生物柴油在低温下析出晶体的热力学规律研究

以大豆油、地沟油、花生油生物柴油为研究对象,利用黏温曲线法得到了生物柴油的浊点,利用高速离心分离法结合气相色谱法得到生物柴油在不同温度下的结晶量及析出晶体的组成,研究生物柴油在低温下析出晶体的热力学规律。试验结果表明:生物柴油在低温下析出的晶体主要由饱和脂肪酸甲酯组成,且析出的晶体中高碳数脂肪酸甲酯的质量分数大于低碳数脂肪酸甲酯;生物柴油中饱和脂肪酸甲酯的含量越高,浊点越高,低温下的结晶量越多,黏度越大,低温流动性能越差。     

生物柴油组成与组分结构对其低温流动性的影响

在分析生物柴油分子结构的基础上,应用色-质联用仪、低温性能测试仪、溶液结晶原理和相似相溶原理研究生物柴油的低温流动性。提出了生物柴油是由高熔点饱和脂肪酸甲酯和低熔点不饱和脂肪酸甲酯组成的伪二元组分溶液的观点。基于46种生物柴油组成与冷滤点的实验结果,建立了相关性很好的冷滤点预测模型。研究表明,生物柴油主要由14～24个偶数碳链的脂肪酸甲酯组成,低温流动性主要取决于饱和脂肪酸甲酯的含量和分子结构;生物柴油的冷滤点随着饱和脂肪酸甲酯含量的增加呈线性增加,饱和脂肪酸甲酯烷基碳链越长增加幅度越大;根据组成可直接预测生物柴油的冷滤点。     

生物柴油组成与组分结构对其低温流动性的影响

在分析生物柴油分子结构的基础上,应用色-质联用仪、低温性能测试仪、溶液结晶原理和相似相溶原理研究生物柴油的低温流动性.提出了生物柴油是由高熔点饱和脂肪酸甲酯和低熔点不饱和脂肪酸甲酯组成的伪二元组分溶液的观点.基于46种生物柴油组成与冷滤点的实验结果,建立了相关性很好的冷滤点预测模型.研究表明,生物柴油主要由14～24个偶数碳链的脂肪酸甲酯组成,低温流动性主要取决于饱和脂肪酸甲酯的含量和分子结构;生物柴油的冷滤点随着饱和脂肪酸甲酯含量的增加呈线性增加,饱和脂肪酸甲酯烷基碳链越长增加幅度越大;根据组成可直接预测生物柴油的冷滤点.     

生物柴油低温流动性能研究

采用气相色谱法测定了菜籽油生物柴油、大豆油生物柴油和花生油生物柴油中脂肪酸甲酯的分布和含量,采用燃料低温性能测定仪和旋转黏度计考察了生物柴油的低温流动性能及流变特性。结果表明:生物柴油的低温流动性能与其饱和脂肪酸甲酯的分布和含量密切相关。花生油生物柴油的饱和脂肪酸甲酯含量比菜籽油生物柴油的高10.5%,其冷滤点和凝点比菜籽油生物柴油的高8℃,0℃时花生油生物柴油黏度比菜籽油生物柴油高57.42 mPa·s。生物柴油在低温下失去流动性的主要原因是析出晶体,并连接成网状结构,将低熔点的柴油吸附于其中。     

食用植物油所制备生物柴油的低温流动性能

以我国常用的7种食用植物油为原料，采用碱催化酯交换法制成纯植物油生物柴油．并测定了各种生物柴油中脂肪酸甲酯的分布、凝点、冷滤点、倾点和粘度。通过比较发现．当植物油制成生物柴油后其凝点和倾点显著升高，但冷滤点降低。从凝点看，其中菜籽油生物柴油能满足我国-10号柴油的要求，葵花籽油、玉米油、芝麻油和大豆油的生物柴油能满足0号柴油的规格，花生油生物柴油的凝点则较高。纯植物油生物柴油的低温流动性能主要与生物柴油中的饱和脂肪酸甲酯的含量和分布有关，饱和脂肪酸甲酯的含量越高，饱和脂肪酸甲酯中的长链脂肪酸甲酯含量越多，该生物柴油的低温性能越差。     

脂肪酸甲酯结构对生物柴油十六烷值的影响

从分子层次,应用杂化轨道理论研究了生物柴油的分子结构及其对十六烷值的影响。研究表明：生物柴油主要由饱和脂肪酸酯（棕榈酸甲酯和硬脂酸甲酯）和不饱和脂肪酸酯（油酸、亚油酸甲酯和亚麻酸甲酯）组成,其十六烷值随着饱和脂肪酸甲酯含量的增加而增加,多不饱和脂肪酸甲酯含量的增加而减少。综合组成对生物柴油低温流动性和氧化安定性影响,生物柴油中饱和脂肪酸甲酯和多不饱和脂肪酸甲酯的含量都应尽量低。提出降低生物柴油NOx排放的新途径：采用减压蒸馏、调合、结晶分馏等措施调整生物柴油的组成,可有效降低生物柴油的NOx排放。     

