大豆油生物柴油低温流动性能影响的研究

以大豆油为原料采用碱催化酯交换法合成生物柴油，测定了其酸值、游离甘油、总甘油、灰分、黏度和磷含量等指标。实验表明,共存的甲醇、水分和甘油酯对生物柴油的低温流动性能影响极少，饱和脂肪酸甲酯的同时析出对生物柴油低温流动性能起关键作用。考察了5种柴油降凝剂、0号和20号柴油以及乙醇对生物柴油低温流动性能的影响。0号柴油有效地改善生物柴油黏度，但对其低温流动性能影响不大。20号柴油和乙醇能显著降低生物柴油的凝点、倾点、冷滤点和黏度。其中3种降凝剂有效降低生物柴油的凝点和倾点，1种降凝剂能小幅度改善冷滤点，5种降凝剂都能使生物柴油的黏度小幅上升。     

几种生物柴油的制备及其流变学性能的比较

以六种常见的动植物油脂为原料,制备生物柴油并测定其脂肪酸甲酯分布、凝点和冷滤点值。以动态流变仪为主要研究手段,研究了六种生物柴油的流体性能及相关影响因素。结果表明,生物柴油的凝点和冷滤点值受其脂肪酸甲酯分布的影响,饱和脂肪酸甲酯含量高的生物柴油,其凝点和冷滤点值也相应较高。流变学测定实验表明,六种生物柴油样品的流体性能受温度和剪切速率的影响。在较低的剪切速率范围内表现为典型的非牛顿流体行为,而在较高的剪切速率下则表现为牛顿流体行为。当流体温度高于生物柴油的相变温度时,六种生物柴油的表观黏度无明显差别,说明在该温度条件下生物柴油的脂肪酸甲酯分布对其流体黏度值影响不大;当流体温度接近其相变温度时,生物柴油流体黏度出现突跃式升高且其突变温度高于其冷滤点温度。     

超高效液相色谱法测定生物柴油中的11种脂肪酸及脂肪酸甲酯

建立了采用超高效液相色谱(UPLC)-蒸发光散射检测器(ELSD)测定生物柴油中11种常见的脂肪酸及脂肪酸甲酯含量的方法。这11种常见的脂肪酸及脂肪酸甲酯为豆蔻酸、亚油酸、棕榈酸、油酸、亚麻酸甲酯、硬脂酸、亚油酸甲酯、棕榈酸甲酯、油酸甲酯、芥酸和硬脂酸甲酯。样品经提取后用甲醇溶解,采用Acquity UPLC BEH Phenyl C18柱(100 mm×2.1 mm,1.7 μm)分离,乙腈-水（体积比为3∶1)混合液为流动相进行等度洗脱,采用的ELSD条件为增益80,漂移管温度为45 ℃,载气压力为172 kPa,雾化器为冷却模式,并用外标法进行定量分析。结果表明,在一定的质量浓度范围内,峰面积的对数和质量浓度的对数线性关系良好。与其他检测生物柴油成分的方法相比,该方法简单,分离效果好,速度快,特别是此方法可以同时实现脂肪酸及脂肪酸甲酯的分离,并进行定量分析,能有效测定反应的进行程度,从而满足生物柴油工艺研究的需要。     

气相色谱法在生物柴油生产工艺研究中的应用

综述了气相色谱法在生物柴油生产工艺研究中的应用,包括反应产物和生物柴油产品中脂肪酸甲酯含量和分布的测定,单脂肪酸甘油酯、二脂肪酸甘油酯和三脂肪酸甘油酯含量的测定,游离脂肪酸含量的测定以及微量甲醇含量的测定等。讨论了进样方式、色谱柱类型、硅烷化等因素对反应产物组成测定的影响;提出了一种采用双柱压力反吹的方式测定生物柴油产品中微量甲醇含量的方法：采用正丙醇作内标,甲醇与内标通过预切柱进入分析柱后,通过压力变化,将其余组分通过分流出口反吹出色谱系统;采用极性聚乙二醇色谱柱测定了8种不同植物油中脂肪酸甲酯的含量和分布。     

用X射线衍射图研究柴油低温流动改进剂的作用

通常,柴油中含有15%～30%的正构烷烃。在低温下,柴油中大分子量的蜡以晶体形式析出,可堵塞导管和滤清器,导致了柴油机供油的困难[1]。柴油在低温下的流动性能不仅关系到柴油机燃料供油系统在低温下能否正常供油,而且与柴油在低温下的储存和运输等作业能否进行有密切的关系。加入低温流动改进剂改善柴油的低温流动性能,以其成本低,操作简便而成为解决柴油低温流动性能的首选方法,并在工业上得到广泛应用[2]。柴油在低温下蜡的析出直至影响其流动性能的过程是一个蜡结晶的过程,由于蜡的组成复杂,其结晶过程也很复杂[3]。用X射线衍射法分…     

