Research On Esterification Process For Vitamin E Enrichment From Soybean Oil Deodorizer Distillate

Soybean oil distillate deodorizer(SODD)is an important feedstock to produce natural vitamin E(VE).The composition of SODD is complicated,which mainly contains tocopherols(VE),sterols,triglycerides(TAG)and free fatty acids(FFA).The current industrialization process for the enrichment of natural VE is a two-step method of acid catalytic esterification and alkali catalytic transesterification.The process has many disadvantages,such as equipment corrosion caused by the acid catalyst,large amount of waste acid water,and high cost for methanol recovery after transesterification.In order to solve these issues,glycerol esterification method was used in this study to enrich natural VE from SODD.Continous systems for glycerol esterification and transesterification processes were developed.In addition,material balance and energy balance for the glycerol esterification process were conducted.This study could provide preliminary data for industrial production.The main contents and conclusions are as follows:(1)The effects of reaction temperature,the amount of glycerol,and reaction time on glycerol esterification of SODD in a single reactor were investigated.The reaction dynamics of glycerol esterification was studied.The results showed that the optimal temperature,glycerol to fatty acid mole ratio,and reaction time were 240 ?,1.1:1,and 3 h,respectively.The reaction of fatty acid followed first-order reaction and the reaction constant k increased with temperature,indicating that glycerol esterification was endothermic reaction.The activation energy was calculated to be 231.2 J/mol.(2)For glycerol esterification of SODD in series complete mixing flow reactors,at least four stage reactors were needed to reduce the acid value of SODD to below 1mg KOH/g.The material balance and energy balance for 10,000 ton/a SODD glycerol esterification were conducted.The fatty acid conversion in four-stage series complete mixing flow reactors reached 99.24%.The energy required for the entire continous esterification process was 150,300 kcal/h.In addition,glycerol esterification process has negligible effect on VE yield.The continous glycerol esterification process in series reactors can replace the single reactor for the pretrement in VE enrichment from SODD.(3)The transesterification of products from SODD glycerol esterification was conducted.The effects of catalyst amount,reaction time,and transesterification reaction order on the transesterification process were investigated.The results showed that the optimal catalyst amount and reaction time were 1% of triacylglycerol and 1 h,respectively.A second-order transesterification process was needed after the first-order transesterification process.The highest content of methyl esters was obtained when 20% methanol and 0.5% KOH were added in the first-order reaction,and 10% methanol and 0.5% KOH were used in the second-order reaction.Reactor coupled with sedimentation tank was developed and used in the two-order continous transesterification process.The content of methyl esters kept at 76% and complete triglyceride conversion was observed.The continous transesterification process can replace the batchwise single reactor for the transesterification reaction in VE enrichment from SODD.In addition,the transesterification process has negligible effect on VE yield.