共查询到17条相似文献，搜索用时 390 毫秒
1.
利用热力学相平衡分析生物柴油晶体析出规律 总被引：1，自引：1，他引：0
生物柴油主要是由饱和脂肪酸甲酯和不饱和脂肪酸甲酯组成的混合溶液,从热力学角度分析,生物柴油的蜡晶析出是溶液由液相向固相转变的相平衡过程。该文建立将液相组成作为理想溶液且固相成分不互溶的理想溶液模型（模型一）和基于活度系数模型与正规溶液理论的正规溶液模型(模型二),分别计算了蜡晶的析出温度,并且通过模型二计算出在给定的温度下的析蜡量与石蜡的组成。两模型在计算析蜡点的温度精确性方面还是比较理想的误差在5 K左右。研究发现石蜡沉积量与饱和脂肪酸酯的量成一定的比例关系,而且石蜡沉积并不是按照脂肪酸酯熔点高低的顺序进行析出,析出的石蜡中同时包含了低熔点脂肪酸酯。固液平衡常数是表征物质在溶液中析出能力的决定性因素,在一定温度下,不饱和脂肪酸酯的固液平衡常数一般在0.1以下,而饱和脂肪酸酯的固液平衡常数却大得多。该研究阐明的晶体析出规律,可为优化生物柴油低温流动性技术措施,推动生物柴油在低温环境下的应用提供参考。 相似文献
2.
脂肪酸甲酯生物柴油改善低硫柴油的润滑性能 总被引：1，自引：1，他引：0
生物柴油可作为改善低硫柴油润滑性能的天然添加剂。该文将豆蔻酸甲酯(C14:0)、棕榈酸甲酯(C16:0)、硬脂酸甲酯(C18:0)、油酸甲酯(C18:1)、亚油酸甲酯(C18:2)、亚麻酸甲酯(C18:3)、蓖麻醇酸甲酯(C18:1 OH)及蓖麻油甲酯和餐饮废油甲酯按照0.5%、1.0%、1.5%和3.0%的体积分数添加到低硫柴油中,在高频往复试验机(high-frequency reciprocating rig,HFRR)上进行润滑性能测试,探究脂肪酸甲酯的碳链长度、不饱和度及含羟基等结构特征对润滑性能的影响。结果表明,长碳链脂肪酸甲酯一般比短链润滑效果好;碳链长度为十八的脂肪酸酯中,不饱和程度即碳碳双键数目越高则润滑性能越好;而在相同碳链长度和不饱和度条件下,含羟基的蓖麻醇酸甲酯的润滑改善效果优于油酸甲酯。由多种脂肪酸酯构成的混合物生物柴油的润滑性能要优于某单一的纯脂肪酸甲酯。在低硫柴油中,当某饱和脂肪酸甲酯的体积分数比例达3.0%时,或不饱和酯的体积分数达到1.5%时,或生物柴油的体积分数达1.0%时,可使低硫柴油的润滑性能指标满足相关标准。研究脂肪酸甲酯的各种结构特征对其润滑性能的影响及作用机制,有助于筛选合适的生物柴油组分及其添加浓度作为低硫柴油的润滑添加剂。 相似文献
3.
生物柴油的低温流动性主要取决于化学组成。为了量化表征生物柴油组成与其冷滤点的关系,采用气相色谱-质谱与冷滤点分析技术和多元线性回归分析方法,分析了生物柴油的脂肪酸甲酯组成和冷滤点,研究了脂肪酸甲酯组成对冷滤点的影响规律。研究表明：生物柴油主要由14～24个偶数碳原子组成的长链脂肪酸甲酯组成,其中饱和脂肪酸甲酯主要为C14:0～C24:0,不饱和脂肪酸甲酯主要为C16:1～C22:1、C18:2～C20:2和C18:3。120种生物柴油油样中,乌桕梓油生物柴油的冷滤点最低,为-14℃,花生油生物柴油的冷滤点最高,为13℃。生物柴油的脂肪酸甲酯的含量与分布不同,冷滤点差异较大。冷滤点随饱和脂肪酸甲酯含量的增加呈线性升高,且碳链长的较短的增加显著;随不饱和脂肪酸甲酯含量的增加而呈线性降低,且不饱和度高的较低的降低略明显。建立了线性相关性非常显著（R=0.971）的基于组成的冷滤点预测模型。研究结果为不同环境下生物柴油的推广应用提供参考。 相似文献
4.
