Study On The Production Of Biodiesel From Vegetable Oil Catalyzed By Lipase

Biodiesel is a new kind of fuel composed of mixed fatty acid methyl esters. Because of its advantages such as renewable, no pollution and biodegradable, biodiesel is attracting much attention worldwide. Many researches show the combustion performance of biodiesel is similar with diesel oil, and the exhausted cooperation of biodiesel is much better than that of diesel oil. So, biodiesel can be used directly in gas engine as a substitute of diesel oil.Researches on biodiesel began in 1970s, and the industrial production of biodiesel with chemical catalyst has been realized. But, excessive methanol are needed in this process, which result in diffucult separation and higher cost. Furthermore, chemial catalysts are diffcult to separate from the product, and the wast catalysts will make secondary pollution on enviroment. The usuage of chemical catalyst also can make production unsteadily for the reason of saponification. So, some new processes have been proposed to overcome such disadvantages. Using enzyme as catalyst to produce biodiesel is now arousing much attentions around the world for the advantages such as no requirement of excessive methanol, easy separation, mild reaction conditons, repeat use of immobilized lipase and no enviromental pollution. Researches on biodiesel production with enzyme catalyt began in 1990s in China.The industrial production of biodiesel with enzyme catalyst has not been realized till now. The main restricted factors are higher production cost, short life of enzyme, less repeated use times and long production cycle. To overcome such disadvantages, new ways to produce biodiesel with enzyme catalyst were investigated in this work.. Through the innovation of technics, the aims to increase the life of enzyme, enhance the repeated use times and shorten produce periods are expected to achived.This paper is composed of eight chapters. The advances of biodiesel production with enzyme catalyst were introduced in the first chapter, and the research routines were also proposed in this part. In chapter two, the common analysis methods were introduced. The batch reaction conditions, the experiments on repeated use of lipase and the kinetics of rapedseed oil and tung oil were investigated respectively in chapter 3 and chapter 4. In chapter 5, continuous biodiesel production in fix bed reactor and expanded bed reacotr were investigated respectively, and suitable reactor for biodiesel production and the technics were proposed. Furthermore, using tung oil as raw material, the results obtanied in chapter 5 were validated in chapter 6. It was found the reactor and the reaction conditons were fit to thees two different oil. In chapter 7, the purified method was introduced and the equality indexes were analyzed. Finally, the summary was propoesd in chapter 8.Researches on the batch production process, continuous production process and the reactor were investigated in this work, and some important results were obtained.1. The tranesterification reactions between rapedseed oil, tung oil and methanol in no-organic solvent system with immobilized lipase NOVO435 as catalyst were investigated. The effect factors in the process were evaluated, and the conditions were further optimized by reponse surface analysis methdology. Two optimimal conditions for biodiesel production in no-organic solvent system were obtained.2. Under the optimal conditions, experiments on repeated use of lipase were carried on. The results show that lipase can be used repeatedly without any dealing with. Lipase can be used 20 times 520h in rapeseed oil system, and 10 times 360h in tung oil system. Batch experiments scaled up for 50 times with the same reaction conditions show that higher yields can be achived without distinct change.3. The mechanisms and kinetics of enzyme reaction were investigated under the batch conditions. Two kinetics equations were obtained, which can lay fondations for scale up and optimization of the reaction. The kinetics results show that the process of transesterification between oil and methanol with lipase as catalyst is accord with Bing-Bang mechanism with substrate inhibitation, and the initial reaction rate of transesterification reaction between rapeseed oil and methanol is faster than that in the tung oil system. Furthermore, the reaction process can be deduced as a three-step reaction models, which validated by the existence of intermediate products such as monoacylglyceral and diacylglyceral.4. Effects of different feed ways of raw materials and filled ways of catalyst on continuous biodiesel production were studied. An expanded reactor was built up and used for continuous biodiesel production successfully. The routine for continuous biodiesel production was proposed with higher convension yield, hiher productivity and long using life.5. The purification method proposed in this paper is simple and lower energy cost, and the equality indexes meet to the American biodiesel standard.