Under the WP3 (ABE fermentation and solvent recovery), since the last status update TU Wien has conducted extensive research regarding different membrane materials as well as potential membrane module designs for the separation of ABE from fermentation broth. The focus was put on commercially available PDMS (polydimethylsiloxane) and newly developed POMS (polyoxymethylsiloxan) membranes by different vendors. Flat sheet modules were tested for both materials while hollow fiber modules were only considered for PDMS membranes as they are not commercially available yet for POMS.
Influence of temperature, glucose and salt concentration on separation performance was tested. While an increase in temperature led to improved results, addition of glucose and ammonia chloride did not show negative impacts in the relevant concentration range. Both materials showed promising results although certain differences exist. POMS offers slightly higher butanol selectivity but PDMS has a slightly higher permeance and therefore overall higher flux. Which option is preferable must be further researched in the context of the overall process and its energy demand in the final upgrading steps.
Concluding, it was possible to show solvent enrichment from 1.5 wt% BuOH up to 31.5 wt% in a single upgrading step while also considering the influence of potential secondary components in the fermentation broth.