Technical optimization of a treatment process on ABE effluent by membrane technologies

In the last decades, the interest in biofuel production is sensibly growing as a good source of sustainable energy and a valid alternative to fossil ones. One of the most promising biofuel is butanol and might be produced by starting from different substrates, such as second generation ones, that have the advantage to be in the future more cost effective, as soon as the relevant production processes will be fully developed and optimized. In this case, the entering lignocellulosic material undergoes biological digestion up to a mixture mainly of acetone, butanol and ethanol, respectively. The digestion product, called ABE, requires the separation of almost pure butanol from the other components, in order to qualify as a biofuel. A possibility to perform this separation is by fractioned distillation, which has the advantage to be operated with ease, but leads to very high operating costs. In this work, the separation of n-butanol from ABE was performed by means of membrane technology in four subsequent steps: ultrafiltration (UF), pervaporation (PV), nanofiltration (NF) and a last step of demixing once the n-butanol concentration reaches values within the miscibility gap. The study focused on the productivity, selectivity and longevity of the adopted membranes; in particular, it was observed by experimental campaign that membrane fouling must be strongly inhibited to achieve technical and economical feasibility of the overall proposed process.