超声作用下KF/CaO催化酯交换反应制备生物柴油

等体积浸渍法制备了KF/CaO固体碱催化剂,用于催化大豆油与甲醇酯交换反应制备生物柴油,在反应体系中引入超声作为辅助条件。研究表明,KF/CaO催化活性高。在超声的辅助作用下,酯交换反应速率加快,生物柴油的收率提高。实验考察了反应条件对产品中脂肪酸甲酯含量的影响。醇油摩尔比为12∶1,反应温度65℃,催化剂与大豆油的质量比为3%,反应1 h,超声频率20 kHz,超声声强1.01 W/cm2,在此反应条件下,产品中脂肪酸甲酯的质量分数达到99.6%。     

低温下生物柴油的胶凝特性研究

利用流变仪在小振幅振荡剪切模式下对地沟油、花生油和大豆油生物柴油的胶凝特性进行了研究。结果表明,低温下生物柴油不仅具有冷却胶凝特性,还表现出明显的等温胶凝特性。分析了冷却速率和剪应力对地沟油生物柴油胶凝特性的影响。结果表明,静态降温时降温速率越大,生物柴油的胶凝温度越低,降温及恒温静置过程中同一温度下的胶凝结构越弱。相同降温速率下,生物柴油的胶凝结构和胶凝温度随剪应力的增加而降低,但经受不同剪应力作用的生物柴油恒温静置后胶凝结构相差不大。降温过程中施加的剪应力较小时,冷却胶凝结构随降温速率的增大而降低;剪应力较大时,冷却胶凝结构随降温速率的增大而加强。不管施加的剪应力多大,等温胶凝结构随降温速率的增大而加强。     

酸性离子液体催化脂肪酸甲酯聚合制备二聚酸甲酯

 以 Brönsted-Lewis 酸性离子液体为催化剂, 用于催化生物柴油中不饱和脂肪酸甲酯聚合制备二聚酸甲酯反应, 考察了催化剂种类、催化剂用量、反应温度和时间等因素对聚合反应性能的影响, 得到较佳的反应条件. 结果表明, 当以 1-(3-磺酸)-丙基-3-甲基咪唑氯锌酸盐[HO3S-(CH2)3-mim]Cl-ZnCl2 (ZnCl2 摩尔分数为 0.67) 为催化剂, 生物柴油 15 g, m(生物柴油):m(离子液体) = 15:1, 于 240 oC 下反应 6 h 时, 二聚酸甲酯收率为 63.2%, 其中三聚体含量小于 5%. 另外, 该催化剂重复使用 5 次后, 二聚酸甲酯收率仍超过 63%, 表明其具有较好的重复使用性能. 离子液体的 Brönsted 和 Lewis 酸位的协同效应显著提高了其催化活性.     

近红外光谱方法预测生物柴油主要成分

采用近红外光谱快速测定法对生物柴油的成分(脂肪酸甲酯、单甘酯、二甘酯、三甘酯和甘油)进行了研究.采用气相色谱方法获得其成分的基础数据,通过偏最小二乘方法与近红外光谱数据进行回归运算,分别建立以文冠果油生物柴油为例的单原料油校正模型及多种原料油生物柴油的混合校正模型,并以花椒油生物柴油为例考察了校正模型的适用性.结果表明: 通过偏最小二乘方法可以建立适合多种原料油生物柴油的通用校正模型.对于新型生物柴油,向校正集中添加10个以上样本,扩充校正模型后,便可较为准确地测定这类新生物柴油样本的成分含量.此方法分析速度快、成本低、操作便捷、重复性好,适合于生物柴油生产过程的中间控制分析.     

生物柴油的催化改性对其冷滤点的影响

利用HZSM-5型分子筛作为催化剂,在250℃～350℃、0.01MPa～0.04MPa的条件下,对生物柴油的主要组分油酸甲酯、棕榈酸甲酯、硬酯酸甲酯、亚油酸甲酯、月桂酸甲酯进行催化改性,以达到降低生物柴油冷滤点（CFPP）的目的。实验研究了反应温度和反应真空度对各脂肪酸甲酯产物的冷滤点、结炭率、碘值的影响,以该实验数据为依据,将动物油经过酯交换制备的生物柴油（AFE）进行催化改性。结果表明,在300℃~350℃,对饱和脂肪酸甲酯改性有很好的降凝效果,产物碘值升高;油酸甲酯通过改性,也取得了很好的降凝效果,产物碘值下降,在该反应条件下改性饱和脂肪酸甲酯和油酸甲酯催化剂的结炭率保持在5%以下;而亚油酸甲酯仅在350℃时改性才有降凝效果,且结炭率在10%以上。生物柴油（AFE）催化改性达到最佳降凝效果的条件为300℃~325℃,0.01MPa,改性后的的酸值小于0.6mg/g,冷滤点下降了19℃,碘值（I.V）为44.32g/100g,运动黏度（μ_t）为4.397mm²/s,并且催化剂结炭率保持在5%以下。     

