三种脂肪酸乙酯声速的实验测量与理论估算

生物燃料作为化石燃料的替代物越来越受到人们的关注,脂肪酸乙酯(FAEEs)是生物燃料中的重要成分。为了获取生物燃料组分的物性参数,补充现有数据不足,利用布里渊散射法对3种脂肪酸乙酯的声速进行了测量,测量温度范围为293.15~473.15 K,压力为0.1 MPa。为方便工程应用,实验数据被拟合成温度的函数,实验值与关联式计算值的相对偏差绝对平均值为:0.13%(己酸乙酯)、0.11%(庚酸乙酯)、0.08%(辛酸乙酯)。实验数据也被用来评估两种生物燃料声速预测方法,结果表明,Wada模型优于Auerbach模型,更适合脂肪酸乙酯的声速预测。     

癸酸乙酯的液相音速测量与理论估算

脂肪酸乙酯（FAEEs）是生物柴油中的重要成分,为了获取生物柴油组分的物性参数,利用布里渊散射法,分别沿0.1、2、4和6 MPa四条等压线,覆盖温度范围为298.15~508.15 K,测量了癸酸乙酯的液相音速。为方便工程应用,依据实验数据,给出了癸酸乙酯音速与温度和压力的关联式。在实验p - T范围内,实验值与关联式计算值的相对偏差绝对平均值为0.28%。常压下的实验数据也被用来评估Wada模型,结果表明Wada模型适用于预测癸酸乙酯常压下的音速。     

三种脂肪酸甲酯音速测量与相关热物理性质推算

脂肪酸甲酯（FAMEs）是生物燃料的重要成分,为了获取它们的热物理性质数据,利用布里渊散射法测量了3种脂肪酸甲酯常压下的音速,测量温度范围为293.15~423.15 K（己酸甲酯）、293.15~443.15 K（庚酸甲酯）、463.15 K（辛酸甲酯）。为方便工程应用,将文献数据和本文实验数据拟合成温度的关联式,实验值与关联式计算值的相对偏差绝对平均值为：0.29%（己酸甲酯）、0.24%（庚酸甲酯）、0.27%（辛酸甲酯）。应用音速实验数据,分别结合Wada模型和Auerbach模型估算3种脂肪酸甲酯的密度和表面张力。结果表明,Wada模型可以很好地用来估算密度,而Auerbach模型对表面张力的估算结果与文献值偏差较大。     

癸酸甲酯、月桂酸甲酯和肉豆蔻酸甲酯的液相声速测量

癸酸甲酯、月桂酸甲酯和肉豆蔻酸甲酯3种脂肪酸甲酯是生物柴油的主要成分,其声速是喷油系统优化设计和等熵压缩因子计算中所必需的参数之一。针对癸酸甲酯、月桂酸甲脂和肉豆蔻酸甲脂3种物质声速实验数据缺乏的现状,利用布里渊光散射法,沿0.1、2.5、5.5和8.5 MPa 4条等压线,在288.15~498.15 K温度范围内,分别测量了癸酸甲酯、月桂酸甲酯和肉豆蔻酸甲酯的液相声速;分析了声速随温度、压力的变化规律;依据实验数据,给出了在本文p-T热力学区域内,3种物质液相声速与温度和压力的关联式;关联式计算值与实验数据的相对偏差绝对平均值分别为：0.17%（癸酸甲酯）、0.10%（月桂酸甲酯）和0.15%（肉豆蔻酸甲酯）,满足工程应用需求。     

三种脂肪酸甲酯音速测量与相关热物理性质推算

脂肪酸甲酯(FAMEs)是生物燃料的重要成分,为了获取它们的热物理性质数据,利用布里渊散射法测量了3种脂肪酸甲酯常压下的音速,测量温度范围为293.15~423.15 K(己酸甲酯)、293.15~443.15 K(庚酸甲酯)、463.15K(辛酸甲酯)。为方便工程应用,将文献数据和本文实验数据拟合成温度的关联式,实验值与关联式计算值的相对偏差绝对平均值为:0.29%(己酸甲酯)、0.24%(庚酸甲酯)、0.27%(辛酸甲酯)。应用音速实验数据,分别结合Wada模型和Auerbach模型估算3种脂肪酸甲酯的密度和表面张力。结果表明,Wada模型可以很好地用来估算密度,而Auerbach模型对表面张力的估算结果与文献值偏差较大。     

