| The main composition of the biodiesel is various kinds of fatty acid methyl ester, studies showed that the CFPP of methyl ester biodiesel was higher, limited application of biodiesel in low temperature area, by using FAEEs instead of FAMEs can get good low temperature performance, however, the preparation of FAEEs is more time-consuming and costlier than FAMEs; Therefore, in this paper, in order to improve the cold flow properties of palm oil methyl ester biodiesel, we selected dimethyl carbonate(DMC) and diethyl carbonate(DEC) mixed reagent to prepare FAMEs/FAEEs biodiesel without glycerin by-product by alkali catalysis and supercritical process, established a quantitative analysis method of fatty acid methyl/ethyl ester, optimized the preparation technology, studied the influence of the palm oil fatty acid ethyl ester on the methyl ester.First of all, this paper established the fatty acid methyl/ethyl ester analysis method with the nonpolar capillary column of high temperature, got the quantitative standard curve of each fatty acid methyl/ethyl ester, and did the recovery rate and precision experiments. The results showed that the standard curve of high accuracy, precision and repeatability was also very ideal.Secondly, the preparation of biodiesel by alkali catalytic technology, by single design investigated the influence of factors on the methyl/ethyl ester molar ratio and yield, only the temperature had a significant impact on methyl/ethyl ester molar ratio; Orthogonal design to process further optimization, it was concluded that the order of factors affecting the yield of ester exchange reaction:reaction temperature> reaction time> ester and oil mole ratio> catalyst dosage, and when reaction temperature was100℃, reaction time was20h, ester oil molar ratio of15:1, catalyst dosage was15%, the reaction got the highest yield above92%.Then, the preparation of biodiesel by supercritical technology, by single design investigated the influence of factors on the methyl/ethyl ester molar ratio and yield, all factors had no significant impact on methyl/ethyl ester molar ratio; response surface to process further optimization, we established the regression equation, the degree of fitting was good. The best preparation conditions for supercritical reaction temperature was309.3℃, the reaction time was34.7min, ester oil molar ratio of was26.9:1, the catalyst was0.2%, the yield could reach91.4%.The influence factors on yield sequence was reaction time> reaction temperature> ester oil mole ratio, the interaction between factors was very significant.Finally, in order to study the influence of different process conditions on biodiesel physical and chemical properties, comparing biodiesel properties prepared by the two technology conditions. The results show that density, viscosity, acid value, oxidation stability and corrosion resistance of the two kinds of biodiesel can meet the requirement of national standard, calorific value increases, power performance improved, and the addition of fatty acid ethyl ester improved low temperature performance of fatty acid methyl ester biodiesel, so biodiesel in the paper can satisfy the use of0#diesel oil area. By adding a certain proportion of biodiesel in diesel (B5-B30) can reduce the cold filter plugging point and condensation point of blend oil, combined with DSC study on low temperature crystallization properties of biodiesel, we found that with the increase of the proportion of biodiesel in blend oil the crystallization heat reduced first and then increased, the crystallization quantity of blend oil was lower than diesel (B5-B20), the addition of biodiesel in blend oil improved low temperature performance. Linear fitting of CFPP and DSC cooling curve peak temperature, the relationship was CFPP (℃)=0.7758Tpeak+2.5036℃, the fitting degree R2=0.984. So CFPP and peak temperature (TPeak) of DSC curve of cooling crystallization had a good correlation. |
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