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1、西北师范大学 硕士学位论文 固定化脂肪酶催化酯交换反应合成生物柴油的研究 姓名：王冰 申请学位级别：硕士 专业： 指导教师：王云普 2008-05 摘 要 摘 要 生物柴油，即脂肪酸甲酯，是以动植物油为原料生产的可再生绿色能源。 目前生物柴油的工业化生产均采用化学法，这种方法存在醇必须大大过量、能耗 高、产物难于回收和废碱液污染环境等缺点，并且对原料的要求高，导致生产成 本过高。为此，酶法生产生物柴油在国内外受到广泛关注，酶法生产生物柴油具 有反应条件温和、醇用量小、产物易分离和无污染排放等优点。目前国内酶法相 关的研究主要集中在精制豆油方面，而对其它丰富的植物油尚未触及。因此，本 文选取棉籽
2、油、沙蒿油为原料对固定化脂肪酶(Candida Antarctica)催化制取生物 柴油的酯交换反应条件进行了较为系统的研究，具体工作如下: （1）首次以沙蒿多糖-壳聚糖复合磁性微球为载体，采用物理吸附法固定化 脂肪酶，对固定化过程中对酶活力有影响的各种因素做了研究，对固定化酶做了 部分表征，以及对固定化酶的部分理化性质最佳 PH, 最佳温度，酶的热稳定性 以及表观米氏常数与游离酶的做了比较，固定化酶的 Km 小于游离酶的 Km，固 定化酶的最佳 PH 和最佳温度分别为 8.0 和 50，而且固定化脂肪酶具有良好的 热稳定性，可重复使用。 （2）对固定化脂肪酶催化棉籽油和沙蒿油制备生物柴油进行
3、了条件实验。 通过条件实验，得出：反应时间 36h, 反应温度在 45时，生物柴油转化率达到 最高；当固定化酶浓度为 5mg/25ml，生物柴油转化率已达峰值；当反应体系的 醇油比为 3： 1 时， 生物柴油转化率达到最大， 反应 12h 分别达到 53.0%和 29.1%， 增加或减小醇油比转化率均下降； 两种原料均不适合加入水分； 正己烷、 石油醚、 乙醚三种不同有机溶剂中， 正己烷可显著提高酶的活性， 而体系不加有机溶剂时， 酶几乎失去催化活性；在醇油比为 3：1，甲醇投加总量一致的情况下，甲醇一 次性加入时反应转化率较低，当总反应时间为 24h 时，甲醇分 3 次投加，转化率 可达到最
4、大 85.9%和 74.3%，如果再增加醇投加次数，反应转化率无明显变化； 摇床转速达到 200rpm-250rpm 时，转化率达到最高值。 最终通过试验确定了最佳方案为:油酯/甲醇=1:3 (mol:mol) ,分三次等摩尔加 入，酶溶液浓度 5/25（mg/ml),以正己烷为溶剂，加入一定量的变色硅胶，反应 时间为 36h，温度 45，转速 200rmp-250rmp, 棉籽油的转化率达到 92.1%，沙 蒿油的转化率达到 75.8% 。 关键词：复合磁性微球，固定化脂肪酶，棉籽油，沙蒿油，酯交换，生物柴油 ABSTRACT Biodiesel, fatty acid alkyl este
5、r, is made from renewable bioenergy such as vegetable oils and animal fats. Although conventional chemical technology using alkaline catalysts has been applied to the industrial production of biodiesel fuel,there are several drawbacks to this approach, including excessive methanol, high energy consu
6、mption, difficulties in the recovery of products,environmental pollution caused by lye exclusion, strict requests for material and so on, and all of them reduce exorbitant cost. Compared with those, the enzymatic transesterification of biodiesel attracts widely attention because of circumventing the
7、se problems and lots of advantages, such as mild reaction conditions, low dosage of methanol, easy recovery of products and no waste production and so on. Presently, the domestic studies about the enzymatic transesterification mainly concentrate on the soybean oil so far reported, and other rich fee
8、dstock still doesnt touch. Based on this context, the transesterification conditions from Cotton seed oil and Artemisia seed oil by the immobilized lipase (Candida Antarctica) were studied in this paper. The works are listed as follow: (1) Lipase from Candida Antarctica was immobilized on composite
9、magnetic microsphere by physical adsorption. In this article, different factors which effect enzymatic activities was investigated by measuring the hydrolysis of olive oil, and comparative studies of PH ,temperature, thermal stability and apparent Km between free lipase and immobilized lipase were c
10、onducted. The value of apparent Km of immobilized lipase was lower than that of the free lipase. The optimum PH and temperature of the immobilized lipase were 8.0 and 50 . Meanwhile, the immobilized lipase has a good thermal stability, adaptability and reusability. (2) The optimum conditions for the
11、 preparation of biodiesel using immobilized lipase catalyzing Cotton seed oil and Artemisia seed oil were studied,the results showed that, the reaction time 36h ,the optimal reaction temperature 45, the conversion reached maximum.Using level of enzyme 5mg/25ml (lipase/water)for immobilization, the c
12、onversion also reached maximum.The ratio of the methanol and oil 3:1,the conversion reached 53.0%and 29.1% in 12h respectively.Water addition were not favorable for the reaction .Among n-hexane,petroleum ether and aether,the activity of lipase was improved in the n-hexane,while there is no organic s
13、olvent added,the catalytic activity would be lost.When the ratio of methanol and oil was 3:1,the methahol amount was consistent,the conversion of one-time adding was lower,if it was added for 3 times in 24h,the conversion reached as high as 85.9%and 74.3% respectively,the more times of the alcohol a
14、dded,the yield had no obvious changes.The optimal rotating speed 200-250rpm, the conversion reached maximum. The results show that the optimal reaction conditions are: the molar ratio of methanol to oil 3:l ,flinging methanol for 3 time,enzymy concentration 5mg/25ml(lipase/water) for immobilization,
15、 solvent n-hexane , adding some silica gel,the reaction temperature 45 and reaction time 36h, the rotation rate 200-250rpm. the conversion of biodiesel can reached 92.1%and 75.8% respectively. Keyword: composite magnetic microsphere, immobilized lipase, cotton seed oil artemisia seed oil, transester
16、ification ,biodiesel 独创性声明 本人声明所呈交的论文是我个人在导师指导下进行的研究工作 及取得的研究成果。尽我所知，除了文中特别加以标注和致谢的地方 外，论文中不包括其他人已经发表或撰写过的研究成果，也不包含为 获得西北师范大学或其他教育机构的学位或证书而使用过的材料。 与 我一同工作的同志对本研究所做的任何贡献均已在论文中作了明确 的说明并表示了谢意。 签名： 日期： 关于论文使用授权的说明 本人完全了解西北师范大学有关保留、 使用学位论文的规定， 即： 学校有权保留送交论文的复印件，允许论文被查阅和借阅；学校可以 公布论文的全部或部分内容，可以采用影印、缩印或其他复制手段保 存论文。 （保密的论文在解密后应遵守此规定） 签名： 导师签名： 日期： 硕士学位论文 王冰 固定化脂肪酶催化酯交换反应合成生物柴油的研究 1 第一章 文献综述 第一章 文献综述 11 引 言 11 引 言 能源安全是国家战略安全保障基础之一，1998 年至 20
