| Energy, environment and climate are three major problems which human beings have to confront in the 21st century.Coal, petroleum and natural gas are important material basis for survival and development of human.However,these fossil energy are non-renewable and depleting day by day with enormous consumption.According to the proved reserves of fossil energy all of the word,it is estimated that oil can be supplied for 50 years,natural gas for 60 years and coal for 160 years.Moreover,their use cause environmental pollution and global warming,which attracted worldwide attention.Under such circumstances,all countries speed up the pace of research and development of new energy sources such as wind energy,solar energy, nuclear energy and biomass energy,etc.Because of its renewable and environmentally friendly,biomass energy became the focus of the study,biodiesel is one of them.Biodiesel, also known as fatty acid methyl ester,is made of animal fat,plant oil and waste oil by esterification or transesterification.It is a new clean fuel as an replacement of petroleum diesel oil,which can be used in boilers,turbines,and diesel engines,etc.Catalysts for biodiesel preparation can be divided into homogeneous and heterogeneous catalysts. Homogeneous catalysts have advantages of faster reaction velocity, higher conversion,but they also have many disadvantages, such as difficulty for catalyst separation,producing much liquid waste, side reactions,corrosion of the equipment. Heterogeneous catalysts not only can solve these problems of homogeneous catalysts,but also have the advantages of mild reaction conditions,good stability and regeneration.Therefore,using heterogeneous catalysts for biodiesel preparation is a hotspot in current research.Preparing a solid superacid catalyst of SO42-/ZrO2-CeO2 with high catalytic active for biodiesel production was presented in this paper.First,the solid superacid SO42-/ZrO2-CeO2 was prepared as catalyst for esterification of oleic acid with methanol.By single factor experimentation,the influence of reaction temperature,reaction time, amount of catalyst and volume ratio of raw materials on the conversion rate were discussed.The kinetics calculation indicates that the reaction order and activation energy of oleic acid esterification with methanol is 1.46 and 27.35kJ/mol,kinetic model Secondly,in order to obtain higher catalytic performance,12 conditions in the process of catalyst preparation were optimized respectively,such as load of CeO2, ammonia concentration, concentration of impregnating solution,pH of titration end point,aging time,calcination temperature etc.Catalytic activity of these catalysts were measured by the yield of biodiesel at same reaction conditions by esterification of Jatropha curcas L. oil fatty acid with methanol.Besides,the catalysts were characterized and analyzed by XRD, BET, TEM, TG, TPD, FTIR,etc.The results indicated that adding CeO2 could improve the catalytic activity of SO42-/ZrO2.The yield of biodiesel increases with aging time,however,has few of influence when above 24h. Calcination in humid atmosphere would reduce specific surface area. Ammonia concentration,concentration of impregnating solution and calcination temperature have influence on acid-situ quantity of catalyst. Calcination time can affect catalytic activity.Non pre-calcined catalyst was superior to pre-calcined catalyst.The best preparation conditions were load quantity of CeO2 is 5%, using ammonia of 25% concentration to titration with speed from slow to fast,pH value of titration endpoint was around 8.6, aging under room temperature for 24h, rubbing to pass through sample sifter of 100 mesh, impregnation with 0.5mol/L of H2SO4 for 1h and calcinated at 500℃for 3h.Finally,under the best preparation conditions,catalyst was obtained and used for esterification of Jatropha curcas L. fatty acids with methanol. Single factor experiments and kinetic analysis indicates that the reaction order and activation energy were 1.44 and 45.31kJ/mol, respectively, kinetic model was -(dCA)/(dt)=38371 e -(45310)/(RT)CA1.44.The composition of Jatropha curcas L fatty acids were analyzed qualitatively and quantitatively by UPLC.The result show that the primary components of Jatropha curcas L. fatty acids are linoleic acid,oleic acid,palmitic acid and stearic acid. |
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