为了研究超高压处理及加热处理对羊乳中脂肪酸组成的影响,该文以崂山奶山羊乳为研究对象,通过氯仿-甲醇法和碱催化法分别对乳脂肪进行提取和甲酯化,采用气相色谱-质谱（gas chromatography-Mass Spectrometry,GC-MS）方法分析在100、200、300、400 MPa超高压条件和65℃/30 min、75℃/15 min、90℃/1 min、煮沸加热条件下羊乳中各脂肪酸组成的变化,结果显示：经超高压处理,羊乳中的短链脂肪酸、饱和脂肪酸和不饱和脂肪酸含量的变化均不显著（P>0.05),而经加热处理羊乳中的短链脂肪酸和饱和脂肪酸含量均显著升高（P<0.01）,不饱和脂肪酸的含量显著降低（P<0.001）。经超高压处理羊乳中C6:0、C8:0和C10:0含量的变化均不显著（P>0.05）;C12:0、C14:0含量显著增加（P<0.01）,C16:0变化不显著（P<0.05）,C18:0含量显著降低（P<0.05）;C18:1含量的变化不显著（P>0.05）,C18:2和C18:3含量显著降低（P<0.01,P<0.05）,C20:4含量变化不显著（P>0.05）。而经加热处理羊乳中C10:0含量显著升高（P<0.01）;C12:0、C14:0和C16:0含量也均显著升高（P<0.05）,C18:0含量的变化不显著（P>0.05）;C18:1、C18:2、C18:3含量均显著降低（P<0.001,P<0.05,P<0.001）,而C20:4为检测出来。研究结果表明超高压处理能够更好的保持羊乳中脂肪酸的含量及组成,进而为超高压技术和加热处理在乳品中的应用及羊乳资源的开发提供了理论依据。 相似文献
5.
菜籽油脱臭馏出物中生物柴油的分子蒸馏分离工艺研究 总被引：10，自引：5，他引：5
为了实现脱臭馏出物的清洁加工,运用分子蒸馏技术分离菜籽油脱臭馏出物中合成的生物柴油,考察了分子蒸馏的操作参数对生物柴油回收率的影响,研究结果表明：当系统压力为5.3 Pa,蒸发面温度120℃,进料温度70℃,刮膜转速150 r/min,进料速率120 mL/h时,生物柴油回收率达到41 g/100 mL。馏出物经高分辨气相色谱-质谱进行分离鉴定,共检出6种脂肪酸甲酯成分：其中棕榈酸甲酯33.61%,油酸甲酯16.14%,亚油酸甲酯18.25%,硬脂酸甲酯8.81%,芥酸甲酯7.39%,贡多酸甲酯3.78%,脂肪酸甲酯总含量占89%以上。 相似文献
6.
