大豆油基生物柴油氧化动力学方程研究

作为衡量生物柴油品质的重要指标,氧化安定性优劣直接关系到生物柴油的应用前景。利用气相色谱及生物柴油氧化安定性测定仪测定了大豆油生物柴油在不同温度下脂肪酸甲酯质量浓度随时间的变化规律,得到了大豆油生物柴油的降解动力学曲线以及不同脂肪酸甲酯的反应速率常数K、活化能Ea,研究表明生物柴油氧化降解为拟一级反应;大豆油生物柴油、棕榈酸甲酯、油酸甲酯、亚油酸甲酯和亚麻酸甲酯的表观活化能分别为82.15、85.31、88.54、80.52、75.49 k J/mol,碳链长度缩短、不饱和双键增多会促进其氧化降解;生物柴油的氧化诱导时间与氧化速率常数的倒数成正比关系。     

生物柴油氧化前后成分分析的研究

分别以地沟油、橡胶籽油和小桐子油为原料制备生物柴油,测定了3种生物柴油的氧化稳定性,并采用傅里叶红外光谱及GC-MS分析氧化前后此3种生物柴油的成分。结果表明,地沟油生物柴油、橡胶籽油生物柴油和小桐子生物柴油的氧化诱导时间分别为1.61、0.81、1.05 h,远不能达到我国生物柴油国家标准的6 h;生物柴油主要成分是脂肪酸甲酯,氧化后脂肪酸甲酯中CC—H基团基本消失;地沟油生物柴油、橡胶籽油生物柴油和小桐子生物柴油主要由棕榈酸甲酯、亚油酸甲酯、油酸甲酯及硬脂酸甲酯组成,氧化前3种生物柴油中此4种脂肪酸甲酯总含量分别为93.07%、95.82%和97.68%,氧化后分别降为77.23%、84.51%和63.66%。氧化后生物柴油成分十分复杂,含有不同的醛、酸、酮、醇及小分子的酯等物质,且亚油酸甲酯的含量大大降低,证实了生物柴油氧化主要是含有不饱和双键或三键的脂肪酸甲酯的氧化。     

气相色谱法测定生物柴油中多种脂肪酸甲酯

研究了生物柴油中硬脂酸甲酯、油酸甲酯、亚油酸甲酯的气相色谱分析方法,确立了最佳分析条件.实验以水杨酸甲酯为内标,采用Hp-1大口径毛细管色谱柱,不分流进样,使生物柴油中多种脂肪酸甲酯得到良好分离,建立了一种简单、快速、准确的生物柴油测定方法.硬脂酸甲酯、油酸甲酯、亚油酸甲酯的平均回收率为95.00%～99.27%(n=5),相对标准偏差为0.64%～3.05%(n=5).     

热分析在生物柴油中的应用

在利用GC-MS分析石油柴油和生物柴油组成的基础上,应用热分析法研究石油柴油和生物柴油的挥发性和可燃性.结果表明:石油柴油主要为8～26个碳原子的烷烃,生物柴油主要为14～24个偶数碳原子的脂肪酸甲酯:豆蔻酸甲酯C14:0、棕榈酸甲酯C16:0、硬脂酸甲酯C18:0、花生酸甲酯C20:0、山嵛酸甲酯C22:0、木焦油酸甲酯C24:0、棕榈油酸甲酯C16:1、油酸甲酯C18:1、二十碳烯酸甲酯C20:1、芥酸甲酯C22:1、亚油酸甲酯C18:2和亚麻酸甲酯C18:3.随着升温速率的增加,生物柴油的挥发和分解向高温区移动.生物柴油在氮气气氛下发生热解,分为挥发与分解两个阶段;在空气气氛下发生燃烧,分为挥发与燃烧两个阶段.生物柴油比石油柴油难挥发,但可燃性比石油柴油好.     

