Preparation Of Biodiesel By Transesterification Of Castor Oil Catalyzed By Lithium-Based Catalyst

Biodiesel is a renewable,sustainable and biodegradable alternative to fossil diesel.Heterogeneous alkali catalyst has the advantages of high activity,easy separation and low corrosion.It is of great significance to research and develop heterogeneous alkali catalyst for the industrial production of biodiesel.In this paper,the transesterification of castor oil and ethanol catalyzed by heterogeneous base is the main research object.The specific research contents are as follows:?1?Firstly,the physical and chemical properties of castor oil were tested and analyzed.The acid value was determined with reference to GB/T 9696-2008,the saponification value was determined with reference to GB/T 5534-2008,the average molecular weight was calculated by acid value and saponification value,and the water content was determined with reference to GB/T 9696-2008.The results showed that the value of ricinoleic acid and the content of water were very low,0.93 mg KOH/g and 0.16%respectively,which could be directly used for transesterification without further treatment.?2?Li/Na Y zeolite catalyst with different Li₂CO₃/Na Y molar ratios was synthesized by microemulsion assisted coprecipitation method,which was used to catalyze transesterification of castor oil with ethanol.The structure,composition and morphology of Li/Na Y zeolite were characterized by TG,XRD,SEM,bet and FT-IR.The results showed that Li was successfully mixed into Na Y zeolite to form strong alkaline sites,and the catalyst had complex porous structure due to the CO₂ gas produced by solid-phase reaction.Under the optimum conditions of Li₂CO₃/Na Y molar ratio of 1:1,calcination temperature of 750^oC,calcination time of 4h,catalyst amount with respect to oil of 3 wt.%,ethanol/oil molar ratio of 18:1,reaction temperature of 75^oC and reaction time of 2 h,the yield of FAEE reached 98.6%.The catalyst remained high activity?92.6%?after exposure to air for240 h.The yield of FAEE was over 80%after 5 times of catalyst use.In the sixth reaction cycle,the yield of FAEE after activation was 17%higher than that without activation.By comparing the kinetic models of pseudo first-order reaction and pseudo second-order reaction,the proposed reaction mechanism was verified.The results showed that the pseudo first order kinetic model?R²=0.9906?was more consistent with the experimental data.The activation energy of 57.37 k J/mol was required for the transesterification of castor oil to biodiesel over Li/Na Y zeolite catalyst.?3?The composition of castor oil biodiesel was detected by gas chromatography.The results showed that the content of ethyl oleate was the highest in castor oil biodiesel,accounting for 88.3%of the total.The content of ethyl hexadecenoate was the lowest,accounting for 1.3%of the total amount of castor oil biodiesel.In addition,ethyl oleate accounted for 5.7%,ethyl palmitate 2.8%and ethyl stearate 1.9%.According to the method recommended in B5 diesel?GB 25199-2017?,the main physical and chemical properties of self-made castor oil biodiesel were tested.Its physical and chemical properties were as follows:density 915 g/m³,viscosity 11.2 mm²/s,flash point 152^oC,cold filtration point4.9^oC,cetane number 56.2,acid value 0.2883 mg KOH/g,copper corrosion grade 1,calorific value 38 MJ/kg.The results showed that most of the physical and chemical properties of castor oil biodiesel are close to the domestic and foreign biodiesel standards,but the viscosity and density were higher than the national standards.