美国大豆生产、科研、推广和市场体系(续四)

(接续三)2.1.2.3生物柴油生物柴油是通过酯基转移作用(transesterification)把脂或植物油中的甘油脱去后生产的长链脂肪酸单烷基酯(甲酯)。生物柴油的基本工艺是在豆油中加甲醇和氢氧化钠,经过几次水洗步骤,把甘油分离出去。1 L豆油可生产出0.95 L生物柴油,每1浦氏耳大豆(27.24     

大豆油甲酯-柴油混合燃料特性研究

近年来,生物柴油作为一种无毒的、可生物降解的、可再生的柴油机代用燃料倍受关注.为优化生物柴油的应用,对比分析了大豆油甲酯生物柴油与柴油混合液的低温流动性、雾化和蒸发性、安定性、腐蚀性、清洁性和互溶性.结果表明:与柴油相比,B5、B10、B15、B20、B25和B30的凝点和冷滤点保持不变;闪点、20℃运动粘度、40℃运动粘度、密度和50%馏出温度分别平均增加26.8%、7.2%、10.8%、1.3%和12.6%,而90%和95%馏出温度基本不变;胶质和残碳分别平均增加62.3%和6.5%;硫含量平均降低15.7%,但酸度平均升高4.1%;灰分平均增加22.7%.但机械杂质平均降低13.7%.经分析,大豆油甲酯生物柴油与柴油混合液基本符合国家标准GB252-2000对轻柴油的要求.     

生物柴油/矿物柴油混合燃料低温流动特性及流变特性研究

采用多功能低温测定仪和旋转粘度计测定了生物柴油/矿物柴油混合燃料的冷滤点、凝点和粘度,研究了混合燃料的低温流动性能及流变学性能.结果表明:0#柴油调入生物柴油后,混合柴油的冷滤点降低,粘温性提高,低温流动性改善;不同温度下,剪切速率对混合燃料表观粘度影响不同.当温度高于冷滤点时,剪切速率对混合燃料表观粘度影响较小;当温度低于冷滤点时,剪切速率增大,混合燃料表观粘度降低,且随温度降低,表观粘度随剪切速率增大而降低更为明显.     

大豆油及其生物柴油低温流动特性研究

采用燃料低温性能测定仪考察了大豆油及其生物柴油的冷滤点、凝点和运动粘度,采用偏光显微镜和示差扫描量热分析仪探讨了大豆油及其生物柴油低温下失去流动性的机理.结果表明:大豆油制成生物柴油后,运动粘度显著降低,冷滤点降低,凝点略有升高.在低温下,大豆油形成无定形粘稠玻璃状物质,粘度增大,使其失去流动性:大豆油生物柴油中的晶态物质析出,连接成网状结构,包络和吸附了处于液态的生物柴油,使其失去流动性.     

生物柴油物理特性参数的估算与误差分析

以生物柴油脂肪酸酯含量为基础,应用Matlab编制了包含15种脂肪酸酯的生物柴油物性参数预测程序,并应用所编程序估算了大豆油甲酯生物柴油的密度、表面活力、黏度和导热系数;分析比较了各种估算方法的精度.结果表明:在生物柴油密度估算中,修改Raekett方程的估算精度较高;Sastfi-Rao方法估算生物柴油低温黏度所得结果与实测值最接近,其估算精度较高;Miller方法和Macleod-Sugden关联式估算生物柴油表面张力的精度较其它几种方法高;建议在生物柴油导热系数估算中应用Sastri方法.     

生物柴油能源作物研发现状

能源工业是经济高速发展的源动力，柴油作为一种重要的石油炼制产品，在各国燃料结构中占有较高的份额，已成为重要的动力燃料。随着世界范围内车辆柴油化趋势的加快，未来柴油的需求量会愈来愈大，而石油资源的日益枯竭和人们环保意识的提高，大大促进了世界各国加快柴油替代燃料的开发步伐，尤其是进入20世纪90年代，生物柴油以其优越的环保性能受到了各国的重视，具有环保再生型绿色能源是人类面临新的研究课题。     