Synthesis of Biodiesel from Palm Oil in Capillary Millichannel Reactor: Effect of Temperature,Methanol to Oil Molar Ratio,and KOH Concentration on FAME Yield

Application of microtube reactor for the continuous synthesis of biodiesel has been widely studied due to excellent performance in liquid-liquid phase reaction. In order to commercialize biodiesel production, integration of microtube reactor is highly recommended. Therefore, in this study, synthesis of biodiesel was carried out in capillary millichannel reactor with inner diameter of 1.59 mm using methanol and potassium hydroxide (KOH) as base catalyst with palm oil as a feedstock. The influences of reaction temperature, methanol to oil molar ratio, and KOH concentration on the production of fatty acid methyl ester (FAME) were examined. The highest FAME yield was achieved at 60 ˚C with 23:1 methanol to oil molar ratio and 5 wt% of KOH concentration.     

Biodiesel Production via the Transesterification of Soybean Oil Using Waste Starfish (Asterina pectinifera)

Calcined waste starfish was used as a base catalyst for the production of biodiesel from soybean oil for the first time. A batch reactor was used for the transesterification reaction. The thermal characteristics and crystal structures of the waste starfish were investigated by thermo-gravimetric analysis and X-ray diffraction. The biodiesel yield was determined by measuring the content of fatty acid methyl esters (FAME). The calcination temperature appeared to be a very important parameter affecting the catalytic activity. The starfish-derived catalyst calcined at 750 °C or higher exhibited high activity for the transesterification reaction. The FAME content increased with increasing catalyst dose and methanol-over-oil ratio.     

Effect of temperature and composition on density,viscosity and thermal conductivity of fatty acid methyl esters from soybean,castor and Jatropha curcas oils

This work is focused on experimental determination of density, viscosity and thermal conductivity as a function of temperature and composition for fatty acid methyl esters (FAME) from soybean, castor and Jatropha curcas oils. Results show that an increase in temperature, over the range of (273 to 363) K, resulted in a decrease of all properties studied. FAME from soybean and J. curcas oils presented similar rheological behaviour, while FAME from castor oil presented higher values for density and viscosity. Density, dynamic viscosity and thermal conductivity data for all systems obtained here were correlated using empirical equations with good agreement between experimental and calculated values. Experimental data presented here may be useful as a database for specification purposes and equipment design and plant operation in the biodiesel industry.     

Identification of minor C18 triene and conjugated diene isomers in hydrogenated soybean oil and margarine by GC-MI-FT-IR spectroscopy

Vegetable oils are partially hydrogenated in order to produce palatable products of suitable plasticity. The constituents of these new dietary products are complex mixtures of fatty acid isomers with different nutritional properties. A rapid method is described for separating and identifying fatty acid methyl ester (FAME) isomers of linolenic (octadecatrienoic, 18:3) acid and of conjugated octadecadienoic (18:2) acid, minor species found in hydrogenated soybean oil and margarine, by capillary gas chromatography-matrix isolation-Fourier transform-infrared (GC-MI-FT-IR) spectroscopy. FAMEs of 18:3 acid isomers in margarine, soybean oil hydrogenated in our laboratory, and isomerized linolenic acid were identified by this method, and MI-FT-IR spectra of FAME geometric isomers of octadecatrienoic and conjugated octadecadienoic acids are reported for the first time. Five major C18 triene GC peaks are found in chromatograms of isomerized methyl linolenate, representing species with tri-cis and tri-trans configurations and three species with cis-trans mixed configurations. FAME isomers with these configurations are also found for a hydrogenated soybean oil having an iodine value of 111. Methyl linolenate (tri-cis) is no longer found when soybean oil is further hydrogenated to an iodine value of 96. IR spectra characteristic of a tri-trans isomer are obtained for two test samples with iodine values of 111 and 96. Besides methyl linolenate, only isomers with a mono-trans di-cis configuration are found for the margarine analyzed. Conjugated cis-trans and trans-trans 18:2 FAME isomers are also found in all the hydrogenated soybean oil and margarine analyzed.     