改进的Tait方程用于预测高压液体密度

Tait方程被普遍认为是流体高压液相密度的最佳关联式,为了将该方程变为具有预测功能的模型,在7种直链烷烃高压密度数据的基础上,对Tait方程进行了研究分析,提出了一种形式简单的可以预测流体高压液相密度改进的Tait方程。在此基础上,将该模型拓展到了脂肪酸酯类物质,分别建立了脂肪酸甲酯和脂肪酸乙酯高压液相密度预测模型。此外,采用未参与回归的6种脂肪酸甲酯(包括丁酸甲酯、戊酸甲酯、己酸甲酯、庚酸甲酯、辛酸甲酯和壬酸甲酯)的实验数据对模型预测的可靠性进行了验证,预测值与实验值之间的绝对平均偏差均小于1%,可以满足实际工程的需要。     

癸酸甲酯、月桂酸甲酯和肉豆蔻酸甲酯的液相声速测量

癸酸甲酯、月桂酸甲酯和肉豆蔻酸甲酯3种脂肪酸甲酯是生物柴油的主要成分,其声速是喷油系统优化设计和等熵压缩因子计算中所必需的参数之一。针对癸酸甲酯、月桂酸甲脂和肉豆蔻酸甲脂3种物质声速实验数据缺乏的现状,利用布里渊光散射法,沿0.1、2.5、5.5和8.5 MPa 4条等压线,在288.15~498.15 K温度范围内,分别测量了癸酸甲酯、月桂酸甲酯和肉豆蔻酸甲酯的液相声速;分析了声速随温度、压力的变化规律;依据实验数据,给出了在本文p-T热力学区域内,3种物质液相声速与温度和压力的关联式;关联式计算值与实验数据的相对偏差绝对平均值分别为:0.17%(癸酸甲酯)、0.10%(月桂酸甲酯)和0.15%(肉豆蔻酸甲酯),满足工程应用需求。     

用激光技术测定液体中的声速和等熵压缩性系数

本文应用根据激光光声原理和技术建立的流体热力学性质测量实验装置，测定了七个温度下苯、四氯化碳液体中，苯与四氯化碳二元溶液中的声速（ｕ）、密度（ρ），计算了等熵压缩性系数（Ｋ＿ｓ）等热力学数据。用多项幂级数，以最小二乘法拟合声速ｕ与温度ｔ的数学关系。实测的声速值与文献值比较，相对误差小于０．０４％，等熵压缩性系数与文献数据也相当吻合。     

碳氢燃料JP-10高温液态黏度测量和推算模型构建方法研究

基于流体动力学层流哈根-泊肃叶（Hagen-Poiseuille）定律,利用双毛细管法,对高密度空天动力燃料JP-10液态黏度进行实验测量,测温范围326.6~671.2 K,测量压力2.0、 3.0、 4.0 MPa,扩展相对不确定度2.88%~4.96%（置信因子k=2）。通过纯物质环己烷动力黏度的测量,对实验系统进行了标定,实验结果与NIST数据库平均相对偏差在1.22%以内,最大相对偏差绝对值为2.04%,实验结果与推荐黏度值在2.0 MPa时平均相对偏差为1.25%,4.0 MPa时平均相对偏差为1.61%,最大相对偏差绝对值为3.50%,验证了实验系统的可靠性。选取临界压力状态的黏度值作为参考状态值,通过引用Yaws液相有机化合物的黏度经验公式,结合SRK状态方程对绝对速率理论黏度模型进行了改进,耦合实验数据,建立了一种适用于碳氢燃料的高温高压液相黏度的推算模型。采取共轭梯度法和遗传算法对模型参数进行拟合,计算结果与实验结果的平均相对偏差值在2.00%以内,最大相对偏差绝对值小于4.50%,验证了模型的精确性。     

