Preparation Of Fatty Acids, Biodiesel And Glycerol From Rapeseed Oil Soapstock

Rapeseed oil soapstock is a by-product from the vegetable oil refining.which is formed during the deacidification with alkali.The content of total fatty acids reaches 40%—60%,which can be exploited as an industry material.Nevertheless,it hasn't been comprehensively utilized.It is mostly used to make soaps,thus leading to the waste of resources and pollution of environment. Therefore, it's a meaningful task to work on the value-added process of soapstocks.The preparation of fatty acids and biodiesel from soapstock coupling molecular distillation was studied and the respective reaction conditions were optimized.Then the glycerol was recovered from acidic and alkaline sweet water.The main conclusions of the experiments were as follows:(1)The effect of deacidification temperature on the separation of fatty acid was simply investigated.The results showed that fatty acids and triglycerides were efficiently separated at 180℃.The hydrolysis of glyceride with different acid value indicated that the degree of hydrolysis was improved with the decrease of fatty acid content.(2)The process of fatty acids production was optimized by orthogonal emperiments with ratio of hydrolysis as the index.The optimal conditions were:the amount of water was 100%, the amount of catalys was 3.2%, the amount of sulfuric acid was 6%,and reaction time was 5h at 150℃,under which the ratio of hydrolysis was 97.57%.(3)The optimal conditions of the first methyl esterification through the optimization of single factor and orthogonal experiments were:the amount of sulfuric acid as catalyst was 1.5%,the amount of methanol was 200%,the reaction temperature was 60℃,and the reaction time was 2h,under which the ratio of esterification was 97.2%.And then the second esterification was conducted on the basis of the first one.The results showed that the the requirement of following transesterification was reached while the acid value was lowered to 1.67mgKOH/g.The optimal conditions of the transesterification through the optimization of single factor and orthogonal experiments were:the amount of sodium methoxide as catalyst was 0.5%,the amount of methanol was 25%,the reaction temperature was 65℃,and the reaction time was 30min,under which the ratio of conversion was 95.84%.The biodiesel was well produced through twice esterifications followed by transesterification.(4)The purities of both fatty acids and biodiesel were detected by GC-MS,which were 98.01% and 98.18% respectively.5.The purity and yield of glycerol that was recovered through the procedure of deacidification,degumming,alkaline processing,condensation and distillation was 98.62% and 77.87% respectively. Accordingly,the purity and yield of glycerol that was recovered through the procedure of neutralization,centrifugation,condensation and distillation was 99.01% and 82.78%.A high level of separation and yield was obtained.