Technoeconomic Assessment of a Biomass Pretreatment + Ionic Liquid Recovery Process with Aprotic and Choline Derived Ionic Liquids

Abstract

Ionic liquids have shown promising results in biomass pretreatment; however, an extensive water washing step is necessary. This fact increases not only the processing costs but also those associated with the ionic liquid recovery step. In this work, Eucalyptus globulus wood pretreated with two acetate-based ionic liquids, namely 1-ethyl-3-methylimidazolium acetate and choline acetate, has been washed with increasing volumes of water in order to analyze the influence of the amount of washing water used on the subsequent enzymatic hydrolysis stage and on the IL recovery costs. Vapor−liquid equilibria data of recovered ionic liquid/water mixtures have been determined to simulate the IL recovery step with Aspen Plus, calculating the operating costs using the Aspen Plus Economics Analyzer afterward. [Emim][OAc] was more efficiently washed and more effective toward wood pretreatment than [Ch][OAc]. Both IL/water systems were successfully modeled, and simulation studies showed that incremental volumes of water led to higher operating costs in the IL recovery step that are compensated with less IL makeup costs. Therefore, this work offers a technoeconomical analysis of the IL recovery step in a real biorefinery pretreatment process as a function of the volume of water used in the pretreated wood washing stage.