Sub-critical Water - Supercritical Methanol Two-step Biodiesel Pilot Study

With the increasing exhaustion of petrochemical resources in the world, the biodiesel has becoming more and more attracted the attention of people as the green energy resource. The most usual preparation method for biodiesel is base catalysis or acid catalysis. Although the method features mature technology, there are some shortcomings including emulsion formation during the reaction, which results in the difficulty in separation the products, and wastewater produced from the washing of the products to remove the base catalyst. The recently developed supercritical transesterification can overcome the above shortcomings. However, it must be operated at high temperature and pressure.The author proposed a new method for the production of biodiesel, which including near-critical hydrolysis reaction and supercritical esterification reaction. In this way, high temperature and pressure of the supercritical condition can be avoided and high yield of the product can be maintained. So, the rapeseed oil choosed for the reaction material and study the different conditions influence on the reactionIn this paper, the influence of reaction temperature, reaction time, reaction pressure and mole ratio are discussed. The detecting methods are acid value determination and ultra performance liquid chromatography detection. The results showed that the increase of reaction temperature, reaction time, reaction pressure, mole ration can get a better conversation. However, these factors and conversation is not simple proportional relation. There are best conditions for the two reactions. For the near-critical hydrolysis reaction, the optimum reaction conditions are 290℃,30min,24MPa, the mole ratio of water and rapeseed oil is 220:1, the highest conversion is 92%,.For the supercritical esterification reaction, the optimum reaction conditions are 270℃,40min,15MPa, the mole ratio of methanol and fatty acid is 24:1, the highest conversion is 98%.