响应面法优化大豆油下脚料制备生物柴油工艺的研究

随着全球性能源的日益短缺与环境的逐渐恶化,生物柴油作为一种无毒、可生物降解和再生的替代燃料正受到越来越多的关注.研究了利用大豆油下脚料(油脚、皂脚混合物)制取生物柴油的工艺过程.先用乙醚室温下萃取下脚料,料液比1∶2(g∶mL),萃取时间2 h.离心后分为3层,上层有机相再经丙酮萃取分离出磷脂和中性油,磷脂作为高附加值副产品回收再利用以降低生物柴油的生产成本.分离出的皂相经酸化转化为混合脂肪酸,混合脂肪酸用于酸催化的酯化反应.利用响应面法对酯化反应工艺参数进行了优化,并得到回归方程.方差分析结果表明:在各影响因素中,醇酸摩尔比对转化率的影响最大,其次是反应温度和反应时间,醇酸摩尔比和反应温度的交互作用显著.酯化反应优化后的工艺条件为醇酸摩尔比为5∶1,催化剂(H2SO4)添加量3%(wt.%),反应温度为87℃,反应时间4.74 h,在此条件下转化率达到92.5%.     

绿色液体燃料-大豆生物柴油的制备研究

大豆生物柴油是一种对环境友好的、可再生的生物质燃料,大豆生物柴油的应用可以减少人类对矿物燃料的依赖,而且可以大大减少对环境的污染.试验分别利用精制大豆油和煎炸废油成功制得符合国内外现有质量标准的大豆生物柴油.     

碱催化下大豆生物柴油的制备研究

以大豆油和甲醇为原料,研究了氢氧化钠催化下大豆油脂肪酸甲酯-生物柴油的合成反应.并对影响酯化率的反应物料比、催化剂用量、反应温度、反应时间进行研究,通过正交试验,确定了制备生物柴油的最佳工艺条件:甲醇与大豆油摩尔比5∶ 1,0.5%的NaOH为催化剂,反应温度60℃,反应时间50 min.在优化条件下酯化率高达94.5%.     

发展油菜生物柴油的潜力、问题与对策

分析了我国石油资源现状及供需状况,认为柴油在动力燃料结构中占主导地位,但供需矛盾十分突出,寻找和开发新的柴油替代能源势在必行.根据菜油的特点及油菜在我国的发展前景,认为油菜是我国发展生物柴油最理想的原料,发展油菜生物柴油对保障我国柴油供给安全及农民增收均具有重要的战略意义.指出了我国目前发展油菜生物柴油存在的问题,并提出了相应的对策.     

Methyl ester of Sal oil (Shorea robusta) as a substitute to diesel fuel—A study on its preparation, performance and emissions in direct injection diesel engine

Many research reported vegetable oil as a potential substitute for diesel engines with its ester form known as biodiesel. The biodiesel can be prepared by different process using vegetable oil and alcohol. The common process used for biodiesel preparation is known as transesterification. This paper presents the transesterification of Sal oil (Shorea robusta) into Sal oil methyl ester (SOME) and its performance in direct injection diesel engine. Several process parameters such as catalyst quantity, molar ratio of alcohol, reaction temperature and reaction time were studied and the optimized process conditions are amount of catalyst (NaOH) - 0.25 wt%, alcohol (methanol) - 150% excess, reaction temperature - 65 °C and reaction time - 1.5 h. The studies with SOME as fuel in the direct injection diesel engine shows that the exhaust emissions such as CO, HC and NO_x are reduced by 25%, 45% and 12%, respectively compared to diesel without significant difference in thermal efficiency. Based on this study it is concluded that the SOME can be used as fuel without any modifications in the engine and hence this biodiesel can be a potential substitute to standard diesel fuel.     

