黄连木油脂基生物柴油的合成及其性能分析

以黄连木油脂为原料,对预酯化和酯交换两步法制备生物柴油的工艺进行了研究.通过正交实验,得出预酯化最佳工艺条件为:醇油摩尔比8∶1、催化剂加入量为0.8%、反应时间为3 h;酯交换最优工艺为:催化剂用量为0.6%、醇油摩尔比6∶1、反应时间为2 h、反应温度为50℃;此条件下制备的生物柴油得率达到92.3%;通过二聚化反应,所得生物柴油的主要性能指标均达到了国家标准GB/T 20828-2007.     

Continuous production of biodiesel fuel from vegetable oil using immobilized Candida antarctica lipase

Candida antarctica lipase is inactivated in a mixture of vegetable oil and more than 1∶2 molar equivalent of methanol against the total fatty acids. We have revealed that the inactivation was eliminated by three successive additions of 1∶3 molar equivalent of methanol and have developed a three-step methanolysis by which over 95% of the oil triacylglycerols (TAG) were converted to their corresponding methyl esters (ME). In this study, the lipase was not inactivated even though 2∶3 molar equivalent of methanol was present in a mixture of acylglycerols (AG) and 33% ME (AG/ME33). This finding led to a two-step methanolysis of the oil TAG: The first-step was conducted at 30°C for 12 h with shaking in a mixture of the oil, 1∶3 molar equivalent of methanol, and 4% immobilized lipase; the second-step reaction was done for 24 h after adding 2∶3 molar equivalent of methanol (36 h in total). The two-step methanolysis achieved more than 95% of conversion. When two-step reaction was repeated by transferring the immobilized lipase to a fresh substrate mixture, the enzyme could be used 70 cycles (105 d) without any decrease in the conversion. From the viewpoint of the industrial production of biodiesel fuel production, the two-step reaction was conducted using a reactor with impeller. However, the enzyme carrier was easily destroyed, and the lipase could be used only several times. Thus, we attempted flow reaction using a column packed with immobilized Candida lipase. Because the lipase packed in the column was drastically inactivated by feeding a mixture of AG/ME33 and 2∶3 molar equivalent of methanol, three-step flow reaction was performed using three columns packed with 3.0 g immobilized lipase. A mixture of vegetable oil and 1∶3 molar equivalent of methanol was fed into the first column at a constant flow rate of 6.0 mL/h. The eluate and 1∶3 molar equivalent of methanol were mixed and then fed into the second column at the same flow rate. The final step reaction was done by feeding a mixture of eluate from the second column and 1∶3 molar equivalent of methanol at the same flow rate. The ME content in the final-step eluate reached 93%, and the lipase could be used for 100 d without any decrease in the conversion.     

固定化脂肪酶催化废油合成生物柴油

研究了固定化假丝酵母99-125脂肪酶在有溶剂的体系下催化废油合成生物柴油过程中,油醇摩尔比、有机溶剂性质、底物浓度、体系含水量、甲醇流加等因素对反应过程的影响.研究结果表明,在最佳实验条件下,反应转化率最高可达92％,酶的使用寿命可达7批以上.     

Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase

Biodiesel derived from vegetable oils has drawn considerable attention with increasing environmental consciousness. We attempted continuous methanolysis of vegetable oil by an enzymatic process. Immobilized Candida antarctica lipase was found to be the most effective for the methanolysis among lipases tested. The enzyme was inactivated by shaking in a mixture containing more than 1.5 molar equivalents of methanol against the oil. To fully convert the oil to its corresponding methyl esters, at least 3 molar equivalents of methanol are needed. Thus, the reaction was conducted by adding methanol stepwise to avoid lipase inactivation. The first step of the reaction was conducted at 30°C for 10 h in a mixture of oil/methanol (1:1, mol/mol) and 4% immobilized lipase with shaking at 130 oscillations/min. After more than 95% methanol was consumed in ester formation, a second molar equivalent of methanol was added and the reaction continued for 14 h. The third molar equivalent of methanol was finally added and the reaction continued for 24 h (total reaction time, 48 h). This three-step process converted 98.4% of the oil to its corresponding methyl esters. To investigate the stability of the lipase, the three-step methanolysis process was repeated by transferring the immobilized lipase to a fresh substrate mixture. As a result, more than 95% of the ester conversion was maintained even after 50 cycles of the reaction (100 d).     

