Optimization of the Particle Diameter Profile in a Fixed Bed for Separation of ?-Valerolactone

Abstract

Conversion of polysaccharides – cellulose and hemicellulose – into fermentable sugars is one of the factors that makes the production of lignocellulosic ethanol more complex in relation to ethanol produced from feedstock containing sugars or starch. The use of ?-valerolactone (GVL) solvent was recently indicated as an alternative to improve the conversion of these biomass polysaccharides. However, GLV removal before fermentation is an essential step, because its presence has negative effects on the metabolism of sugars by microorganisms. The extraction technique using subcritical CO2 is able to separate a large amount of GVL. Nonetheless, a complementary method is still required to separate small quantities of GVL remaining in the sugar solution, which can be efficiently performed by fixed bed adsorption. In this process the size of the adsorbent particles plays an important role, because it influences both the mass transfer and the pressure drop in the column. While small diameters favour mass transfer rate, but increase pressure drop, the opposite effect is observed for larger particle sizes. Hence, the aim of this study was to optimize the particle diameter profile of a fixed bed column to perform the separation of ?-valerolactone from a sugar solution with minimum pressure drop and a satisfactory mass transfer coefficient. The optimization problem was formulated as a nonlinear programming and solved by means of the General Algebraic Modeling System (GAMS) software and the IPOPT (Interior Point OPTimizer) solver.