Simulation of a hybrid fermentation-separation process for production of butyric acid

Simulation of a hybrid fermentation-separation process for the production of butyric acid (BA) based on published data was done. A unit consisting of a bioreactor with immobilized cells in the fibrous bed and of separation by pertraction through supported liquid membranes (SLM) was considered. Productivities of the unit volume of a fixed bed bioreactor in continuous and fed-batch fermentation at pH 5.5 and 6.0 were used. Concentration of BA in the bioreactor outlet stream was assumed to be in the interval from 0.11 kmol m(-3) to 0.45 kmol m(-3). Data on the pertraction through SLM with phosphonium ionic liquid (IL) and bulk liquid membrane with trioctylamine (TOA) as carriers were used. A strong increase in the required membrane area was found for both carriers at the pH of pertraction above 4. pH values of fermentation and pertraction should be optimized independently. It is advantageous to have pH of the feed into the pertraction unit of about 4. Dependences of the membrane area on the pertraction efficiency are nearly linear and not very sharp, especially for IL, what enables working at the pertractor efficiency exceeding 90 %. Application of phosphonium IL is promising compared to classical extractant TOA because of lower demand of the membrane area in a large interval of BA concentrations in the pertractor feed.