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.
Highlights
Lignocellulosic biomass can be considered as one of the main alternatives to fossil fuels.[1]
A decrease in solid recovery is observed for both ionic liquids (ILs), especially in the case of wood pretreated with [Emim][OAc]
The relative composition for wood pretreated with both ILs, compare with the untreated eucalyptus, indicates that biomass fractions are selectively removed.[53]
Summary
Lignocellulosic biomass can be considered as one of the main alternatives to fossil fuels.[1]. The use of washing volumes that ensured the total IL recovery compensates this difference by considering the lower cost of the [Ch][OAc] This would indicate that the economy of the process is mainly affected by the IL cost, a fact that has already been reported, and the capacity of recovering as much IL as possible after pretreatment.[31−33] In this line, studying the IL washing step is necessary, to minimize water consumption and to ensure that the IL is totally (or almost totally) recovered. IL content toxicity toward microorganisms depending on the volume of water employed in the pretreated biomass washing step, as well as including the costs associated with water consumption and stirring power in the economic balance, are considered for further research in the future
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