乌桕梓油酶法制备生物柴油的研究

分析了乌桕梓油和皮油的基本理化特性和脂肪酸组成。同时,以乌桕梓油为原料油,以杂醇油为酰基受体,初步探讨了脂肪酶催化制备生物柴油的研究,比较了无溶剂体系和叔丁醇体系合成生物柴油的效果。结果表明,乌桕梓油和皮油的基本理化性质差异明显,从两者脂肪酸组成分析,它们均适合于用作生物柴油原料。对于无溶剂体系和叔丁醇体系而言,当Novozym 435与Lipozyme TLIM脂肪酶复合比例为2∶4时,生物柴油转化率达到最高,分别为98.279%和76.334%。     

复合固定化脂肪酶催化麻疯树油生产生物柴油

对固定化复合脂肪酶催化麻疯树油合成生物柴油进行了研究,利用3因素5水平中心旋转设计的响应曲面法对反应条件进行了优化,研究了复合酶用量、复合酶配比及底物配比对反应的影响。优化结果为复合酶用量为0.27 g,N435占总酶质量的比例为0.15,乙酸甲酯与麻疯树油的摩尔比为10.10,预测生物柴油得率为72.55 %,与实际产率74.34 %吻合较好。并建立了复合酶催化合成生物柴油反应的动力学方程,反应为双底物抑制,符合乒乓机制。     

废食用油脂固定床酶法合成生物柴油研究

利用废食用油脂合成生物柴油,既能够实现废弃物的清洁利用,又能提供可再生的绿色能源。采用固定化假丝酵母脂肪酶为催化剂,在三级固定床反应器内,采用分级流加甲醇的方式,每级醇油摩尔比为1∶1,探讨了酶质量分数、溶剂质量分数、水质量分数、温度、反应液流速等与产物中甲酯质量分数的关系。实验结果表明,当油中酶、溶剂、水的质量分数分别为25%,15%,10%,反应液流速为1.2 mL/min,温度为45℃时,产物中甲酯质量分数达到最大值91.08%,其中油酸甲酯质量分数最高。产品经过精制后,理化性质符合美国和德国生物柴油标准,绝大多数指标优于我国0#柴油。     

硅基MCF材料固载脂肪酶转化餐饮废油产生物柴油

引言"地沟油"重返餐桌现象日益成为关系民众身体健康、社会和谐发展的焦点,开发合理有效处置方式,挖掘餐饮废油的剩余经济价值,是解决"地沟油"问题的根本出路。长链脂肪酸和低碳醇经过酯化反应后生成的脂肪酸酯,可以替代石油炼制的柴油作为车用燃料[1-2],即生物柴油。研究表明餐     

Utilization of green seed canola oil for biodiesel production

Increasing percentage of green canola seed every year is a serious problem for canola growers. Chlorophyll content of this oil is very high, which makes it more susceptible to photo‐oxidation and ultimately the oxidation stability of the oil is very reduced. Hence green seed canola oil is underutilized for edible purposes. The present work is an attempt to produce high‐quality biodiesel from green seed canola oil and methanol, ethanol and various mixtures of methanol and ethanol using KOH as a catalyst. A mixture of alcohols improved the rate of reaction. After transesterification of green seed canola oil using KOH, the chlorophyll content of the oil was decreased substantially (from 22.1 ppm to 10.3 ppm). Characteristics of the esters prepared from green seed canola oil were well within the limits of ASTM standards. Lubricity of the green seed oil esters was excellent (20% decrease in wear scar area) when added at 1 vol% to the base fuel. Oxidation stability is crucial for long‐term storage of the fuel. Oxidation stability index (OSI) of green seed esters was 4.9 h at 110 °C, which is much less than the European Standard (6 h at 100 °C). The low oxidation stability of green seed esters is attributed to its higher chlorophyll (10.3 ppm) content. An attempt was also made to reduce the chlorophyll content of the oil before transesterification using activated carbon treatment, and it was observed that chlorophyll content was reduced from 22.1 to 2.2 ppm. Copyright © 2006 Society of Chemical Industry     

固定化脂肪酶催化制备香叶树籽生物柴油研究

研究了Novozym 435和Lipozyme TLIM混合脂肪酶催化香叶树籽油制备生物柴油,2种酶按1:3质量比混合使用时,既可提高反应转化率,又可降低酶的使用成本.应用响应面优化法确定了固定化酶催化香叶树籽生物柴油的最优工艺参数,采用叔丁醇作为反应体系的溶剂,最优反应条件为反应温度38.5℃、甲醇与油摩尔比4:1、叔丁醇与油体积比1:1.5、酶用量为油质量的4%,此时反应转化率达90.09%.分析表明香叶树籽油的甘油三酯主要由短链脂肪酸甘油酯组成,生物柴油中原油的甘油三酯已完全转变成脂肪酸甲酯.     

