Study On The Catalysts For The Preparation Of Biodiesel From High Acid Value Oil

With the development of industrialization and modernization,more oil resources are demanded.However,the large use of petrochemical fuels will bring energy crisis and environmental problems.So great attention must be paid to new alternative energy.Biodiesel is considered as the best alternative energy sources due to its advantages of renewable,green and biodegradable.Pure vegetable oils were replaced by high acid value oils in the preparation of biodiesel,which can reduce the production costs and improve the competitiveness of biodiesel.Currently,the process of biodiesel preparation with high acid value oil can be divided into two steps by homogeneous catalyst: pre-esterification and transesterification,while they bring the problems of separation,catalyst recovery and waste water.In order to overcome these problems,two different solid catalysts?mesoporous carbon based solid acid and lithium silicate solid base catalyst?and their application in the preparation of biodiesel with high acid oil were systematically studied.?1?Mesoporous carbon-based solid acid catalyst was prepared by carbonization-sulfonation method with SiO₂ as a template and sucrose as carbon source.The catalyst was characterized and analyzed by acidimetric analysis,BET,XRD,FT-IR and SEM,then the influence of carbonization temperature,sulfonation temperature,the amount of template to the number of SO3 H,specific surface area and pore size was studied.Followed the catalyst was used in transesterification reaction between soybean oil and methanol.Results show that the optimum condition for the preparation of the catalysts were carbonation temperature 400°C,sulfonation temperature 170°C and mSiO₂:mSucrose=1:2;the yield of biodiesel for transesterification reaction between soybean oil and methanol reached 95.94% under the optimum condition of molar of methanol to soybean oil 30:1,reaction time 4 h and catalyst dosage 8%.When the content of fatty acid in the raw materials was as high as 15%,the transesterification conversion rate reached 90.87%,and the conversion rate of fatty acid reached 99%,which can lay a foundation for the preparation of biodiesel with high acid value oil by one-step method.?2?Under the condition of low temperature and atmospheric pressure,the esterification of oleic acid catalyzed by mesoporous carbon-based solid acid catalyst was studied.The results showed that the conversion of fatty acid could be achieved 97.47%,while the molar ratio of methanol to fatty acid,the amount of catalysts,reaction time and reaction temperature were 15:1,8%?based on weight of fatty oil?,3h and 70°C,respectively,and the conversion is over 96% after five-time recycling.The kinetics calculation indicates that the reaction series is 1.38 and the apparent activation energy is 58.7 kJ/mol.?3?Lithium silicate solid base catalysts were synthesized by SiO₂ and Li OH with precipitation method.The catalysts were characterized by SEM and XRD,then the prepared catalysts were used in transesterification reaction between soybean oil and methanol.The optimum reaction conditions were as follows: the molar ratio of alcohol to oil was 12:1,the amount of catalyst was 6%,the reaction temperature was 65°C,the reaction time was 2h,the conversion of biodiesel reached 99.64%,therefore the catalytic effect was similar to liquid base,which can be used for the second step catalytic reaction with high acid value oil,and can also be used for the general fat to produce biodiesel by one-step transesterification process.The yield of biodiesel is still 96.36% after the catalyst was reused five times,which shows that the catalyst has good stability.