【作者】 巫淼鑫；

【导师】 王俊德； 邬国英；

【作者基本信息】 南京理工大学 ， 化学工程与技术， 2008， 博士

【摘要】 本文建立了一批适合于生物柴油指标测定的分析方法;确定了碱催化酯交换法制备生物柴油的条件;初步考察了我国7种常见食用植物油及其生物柴油的低温流动性能以及与生物柴油中饱和脂肪酸甲酯的关系;通过添加猪油于菜籽油后再合成生物柴油以及直接添加棕榈酸甲酯和硬脂酸甲酯于菜籽油生物柴油中,研究了饱和脂肪酸甲酯对生物柴油低温流动性能的影响。研究了5种降凝剂以及共存物(如脂肪酸甘油酯、甲醇和水)对大豆油和菜籽油生物柴油低温流动性能以及黏度的影响;测定了与我国0号、-20号柴油以及乙醇调和后,生物柴油的低温流动性能和黏度;考察了降凝剂对调和油(20%菜籽油生物柴油与80%0号或-20号柴油)低温流动性能和黏度的影响。初步比较了放置前后添加共存物、柴油和降凝剂的大豆油和菜籽油生物柴油低温流动性能和黏度的变化。另外,初步考察了冬季化法对我国大豆油和菜籽油生物柴油低温流动性能的影响。这些方面的研究将为生物柴油的原料选择、制备、低温流动性能改进以及储存、使用和运输等提供依据。本文的主要内容和实验结果如下:1.分析方法的建立以国家和部颁标准为基础建立了一些适合于生物柴油的分析方法如凝点、倾点、冷滤点、黏度、皂化值、酸值、碘值、磷含量、色度、灰分和比重等。另外,建立了乙酰丙酮分光光度测定生物柴油中总甘油和游离甘油含量以及气相色谱法测定脂肪酸甲酯分布的新方法。2.生物柴油制备条件的选择通过测定生物柴油中总甘油含量,选择了以植物油和甲醇为原料,以KOH为催化剂,通过酯交换法制备生物柴油的条件;将醇油摩尔比、反应温度和反应时间分别选择在6:1、50℃和1 h,催化剂用量为植物油的1.2%左右。与通过分析生物柴油中脂肪酸甲酯和甘油酯含量所得的制备条件基本一致,但本文所用的仪器较简单。3.食用植物油生物柴油的低温流动性能以我国食用植物油为原料,制备了7种植物油生物柴油。当植物油制成相应的生物柴油后凝点和倾点显著升高,冷滤点降低,生物柴油40℃时的运动黏度比其原料植物油降低了85%以上。从凝点看,菜籽油生物柴油的低温流动性能最好,能满足我国-10号柴油的要求;然后依次为葵花籽油、玉米油、芝麻油、大豆油和棉籽油生物柴油,与我国0号柴油类似;花生油生物柴油的最差。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和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。4.生物柴油中共存物和饱和脂肪酸甲酯对低温流动性能的影响当添加的共存物甲醇、水分和甘油酯较少时,对大豆油和菜籽油生物柴油的低温流动性能和黏度影响不大,饱和脂肪酸甲酯的同时析出对大豆油生物柴油低温流动性能起关键作用。但添加的甲醇和相应植物油较多时,将对生物柴油的黏度产生影响。在菜籽油与猪油混合脂肪酸甲酯体系中,随猪油添加量增加,冷滤点随体系中总饱和脂肪酸甲酯含量增加呈S型曲线增加,凝点和倾点先增加较快后渐趋缓,其黏度有所改善。在研究范围内,能用一定关系式较好拟合。在菜籽油生物柴油中,随棕榈酸甲酯和硬脂酸甲酯添加量增加,凝点、倾点和冷滤点逐渐升高,倾点与冷滤点逐渐靠近,但凝点和倾点增加变缓,硬脂酸甲酯比棕榈酸甲酯对低温流动性能影响更大。黏度随棕榈酸甲酯增加略有下降,基本不随硬脂酸甲酯含量而变。5.与柴油和乙醇调和生物柴油的低温流动性能0号柴油能有效地降低大豆油和菜籽油生物柴油的黏度,但对大豆油生物柴油低温流动性能影响不大;能使菜籽油生物柴油的凝点和倾点升高,基本不影响其冷滤点。-20号柴油能显著降低两种生物柴油的凝点、倾点、冷滤点和黏度。因此与低温流动性能较好的柴油调和是改善生物柴油低温流动性能的有效途径。另外,乙醇也能有效的改善两种生物柴油的低温流动性能和黏度。6.降凝剂对生物柴油低温流动性能的影响聚乙烯基酯类降凝剂1能改善大豆油和菜籽油生物柴油的低温流动性能,但幅度不大。聚乙烯基酯类降凝剂2和α_-烯烃共聚物降凝剂3能显著降低大豆油生物柴油的凝点和倾点,但对冷滤点无改善作用;能显著降低菜籽油生物柴油的冷滤点,能小幅改善其凝点和倾点。乙丙共聚物类降凝剂4和5对两种生物柴油的低温流动性能无影响。被考察的5种降凝剂都会增加生物柴油的黏度。降凝剂1和降凝剂2能显著改善调和油1(20%菜籽油生物柴油+80%0号柴油)的低温流动性能。降凝剂3对调和油1的冷滤点基本无影响,能小幅降低其凝点和倾点。降凝剂4和5对此调和油的低温流动性能几乎无影响。5种降凝剂能使调和油的黏度小幅上升。降凝剂1能较好的降低调和油2(20%菜籽油生物柴油+80%-20号柴油)的倾点和凝点,但对其冷滤点基本无影响。降凝剂2和3对此调和油冷滤点、倾点和凝点的改善有较好的效果。降凝剂4对此调和油的低温流动性能几乎没有影响。加入这4种降凝剂,都使调和油的黏度有所上升。7.储存对生物柴油低温流动性能的影响对于添加共存物、柴油和降凝剂的大豆油和菜籽油生物柴油,放置后其黏度和酸值有不同程度的增加,黏度增加是不饱和脂肪酸甲酯中双键发生聚合所致。另外,随生物柴油黏度增加,冷滤点有所上升。对于添加共存物和柴油样品,凝点和倾点变化不大。对于有些添加降凝剂的生物柴油,放置时间对其低温流动性能有较大影响。对于添加柴油的生物柴油,添加的柴油越多,放置后其黏度增加越少。即与柴油调和不但可以改善生物柴油的低温流动性能和黏度,而且放置时间对其影响也减少。在250h加热时间内,在60℃和80℃下,加热对大豆油和菜籽油生物柴油及其与80%柴油调和油的凝点、倾点和冷滤点基本没有影响,只是黏度随着加热时间的增加而增加,而且加热温度越高,黏度的增幅越大。8.冬季化对生物柴油低温流动性能的影响直接冬季化处理对纯大豆油生物柴油的低温流动性能和黏度的改善不大;但对添加0.3%降凝剂2后再冬季化处理,能较好的改善大豆生物柴油的冷滤点。直接冬季化法能有效地降低菜籽油生物柴油的冷滤点。但操作比较复杂,时间长,得率不高。更多还原

【Abstract】 A series of analytical methods for biodiesel fuel(BDF)were established on the basis of standard methods such as chinese national standard.The optimum conditions of BDF preparation by transesterification with KOH catalysis were selected by the total glycerol content determined in BDF on spectrophotometric method.The low-temperature flowing properties(LTFPs)of seven edible vegetable oils and their BDFs were inspected.The relation between LTFPs of seven BDFs and the content and distribution of saturated fatty acid methyl esters(FAMEs)in them was studied.The influence of saturated FAMEs on LTFPs of BDF was investigated by changing the distribution of saturated FAMEs in the BDF from rapeseed oil.The influence of five cold-flow additives(CFAs),methanol,water, glyceride,NO.0 diesel fuel(DF0),NO.