Enzymatic acyl modification of phosphatidylcholine using immobilized lipase and phospholipase A2

Ethanol‐soluble (ES) lecithin mainly contains phosphatidylcholine (PC). The incorporation of caprylic acid into PC using immobilized phospholipase A₂ (PLA₂) and lipase was investigated. The Rhizomucor meihei lipase and the porcine pancreatic PLA₂ were immobilized on the hydrophobic resin Diaion HP‐20 and the modification was carried out in hexane as solvent. HPTLC with densitometer technique was successfully used for monitoring the production of structured phospholipids (PL) (ML‐type PC, MM‐type PC, and lysophosphatidylcholine; L: long‐chain fatty acid, M: medium‐chain fatty acid). The various parameters such as the effects of reaction temperature, enzyme loading, and the effect of molar proportion of substrate were studied in order to determine the optimum reaction conditions for the acidolysis reaction. The optimal operating conditions for the PLA₂‐catalyzed reaction were obtained as 50°C temperature, 50% (wt/wt of substrate) enzyme loading, and a 1:12 molar proportion of PC/caprylic acid. For the lipase‐catalyzed reaction, the optimized temperature was the same as for PLA₂, but the enzyme loading and molar proportion were slightly lower, i.e., 40 % w/w of substrate and 1:9 PC/caprylic acid, respectively. The effects of these parameters on the production of structured PL were compared. Under these optimal conditions, the ML‐type PC content was higher in the PLA₂‐catalyzed reaction, i.e., 45.29 mol%, and in the lipase‐catalyzed reaction it was 38.74 mol%.     

固定化脂肪酶催化菜籽油合成蜡酯

以菜籽油、鲸蜡醇为原料,采用实验室自制的固定化Candidia sp.99-125脂肪酶分别在有机溶剂和无溶剂体系下合成了蜡酯,在两种体系下对影响蜡酯合成的各种因素进行了比较研究,研究表明:以正己烷为反应介质,在40℃条件下反应12h,油醇摩尔比1∶2,酶量15%(质量分数,上同),水含量7.5%,蜡酯产率可达85.87%;无溶剂体系中在50℃条件下反应20h,油醇摩尔比1∶1.5,蜡酯产率可达80.68%。通过流加鲸蜡醇可以提高酶的使用寿命。     

Continuous production of biodiesel fuel from vegetable oil using supercritical methanol process

A system for continuous transesterification of vegetable oil using supercritical methanol was developed using a tube reactor. Increasing the proportion of methanol, reaction pressure and reaction temperature can enhance the production yield effectively. However, side reactions of unsaturated fatty acid methyl esters (FAME) occur when the reaction temperature is over 300 °C, which lead to much loss of material. There is also a critical value of residence time at high reaction temperature, and the production yield will decrease if the residence time surpasses this value. The optimal reaction condition under constant reaction temperature process is: 40:1 of the molar ratio of alcohol to oil, 25 min of residence time, 35 MPa and 310 °C. However, the maximum production yield can only be 77% in the optimal reaction condition of constant reaction temperature process because of the loss caused by the side reactions of unsaturated FAME at high reaction temperature. To solve this problem, we proposed a new technology: gradual heating that can effectively reduce the loss caused by the side reactions of unsaturated FAME at high reaction temperature. With the new reaction technology, the methyl esters yield can be more than 96%.     

