Continuous Process Of Biodiesel Production By Supercritical Extraction Coupling Transesterification Reaction

With the changes of global energy structure, as well as the designable and strategic position of renewable energy sources has been established, biodiesel has received highly attention all over the world since it is a kind of clean and renewable alternative energy, also the new production methods, new technologies and new processes have been researched and developed constantly.Supercritical methanol transesterification technology is a simple, high-efficient and oligosaprobic preparation method, however, the traditional batch production is low-yield and low-energy-efficient, also the reaction conditions are harsh. Basing on these, this article discussed the process conditions and main influencing parameters of continuous production method of biodiesel, then strengthened process by adding a tiny quantity of alkali catalyst to improve the harsh reaction conditions. Morever, this paper coupled the supercritical extraction and supercritical transesterification to produce biodiesel, completed the one-step process from raw materials to biodiesel, achieved the possibility of raw materials and local production. The main contents were as follows:1. In order to improve the disadvantages of supercritical transesterification batch production such as low-production and low-energy-utilization, in this work, the continuous process of supercritical method was studied. The materials were soybean oil and methanol, the temperature, pressure, mole ratio of methanol to oil, operating time and flow rate of reaction were discussed. The experimental results showed that, when the reaction conditions were350℃,18MPa, mole ratio was42:1, the flow rate of methanol and oil was0.18ml/min and0.10ml/min respectively, the biodiesel yield achieved the biggest72%, the settling time was2hours. Further reducing the flow rates to0.06ml/min and0.033ml/min, the final yield could be87.2%.2. With traces of alkali catalyst to strengthen the process of supercritical biodiesel technology, reaction temperature and pressure had been reduced. Using KOH as catalyst, temperature, pressure, the amount of catalyst and some other parameters had been studied to find the influence on yield. When the reaction conditions were160℃,14MPa, molar ratio24:1and flow rate of both two materials were0.04ml/min, the yield of biodiesel could be increased to97.1%by adding0.1wt%KOH. 3. Taking soybean flours and soybean pieces as raw materials to discuss the process of supercritical CO2extraction of vegetable, and found that the extraction system could reach equilibrium when the extraction temperature was40℃, pressure was20MPa and CO2flow rate was2L/min (in atmosphere environment), the extraction rate was80%approximately; adding n-hexane as co-solvent could improve the extraction yield.4. Try to couple supercritical extraction and supercritical transesterification by continuous process to produce biodiesel, which can improve the utilization of materials and the yield of biodiesel, and realized the one-step process from raw materials to biodiesel; fixing the extraction temperature40℃, n-hexane0.4ml/min, CO22L/min, reaction temperature350℃, pressure of system18-20MPa, molar rate of methanol to oil42:1, the yield of biodiesel could be86%when system achieved stabilization.