-20 diesel fuel(DF-20)and ethanol on LTFPs and viscosity(v)of methyl esters from soybean oil(SME)and rapeseed oil(RME)was researched.LTFPs and v of blending oils(RME and DF0 or DF-20)with CFAs were determined.LTFPs and v of RME and SME with impurities,CFAs,DF0 and DF-20 after a period of laid time have been measured.Then the influence of winterization on LTFPs and v of RME and SME has been studied.These investigations will have a help for us to select raw materials,prepare,store,use and transport BDF,improve LTFPs of BDF.The major content and results was descried as follows:1.Establishment of Analytical MethodsIn this paper,a series of analytical methods such as solidification point(SP),pour point(PP),cold filter plugging point(CFPP),v,saponification value(SV),acid value(AV), iodine value(IV),phosphorus content,chroma,ash content and specific gravity have been established for BDF on the basis of chinese national and department standard.Moreover we have established other analytical methods such as acetyl acetone spectrophotometric method for the total and free glycerol content and gas chromatography for the distribution of FAMEs in the BDF.2.Selection of Optimum Conditions in BDF PreparationIn this paper,BDFs were prepared from vegetable oils and animal fat by transesterification with KOH catalysis.The optimum conditions of BDF preparation from soybean oil and methanol were obtained by the total glycerol content determined in BDF on spectrophotometric method.The conclusion from this method is in keeping with what to be obtained by FAMEs and glyceride content determined in BDF on GC.This method is fairly simple.3.LTFPs of BDFs from Edible Vegetable OilsBDFs were prepared from seven common edible vegetable oils.LTFPs(SP,PP and CFPP)and v of vegetable oils and their BDFs were determined.Experimental results showed that the SP and PP of the BDF were higher than those of the related vegetable oil,as to CFPP and v were reversed.The v(40℃)of the BDF is only about 15%of the related vegetable oil.Judged by SP,RME is the best,then BDFs from sunflower oil, corn oil,sesame oil,soybean oil and cottonseed oil,the BDF from peanut oil is the worst. The SP of RME reached the requirement of NO.-10 diesel fuel;other BDFs,except from peanut oil,met the SP requirement of DF0.The LTFPs of the BDF depend on the content and distribution of the saturated FAMEs in the BDF:the higher the esters content of the saturated FAMEs and the longer the carbon chains are,the worse will the LTFPs be.4.Influence of Coexisting Materials and Saturated FAMEs in BDF on Its LTFPsThe LTFPs of SME or RME are hardly influenced by methanol,water and glyceride that exist in SME or RME when their contents are less.When SME is cooled,the saturated FAMEs in SME will co-crystallize and influence its LTFPs.The v of SME will be influenced when the methanol or vegetable oil content is higher.When BDFs were prepared from rapeseed oil and lard,experimental results showed that the content of the saturated FAMEs in these samples increased when the lard was added;their viscosities were improved,but the SP,PP and CFPP increased in varying degrees.The CFPP increased according to the S-shape curve when the saturated FAME increased.The SP and PP increased relatively fast first but slow then.The curves of the SP, PP and CFPP versus the total content of the saturated FAMEs in these samples have been fitted by the nonlinear function.When the methyl palmitate and methyl stearate