Pervaporation Separation Integrated With Acetone-butanol Fermentation

Due to extensive oil depletion and its increasing price trend over the past decades, the use of biofuels as a partial replacement for fossil fuels has attracted both academic and industrial attentions.Among alternative biofuels,biobutanol is expected to play an important role in the next generation of biofuels.In this paper,HTPB-PU membrane and PDMS/PVDF membrane have been prepared for recovery of acetone and butanol from dilute aqueous solutions.Furthermore,potential of the membrane for separation of organics from fermentation was also studied by testing the pervaporaton performance.The main contents of this work were as follows:1.HTPB-PU membraneHydroxyterminated polybutadiene-based polyurethaneurea(HTPB-PU) pervaporation membranes were prepared and used for recovering acetone and n-butanol from dilute aqueous solutions.The effects of operation temperature and feed composition on the pervaporation performance were investigated.The differences of separation performance between ternary mixture and binary mixture were also studied through evaluating permeability coefficient,swelling degree of membrane and activity coefficient.The results indicated that the pervaporation performance for ternary mixture was superior to that for binary mixture because of the permeant-permeant and permeant-membrane interactions.A high selectivity towards acetone and n-butanol was obtained.Acetone and butanol were condensed from 1.5 to 11.9 wt%and 3.0 to 43.5 wt%at 40℃for the ternary mixtures,respectively. Furthermore,potential of the membrane for separation of organics from fermentation was also studied by testing the pervaporaton performance,and acetone and butanol were condensed from 0.5 to 8.7 wt%and 1.1 to 16.4 wt%at 45℃,respectively.2.PDMS/PVDF membranePDMS/PVDF composite membranes were prepared with the crossing-agent (tetraethyl orthosilicate or triethoxyoctylsilane) and used for separating acetone-butanol(AB) from its dilute aqueous solution to evaluate pervaporation separation performance at various feed concentrations,operating temperatures and feed pH.Furthermore,potential of the membrane for separation of organics from fermentation was also studied by testing the pervaporaton performance,and separation factor of acetone and butanol were 19.1 and 22.2 at 45℃,respectively.3.Pervaporation integrated with fermentationPDMS(tetraethyl orthosilicate)/PVDF membrane was integrated with acetone-butanol fermentation and fed-batch fermentation.Effect of pervaporation for the acetone-butanol fermentation was investigated.The results showed that the total solvent concentration of permeant was about 20 wt%for pervaporation-batch fermentation system at 39℃.Comparing with batch fermentation,solvent production rate increased form 0.19g l^-1 h^-1 to 0.44 g l^-1 h^-1.For pervaporation-fed-batch fermentation system,the total solvent concentration of permant was about 28 wt%, and during the total solvent yield of coupling separation process(63.5 h-74 h) is up to 0.58 g l^-1 h^-1.