Synthesis and characterization of hazelnut oil-based biodiesel

The demand for diesel fuel far exceeds the current and future biodiesel production capabilities of the vegetable oil and animal fat industries. New oilseed crops that do not compete with traditional food crop are needed to meet existing energy demands. Hybrid hazelnut oil is just such an attractive raw material for production of biodiesel. Hazelnut oil was extracted from hybrid hazelnuts and the crude oil was refined. Hazelnut oil-based biodiesel was prepared via the transesterification of the refined hazelnut oil with excess methanol using an alkaline catalyst. The effects of reaction temperature, time and catalyst concentration on the yield of diesel were examined, and selected physical and chemical properties of the biodiesel were evaluated. The biodiesel yield increased with increasing temperature from 25 to 65 °C and with increasing catalyst concentration from 0.1 to 0.7 wt%. The increase in yield with reaction time was nonlinear and characterized by an initial faster rate, followed by a slow rate. Hazelnut oil-based biodiesel had an average viscosity of 8.82 cP at 25 °C, which was slightly higher than that of the commercial soy-based diesel (7.92 cP at 25 °C). An approximate 12 °C higher onset oxidative temperature and a 10 °C lower cloud point of hazelnut oil biodiesel than those of its commercial soy counterpart indicated a better oxidative stability and flowability at low temperature. The average heat of combustion of hazelnut oil biodiesel was 40.23 kJ/g, and accounted for approximately 88% of energy content of diesel fuel. The fatty acid composition of hazelnut oil-based biodiesel was the same as the nature oil.     

Physicochemical properties of stillingia oil: Feasibility for biodiesel production by enzyme transesterification

The physicochemical properties, fatty acids profile and triglyceride compositions of the stillingia oil were analyzed. The stillingia oil was found to contain 98.79% neutral lipids, 0.22% phospholipids and 0.99% glycolipids, which exhibited varying contents of fatty acids. The major triglyceride was double linoleic acid linolenic acid triglyceride, which accounted for approximately 79.49% of the total triglycerides. Preparation of biodiesel from stillingia oil was investigated by enzyme transesterification with methanol as the acyl acceptor. The results showed that lipase type (Novozym 435, Lipozyme TLIM and Lipozyme RMIM), reaction systems (in solvent-free and tert-butanol system) and operational parameters (lipase loading, reaction time, temperature, and molar ratio of alcohol to oil) influenced the biodiesel yield. Fuel properties of biodiesel from stillingia oil were evaluated and all were in acceptable range for use as biodiesel in diesel engines, and had remarkable flash point and satisfactory cold flow properties. It was concluded that stillingia oil was an alternative potential feedstock oil for biodiesel production.     

Preparation of biodiesel from Idesia polycarpa var. vestita fruit oil

The feasibility of producing biodiesel from Idesia polycarpa var. vestita fruit oil was studied. A methyl ester biodiesel was prepared from refined I. polycarpa fruit oil using methanol and potassium hydroxide (KOH) in an alkali-catalyzed transesterification process. The experimental variables investigated in this study were catalyst concentration (0.5–2.0 wt.% of oil), methanol/oil molar ratio (4.5:1 to 6.5:1), temperature (20–60 °C) and reaction time (20–60 min). A maximum yield of over 99% of methyl esters in I. polycarpa fruit oil biodiesel was achieved using a 6:1 molar ratio of methanol to oil, 1.0% KOH (% oil) and reaction time for 40 min at 30 °C. The properties of I. polycarpa fruit oil methyl esters produced under optimum conditions were also analyzed for specifications for biodiesel as fuel in diesel engines according to China Biofuel Systems Standards. The fuel properties of the I. polycarpa fruit oil biodiesel obtained are similar to the No. 0 light diesel fuel and most of the parameters comply with the limits established by specifications for biodiesel.     

Characterization of biodiesel and bio-oil from Sterculia striata (chicha) oil

This work describes the mechanical and solvent extraction of Sterculia striata seed oil. It was determined that the seeds contain up to 41% in oil, which has an unusual composition. Indeed, up to 50% of the fatty acid contain cyclopropenoid ring. The oil was used as raw material to produce bio-oil and biodiesel and their physical-chemical properties were evaluated. Some of the studied physical-chemical properties of the S. striata biodiesel are in acceptable range for use as biodiesel in diesel engines, showing a promising economic exploitation of this raw material in semi-arid regions. It was also observed that the cyclopropenoid ring remains after transesterification and is decomposed during pyrolysis.     

