Study On Influencing Factors Of Low-temperature Flowing Properties Of Biodiesel Fuel

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.