Constructing And Mechanism Of Biodiesel Nano-scale Magnetic Solid Base Catalysts

Currently, liquid bases are the primary catalysts used in biodiesel industry, which may bring about problems such as equipment corrosion, catalyst non recyclability, environmental pollution and complex processing. At the same time, nano scale magnetic solid base catalysts, assembled from magnetic materials and living matter, have become one of the research focuses in recent years, due to its high catalytic activity, recyclability, and rapid recycling, etc.In this study, nano scale magnetic solid catalyst Na₂O·SiO₃/Fe₃O₄ was produced which aimed to these problems in key technical environmentally friendly for biodiesel production, and the structure and properties of the catalyst were analyzed by various technologies. The result showed that its catalytic performance is better than the same catalysts reported at home and broad. The transesterification reaction kinetics models were established and the mechanism of transesterification reaction was speculated.The nano scale magnetic solid base catalyst was applied for the first time in the magnetically stabilized bed reactor for biodiesel production. Compared with the existing reaction mode, transesterification technics employing magnetically stabilized bed reactor enhanced reaction efficiency of nano scale magnetic catalyst, and reduced the loss of catalyst. The main results are as follows:1. Nano scale Fe₃O₄ was prepared by coprecipitation method and the process was optimized. The nano scale Fe₃O₄ particle from our lab has good specific saturation magnetization and paramagnetism.2. The catalytic activity of sodium silicate was the best when SiO₂ and Na₂O modulus was one through filtrating and optimizing. The results from thermogravimetric analysis, X Ray Diffraction and Infrared spectra indicated that the active site was Na O Si.3. The best preparing method and process of the catalyst were confirmed and optimized, the structure and properties of the catalyst were analyzed by various technologies. The nano scale catalysts with mean diameter of 87.63 nm and BET of 107.9 m2/g were prepared.4. Process conditions of making biodiesel via the transestrification from cottonseed oil and methanol were investigated in the autoclave stirred reactor. The first transesterification rate exceeded 98% and the catalytic activity exceeded 90% after eleven batches under the optimized conditions. The first catalytic activity of the regenerated catalyst exceeded 98%. The recycle technic of catalyst was optimized, and the catalytic activity of regenerated catalyst exceeded 90% after eight batches, with a mass recycle rate of 88.27% and a magnetism recycle rate of 86.44%. Compared with the results in relevant research, the transesterification reaction conditions using Na₂O·SiO₃/Fe₃O₄ as catalyst were moderate, the catalytic activity of the catalyst was high, and the reaction time was short.5. The transesterification reaction kinetics results from cottonseed oil and methanol showed that the reaction can be divided into the initial, growing and equilibrium stages. The reaction orders in the different stages were 0.5, 2.0 and 0 respectively. In the initial stage, the activation energies of C16 methyl esters, C18 methyl esters and C20 methyl esters were 103.41kJ/mol, 154.39kJ/mol and 102.58kJ/mol respectively. In the growing stage, the activation energies were 50.41kJ/mol, 52.17kJ/mol and 43.16kJ/mol respectively. Based on these results, the mechanism of transesterification reaction was speculated.6. Biodiesel was prepared with transesterification from cottonseed oil and methanol in the magnetically stabilized bed reactor. The results showed that the catalytic activity of the catalyst exceeded 90% after 210 hours.