Viscosity reduction of castor oil esters by the addition of diesel, safflower oil esters and additives

The high viscosity of vegetable oil can be reduced by transesterification with alcohols and converting it into biodiesel. Biodiesel can be used neat or blended with diesel as engine fuel. This study demonstrates that esters of castor oils have a higher viscosity than safflower oil derived esters and the viscosity can be reduced by blending with diesel. The viscosity increased in a non-linear fashion as the percentage of castor esters increased in castor esters diesel blends and in castor esters safflower esters blends. Only slight increases in viscosity were observed for B40 and B60 mixtures with No. 2 diesel. Addition of ten chemical additives in castor esters at the rate of 0.01%, 0.1% and 1.0% showed limited viscosity reduction.     

Synthesis of Jatropha curcas oil-based biodiesel in a pulsed loop reactor

Jatropha curcas oil (JCO) has a high content of free fatty acids and has been used extensively as a feedstock in biodiesel production. In the present study, the transesterification reaction of JCO to Jatropha curcas methyl ester (biodiesel) was performed in a continuous pulsed loop reactor under atmospheric conditions. The JCO was pre-treated prior to the reaction to reduce the free fatty acid content to below 1% (w/w). The operating parameters of the loop reactor were optimised based on the conversion of the JCO to Jatropha curcas biodiesel and included reaction temperature, molar ratio of oil to MeOH, reaction time and oscillation frequency. The findings show that the highest reaction conversion of 99.7% (w/w) was achieved using KOH catalyst and 98.8% conversion was obtained using NaOCH₃ catalyst. The optimal operating conditions were a molar ratio of 6:1, an oscillation frequency of 6 Hz, temperature of 60 °C, feedstock FFA content of 0.5% (w/w) and only 10 min of reaction time. As a commercial commodity, the physical properties of biodiesel were analysed, and they compared well with the characteristics of fossil-based diesel fuel.     

Fuel properties of oil from genetically altered Cuphea viscosissima

A genetically altered plant strain (Cuphea viscosissima VS-320) was identified which produces an oil with elevated levels of medium- and short-chain triglycerides. Previous studies have suggested that such an oil may be appropriate for use as a substitute for diesel fuel without chemical conversion of component triglycerides to methyl esters. This oil is also of interest for other industrial applications. This paper discusses the oil composition of C. viscosissima VS-320 and presents the analysis of several important alternative fuel screening properties of this oil: dynamic viscosity for shear rates of 1.617–64.69 s⁻¹ at temperatures of 25–80°C, boiling point at atmospheric pressure, temperature dependence of vapor pressure (from 40 to 760 mmHg for the 300–400°C temperature range), and heat of vaporization (ΔH_v). These properties have been established as indicators of fuel performance and can be used for initial screening of possible diesel fuel substitutes. These properties are compared to those of diesel, biodiesel, and vegetable oils. Analysis of these properties suggests that further genetic development of this plant as a source of diesel fuel is warranted.     

新型固体碱催化大豆油制备生物柴油的工艺研究

制备了新型固体碱催化剂KNO3/AlSBA-15,并以此催化大豆油与甲醇酯交换反应制备生物柴油,对其工艺条件进行了优化.结果表明:醇油物质的量比为12∶1,催化剂用量为大豆油质量的3％,反应温度65C,反应时间4h,生物柴油的产率可达81％以上.该催化剂对酯交换制备生物柴油具有较高的催化活性和良好的重复使用性.     

茶籽油制备生物柴油工艺研究

以茶树[Camellia sinensis (L.) O. Kuntze]茶籽油为原料,研究了茶籽油甲酯化制备生物柴油的工艺条件。在单因素试验的基础上,选取反应温度、催化剂用量（占精炼油质量百分比）、反应时间和醇油摩尔比为影响因子,以酯交换率为响应值,应用Box-Behnken中心组合试验设计建立数学模型,进行响应面分析。结果表明,茶籽油制备生物柴油的最佳工艺条件为：反应温度58℃、催化剂用量1.05%、反应时间66min、醇油摩尔比9.7∶1。在此条件下,酯交换率达到98.73%。对生物柴油进行红外光谱和GC-MS分析,产品质量达到国家生物柴油标准。