The Research Of Biodiesel Preparation And Its Emergy Analysis

With soybean oil as raw material, three technics of biodiesel preparation, namely supercritical methonal technics, solid acid technics and solid base technics, were explored respectively. And on the basis of theory of emergy analysis, comprehensive evaluation of three technics, which including the economic and environmental benefits evaluation, were conducted. The results were obtained as follows:1. The effects of molar ratio of methanol to soybean oil, temperature, pressure, reaction time, water contents and acid values of the oil on the yields of biodiesel and glycerol were investigated in biodiesel production by supercritical technics. The results showed that the effects of molar ratio of methanol to soybean oil, temperature, pressure, reaction time on the yields of biodiesel and glycerol were remarkable, and the effects of water contents and acid values of the oil on the yields of biodiesel and glycerol were not remarkable. And the highest temperature and water content shouldn't exceed 280℃and 10% respectively. Through orthogonal experiments, the optimal conditions were obtained when molar ratio of methanol to vegetable oil was 30:1, operation pressure was 20 MPa, reaction temperature was 280℃and reaction time was 60 min, under which the yields of biodiesel and glycerol could reach 89.14% and 88.73%, respectively.2. A new type of solid acid was prepared by calcination of titanium sulphate doped with lanthanum oxide. Preparation of biodiesel was studied from soybean oil and methanol catalyzed by the above solid acids, The experiment showed that the optimal conditions were obtained when catalyst amount was 3wt% (catalyst/oil), molar ratio of methanol to vegetable oil was 12:1, reaction temperature was 150℃and reaction time was 5h, under which the yields of biodiesel could reach above 90%. The catalyst also showed its activity for esterification. Therefore, it could be used for biodiesel production from many kinds of raw material. The catalysts could also be reused after some treatment.3. Transesterification of soybean oil and methanol to produce biodiesel were investigated using CaO/NaY as catalyst. The results showed that molar ratio of methanol to soybean oil was 9:1, catalyst amount was 3%(catalyst/oil), reaction temperature was 65℃and reaction time was 3h, under which yield of biodiesel could reach about 95%. The results also indicated that the CaO/NaY catalyst was more tolerant to free fatty acid and water and its activity was still high when acid value and water content were 4mgKOH/g and 1.5%, respectively.4. After emergy analysis of Three technics , it can be drawn that the ratio of unrenew resource to overall invested emergy in supercritical technics, solid acid technics and solid base technics for biodiesel production were less than the traditional liquid base technics in terms of pressure on the environment. The overall system transform ratioes of every technics were all relatively low, among which that of liquid base technology was lowest, which is 3.48E-01sej/t. The net emergy yield ratioes of supercritical technics, solid acid technics and solid base technics were higher than that of liquid base technics. Moreover, the emergy investment ratioes of supercritical technics, solid acid technics and solid base technics were higher than that of liquid base technics, meanwhile, supercritical technics, solid acid technics and solid base technics were lower than that of liquid base technics, which suggested that the former three technics were relatively low at present. There were good sustainable development for all four technics.