n-3多不饱和脂肪酸具有多种重要生理功能,哺乳动物只能通过食物摄取n-3多不饱和脂肪酸,以满足机体的健康所需。脂肪酸去饱和酶-1基因(fatty acid desaturase-1,fat-1)以18~20碳的n-6多不饱和脂肪酸为底物进行脱氢反应,产生相应的n-3多不饱和脂肪酸,为了解转fat-1基因绵羊(Ovis aries)具体脂肪酸的组成,本研究利用fat-1表达质粒转染绵羊胎儿成纤维细胞,筛选获得阳性单克隆细胞系,通过体细胞核移植,得到转fat-1基因绵羊。通过脂肪酸质谱测定仪对5种组织脂肪酸含量进行测定,研究了fat-1基因对5种组织3类32种脂肪酸含量变化的影响。结果发现,在脑和臀肌中,饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸类别百分含量变化不显著;在肝脏、心脏和睾丸中,fat-1基因能够使饱和脂肪酸下降、使肝脏和睾丸的单不饱和酸量升高、使心脏中单不饱和脂肪酸含量降低;单不饱和脂肪酸中C18:1n-9c和饱和脂肪酸中C16:0、C18:0的含量变化决定了转基因绵羊组织单不饱和脂肪酸和饱和脂肪酸的变化趋势,在脑和臀肌中,这3种脂肪酸在转基因与对照组之间差异不显著;fat-1基因引起肝脏多不饱和脂肪酸降低,心脏和睾丸中多不饱和脂肪酸含量增高,主要由二十碳二烯酸C20:2(eicosadienoic acid,EDA)、二十碳三烯酸C20:3n-3(eicosatrienoic acid,ESA)、花生四烯酸C20:4n-6(arachidonic acid,ARA)、二十碳五烯酸C20:5n-3(eicosapentaenoic acid,EPA)和二十二碳六烯酸C22:6n-3(docosahexaenoic acid,DHA)的含量起主导作用;在5种组织中,转基因组EPA与DHA的含量均升高,尤其是EPA差异显著(P0.05)。fat-1基因降低了多不饱和脂肪酸中C20:3n-3和C20:4n-6的含量而增加了C20:5n-3和C22:6n-3的含量,从而提高了n-3/n-6的比值。本研究解析了转fat-1基因绵羊的脂肪酸组成和特点,对开发优质绵羊品种、改善人类膳食中脂肪酸结构及降低肥胖症风险提供了理论依据。 相似文献
7.
该文利用分子蒸馏模型模拟分离皂脚中脂肪酸,进而为后续高效率制备生物柴油奠定基础.根据建立的分子蒸馏模型和物化参数的估算,对菜籽油皂脚中游离脂肪酸的分离进行模拟,并与实际试验数据进行了比较.研究结果表明:该模型在模拟分离菜籽油皂脚中游离脂肪酸时的结果与试验结果曲线趋势相近.随着蒸馏温度的增加,蒸馏量增大,蒸馏量模拟值与实验值的相对误差不超过16%.随着蒸馏温度的增加,重组分中游离脂肪酸含量不断降低,试验结果的脂肪酸浓度都大于模拟值,而相对误差随温度升高不断降低,蒸馏温度为453 K时较蒸馏温度为423 K时,相对误差降低近50%. 相似文献
8.
以碱催化剂为媒介的转酯化反应制备生物柴油方法因其转化率高而倍受重视。该文以菜籽油为原料,在小型试验装置上,采用均相碱催化法,研究了菜籽油在碱性催化剂NaOH的作用下与甲醇经酯交换反应制备生物柴油的工艺条件。考察了醇油摩尔比（4︰1～8︰1）、催化剂用量（0.5%～2%）、反应温度（30～60℃）和反应时间（30～150 min）等工艺参数对酯交换反应的影响,对生物柴油的组成成分进行了气相色谱/质谱联用(GC-MS)分析。结果表明,在醇油摩尔比6︰1,催化剂用量为油质量的1%,反应温度为50～60℃,反应时间为60 min时,酯交换反应转化率最高可达到96.7%。该生物柴油主要由油酸甲酯、芥子酸甲酯、9,12-十八碳二烯酸甲酯、11-二十碳烯酸甲酯、亚麻酸甲酯等脂肪酸甲酯组成,其中油酸甲酯含量最高,相对质量分数高达50.30%。 相似文献
9.
