Salting-out And Sugaring-out Extraction Of Biobutanol With The Mechanism And Converting Biobutanol Into Fuel Precursors

Bio-butanol,a bio-fuel with high energy with biomass as feedstock,has a better application prospect than bioethanol with the decrease in oil resources.It is the preferred substitute for petroleum and other fossil fuels.However,besides butanol,the fermentation broth contains acetone and ethanol,and most of water.The poor separation efficiency and high cost for separation were bottlenecks in the development of bio-butanol.Thus developing energy-saving separation technology is the key to the bio-butanol industrialization.The traditional distillation process for the production of 1-butanol was improved by using salting-out and sugaring-out extraction as the separation technology,due to the difficulty of separating the biobutanol fermentation broth system.The selection of salting-out agents,the effects of salt（sugar）concentration,extraction temperature and salting-out factor on the salting-out（sugaring-out）of acetone,1-butanol,and ethanol（ABE for short）from the enriched ABE system and ABE fermentation broth were systematically investigated.The salting-out technology was optimized.Salting-out+distillation process was designed.The effects of salting-out agents on the phase equilibria for the aqueous ethanol solution,acetone aqueous solution and 1-butanol+water system were studied.The molecular mechanism of salting-out（sugaring-out）was revealed by the chemical shift changes of the ethanol molecule,acetone molecule and 1-butanol molecule in the process of salting out（sugaring-out）.In view of the problem that biobutanol with short carbon chain can not be used as an upgraded fuel,ABE from the enriched ABE system was salted out by the additions of K₃PO₄ and palladium on activated carbon,and converted into long chain products at high temperature at the same time.Meanwhile the water from the enriched ABE system was removed.The most promising salting-out agents among more than twenty salts for the separation of the concentrated ABE solution were alkali potassium carbonate,dipotassium hydrogen phosphate,tripotassium phosphate,and potassium pyrophosphate.With the increase in salt concentration,the water content and salt content of the organic phase decreased gradually,and the ABE contents of the aqueous phase also decreased gradually.The water content of the organic phase can be reduced to 2.96 wt%,and ABE can be fully recovered at the higher salt concentration.More than 96%of the water from the concentrated ABE solution was removed and the recovery of ABE was about 100%when salt solution was used.The experimental results in the K₃PO₄ salting-out system were correlated with an excellent agreement by using the Othmer-Tobias equation where acetone,1-butanol,and ethanol were taken as one fictitiously chemical compound.The water content of the organic phase could be predicted by the initial K₄P₂O₇ concentration.The water content of the organic phase and the mass fraction of salt in the aqueous phase were correlated satisfactorily by a new linear equation.The water in the enriched ABE solution was largely removed by the salting-out method.Therefore,the energy requirements for the prefractionator and the butanol column were largely reduced respectively.The optimization of the total energy requirements for the recovery of acetone,butanol,and ethanol by the（salting-out+distillation）method was 21.87MJ/kg butanol.With the salting-out process,the（salting-out+distillation）method was more energy-saving than the conventional one（42.96 MJ/kg butanol）.The liquid-liquid equilibria for the fermentation broth were mainly determined by the salt content and slightly affected by temperature.Higher solvents level permits higher recovery of ABE.More than 90 wt%of ABE was recovered from the model solutions/fermentation broth and more than 99.75%of water was removed.The linear correlation between the solubility of ABE and the molality of salt was demonstrated.The salting-out effects of different salt solutions on the ABE fermentation broth were determined in the order:K₄P₂O₇ solution>K₃PO₄ solution>K₂HPO₄ solution>K₂CO₃ solution.The water content in the organic phase under sugar-free condition decreased from 60.00wt%to 14.31 wt%and 16.72 wt%after the sugaring-out process induced by sucrose and glucose,respectively.More than 89.5 wt%water from the ABE solution was removed.The extended Bancroft Equation was used to correlate the tie-line data with a high accuracy,where ABE was taken as one component.The water content in the organic phase under sugar-free condition could be satisfactorily predicted by the initial concentration of sugar.The salting-out effects were determined in the following order:K₄P₂O₇>K₃PO₄>K₂HPO₄>K₂CO₃ by the correlation between the solubility of ABE and the molality of the salts,and the obtained setchenow salting-out constant?.The order of inducing the salting-out effect was determined as:1-butanol>Acetone>Ethanol,suggesting that the solute with stronger polarity was more difficult to be salted out from the aqueous solution.The molecular mechanism indicates that the polar groups of the ABE molecules and the?methyl/methylene groups are the main interaction sites of the anion.The addition of salting-out agents does break the hydrogen bonds formed by ABE molecules and water molecules.The glucose molecule showed weak interaction with the?methyl/methylene groups,leading to far weaker sugaring-out effect than the salting-out effect.We report a palladium-catalysed alkylation of acetone with ethanol and 1-butanol to produce C₅-C₁₁ petrol-range,diesel-range and jet-range fuel precursors in a reactor,where all the precursors and reactants were separated simultaneously by the salting-out effect of K₃PO₄.The precursors include ketones and a small amount of alcohols that can be reduced to alkynes for use as liquid transportation fuels.Tuning the reaction conditions can obtain different proportions of C₅-C₇ products（monoalkylation）and C₉-C₁₁ products（double alkylation）and the overall product contents accounted for up to 82 wt%of the water-free organic phase.