| Along with adjusting the strategy of global energy development, it is the trend that the green and renewable energy occupies more and more important position in the development of the energy industry and gradually replaces the traditional fossil energy. As a typical green energy, biodiesel has been paid much attention by various countries and regions in recent years.Supercritical low carbon alcohol transesterification is a a new process for biodiesel production,which has the advantages of green, fast, high yield and high efficiency.Compared with the intermittent preparation technology, the continuous preparation technology can reduce the production cost and energy consumption, as well as benefit industrialisation production. Therefore, based on the continuous supercritical methanol transesterification, the effect of different reactors was discussed. The reaction process was optimized, and biodiesel can be directly produced by soybean flakes by the coupling process which coupled the continuous supercritical methanol transesterification with the supercritical fluid extraction. Besides the control steps and the optimum reaction conditions of the coupling technology were determined, and the control steps and the optimum reaction conditions of the coupling technology were determined. At the same time, the continuous reaction kinetics and the thermodynamics behavior were calculated in terms of theory, which provided the theoretical basis for process promotion. The main research contents were as follows:1.In order to shorten the stable time of the system and improve the yield of the reaction, the experimental research of the coil tubular reactor and the straight packing bed reactor was conducted using soybean oil as raw material. The stable time, the reaction temperature, the reaction pressure, the mole ratio of oil and methanol and the feed flow rate of the reactant were investigated. The result showed that, the effect of the straight packing bed reactor was superior to the coil tubular reactor, it owned shorter stable time and higher yield. When the condition of the straight packing bed reactor was 300℃,22MPa, the mole ratio of oil and methanol was 42:1,the stable time was 30min,the yield was 80.26%,and the packing iron wire can be used for 11 times.2.In the system research of extraction coupling with transesterification, the reaction process was the controlling step of the coupling technology before the reaction achieved stability, and the extraction process was the controlling step after the reaction achieved stability. Therefore, based on the research of the reactor and reaction process, the extraction process was optimized. The suitable amount of n-hexane adding to the supercritical CO2 can significantly improve the soybean oil yield. The specific conditions were 20g0.4mm thick soybean flakes, layered filling,40℃,20MPa, the mass ratio of CO2 and n-hexane was 21:1, and the extraction rate reached 99.99% after 120min.3.As cosolvent of the supercritical fluid extraction, n-hexane can enhance the supercritical transesterification. In the synthetic consideration of the influence on the yield of methyl ester, the extraction kinetics and the reaction kinetics were needed to be optimizing matched. The optimum reaction condition was that the extraction temperature was 40℃, the reaction temperature was 300℃, the pressure was 18MPa-20MPa, the mass ratio of CO2 and n-hexane was 14:1, and the flow rate of CO2 and n-hexane were 2L/min and 0.4ml/min, respectively.4.In order to discuss the formation procedure mechanism of continuous supercritical transesterification deeply, provide criterions of more experimental conditions, and benefit expanded production and industrial application, it was necessary to calculate the continuous reaction kinetics and the thermodynamics behavior. The reaction rate constants, the equilibrium constants, the critical parameters of the mixture of the soybean oil and methanol and the solubility parameters were confirmed. |
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