棉籽油基生物柴油铜片腐蚀特性 总被引：1，自引：0，他引：1
参照国家标准《发动机燃料铜片腐蚀试验方法》（GB/T378-1990）,在温度为25℃和50℃条件下,研究棉籽油基生物柴油铜片腐蚀特性,同时考察了棉籽油甲酯和乙酯理化性质的变化,并与0#柴油作了对比。结果表明：在25和50℃条件下,腐蚀试验历时2个月,棉籽油甲酯、乙酯对铜片具有不同的腐蚀现象,且棉籽油甲酯比乙酯的腐蚀性更大。在温度25℃条件下,棉籽油甲酯的铜片腐蚀率达到0.0926?cm/d,腐蚀后棉籽油甲酯的酸值、过氧化值、运动黏度分别提高10.4、1.44、1.13倍;温度升高到50℃时,棉籽油甲酯的铜片腐蚀率达到0.4115?cm/d,腐蚀后棉籽油甲酯的酸值、过氧化值、运动黏度分别增加12.8、2.16、1.13倍。温度升高,铜片腐蚀加剧,油品性质变化增大,乙酯生物柴油也具有类似的变化趋势,而0#柴油对铜片几乎无腐蚀。铜片的腐蚀是由生物柴油变质导致的。该研究可为棉籽生物柴油的工业化应用提供腐蚀数据。 相似文献
10.
狭鳕鱼皮脂肪酸组成分析及其营养评价 总被引：2，自引：0，他引：2
为研究狭鳕鱼皮脂肪酸的营养价值,对狭鳕鱼皮的一般营养成分和脂质组成进行分析,同时采用气相色谱-质谱法对其脂肪酸组成进行分析和营养评价。结果表明,狭鳕鱼皮总脂含量为干重的6.09%,且总脂以甘油三酯(53.85%)和磷脂(25.54%)为主;脂肪酸组成丰富,以C16∶0、C18∶1n-9、C20∶1n-11、C20∶5n-3(EPA)和C22∶6n-3(DHA)为主,且C20∶5n-3和C22∶6n-3占总脂肪酸含量的27.64%;饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸三者之比为0.85∶1.00∶0.92,且脂肪酸致动脉粥样硬化指数和血栓形成指数分别为0.50和0.23,表明狭鳕鱼皮具有促进神经系统发育以及降血脂、抗动脉粥样硬化和抗血栓形成等功效。本研究为狭鳕鱼皮的营养评价及其产品的高值化综合利用提供理论依据。 相似文献
11.
采用催化转移加氢法对大豆油生物柴油(SME,soybean methyl ester)进行适度加氢制备部分加氢大豆油生物柴油(PHSME,partially hydrogenated soybean methyl ester),分析比较生物柴油加氢前后的组分、过氧化值、碘值、十六烷值与运动黏度等燃料特性参数,并基于热重-差示扫描量热法(TG-DSC,thermogravimetry-differential scanning calorimeter)研究加氢提质生物柴油的着火燃烧性能。结果表明:以异丙醇为供氢体、水为反应介质和Raney-Ni为催化剂,在温度85℃和常压下对SME进行催化转移加氢反应,经GC-MS(gas chromatography-mass spectrometry)检测发现高不饱和组分选择性转化为低不饱和或饱和组分,不饱和程度降低了46.2%。尽管PHSME的运动黏度略有增加,但其氧化安定性得到明显改善,且十六烷值也升高至合理的范围。在空气氛围下,由于PHSME相比于SME的分子结构变化及运动黏度增加,其在初始阶段不易挥发,但在高温阶段平均氧化速率更高,其终了失质量温度比SME提前7.2℃。由于PHSME的适度的高十六烷值属性,在DSC曲线可见其放热始点温度比SME提前10.7℃,说明提质生物柴油具有优越的着火性能。 相似文献
12.
