Lipozyme TL100L催化米糠酸化油制备 生物柴油的工艺研究Preparation of biodiesel from acidified rice bran oil catalyzed by Lipozyme TL100L

旨在为米糠酸化油的产业化应用提供参考，以米糠酸化油为原料，经丙酮提取预处理后，采用酶法催化制备生物柴油。通过单因素实验考察脂肪酶种类、酶添加量、醇油物质的量比和反应温度对生物柴油产率的影响，结合正交实验对生物柴油制备的工艺条件进行优化，并采用分子蒸馏对生物柴油进行精制，同时对精制生物柴油进行表征。结果表明：米糠酸化油经预处理后，过氧化值、谷维素及不皂化物含量无显著变化，酸值、皂化值显著升高，水分及挥发物含量、磷脂含量、灰分和皂含量显著降低；生物柴油制备的最优工艺条件为醇油物质的量比3∶ 1、液体脂肪酶Lipozyme TL100L添加量4%、反应温度30 ℃、反应时间4 h，在此条件下生物柴油产率达（86.77±0.54）%，经分子蒸馏纯化后脂肪酸甲酯含量达（97.00±0.04）%；精制生物柴油理化指标均符合GB 25199—2017 要求；傅里叶红外光谱分析证实了产物中含脂肪酸甲酯，热重分析表明精制生物柴油在178.0~293.2 ℃区间内失重最快，差示扫描量热分析表明-37.5～-47.2 ℃的峰与不饱和脂肪酸甲酯的晶体有关，-7.9～-3.7 ℃的峰与饱和脂肪酸甲酯的晶体相关，生物柴油的结晶起始温度为-8.87 ℃。综上，以米糠酸化油为原料采用酶法制备生物柴油具有极大的发展潜力。Aiming to provide reference for the industrial application of acidified rice bran oil, biodiesel was prepared by enzyme catalysis of acetone extract of acidified rice bran oil. The effects of lipase type, enzyme dosage, alcohol-oil molar ratio and reaction temperature on biodiesel yield were investigated through single factor experiments. The process conditions for biodiesel preparation were optimized by orthogonal experiments. The biodiesel prepared was refined by molecular distillation, and the refined biodiesel was characterized. The results showed that after the pretreatment of the acidified rice bran oil with acetone extraction, the peroxide value, oryzanol content and unsaponifiable matters content did not change significantly, the acid value and saponification value increased significantly, and the contents of moisture and volatile matter, phospholipid, ash and soap reduced significantly. The optimal process conditions for biodiesel preparation were as follows: alcohol-oil molar ratio 3∶ 1, liquid lipase Lipozyme TL100L dosage 4%, reaction temperature 30 ℃, and reaction time 4 h. Under the optimal conditions, the biodiesel yield reached (86.77±0.54)%, and the content of fatty acid methyl ester reached (97.00±0.04)% after purification by molecular distillation. The physicochemical indexes of refined biodiesel were in accordance with the requirements of GB 25199-2017. Fourier infrared spectroscopy (FTIR) analysis confirmed that the product contained fatty acid methyl ester, thermogravimetric (TG-DTG) analysis showed that the weight loss of refined biodiesel was the fastest in the temperature interval of 178.0-293.2 ℃; differential scanning calorimetry (DSC) analysis showed that the peaks at temperatures from -37.5 ℃ to -47.2 ℃ were related to the crystals of unsaturated fatty acid methyl ester, and the peaks at temperatures from -7.9 ℃ to -3.7 ℃ were related to the crystals of saturated fatty acid methyl ester, and the crystallisation starting temperature of biodiesel was -8.87 ℃. In conclusion, the enzymatic preparation of biodiesel from acidified rice bran oil has great potential for development.