生質柴油為從植物油或動物脂肪製造之再生燃料。使用精製植物油為生產生質柴油之原料不利於未來食物之永續性。 以廢食用油取代植物油可紓緩此問題。以傳統酸、鹼催化法將廢食用油轉換成生質柴油時，由於廢食用油中高含量之水及游離脂肪酸將會造成問題。兩步驟無觸媒法，亦即水解-酯化，可用來處理此問題。本研究利用合成之含銅廢水來水解廢食用油，再進行酯化反應。在水解溫度為225°C、水對三甘油酯莫耳比為30:1、反應時間為8小時，使用500 mg/kg CuSO4溶液可得到脂肪酸產率約80%。水解過程中，CuSO4 透過離子交換與脂肪酸反應產生H2SO4及疏水性溶於油相之Cu皂鹽。透過從水相轉移Cu2+到油相可得到50%移除率，經過5次批式反應此數字可增加至98.9%。將水解油所得脂肪酸酯化之最佳條件為溫度219.7°C、甲醇對脂肪酸莫耳比12:1、反應時間131.6分鐘，此時可得含低濃度皂鹽之生質柴油，其產率為96-97%。

Biodiesel is a renewable fuel derived from vegetable oils or animal fats. Common use of refined vegetable oils as oil feedstock for biodiesel is threat to the sustainability of food in the future. Replacing refined vegetable oils with waste cooking oil potentially solves this problem. Despite of the economic and environmental benefits in the use of waste cooking oil, typical acid- and base-catalyzed biodiesel production process from waste cooking oil often find some problems related to the considerable moisture and free fatty acid content in the waste cooking oil. Two steps non-catalytic process namely hydrolysis-esterification has been proposed to overcome this problem. This study utilized synthetic Cu wastewater for hydrolysis of waste cooking oil prior to the esterification process. Hydrolysis at 225°C and water to triglycerides molar ratio of 30:1 for 8 h using 500 mg/kg CuSO4 solution was found to produce considerable fatty acid yield about 80%. During hydrolysis, CuSO4 underwent ion exchange reaction with fatty acids to produce H2SO4 and hydrophobic Cu soap that tended to dissolve in the oil phase. Transfer of Cu2+ from water to oil phase brought about 50% of removal, which could be extended to 98.9% after 5 series of batch reactions. Esterification of hydrolyzed oil was optimum at temperature of 219.7°C, methanol to total fatty acid molar ratio of 12:1, and reaction time of 131.6 min. Optimum biodiesel yield achieved was about 96-97% with low Cu soap concentration.

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