Effects of Synthesis Conditions on the Pervaporation Properties of Poly[1-(Trimethylsilyl)-1-Propyne] Useful for Membrane Bioreactors

An integrated fermentation and membrane-based recovery (pervaporation) process has certain economical advantages in continuous conversion of biomass into alcohols. This article presents new pervaporation data obtained for poly[1-(trimethylsilyl)-1-propyne] (PTMSP) samples synthesized in various conditions. Three different catalytic systems, TaCl₅/n-BuLi, TaCl₅/Al(i-Bu)₃, and NbCl₅ were used for synthesis of the polymers. It was found that the catalytic system has a significant influence over the properties of membranes made from PTMSP. Although a combination of a high permeation rate and a high ethanol-water separation factor (not less than 15) was provided by all PTMSP samples, the PTMSP samples synthesized with TaCl₅/n-BuLi showed significant deterioration of membrane properties when acetic acid was present in the feed. In contrast, the PTMSP samples synthesized with TaCl₅/Al(i-Bu)₃ or NbCl₅ showed stable performance in the presence of acetic acid. When using a multicomponent mixture of organics and water, the copermeation of different organic components results in lower separation factor for both ethanol and butanol. These data are consistent with nanoporous morphology of PTMSP. It was demonstrated that pervaporative removal of ethanol improved the overall performance of the fermentation process.