双核酸性离子液体[DABCO-PS][HSO_4]催化蓖麻油制备生物柴油研究

研究合成了双核酸性离子液体[DABCO-PS][HSO_4],并将其用于催化蓖麻油酯交换制备生物柴油。优化后得离子液体前体[DABCO-PS]合成最佳条件为n(1,3-丙烷磺酸内酯)∶n(三乙烯二胺)=2∶1、反应温度60℃、反应时间3 h,在此条件下离子液体前体收率达93.4%。采用红外光谱、核磁共振和质谱对[DABCO-PS][HSO_4]进行表征,确定产物为目标离子液体。优化得到[DABCO-PS][HSO_4]催化蓖麻油制备生物柴油的最佳条件为n(甲醇)∶n(蓖麻油)=12∶1、离子液体用量4%(以蓖麻油质量计)、反应温度50℃、反应时间1 h,在此条件下生物柴油收率达90%。采用气相色谱确定生物柴油主要成分是棕榈酸甲酯、亚油酸甲酯、油酸甲酯、亚麻酸甲酯、硬脂酸甲酯和蓖麻油酸甲酯,且脂肪酸甲酯占生物柴油的90%以上。     

生物柴油及其柴油混合物的溶解性和橡胶兼容性研究

生物柴油具有良好的溶解能力.采用贝壳松脂丁醇值法(KB值法)测试了大豆油甲酯、棕榈油甲酯、菜籽油甲酯、麻疯树籽油甲酯的KB值及其与0#柴油混合物的KB值,研究了氟橡胶、丁腈橡胶、氯丁橡胶与棕榈油甲酯的兼容性.研究结果表明,大豆油甲酯、棕榈油甲酯、菜籽油甲酯和麻疯树籽油甲酯的KB值分别为77.6,79.7,78.7,76.1,0#柴油的KB值为21.6.它们的混合物的KB值与其组成变化呈线性关系,生物柴油的溶解能力明显强于0#柴油.氟橡胶与生物柴油有较好的兼容性,其次是丁腈橡胶.氯丁橡胶与生物柴油不具备兼容性.#柴油;混合物;溶解能力;橡胶兼容性     

小桐子生物柴油在氧化期间的特性分析

本研究通过Rancimat法加速氧化实验进行生物柴油氧化特性研究,并采用气相色谱-质谱联用仪(GC-MS)分析氧化期间的成分组成变化。研究结果表明:在小桐子生物柴油的加速氧化期间主要是含碳碳双键的脂肪酸甲酯被氧化,氧化期间会有醛、酮、分子质量较高的含氧化合物及其可溶性聚合物生成;小桐子生物柴油的氧化使其C和H的含量降低导致热值降低12.8%;小桐子生物柴油的氧化产物使其润滑性能变差,磨斑直径增加幅度较大,从184.14μm增至441.86μm;小桐子生物柴油的密度和运动黏度伴随着氧化分别增加3.3%和20.8%。     

正交法探讨制备生物柴油的优化条件

报道了大豆油在NaOH为催化剂的作用下通过甲醇酯交换反应生成脂肪酸甲酯即生物柴油的试验研究。考察了反应条件如醇油比、催化剂用量、反应温度、反应时间等的变化对生物柴油得率的影响。应用正交实验的方法找出大豆油酯交换反应的最佳反应条件为:反应温度40℃,醇油物质的量比6∶1,催化剂用量0.8%,反应时间60 m in。在此反应条件下生物柴油得率可达99.2%。实验所得的生物柴油主要质量指标已达到德国D INV51.606生物柴油质量标准。     

菜籽生物柴油合成反应程度的气相色谱法判断

以十三酸甲酯为内标,建立了菜籽生物柴油中主要脂肪酸甲酯的气相色谱测定法。进样中各脂肪酸甲酯含量在各自线性范围内的线性相关系数r≥0.9963、平均回收率在97.59%~101.42%、相对标准偏差在1.32%~2.89%。通过测定反应试样中的脂肪酸甲酯总量,再与原料油脂完全甲酯化产品中的甲酯总量相比较,可以准确地判断生物柴油合成反应程度。     

