Enrichment Of Vitamin E From Soybean Oil Deodorizer Distillate

The soybean oil distillate deodorizer(SODD)is an important source for natural vitamin E.The composition of SODD is complicated,which mainly contains tocopherols(VE),sterols,triglycerides(TAG)and free fatty acids(FFA).In order to better separate VE,the feedstock was pretreated through esterification process in this study,based on conventional techniques.Natural VE T50 product(VE content is higher than 50%)was then extracted from SODD using a two-step process of high vacuum distillation coupled with molecular distillation.In addition,Aspen simulation and design and selection of wiped film molecular distillation were carried out,which provided preliminary data for industrial production.Firstly,for the esterification pretreatment,the acid value was reduced below 2 mg KOH/g after the primary esterification,which satisfied the requirements of subsequent transesterification and effectively reduced soap generation.The FFA and glycerides were converted to fatty acid methyl ester(FAME)through the transesterification process.Acidification and washing were then conducted followed by cooling and filtration,and the filtrate was the mixture of FAME and natural VE.Finally the esterification rate,transesterification rate and yield of natural VE were higher than 98%,99%and 98%,respectively.Sterol was removed and crude tocopherol was obtained after the esterification,transesterification and freezing crystallization processes.A self-developed high vacuum distillation unit was used to remove the FAME from crude tocopherol.The effects of column bottom temperature on the FAME removal rate at the column top and VE yield at the column bottom were investigated.Results showed that the optimal temperature of column bottom was 230?,under which the FAME removal rate at the column top,VE concentration and yield at the column bottom were 95%,42.3%and 97%,respectively.The physical properties of FAME,glycerides and VE were estimated using Aspen Plus software.The concentration of natural VE at the column bottom was estimated to be40%under the optimal conditions.Good correlation between the simulation results and experimental data for the temperatures of column top and bottom was observed.After FAME was romoved by high vacuum distillation,two-grade molecular distillation was conducted.The optimum operating conditions for the primary molecular distillation were:preheating temperature of 60?,distillation temperature of 190?,rotary speed of 300 r/min,and feed rate of 10.3 g/min.The VE yield extracted from the primary product through secondary molecular distillation reached 99.6%.The VE content in the final VE T50 product was 51.0%.The overall VE yield through the two-step process of high vacuum distillation coupled with molecular distillation was about 96.8%.On the basis of laboratory test data,a molecular distillation unit with an annual VE T50 output of 1,000 tons was designed.According to the relative formulas,the film thickness and mean residence time were calculated to be 0.403 mm and 10.25 s,respectively.The inner diameter and height of the molecular distiller were then determined,i.e.,500 mm and 1700 mm,respectively.Finally,the heating evaporation area and the condensation area of condenser were determined to be 2.67 m~2 and 3.25 m~2,respectively.