Study On The Salting-out Extraction Technology Of Typical Bio-alcohol

The exhaustion crisis of fossil fuels has promoted fuels diversification,and renewable biofuels can be used as an alternative energy source.Moreover,many typical fermentation products can also be used as chemical platforms to synthesize more high value-added chemicals.However,the bulk of water,by-products and impurities in the fermentation broth makes the traditional separation method lose economic advantages.Therefore,the exploration of energy-saving and efficient separation methods is the key to the resource utilization of downstream fermentation products.In this article,three typical bio-alcohols were separated by salting-out or salting-out extraction technology.Isopropanol,n-butanol,and ethanol could be recovered from model aqueous solutions by salting-out.The results showed that the increase of K₄P₂O₇ concentration could significantly increase the distribution coefficient and selectivity coefficient of each component.The order of initiating solvation effect was as follows:n-butanol>isopropanol>ethanol.Temperature had little effect on the salting-out system.When the salting-out factor was 2.5:1,over 95%of the organic compound was recovered,and the dehydration ratio of the system was above 99.8%.Higher total organic content could improve the separation efficiency of the system,but it would decrease the dehydration ratio.The water content of the extract phase and the organic compound content of the water-rich phase could be obtained by solubility correlation,which could be used to calculate the extraction efficiency.A novel aqueous two-phase extraction system was used to separate 2,3-butanediol in the model aqueous solution.It was found that the separation ability of K₄P₂O₇ for isopropanol aqueous solution was significantly better than other three salting-out agents.Moreover,the system could reach the condition of no salt in the organic phase and no extractant solvent in the aqueous phase.The solubility equation could approximately calculate the extraction efficiency of the aqueous two-phase system.The salting-out effect of the four salting-out agents on the isopropanol aqueous solution showed the following order:K₄P₂O₇>K₃PO₄>K₂HPO₄>K₂CO₃.When K₄P₂O₇+isopropanol+water system was used to recover 2,3-butanediol,the recovery ratio of 2,3-butanediol could reach 100%,and the concentration coefficient could come to 5.74.In addition,the existence of 2,3-butanediol in the organic phase could increase the recovery ratio of the extractant.Acetoin could be recovered from model fermentation broth by salting-out.The result showed that the distribution coefficient and selectivity coefficient of acetoin increased significantly with increase of initial salt concentration.A higher acetoin content could increase the recovery of acetoin but could decrease the dehydration ratio.Especially when the concentration of acetoin was 10wt%and the K₄P₂O₇concentration was 550g/kg,the recovery ratio of acetoin could reach to 99.7%,and above 99.11%of water was removed.The solubility correlation could effectively evaluate the salting-out effect of acetoin.Moreover,the salting-out effect of salting-out agents on the acetoin aqueous solutions was arranged in this order:K₄P₂O₇>K₂HPO₄>K₂CO₃.More importantly,non-experimental points could be effectively predicted from the initial salt concentration and acetoin content.