几种脂肪酸甲酯的热解特性及动力学研究

采用热重分析法研究了硬脂酸甲酯、油酸甲酯和亚油酸甲酯在氮气气氛中的热分解特性,并采用Coats-Redfern积分法对硬脂酸甲酯、油酸甲酯和亚油酸甲酯的热分解过程进行动力学分析,建立热分解模型。结果表明:硬脂酸甲酯和油酸甲酯的热分解过程表现为简单的一步分解,而亚油酸甲酯则呈现出较复杂的两步分解过程;随着升温速率提高,热分解区间向高温区移动,热分解活化能和指前因子呈现出较好的动力学补偿效应,且在不同升温速率下具有不同的热分解反应机理函数;模拟计算的热分解率与实验数据误差基本在10%左右。动力学模型能够很好地预测各脂肪酸甲酯热分解过程,为进一步扩大试验和生物柴油应用中的高温热分解衰变模型提供理论依据。     

The distribution of 4-hydroxy-hexenal and 4-hydroxy-nonenal in different vegetable oils and their formation from fatty acid methyl esters

The formation of 4-hydroxy-hexenal (HHE) and 4-hydroxy-nonenal (HNE) in eight vegetable oils was investigated at 180 °C. HHE was only detectable in soybean (SBO), rapeseed (RO) and linseed oils (LO). HNE was measured in all tested oils, but was found mainly in corn (CO), sunflower (SO) and soybean oil (SBO). Oil-dependent formation of HHE/HNE was remarkably observed. Furthermore, different fatty acid methyl esters in tricaprylin, as model oil systems, were constructed to demonstrate their characteristic contribution to HHE/HNE formation. As expected, HHE and HNE originated from the oxidative degradation of methyl linolenate (MLN) and methyl linoleate (ML) respectively. Whereas low concentrations of MLN (<5.0%) and ML (<1.0%) produced no detectable HHE/HNE. The results suggested MLN/ML could induce both HHE/HNE formation and pro-oxidation at higher concentrations. Unexpectedly, methyl stearate and methyl oleate slightly promoted HHE/HNE formation, which might be attributed to free radical transfer mechanisms during thermal oxidation.     

生物柴油组分与十六烷值关系研究

采用气相色谱/质谱联用仪对菜籽油甲酯(RME)、地沟油甲酯(WME)、棉籽油甲酯(CME)、棕榈油甲酯(PME)和大豆油甲酯(SME)5种不同生物柴油的组分进行了测定,并通过测定燃料自燃点的方法计算出5种生物柴油的十六烷值.通过对试验数据和相关文献的分析,提出了生物柴油十六烷值预测公式,通过与实测值相比较,证明预测公式可行.     

大豆生物柴油氧化稳定性影响因素的研究

以大豆生物柴油为原料,通过Rancimat酸败法测定大豆生物柴油氧化稳定性,研究了大豆生物柴油的不饱和度、制备过程和存储过程中相关因素对大豆生物柴油氧化稳定性的影响。结果表明:大豆生物柴油不饱和度越低,其氧化稳定性越好;大豆生物柴油中水分残留量和甲醇残留量越高,其氧化稳定性越差,甘油残留量对大豆生物柴油氧化稳定性的影响较小,因此大豆生物柴油中水分残留量应低于0.05%,甲醇残留量应低于0.2%;大豆生物柴油的氧化诱导期随温度的升高而迅速缩短,且随空气流量增加呈线性下降,金属离子对大豆生物柴油氧化降解起催化作用,光照和通风导致大豆生物柴油极易氧化,因此大豆生物柴油应在避光不通风条件下,低温存储在含金属离子少的碳钢容器中。     

Biodiesel fuel production from plant oil catalyzed by Rhizopus oryzae lipase in a water-containing system without an organic solvent

A new enzymatic method of synthesizing methyl esters from plant oil and methanol in a solvent-free reaction system was developed. It is anticipated that such plant oil methyl esters can be used as a biodiesel fuel in the future. Lipase from Rhizopus oryzae efficiently catalyzed the methanolysis of soybean oil in the presence of 4-30 wt% water in the starting materials; however the lipase was nearly inactive in the absence of water. The methyl ester (ME) content in the reaction mixture reached 80-90 wt% by stepwise additions of methanol to the reaction mixture. The kinetics of the reaction appears to be in accordance with the successive reaction mechanism. That is, the oil is first hydrolyzed to free fatty acids and partial glycerides, and the fatty acids produced are then esterified with methanol. Although R. oryzae lipase is considered to exhibit 1(3)-regiospecificity, a certain amount of 1,3-diglyceride was obtained during the methanolysis and hydrolysis of soybean oil by R. oryzae lipase solution. Therefore, the high ME content in the reaction mixture is probably attributable to the acyl migration from the sn-2 position to the sn-1 or sn-3 position in partial glycerides.     