基于光谱分析的生物柴油氧化过程结构变化研究

分别以大豆油、菜籽油、餐饮废油为原料制备三种不同原料来源的生物柴油,利用气相色谱测定了其脂肪酸甲酯含量。对三种生物柴油的氧化安定性进行了评价,并利用红外光谱和紫外光谱分析了菜籽油生物柴油 (RME)、大豆油生物柴油 (SME) 及餐饮废油生物柴油 (WME)中不饱和脂肪酸甲酯分子在氧化过程中分子的构型变化,结果表明：不同原料来源生物柴油的氧化安定性与脂肪酸甲酯的组成及分布密切相关,多双键不饱和脂肪酸甲酯的含量越高,生物柴油的氧化安定性越差。不饱和脂肪酸甲酯分子中的双键在氧化过程中会发生顺-反异构化,并生成共轭双键,多双键不饱和脂肪酸甲酯含量越高,共轭双键生成量越多,生物柴油的氧化安定性也越差。     

典型原料生物柴油低温流动性的研究

在应用气-质联用仪和杂化轨道理论研究典型原料生物柴油的组成及其分子结构的基础上,运用结晶理论研究其低温流动性。提出了与低温石油柴油调合和添加低温流动性改进剂两种改善低温流动性的措施。研究表明：生物柴油的主要组成为长链脂肪酸甲酯（C14∶0～C24∶0、C16∶1～C22∶1、C18∶2和C18∶3）,其中饱和脂肪酸甲酯的碳链呈直线＂之＂字形排列;不饱和脂肪酸甲酯的C-C碳链呈直线＂之＂字形排列,C=C使碳链发生弯曲。生物柴油的低温流动性随着饱和脂肪酸甲酯含量的增加而变差,-10PD、PME、CME、SME和RME的冷滤点分别为-7℃、8℃、6℃、-5℃和-7℃;与-10PD调合冷滤点最低降到-12℃;在添加FlowFit、FlowFitK和T818的体积分数〈1.5%时,PME、CME、SME和RME的冷滤点分别最低降到2℃、0℃、-7℃和-11℃。     

氧化前后生物柴油的红外和紫外光谱分析

利用红外光谱和紫外光谱分析了菜籽油生物柴油、大豆油生物柴油及餐饮废油生物柴油中不饱和脂肪酸甲酯(FAME)在氧化过程中分子构型的变化。结果表明,生物柴油的氧化安定性与其脂肪酸甲酯的组成密切相关,即不同来源的生物柴油的氧化安定性不同。在氧化过程中,不饱和脂肪酸甲酯分子中的双键会发生顺 反异构化,并生成共轭双键;多双键不饱和脂肪酸甲酯含量越高,共轭双键生成量越多,生物柴油的氧化安定性也越差。     

棕榈油生物柴油低温流动性能及结晶形态的研究

针对棕榈油生物柴油(PME)流动性差的问题,分析了PME的化学组成,测定PME、0号柴油(0PD)及PME与0PD调合油的冷滤点,观测PME和调合油在低温环境下的结晶过程。实验结果表明,PME中的饱和脂肪酸甲酯与不饱和脂肪酸甲酯的质量分数分别为40.13%和59.57%,饱和脂肪酸甲酯含量较高使PME流动性变差;PME和0PD的质量比为10∶90时,调合油的冷滤点可达到-4℃;随温度的降低,PME结晶为规则的薄片状,并逐渐变大相互联结在一起;PME与0PD调和能使PME不能形成规则的结晶形状,从而改善PME的低温流动性能。     

生物柴油低温凝固机理探讨

采用气相色谱法研究菜籽油生物柴油、大豆油生物柴油和花生油生物柴油中脂肪酸甲酯的分布和含量;采用多功能低温性能测定仪和旋转粘度计研究生物柴油的低温流动性及粘温性。结果表明,生物柴油低温流动性与其脂肪酸甲酯相对含量关系密切;温度高于生物柴油冷滤点时,其表观粘度与温度关系不大;温度低于生物柴油冷滤点时,其表观粘度随温度降低而增大;随温度降低,生物柴油中析出针状蜡晶,并逐渐聚结形成三维网状结构,将液态的生物柴油吸附于其中,使生物柴油整体上失去流动性。     

