Study On Base Oil Of Bio-Based Transformer Oil

Transformer oil is an important insulating medium in power equipment,which mainly plays the role of insulation,arc extinguishing,heat dissipation and cooling.Common mineral insulating oil has limited resources and is difficult to biodegrade,while natural ester insulating oil will become a green substitute for mineral oil due to its advantages of environment-friendly and renewable resources.However,plant transformer oils have high viscosity,high freezing point,and poor heat dissipation performance,which have become the main problems in the industrial application of plant insulating oil.Therefore,the low temperature fluidity and electrical properties of methyl oleate and ethyl oleate were studied.In this study,biodiesel（methyl oleate）is used as the raw material,which can be used as the base oil of transformer oil,but it has a high freezing point and poor low-temperature fluidity.Therefore,urea and thiourea are used for dewaxing of biodiesel.The effects of the urea to thiourea ratio,the amount of activator,the complexing temperature,the complexing time and the type of activator on the properties of the base oil were investigated.The complexing agent urea and thiourea are different in structure,so urea and thiourea can complex fatty acid methyl esters of different structures.Therefore,when using a mixture of urea and thiourea to treat biodiesel,it can reduce the content of saturated fatty acid methyl esters in the base oil,lower the freezing point of the base oil,and improve the low-temperature fluidity of the oil.The results show that when the biodiesel is treated with 75%urea,25%thiourea,and 75%methanol,at a complexing temperature of 25℃and a complexing time of 3h,the yield of the obtained bio-based oil is 87%.This study uses two ideas to synthesize ethyl oleate.One is the transesterification of biodiesel and ethanol under alkaline conditions;the other is the esterification of vegetable oleic acid and ethanol under the catalysis of p-toluenesulfonic acid.The results show that the solidification point of synthesized ethyl oleate by transesterification is higher.The process conditions of the esterification reaction were investigated,and the suitable reaction conditions were obtainded:the molar ratio of ethanol to vegetable oleic acid was 6:1,the reaction time was3h,the reaction temperature was 78℃,and the amount of catalyst was 2%of the total mass of the reaction raw materials.At this time,the yield of ethyl oleate was about 95%.When the mass ratio of biodiesel dewaxed oil and ethyl oleate is 1:1,the breakdown voltage of the obtained base oil is 38k V,the freezing point is-13℃,and the kinematic viscosity at 40℃is 6.34 mm².s^-1,and the acid value is 0.06 mg KOH.g^-1 after deacidification.Combined with international and national standards,the base oil obtained can meet the requirements of low temperature performance and electrical performance of U0℃transformer oil.