固定酶法生产生物柴油

探讨了利用本实验室自制的Candidasp.99-125脂肪酶转酯化合成生物柴油的过程。深入研究了甲醇对反应的抑制作用,酶用量、溶剂、底物浓度、反应温度、时间、水含量、pH值对生物柴油合成的影响,以及反应中固定化酶的寿命等问题。试验结果表明,采用最佳转酯化反应条件和分批加入甲醇的工艺条件下,最高单批转化率可以达到96%,固定化酶的使用半衰期可达到200h以上。     

Structured lipids from rice bran oil and stearic acid using immobilized lipase from Rhizomucor miehei

The major objective of the present study was to prepare structured lipids rich in stearic acid from rice bran oil (RBO) using immobilized lipase (IM 60) from Rhizomucor miehei. The effects of incubation time and temperature, substrate molar ratio, and enzyme load on incorporation of stearic acid were studied. Acidolysis reactions were performed in hexane. Pancreatic lipase‐catalyzed sn‐2 positional analysis and tocopherol analyses were performed before and after enzymatic modification. The kinetics of the reaction was studied and maximum incorporation of stearic acid was observed at 6 h, at 37 °C, when the triacylglycerol and stearic acid molar ratio was maintained at 1 : 6 and the enzyme concentration was 10% of total substrates weight. Stearic acid in RBO after acidolysis was increased from 2.28 to 48.5%, with a simultaneous decrease in palmitic, oleic and linoleic acids. HPLC analysis of tocopherols and tocotrienols was carried out and their content in modified RBO was not significantly affected compared to that of native RBO. The oryzanol content of the modified RBO was reduced from 1.02 to 0.68%. Melting and crystallizing characteristics of the modified fat were studied using differential scanning calorimetry. The total solid fat content at 25 °C increased from 26.12 to 34.8% with an increase in stearic acid incorporation into RBO from 38 to 48%, but it was comparatively less than for cocoa butter and vanaspati. However, the modified RBO completely melted at 37 °C and was useful as plastic fat for various culinary purposes, bakery and confectionary applications. The results of the present study indicated that structured lipids prepared from RBO rich in stearic acid retained their beneficial nutraceuticals; in addition, they do not contain any trans fatty acids.     

Synthesis of monoglycerides by glycerolysis of rapeseed oil using immobilized lipase

Reaction conditions for the synthesis of monoglycerides (MG) by enzyme-catalyzed glycerolysis of rapeseed oil using Lipozyme® IM have been studied. Silica gel was used to adsorb the glycerol to overcome the problems of low glycerol solubility in the organic phase. An experimental design was used where temperature, time, the ratio of silica gel to glycerol (w/w), the water activity (a) _w , the isooctane concentration, and the ratio of glycerol to triglycerides (mol/mol) were varied. Response surface methodology was used to evaluate initial reaction rate and yield for the different products. The best yield of MG achieved under the studied conditions was 17.4% (mol fatty acid in substance/total mol fatty acid in mixture) (75°C, 20 h, silica gel/glycerol 2:1, a _w =0.17, 48% isooctane, glycerol/triglycerides 6:1). The same conditions yielded 36.8% diglycerides, 13.6% free fatty acids (FFA), and 36.9% triglycerides. This is at the same level as the equilibrium yield. The yield of MG is low compared to the final yield achieved with solid-phase glycerolysis. However, in solid-phase glycerolysis the reaction mixture becomes solid, and therefore the solid-phase process is not suitable for industrial application. The formation of FFA was very fast compared to the synthesis of MG. Equilibrium for FFA was reached within 2 h, and the yield was strongly affected by the a _w . Increasing a _w greatly increased the formation of FFA. In the a _w ratio 0.06–0.3, the yield of FFA increased from 4 to 19% while the yield of MG was nearly unaffected. As FFA is an undesired product, it is important to keep the a _w as low as possible.     

Synthesis of structured triglycerides from peanut oil with immobilized lipase

Structured triglycerides (ST) that contain medium- and long-chain fatty acids were synthesized by lipase-catalyzed interesterification between tricaprylin and peanut oil. To select appropriate enzymes, we investigated nine commercial lipase preparations for their ability to hydrolyze pure triglycerides as well as natural oils. Three microbial lipases from Rhizomucor miehei (RML), Candida sp. (CSL), and Chromobacterium viscosum (CVL) gave good results, and immobilized preparations were used in the interesterification. RML gave the highest yields of ST (73%, 40°C), although its hydrolytic activity toward triolein was low. As the temperature was raised to 50°C, the yield of ST increased to 79%. After 120 h reaction time, remaining activities were high for CSL (71%), moderate for CVL (48%), and low for RML (20%). Parts of this paper were presented as a poster at the Biochemical Engineering Conference IX, May 1995, Davos, Switzerland.