响应面法优化大豆油下脚料制备生物柴油工艺的研究

Response Surface Methodology to Optimize Production of Biodiesel from the Mixture of Soybean Oil Sediments and Soapstock

随着全球性能源的日益短缺与环境的逐渐恶化,生物柴油作为一种无毒、可生物降解和再生的替代燃料正受到越来越多的关注。研究了利用大豆油下脚料(油脚、皂脚混合物)制取生物柴油的工艺过程。先用乙醚室温下萃取下脚料,料液比1∶2(g:mL),萃取时间2 h。离心后分为3层,上层有机相再经丙酮萃取分离出磷脂和中性油,磷脂作为高附加值副产品回收再利用以降低生物柴油的生产成本。分离出的皂相经酸化转化为混合脂肪酸,混合脂肪酸用于酸催化的酯化反应。利用响应面法对酯化反应工艺参数进行了优化,并得到回归方程。方差分析结果表明:在各影响因素中,醇酸摩尔比对转化率的影响最大,其次是反应温度和反应时间,醇酸摩尔比和反应温度的交互作用显著。酯化反应优化后的工艺条件为醇酸摩尔比为5∶1,催化剂(H2S04)添加量3%(wt.%),反应温度为87°C,反应时间4.74 h,在此条件下转化率达到92.5%。

As the global fossil fuel deficiency and environmental degradation are becoming more and more serious, biodiesel is received increasing attention as an alternative, non- toxic, biodegradable and renewable diesel fuel. The production of biodiesel from the mixture of soybean oil sediments and soapstock was investigated in this work. In the first step, the mixture was extracted with ethyl ether and the mixture was divided into three phases. Ratio of the weight of mixture to the volume of solvent was 1：2 （g ： mL）, and extracted at room temperature for 2 h. The organic top phase contained triglycerides and phosphatides was extracted with cooled acetone and the acetone insoluble （phosphatides）, a fairly high value by-product, was obtained,which could reuse and reduce the cost of biodiesel production. The triglycerides were also separated. In the second step, soap phase was then acidified with sulfuric acid to yield fatty acid. The mixed fatty acid was efficiently converted to methyl esters by acid-catalyzed esterification. The response surface methodology was used to optimize the esterification reaction conditions of fatty acid. Results showed the factors influence the esterification reaction was the molar ratio of methanol to oil, reaction temperature and reaction time, orderly. The molar ratio of methanol to oil and the reaction temperature had significant interaction. The optimal reaction were 5：1 methanol/fatty acid（mol/mol） with 3% H2SO4 （ wt% ） reacted at 87℃ for 4.74 h,giving a maximum ester yield of 92.5%.