the two-step process is about 50%, and the recovered crude glycerol can be reused in the esterification reaction without significant negative effects. The FFAs-based biodiesel had the cold filter plugging point of -15 oC, density of 883 kg/m3 at 15 oC, iodine value of 118.66 g I2/100 g, kinematic viscosity of 4.93 mm2/s at 40 oC, and oxidation stability of 0.32 h.