Separation of diluted butanol–water solutions via vapor phase by organophilic membranes based on high permeable polyacetylenes

The diluted organic-water solutions are convenient products of biomass treatment to biofuels (e.g., ABE fermentation). A continuous membrane-assisted method by example of butanol recovery from fermentation media is considered in present work. The method is based on combination of the gas stripping (convenient process) with membrane vapor separation (with preferable butanol vapor permeability). In comparison with known membrane pervaporation method the suggested one possesses such advantageousness as an expanded membrane module area and resistance to fouling. Main attention is put on fundamental aspects of separation: (1) the contribution of liquid/vapor phase transition and (2) vapor selective properties of organophilic membranes. Two polymers: poly-1-trimethylsilyl-1-propyne (PTMSP) and poly-4-methyl-2-pentyne (PMP), and two their block copolymers (with PTMSP–PMP ratio 60:40 and 25:75) are suggested as membrane materials for this purpose. Vapor permeability of water, butanol and butanol–water solutions are determined for selected polymers and block copolymers at different temperatures and butanol–water solution concentrations. Apparent activation energy and temperature parameter of permeability of water and butanol vapors in PTMSP and PMP membranes are obtained. The methodology of study can be used for the systematic research of the vapor permeability membrane properties influence on separation of liquid multi-component mixtures with taking into account of liquid/vapor equilibrium.

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► Vapor phase membrane-assisted method of fermentation butanol recovery is considered.
► New block copolymers are suggested as materials for butanol/water vapor separation.
► Selectivity of butanol/water mixture vapor separation is lower than one for pure components.
► Contributions of phase transition and vapor selective properties of membranes are estimated.