The Fractionation, Development And Utilization Of Methyl Palmitate By-products From CVT Biodiesel

Biodiesel can be used as perfect substituting for petroleum diesel, which is aenvironmental protection and renewable green energy, but lacking of oil source andcostly production effect its abroad using. Chinese Vegetable Tallow (CVT, i.e.Chinese tallow tegument oil), produced by the seed-coat of Chinese Tallow Tree(CTT), which is special woody oil plant, is one of top four wood with high oilcontent in seed, including 26-27% CVT in CTT seed. CVT has a simple fatty acidcomposition with about 65% palmitic acid, 32% oleic acid. CVT can be used as asource of edible oil and industrial oil. Moreover, CTT can extract high yield of oilthat is more than palm tree and having long economic life, can provide stable oilsource. But because including excessive palmitic acid, its ester production alsoinclude excessive methyl palmitate that had disadvantaged influence in lowtemperature fluidity of fatty acid methyl ester, confining the appliance of CVT inbiodiesel.Based on raw CVT materials behaving high acid value, the research studied themethod two step esterify and using solvent crystallizing fractionation technology,fractionated and purified the MP the outgrowth of biodiesel, continue to synthesizethe MP and Vc to be Ascorbyl Palmitate (AP), at last, adding AP into the bean oiland rap oil, in order to test its antioxidant ability.The physical and chemical characteristics and quality of material were the baseof technical course, so we have studied its interrelated characteristics of CVT. Theresults follow as: acid value, 20.8 mgKOH/g, iodine value, 25.4 I₂/100g, peroxidevalue, 28.9 meq/kg, density, 0.91 g/cm³ (d₅₀⁵⁰), , melting point, 35.6-39.5℃,saponification value, 99.4 mgKOH/g, content of phosphatide after centrifugal is168.4mg/kg, all these show that pre-esterify with acid, transesterification with alkalican effectively advance the utilization of the free fatty acid. In virtue of GC,palmitic acid in CVT, with a content of 66.80%, is more 2.4 times than oleic acid,far more than contents of laurie acid, stearic acid,and linoleic acid, their sum content is lower than 5%, so CVT is good source of palmitic acid, oleic acid and their esters,CVT can be used as material of palmitic acid and its production or MP could used inother purpose after separated from FAME, the remains may used as fuel or to besaled as pure methyl oleate after refined which has more added value.The optimum degumming condition were: citric acid dosage, 1.5g/kg, reactiontemperature, 90℃, water dosage, 60g/kg, mixed time, 50min, content ofphosphatide, 35.48mg/kg, the last is still high than request of standard, and will beimproved by methyl esterify reaction in next step.The best esterify with acid condition were: reaction time, 8h, molar ratio ofmethanol and oil, 35:1, reaction temperature, 75℃, catalyzer dosage, 3%, accordingto this technics, acid value be fell as 0.37mg/g, esterfied ratio, 98.2%, yield is 99.6%.Subsequently, working catalytic reaction with alkali, and best condition is: reactiontime, 35min, catalyzer dosage, 0.8%, the molar ratio of methnal and oil, 6:1, reactiontemperature, 65℃, esterfied ratio 93.1%, melting point range, 23.2-24.7℃, acidvalue 0.12mgKOH/g, content of phosphatide, 5.76mg/kg, it is less than request ofGerman Standard with 10mg/kg. The main components of FAME were: methylpalmitate, 69.02%, methyl oleate 27.66%, methyl laurate, 1.94%, methyl stearate,1.78%, because its simple composing and plentiful methyl palmitate and methyloleate, it is good source of methyl palmitate and biodiesel.Separating and purifying MP from FAME with crystallizing fractionationtechnics with solvent, according to primary experiment and result of solubilityparameter, ethanol is right solvent for separating MP, and due to stronge polarityhydrogen bond of methanol, it also in favor of crystallization of MP; The result showthat, we can get more pure and good quality with ethanol. In condition of ratio ofFAME and solvent, 1:2, final crystal temperature, 10℃, the purity of MP achieve91.2%, continue to purify this product 2times and purity advanced to 96.9%, at thesame time, ethanol has effect of decolor and deodorize, its production reach therequest of of usual chemical industry product. All these results show that ethanol isexcellent solvent for the separation of MP from FAME.Using ascorbic acid (Vc) overdosage and adopting 98% H₂SO₄ as catalyzer, tosynthesized Vc and MP to be AP. At 25℃, the molar ratio of Vc and MP is 1:0.8, reaction time 17h, molar ratio of sum of Vc plus MP and H2SO4 is 0.14:1, the yieldachieve 69.4%, and it's white. According this condition, could increasing yield of AP,reducing waste of Vc. After testing, indexs of AP as follows: purity 96.7%, metlingpoint, 112.6-119.5℃, heat loss, 0.11%, burned residue, 0.053%, and its qualityachieve the National Standard 16314-1996 of Ascorbyl Palmitate. All these showthat synthesizing MP which come form outgrowth of biodiesel and Vc to be AP is afeasible path. Using the method of overdosage Vc, can simplified the operation,avoided to use a lot of solvents, decreased the cost and energy of solvent reuse,reduced the harm and insecure factors of solvent in productive process.HLB value ofAP is about 8.4 after calculation and test, it is oil-water emulsifier.Using AP we synthesized into bean oil and rap oil, the results show that, APhave best antioxidant ability in bean oil, and its effect is close to TBHQ in rap oil,represents right antioxidant ability, so it is safe, highly efficient and worth to beextend. When AP mixed use with VE, they behaved obvious effect on promotion ofanoxidant ability and postponement of oxidated induce period. Mixed use is morecheap than using V_E alone because the price of AP is lower than V_E.Generally speaking, this research used MP that extracted from fatty acid methylester of CVT, to synthesize AP, this technics is available, on one side, could usingoutgrowth reasonable, and synthesize Vc ramification production which have moreadded value, it may reduce the cost of biodiesel, on the other hand, this technicsmade it come true that CVT used in energy. At the same time, could offered adevelopable route for these oil source which contained excessive unsaturated orsaturated fatty acid and behaved disadvantaged influence for cetane number and lowtemperature fluidity.