Study On Production Of Biodiesel By Microreactor

The shortage of traditional fossil energy and environmental friendliness force people to find a new energy source to replace fossil energy.Biodiesel(fatty acid methyl ester)has become more and more important as a renewable and green energy source.In general,the industrial method for preparing biodiesel is obtained by transesterification of animal and vegetable oils and methanol under the action of a catalyst.This is a liquid-liquid heterogeneous reaction due to partial miscibility of animal and vegetable oils and methanol.Mass transfer is limited in liquid and liquid phases.At present,the reactor used for preparing biodiesel is a tank reactor,which has the disadvantages of long reaction time and high energy consumption.The microchannel reactor refers to a reactor with a channel characteristic size of less than1 mm.Because of its small size,the channel has a large specific area and a short liquid path,so it has good heat transfer and mass transfer,and can be used to strengthen the biodiesel production process.Therefore,this paper uses a PFA(polytetrafluoroethylene)microchannel reactor with an inner diameter of 1mm to prepare biodiesel.The main research contents are as follows:(1)The relationship between the flow pattern and the mass transfer and reaction of the liquid-liquid heterogeneous reaction in the microchannel reactor was studied.The effects of different operating conditions on the liquid-liquid two-phase flow pattern in the microchannel reactor were investigated.A process of dispersing and forming a slug flow in the microchannel reactor was observed.In the initial stage of the reaction,the droplet volume gradually becomes larger,its specific surface area is reduced,and the mass transfer performance is weakened.When the droplets are aggregated to form a slug flow,the mass transfer can be well enhanced because of the internal circulation of the slug flow.,speed up surface renewal,so the reaction rate of the entire transesterification reaction is accelerated.Operating conditions have a significant impact on the formation and evolution of the flow pattern and ultimately affect the biodiesel yield.(2)The mass transfer effect of biodiesel prepared by transesterification in PFA microchannel reactor with inner diameter of 1mm and 50 m L laboratory-scale tank reactor was studied.The results demonstrate that the laboratory-scale tank reactor can achieve mixing and mass transfer at the microreactor level under certain conditions.(3)To study the effect of introducing inert gas into the microchannel reactor on the dispersion of liquid-liquid immiscible two phases and mass transfer and reaction processes.Under the agitation of the inert gas,the alcohol-oil phase can form a good dispersion state,and the degree of dispersion is related to the experimental operating conditions.(4)The kinetics of transesterification reaction of synthetic biodiesel in microchannel reactor and tank reactor was studied respectively,and the pseudo-homogeneous kinetic model was established.The data fitting results showed that there were differences in kinetic parameters between the two methods.It is pointed out that the advantages of chemical reaction kinetics such as short reaction time,mass transfer limitation and strict control of reaction conditions are utilized in the microchannel reactor.