棉籽现场碱催化转酯化联产生物柴油和无毒棉粕

通过棉籽现场碱催化转酯化联产生物柴油和无毒棉粕,考察了棉仁中水的质量分数、粒径对产物中脂肪酸甲酯（FAME）的质量分数和棉粕中游离棉酚（FG）质量分数的影响;对反应过程中的醇油摩尔比、反应时间、催化剂用量、反应温度进行了单因素和正交实验考察。实验得到的反应适宜条件为,棉仁含水量在1.92%左右,棉仁粒径小于0.335mm,反应醇油摩尔比135∶1,反应3h,甲醇中氢氧化钠浓度0.10mol/L,反应温度30℃。在上述反应条件下,反应产物中甲酯的质量分数可达97%,棉粕中游离棉酚的质量分数为0.031%,低于FAO规定的国际标准。     

Catalytic conversions in green aqueous media: Part 4. Selective hydrogenation of polyunsaturated methyl esters of vegetable oils for upgrading biodiesel

This study deals with the influence of operating parameters on the selective hydrogenation of crude polyunsaturated methyl esters of linseed, sunflower and soybean oils in order to achieve high selectivities up to 79.8 mol% of monounsaturated (C18:1) fatty acid methyl esters (FAME) which is 1st generation biodiesel of increased oxidative stability, energy and environmental performance at a low pour point employing water-soluble Rh/TPPTS catalytic complexes [TPPTS = P(C₆H₄-m-SO₃Na)₃] in green aqueous/organic two-phase systems. This study also discloses the great potential of biphasic selective catalytic hydrogenation to produce 2nd generation biodiesel from polyunsaturated FAME of alternative, non-food oil feedstocks which are originally not suitable for biodiesel production or give poor quality biodiesel but combine the advantage that they would not affect food production. Because the mixture of methyl esters of linseed oil mainly consists of C18:3 FAME it constitutes a good model to investigate the effects of parameters on the whole spectrum of the stepwise hydrogenation: C18:3 (linolenates) → C18:2 (linoleates) → C18:1 (oleates)  C18:0 (stearate) and to obtain first information on the selective hydrogenation of alternative, non-food oils with a high C18:3 FAME content to make them suitable for 2nd generation biodiesel formulations.     

Influence of the storage on the thermo-oxidative stability of methyl and ethyl esters by PDSC

Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by base-catalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME.     

Comparison of GC stationary phases for the separation of fatty acid methyl esters in biodiesel fuels

The fatty acid methyl ester (FAME) content of biodiesel fuels has traditionally been determined using gas chromatography with a polar stationary phase. In this study, a direct comparison of the separation of FAMEs present in various biodiesel samples on three polar stationary phases and one moderately polar stationary phase (with comparable column dimensions) was performed. Retention on each column was based on solubility in and polarity of the phase. Quantitative metrics describing the resolution of important FAME pairs indicate high resolution on all polar columns, yet the best resolution, particularly of geometric isomers, is achieved on the cyanopropyl column. In addition, the separation of four C18 monounsaturated isomers was optimized and the elution order determined on each column. FAME composition of various biodiesel fuel types was determined on each column to illustrate (1) chemical differences in biodiesels produced from different feedstocks and (2) chemical similarities in biodiesels of the same feedstock type produced in different locations and harvest seasons.     

Comparison and optimisation of biodiesel production from <Emphasis Type="Italic">Jatropha curcas</Emphasis> oil using supercritical methyl acetate and methanol

In this study, biodiesel has been successfully produced by transesterification using non-catalytic supercritical methanol and methyl acetate. The variables studied, such as reaction time, reaction temperature and molar ratio of methanol or methyl acetate to oil, were optimised to obtain the optimum yield of fatty acid methyl ester (FAME). Subsequently, the results for both reactions were analysed and compared via Response Surface Methodology (RSM) analysis. The mathematical models for both reactions were found to be adequate to predict the optimum yield of biodiesel. The results from the optimisation studies showed that a yield of 89.4 % was achieved for the reaction with supercritical methanol within the reaction time of 27 min, reaction temperature of 358°C, and methanol-to-oil molar ratio of 44. For the reaction in the presence of supercritical methyl acetate, the optimum conditions were found to be: reaction time of 32 min, reaction temperature of 400°C, and methyl acetate-to-oil molar ratio of 50 to achieve 71.9 % biodiesel yield. The differences in the behaviour of methanol and methyl acetate in the transesterification reaction are largely due to the difference in reactivity and mutual solubility of Jatropha curcas oil and methanol/methyl acetate.