Production of biodiesel from unused algal biomass in Punjab, India

Biodiesel from inedible sources has become prominent in last few decades. But it is economically incompatible with petroleum diesel. At the same time, both petro-diesel and biodiesels are concerned with environmental pollution, global warming, etc. Algae, on the other hand, utilize CO2 for their growth and can minimize some sort of pollution level and results in carbon credit for a country. In Punjab, India, algae are seen to grow in many water bodies. But all those are taken away and dumped in vats. Some of this huge biomass was used for production of biodiesel in this work. Extraction of oil from algae was conducted by using Soxtherm(solvent extraction). An amount of 9 wt% of algal oil was extracted by comparatively costly hexane, whereas 8% extraction was done by cheaper acetone. In the transesterification reaction, molar ratio(methanol: oil) of 6:1, catalyst(KOH) concentration of 3 wt%, reaction temperature of 60 °C, 60 min reaction time and a settling time of 2.5 h were found to be optimum conditions to get maximum ester with minimum free fatty acid content and viscosity. A statistical analysis for the transesterification procedure also showed a methanol-to-oil molar ratio of 6:1 and catalyst concentration of 3 wt% to be the optimum. Characterization of biodiesel was done and compared with ASTM/BIS standards. Most important properties of biodiesel ester like viscosity(3.12 c St or 3.12 mm2/s), cloud and pour point(-1 and-6 °C, respectively), flash and fire point(153 and 158 °C), carbon residue content(0.03%), acid number(0.36 mg of KOH/gm) were within the range of concerned standards.     

Fuel properties and emission characteristics of biodiesel produced from unused algae grown in India

The high price of different biodiesels and the need for many of their raw ingredients as food materials are the main constraints to be overcome when seeking the best potential alternative fuels to petro-diesel. Apart from that, some properties like high density, viscosity and acid value along with low cloud and pour points preclude their use in compression ignition(CI) engines as these properties can cause serious damage to the parts of the engine and reduce engine life. In this experiment, biodiesel was produced from the oil of unused algae by a two-step ‘acid esterification followed by transesterification' procedure. Taguchi's method was applied to design the experiment, and a L25 orthogonal array was prepared to optimize the biodiesel production procedure. The optimized conditions for transesterification were: methanol to oil molar ratio of 6:1, catalyst(KOH) concentration of 2.5 wt%, reaction time of 90 min and reaction temperature of 50 ℃,achieving a biodiesel production of 89.7% with free fatty acid content of 0.25%. It was found that the CI engine emitted less CO, CO_2 and hydrocarbon and higher NO_x using algal biodiesel than that using petro-diesel. All properties of the algal biodiesel were within the limit of ASTM standards.     

气相色谱法测定混合生物柴油燃料中三脂肪酸甘油酯含量

混合生物柴油中的脂肪酸甲酯含量是产品质量的重要指标。采用红外光谱法根据酯基官能团的吸光度测定脂肪酸甲酯的总量时,不能区分酯基官能团是来源于脂肪酸甲酯还是未转化或混入的油脂原料中的三脂肪酸甘油酯。采用高温气相色谱法,考察了混合生物柴油中混入不同类型的油脂原料时的色谱分离情况,以三癸酸甘油酯作内标物,建立了混合生物柴油中三脂肪酸甘油酯含量的测定方法。该方法的检测限为0.01%（w）。当三脂肪酸甘油酯含量大于0.1%（w）时,测定的回收率大于91%,相对标准偏差小于6%,可以满足一般测定的要求,需要时可以作为红外光谱法的补充,用于分辨酯基官能团的来源。     

Castor oil biodiesel production and optimization

Biodiesel is evolving to be one of the most employed biofuels for partial replacement of petroleum based diesel fuel, especially in recent years. The most widely used feedstocks for biodiesel production are vegetable oils. In this work, biodiesel production from castor oil has been synthesized by homogenous alkaline transesterification. The influence of catalyst concentration, methanol:oil molar ratio, reaction temperature and reaction time in the methyl ester content reached by castor oil transesterification have been evaluated. A yield of 95?wt% biodiesel was achieved at 1?wt% KOH, 60?°C, 9:1 methanol:oil ratio and 30?min reaction time. Transesterification at temperature 30?°C gave a yield compatibles with that obtained at 60?°C. The composition of the fatty acid methyl ester was determined by Gas Chromatography. The castor oil biodiesel produced was blended with different concentrations of petrodiesel to obtain B5, B10 and B20. The biodiesel properties and its blends were determined according to the standard test methods of analysis. The results showed that Castor oil biodiesel in the blends could lower the cloud point value, but simultaneously, increases the viscosity of the diesel–biodiesel blends. Thus, castor oil biodiesel with its very low cloud and pour points is suitable for using in extreme winter temperatures.