Wang ML Morris JB Tonnis B Pinnow D Davis J Raymer P Pederson GA 《Journal of agricultural and food chemistry》2011,59(17):9250-9256
Castor has tremendous potential as a feedstock for biodiesel production. The oil content and fatty acid composition in castor seed are important factors determining the price for production and affecting the key fuel properties of biodiesel. There are 1033 available castor accessions collected or donated from 48 countries worldwide in the USDA germplasm collection. The entire castor collection was screened for oil content and fatty acid composition by nuclear magnetic resonance (NMR) and gas chromatography (GC), respectively. Castor seeds on the average contain 48.2% oil with significant variability ranging from 37.2 to 60.6%. Methyl esters were prepared from castor seed by alkaline transmethylation. GC analysis of methyl esters confirmed that castor oil was composed primarily of eight fatty acids: 1.48% palmitic (C16:0), 1.58% stearic (C18:0), 4.41% oleic (C18:1), 6.42% linoleic (C18:2), 0.68% linolenic (C18:3), 0.45% gadoleic (C20:1), 84.51% ricinoleic (C18:1-1OH), and 0.47% dihydroxystearic (C18:0-2OH) acids. Significant variability in fatty acid composition was detected among castor accessions. Ricinoleic acid (RA) was positively correlated with dihydroxystearic acid (DHSA) but highly negatively correlated with the five other fatty acids except linolenic acid. The results for oil content and fatty acid composition obtained from this study will be useful for end-users to explore castor germplasm for biodiesel production. 相似文献
13.
Eicosapentaenoic acid (EPA) derived from chemically hydrolyzed sardine oil was concentrated by urea fractionation using methanol at different temperatures (2, 4, and 6 degrees C) and urea/fatty acid ratios (2:1, 3:1, and 4:1 w/w) and purified by argentation neutral alumina column chromatography. The individual fatty acids were determined as fatty acid methyl esters (FAME) by gas-liquid chromatography and gas chromatography-mass spectroscopy as FAME and N-acyl pyrrolidides. In the mass fragmentation pattern of FAME, the base peak was assigned to be the 1-methoxyethenol moiety (m/z = 74) obtained by McLafferty rearrangement. Formation of the cyclic tropylium ion (m/z = 91) in fatty acids with four or more double bonds was apparent in FAME-PUFAs. The base peak of N-acyl pyrrolidides was the McLafferty rearrangement ion, 1-(pyrrolidin-1-yl)ethenol (m/z = 113). The highest concentration of EPA (47.78%) was obtained at the crystallization temperature of 4 degrees C with a urea/fatty acid ratio of 4:1 (w/w) with 93.74% yield. After complexation of saturated and less unsaturated fatty acids by urea complexation, argentation chromatography resulted in an EPA of high purity (99.6%) with an overall recovery of 54.09% using 50% diethyl ether/n-hexane as eluting solvent. The peroxide (POV) and thiobarbituric acid (TBS) values were found to be highest (4.0 mequiv of O2/kg and 5.2 mg of malondialdehyde/kg, respectively) during urea fractionation at the higher crystallization temperature (6 degrees C) and higher urea/fatty acid ratio (4:1). Keywords: Sardine oil; eicosapentaenoic acid (EPA); fatty acid methyl esters (FAME); urea fractionation; argentation column chromatography. 相似文献
14.
Yang FX Su YQ Li XH Zhang Q Sun RC 《Journal of agricultural and food chemistry》2008,56(17):7891-7896
To reduce the cost of biodiesel production, the feasibility of Zanthoxylum bungeanum Maxim seed oil (ZBMSO) was studied to produce biodiesel. A methyl ester biodiesel was produced from ZBMSO using methanol, sulfuric acid, and potassium hydroxide in a two-stage process. The main variables that affect the process were investigated. The high level of free fatty acids in ZBMSO was reduced to < 1% by an acid-catalyzed (2% H2SO4) esterification with methanol to oil molar ratios of 20-25:1 for 1 h. A maximum yield of 96% of methyl esters in ZBMSO biodiesel was achieved using a 6.5:1 molar ratio of methanol to oil, 0.9% KOH (percent oil), and reaction time of 0.5 h at 55 degrees C. Further investigation has also been devoted to the assessment of some important fuel properties of ZBMSO biodiesel produced under the optimized conditions according to specifications for biodiesel as fuel in diesel engines. The fuel properties of the ZBMSO biodiesel obtained are similar to those of no. 0 petroleum diesel fuel, and most of the parameters comply with the limits established by specifications for biodiesel. 相似文献
15.