液相己二酸二乙酯热导率

己二酸二乙酯是有机合成重要的溶剂和中间体,也在日用化学工业和食品工业,如香料、增塑剂等方面应用广泛。近年来,含氧燃料如己二酸二乙酯可以改善油品性能和降低柴油机排放,被认为是良好的柴油添加剂和替代燃料。然而到目前为止,对己二酸二乙酯的热物性研究相对不足。利用钽丝作为热线的瞬态双热线系统对温度区间为283～383K、压力区间为0.1～30MPa的液相己二酸二乙酯热导率进行了实验研究,并将实验数据拟合为温度和压力的关联式。实验数据与热导率关联式计算结果的标准偏差和最大偏差分别为0.14%和0.43%,热导率的标准合成不确定度为±1.0%。     

固定化Candida sp.99-125脂肪酶催化大豆油合成脂肪酸乙酯

探讨了酶法合成脂肪酸乙酯作为生物柴油的可行性. 以大豆油和乙醇为原料,利用本实验室自制的固定化Candida sp. 99-125脂肪酶催化反应,深入研究水含量、溶剂量、脂肪酶量及反应温度等因素对酶法合成脂肪酸乙酯的影响. 结果表明,以大豆油质量为基准,在水含量为 12.5%(w)、溶剂正己烷为3 mL/g、脂肪酶量为20%(w)、温度40℃的优化反应条件下,3次流加乙醇,170 r/min摇瓶反应,12 h后可以达到96.8%的最高酯得率. 进一步研究表明,在此优化反应条件下,连续使用14批脂肪酶酯得率可保持70%以上.     

Enrichment of high-purity nervonic acid ethyl ester from Acer truncatum Bunge seed oil by combination method of urea inclusion and molecular distillation

Acer truncatum Bunge is a type of maple that is unique to China. Its fruit setting rate and seed oil content are both high. The oil is mainly composed of C16–C24 fatty acids and contains 5%–7% nervonic acid (NA). NA and its derivatives can delay ageing and prevent and treat disorders such as senile dementia and Alzheimer's disease. The content of NA ethyl ester prepared by the seed oil of A. truncatum Bunge is 5.84%. We report a new process for the enrichment of NA ethyl ester by urea inclusion (UI) and molecular distillation (MD), with the aim of obtaining highly pure NA ethyl ester. First, based on the difference in fatty acid ethyl ester saturation and carbon chain length, unwanted compounds such as oleic acid ethyl ester, linoleic acid ethyl ester, and sterol were removed by one-stage UI, the content of NA ethyl ester was increased to 18.69%. The oil in the UI compound was used as a feed, and differences in the mean molecular free paths between the components were exploited to separate the C16–C20 fatty acid ethyl esters (FAEEs) by two-stage MD. The total content of C16–C20 FAEEs decreased to 3.69% and the purity of NA ethyl ester increased to 47.47%. A new purification process of UI-MD-UI was established and NA ethyl ester could be purified to 91.8%. The combination of MD and UI has an important reference value for the industrialization of producing high-purity NA ethyl ester.     

Speed of sound and isentropic compressibility of organic solvents + sunflower oil mixtures at 298.15 K

The speed of sound in binary liquid mixtures of organic solvents with sunflower oil was measured over the entire range of concentrations at 298.15 K. The solvents considered were: n-hexane, n-heptane, n-octane, n-nonane, ethanol, 1-propanol, 2-propanol, 1-butanol, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and vinyl acetate. The speed of sound data were used to calculate isentropic compressibilities and excess isentropic compressibilities. The excess isentropic compressibilities vs. concentrations were correlated using Redlich-Kister polynomials. Speed of sound determinations in the mixtures were predicted using two mixing rules proposed in the literature, and values were compared with experimental data. In all cases, SD between predicted and experimental data were less than 3.5%.     

Base/acid-catalyzed FAEE production from hydroxylated vegetable oils

In this study was developed a new methodology to produce fatty acid ethyl esters from castor oil. The base-catalyzed transesterification step was followed by on pot addition of sulfuric acid. That addition implicated the successful separation of FAEEs/glycerin phases due to soap breaking. The study was carried out through an experimental design where the variables studied in the first step were the molar ratio alcohol:oil and the catalyst amount in the transesterification process. As expected, the on pot addition of concentrated sulfuric acid yields FFAs that increase the acid value in the FAEEs phase. A second step esterification of these free fatty acids from FAEE raw mixture was investigated. The esterification of FFA was carried out in 60:1 and 80:1 M ratios (alcohol:free fatty acids) and concentrated sulfuric acid 5% and 10% w/w (based on free fatty acids). Consequently, these two steps yielded more fatty ethyl esters and assure that the following important requirements in the FAEEs production process from castor oil are satisfied: complete reaction, best separation of FAEEs/glycerin phases, removal of catalyst, limpid glycerin, and absence of free fatty acids.     

