Thermokinetic Analysis And Process Study Of Ethanol Fermentation Containing The Ionic Liquid In The Medium

The biomass energy is famous for its renew-ability and environment friendliness.As an important part of biomass energy,the fuel ethanol,especially the lignocellulosic fuel ethanol has drawn much attention from researchers.The lignocellulosic fuel ethanol production consists of two sub-processes: degradation of lignocellulose to fermentable sugars and microbial fermentation of the obtained fermentable sugars to ethanol.The ionic liquid has provided a new technical tool to degrade lignocellulose to fermentable sugars,but some ionic liquid remained in the obtained fermentable sugars is inevitable.Therefore,it is desirable to know how the remained ionic liquid in fermentable sugars affects the subsequent ethanol fermentation process.Some previous studies have shown the remained ionic liquid in the fermentable sugars,for example,1-ethyl-3-methylimidazolium acetate(EMIMAc)has a negative effect on the subsequent ethanol fermentation process.Based on previous studies,this dissertation investigated the effect of the ionic liquid EMIMAc on thermokinetics of ethanol fermentation via microcaloritory.And three technical strategies were explored to alleviate the negative effect the ionic liquid EMIMAc on the subsequent ethanol fermentation process by increasing the amount of inoculum size,stage fermentation and fed-batch fermentation respectively.Firstly,the effect of the ionic liquid EMIMAc on thermokinetics of ethanol fermentation was investigated via microcaloritory at different EMIMAc concentrations.The power-time curves were obtained when the ionic liquid EMIMAc concentrations were 0g/L,0.001g/L,0.01g/L,0.1g/L,1g/L and 5g/L respectively.Based on the power-time data,the yeast growth rate equations were established.In order to correctly understand the power-time data,the parallel experiments were carried out under the same conditions as microcaloritory.The results indicated that the yeast specific growth rate decreased and its metabolic activity reduced with the concentration of the ionic liquid EMIMAc increasing.Then,three technical strategies used to alleviate the negative effect the ionic liquid EMIMAc on the subsequent ethanol fermentation process were examined and compared.The first strategy was increase of the inoculum size.It was found that the yeast growth rate,ethanol production rate and ethanol production amount all increased with the inoculum size increasing on the condition that the inoculum size were 1%,5 %,10%,15 % and 20% respectively.When the inoculum size was 20%,the ethanol productivity reached 3.016 g/L.h.The second strategy was stage fermentation.The results shown that three stage fermentation was better than two stage fermentation.The productivity for three stage fermentation and two stage fermentation was 3.592 and 3.531g/L.h respectively.The third strategy was fed-batch fermentation.The results that the highest ethanol productivity reached 1.567g/L.h under the optimal fed-batch fermentation conditions.By comparison of these three technical strategies,the three stage fermentation could achieve the best result to alleviate the negative effect the ionic liquid EMIMAc on the subsequent ethanolfermentation process.