Ethyl esters (FAEE) and trideuterium-labeled methyl esters (d3-FAME) of fatty acids were prepared and investigated regarding their suitability as internal standards (IS) for the determination of fatty acids as methyl esters (FAME). On CP-Sil 88, ethyl esters of odd-numbered fatty acids eluted approximately 0.5 min after the respective FAME, and only coelutions with minor FAME were observed. Depending on the problem, one or even many FAEE can be added as IS for the quantification of FAME by both GC-FID and GC-MS. By contrast, d3-FAME coeluted with FAME on the polar GC column, and the use of the former as IS requires application of GC-MS. In the SIM mode, m/z 77 and 90 are suggested for d3-methyl esters of saturated fatty acids, whereas m/z 88 and 101 are recommended for ethyl esters of saturated fatty acids. These m/z values give either no or very low response for FAME and can thus be used for the analysis of FAME in food by GC-MS in the SIM mode. Fatty acids in sunflower oil and mozzarella cheese were quantified using five saturated FAEE as IS. Gravimetric studies showed that the transesterification procedure could be carried out without of loss of fatty acids. GC-EI/MS full scan analysis was suitable for the quantitative determination of all unsaturated fatty acids in both food samples, whereas GC-EI/MS in the SIM mode was particularly valuable for quantifying minor fatty acids. The novel GC-EI/MS/SIM method using fatty acid ethyl esters as internal standards can be used to quantify individual fatty acids only, that is, without determination of all fatty acids (the common 100% method), although this is present. This was demonstrated by the exclusive quantification of selected fatty acids including methyl-branched fatty acids, erucic acid (18:1n-9trans), and polyunsaturated fatty acids in cod liver oil and goat's milk fat. 相似文献
16.
2- and 3-hydroxy fatty acids (2- and 3-OH-FAs) are bioactive substances reported in sphingolipids and bacteria. Little is known of their occurrence in food. For this reason, a method suitable for the determination of OH-FAs at trace levels in bovine milk fat was developed. OH-FAs (and conventional fatty acids in samples) were converted into methyl esters and the hydroxyl group was derivatized with pentafluorobenzoyl (PFBO) chloride to give PFBO- O-FA methyl esters. These derivatives with strong electron affinity were determined by gas chromatography interfaced to mass spectrometry using electron-capture negative ion in the selected ion monitoring mode (GC/ECNI-MS-SIM). This method proved to be highly sensitive and selective for PFBO-O-FA methyl esters. For the analysis of samples, two internal standards were used. For this purpose, 9,10-dideutero-2-OH-18:0 methyl ester (ISTD-1) from 2-OH-18:1(9 c) methyl ester as well as the ethyl ester of 3-PFBO-O-12:0 (ISTD-2) was synthesized. ISTD-1 served as a recovery standard whereas ISTD-2 was used for GC/MS measurements. The whole-sample cleanup consisted of accelerated solvent extraction of dry bovine milk, addition of ISTD 1, saponification, conversion of fatty acids into methyl esters by use of boron trifluoride, separation of the methyl esters of OH-FAs from nonsubstituted FAs on activated silica, conversion of OH-FAs methyl esters into PFBO-O-FA methyl esters, addition of ISTD-2, and measurement by GC/ECNI-MS-SIM. By this method, ten OH-FAs were quantified in bovine milk fat with high precision in the range from 0.02 +/- 0.00 to 4.49 +/- 0.29 mg/100 g of milk fat. 相似文献