Water Addition During Oil Extraction Affects on Virgin Olive Oil Ethanol Content,Quality and Composition

Ethanol is the alcoholic precursor of fatty acid ethyl esters (FAEEs) in virgin olive oil (VOO). Because of its miscibility, water addition during oil extraction may affect oil ethanol content and then, the FAEEs synthesis during oil storage. In this work, the effect of water addition on VOO ethanol content and composition is studied. Water addition at two extraction systems (two and three phases) is compared and for vertical centrifuge, water addition at different temperatures is assayed. Ethanol content, quality parameters, and healthy components are determined in the oils. Results indicate three phase system gives oils with a 25% lower ethanol content than two phases. Ethanol reduction because of water addition is more important for three phases system (≈14%). For vertical centrifugation, ethanol is lowered as water dose and temperature increase. In general, water addition for any of the extraction steps analyzed reduces the oil ethanol concentration but other aspects such as fruity intensity and phenol content are also lowered. Practical applications: Virgin olive oil final ethanol content, and then its FAEEs concentration, does not only depend on the health and conservation status of olives, but also on the extraction system used and the amount of water added to the extraction process. The knowledge of the impact on ethanol content of water addition during oil extraction can be useful for olive oil legislators in order to keep the approved limits of FAEEs or to modify them. For oil producers, results can help to reduce the oil ethanol content and then FAEEs synthesis during virgin olive oil storage.     

Using critical fluid carbon dioxide to optimize the enzymatic transesterification of soybean oil and ethyl ferulate to feruloyl soy glycerides

Feruloyl Soy Glyceride (FSG) is an all-natural replacement for petroleum-based ultraviolet absorbing ingredients currently used in sunscreens. It is produced by the Novozym® 435-catalyzed transesterification of ethyl ferulate (EF) with triglycerides. By-product fatty acid ethyl esters (FAEEs) are more soluble in CO₂ than the EF and triglyceride starting materials. It was hypothesized that the preferential removal of the FAEEs over EF would drive the enzymatic reaction towards the desired FSG product. The effect of CO₂ pressure and temperature on the solubilities of components of the FSG reaction mixture was studied to select optimized conditions for the enzymatic reaction and purification. Pressure–temperature conditions were then selected to use in a recycling system. The enzymatic products were analyzed for CO₂ with and without recycling CO₂. The solubilities of all components of the reaction mixture were proportional to CO₂ density but the relative solubilities of individual components were not equal at all pressures and temperatures. At 60°C, the ratio of ethyl linoleate to EF was only 1.1 at 6.9 MPa but 3.1 at 13.8 MPa. The CO₂ was recycled through the reactor at 13.8 MPa (removing more FAEE by-products) and through the receiver at 6.0 MPa (removing less FAEEs). In the recycling treatment, the material left behind in the reactor had 99.6% FSG content. The use of the reduced pressure receiver in a recycling CO₂ system effectively increased the amount of EF incorporated onto the soybean oil increasing the yield of the FSG product.     

Continuous production of soybean biodiesel with compressed ethanol in a microtube reactor

This work investigates the production of fatty acid ethyl esters (FAEEs) from the transesterification of soybean oil in supercritical ethanol in a continuous catalyst-free process. Experiments were performed in a microtube reactor in the temperature range of 523 K to 598 K, from 10 MPa to 20 MPa, varying the oil to ethanol molar ratio from 1:10 to 1:40, and evaluating the effects of addition of carbon dioxide as co-solvent. Results showed that ethyl esters yield obtained in the microtube reactor (inner diameter 0.76 mm) were higher than those obtained in a tubular reactor (inner diameter 3.2 mm) possibly due to improved mass-transfer conditions attained inside the microtube reactor. Non-negligible reaction yields (70 wt.%) were achieved along with low total decomposition of fatty acids (< 5.0 wt.%). It is shown that the use of carbon dioxide as co-solvent in the proposed microtube reactor did not significantly affect the ethyl esters yield within the experimental variable ranges investigated.