应用脂肪酸甲酯快速筛选植物油中掺假地沟油

根据植物油和地沟油中脂肪酸酯存在方式的不同,建立植物油中地沟油掺假的快速筛选方法。植物油中脂肪酸是以甘油三酯的形式存在,地沟油中脂肪酸以脂肪酸甲酯的形式存在,利用气相色谱-质谱的全扫描模式,结合NIST 05标准谱库检索功能,对37 种脂肪酸甲酯进行测定。样品采用直接稀释-气相色谱-质谱全扫描分析脂肪酸甲酯,100 个植物油样品中均未检出脂肪酸甲酯;20 个地沟油样品中13 个检出肉豆蔻酸甲酯（C14∶0）、棕榈酸甲酯（C16∶0）和硬脂酸甲酯（C18∶0）等14 种脂肪酸甲酯,检出率为65%,且70%的检出脂肪酸甲酯的地沟油样品中脂肪酸甲酯种类多、含量较高。因此,若植物油样品脂肪酸甲酯种类多、含量高,则可判定为有地沟油掺假;若脂肪酸甲酯含量低或没有脂肪酸甲酯,则可以进一步用其他指标和方法进行检测,脂肪酸甲酯的检测方法可以作为地沟油掺假的快速粗筛方法。     

Synthesis of high fatty acid starch esters with 1‐butyl‐3‐methylimidazolium chloride as a reaction medium

In this work, high fatty acid esters of corn starch were synthesized by reacting the starch with fatty acid methyl ester using 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) ionic liquid (IL) as reaction media. The effect of reaction variables such as the catalyst amount, molar ratio of fatty acid methyl ester/anhydroglucose unit (AGU) in starch, pyridine/AGU molar ratio, reaction temperature, as well as reaction time on the degree of substitution (DS) of starch esters was investigated. The experimental results showed that the DS value of the obtained starch esters could be varied depending on the process conditions. In the optimum reaction condition, the achieved maximum DS of starch laurate and starch stearate was 0.37 and 0.28, respectively, at a reaction temperature of 110°C for starch laurate and 120°C for starch stearate for a reaction duration of 2 h. Furthermore, the starch esters were characterized by FTIR, SEM, and X‐ray diffractometry (XRD) techniques, respectively. Results from FT‐IR spectroscopy suggested that the hydroxyl groups in the starch molecules were converted into ester groups. SEM and XRD studies showed that the morphology and crystallinity of starch esters were disrupted largely in the IL medium under the reaction conditions.     

Relationship between chlorophyll a and β-carotene in a lipid-containing model system during illumination

The relationship between chlorophyll a (Chl a) and β-carotene during illumination in the presence of fatty acid esters, methyl stearate methyl oleate and methyl linoleate was studied. Mixtures of Chl a, β-carotene and fatty acid esters were exposed to a 40 w light for 3 h. Isomerization and degradation reations of Chl a and β-carotene were monitored using HPLC with diode array detection Three isomers of Chl a and four cis isomers of β-carotene were separated and detected. Both the degradations of total amount of Chl a and β-carotene fit the first-order model. The degradation rate of total amount of β-carotene was highest in methyl stearate, followed by in methyl oleate and in methyl linoleate, while a reverse order was observed for the degradation rate of total amount of Chl a. In the presence of three fatty acid esters, Chl a is more susceptible to isomerization and degradation than β-carotene, and the degradation rates for both Chl a and β-carotene are significantly different (p < 0.05).     

液相色谱法测定生物柴油中多种脂肪酸甲酯

采用液相色谱法分离,液相色谱—质谱联用及标准品对照法对由菜籽油制备生物柴油中各种脂肪酸甲酯进行定性,并利用外标法建立准确测定生物柴油中各种脂肪酸甲酯组成及含量方法。试验结果表明,利用该法,生物柴油中各脂肪酸甲酯均能达到基线分离,且线性关系良好,相关性系数均在0.998以上,回收率达95.4%～104.1%;该法简单快速、准确性好。