Research On Production Of Biodiesel By Microwave Assisted Transesterification

As a kind of renewable and clean energy,biodiesel is of great significance to solve the energy shortage and environmental pollution problems.Currently,the one-step transesterification technology of biodiesel production is the hotspot and difficult point over the world.There are some problems to be solved in production,such as difficulty in preparing high performance catalyst,high energy consumption,low conversion and serious pollution in the process.In this paper,biodiesel was prepared through one-step transesterification technology with a green ionic liquid as the catalyst.The research was focused on the intensification effect of the microwave irridiation on the reaction process.The kinetics of transesterification under microwave irridiation was investigated.In addition,the yield and energy consumption of biodiesel under microwave irradiation and conventional heating were compared.Firstly,the physical and chemical properties of palm oil were analyzed.A fast and reliable method for the determine of biodiesel yield was also provided.In order to screen out the ideal catalyst,the catalytic performance of solid acid,modified attapulgite,self-made supported solid base and three kinds of self-made imidazolium ionic liquids were studied.It was found that[HSO₃-PMIM]HSO₄ and[HSO₃-BMIM]HSO₄ have better catalytic effect,the yield of biodiesel could reach more than 95%.Considering the catalytic effect,the cost of the catalyst and the difficulty in preparation,[HSO₃-BMIM]HSO₄ was chosen as the suitable catalyst for the preparation of biodiesel.The preparations of biodiesel from palm oil under microwave irradiation and conventional heating were investigated,with[HSO₃-BMIM]HSO₄ as catalyst.For conventional heating,the optimum reaction conditions were as follows:alcohol to oil molar ratio of 6.74:1,catalyst dosage 8.96%,reaction temperature 131oC and reaction time 9.14 h.Under these conditions,the biodiesel yield was 98.76%.For microwave irradiation,the optimized conditions were as below,alcohol to oil molar ratio of 11:1,catalyst dosage 9.17%,microwave power 168 W,reaction time 6.43 h,and a maximal yield of 98.93%was obtained under above conditions.The kinetic of transesterification under microwave irradiation was studied,which could be appropriately expressed by the pseudo-first-order kinetic model,with R² of 0.9949.Compared with the conventional experiments,microwave irradiation is an efficient method for preparing biodiesel,which can not only shorten the reaction time,but also saving energy up to more than 44%.Finally,the preparation of biodiesel in a tubular reactor assisted by microwave was investigated.The biodiesel yield was 98.59%under the optimum conditions,with microwave power of 140 W,alcohol to oil molar ratio of 24:1,catalyst dosage of8%,and reaction time of 5 h.Through comparison,we found that the reaction efficiency of tubular reactor is superior to kettle reactor,which not only shorten the reaction time to 5 h,but also decrease energy consumption by about 17%.