added to RME increased,the SP,PP and CFPP of RME increased;the PP was nearing the CFPP;The SP and PP increased relatively fast first but slow then.The influence of methyl stearate on LTFPs of RME was greater than that of methyl palmitate.When the methyl palmitate increased,the v of RME decreased slightly.The v of RME was hardly influenced by methyl stearate.5.LTFPs of Blending Oils with BDF and Fossil Diesel or Ethanol DF0 can obviously reduce the v of SME and RME,but can not greatly affect the LTFPs of SME.When DF0 was added to RME,the SP and PP of RME increased,the CFPP was changed little.DF-20 or ethanol can greatly reduce the SP,PP,CFPP and v of SME or RME.So to blend with the diesel that its LTFPs are good is an effective way to improve the LTFPs of BDF.6.Influence of Depressants on LTFPs of BDFDepressant 1(vinyl ester polymer)can improve the LTFPs of SME and RME. Depressant 2(vinyl ester polymer)and depressant 3(α-olefins copolymer)can greatly reduce the SP and PP of SME,but cann’t improve its CFPP.Depressant 2 and depressant 3 can greatly reduce the CFPP of RME,but only improve the SP and PP of RME a little. Depressant 4 and depressant 5(ethylene-propylene copolymer)cann’t improve the LTFPs of SME and RME.All five cold-flow additives can increase the v of SME and RME.Depressant 1 and depressant 2 can greatly improve the LTFPs of blending oil 1(20% RME and 80%DF0).Depressant 3 can reduce the SP and PP of blending oil 1,but cann’t improve its CFPP.Depressant 4 and depressant 5 can hardly improve the LTFPs of blending oil 1.All five cold-flow additives can increase the v of blending oil 1.Depressant 1 can reduce the SP and PP of blending oil 2(20%RME and 80%DF-20), but can hardly improve its CFPE Depressant 2 and depressant 3 can obviously reduce the CFPP,PP and SP of blending oil 2.Depressant 4 can hardly improve the LTFPs of blending oil 2.All four cold-flow additives can increase the v of blending oil 2.7.Influence of Store on LTFPs of BDFAfter SME and RME with impurity,cold-flow additives and diesel were laid in for a period of time,their v and AV increased in varying degrees.The more the v increases,the less will the IV be.So the increase of viscosity is due to the polymerization of double bond(-C=C-)in the BDF.The CFPP of BDF rises when its v increases.For SME and RME with impurity and fossil diesel,their SP and PP were changed a little;for some SME or RME samples with CFAs,their LTFPs were changed greatly after a period of laid time. For SME and RME with diesel,the more the diesel was added,the less did their v increase after a period of laid time.So to blend with diesel fuel can improve the LTFPs of SME and RME,also reduce the influence of the laid time on their LTFPs.When SME,RME and their blending oils with 80%diesel fuel were heated in the 60℃or 80℃water bath within about 250h,their SP,PP and CFPP were affected hardly,only their v had a slight increment.The longer the heating time and the higher the heating temperature are,the more does the v increase.8.Influence of Winterization on LTFPs of BDFAfter neat SME was cooled directly and filtered,its LTFPs and v were improved slightly.When 0.3%depressant 2 was added to neat SME,then this SME was cooled and filtered,its CFPP was reduced fairly.Direct winterization can improve the CFPP of RME. But the winterization operation is complicated and needs a long time,also the yield is poor.更多还原