Use of Protic Ionic Liquids as Biomass Pretreatment for Lignocellulosic Ethanol Production

Abstract

Although sugar cane bagasse is considered as a promising material for the production of second-generation ethanol, obtained through enzymatic hydrolysis and subsequent fermentation, the strong recalcitrance of its internal structures increases the production costs of this biofuel, requiring the application of pre-treatment and technological routes for its processing, sometimes unfeasible technically and economically. More recently, ionic liquids have been studied as an environmentally friendly alternative. Although the majority of the published works consider aprotic ionic liquids, the interest in protic ionic liquids has grown in recent years, especially due to its capacity to establish strong hydrogen bonds. Moreover, the functionality of the mobile nature of the proton H + makes these materials potential candidates for conducting protons for use in fuel cells and several other applications. In this work, the protic ionic liquid bis(2-hidroxyethylammonium) acetate, 2HE2AA, was produced and purified and then evaluated as a pre-treatment agent for sugarcane bagasse. The pre-treated material was enzymatically hydrolyzed for subsequent ethanol fermentation. The expectation is that a high yield be achieved in second-generation ethanol production, so that it can provide scientific and economic basis for a biomass conversion integrated and environmentally friendly process. Preliminary results indicated a yield of 84% in the pre-treatment step. The enzymatic saccharification showed a yield of 77% and a glucose conversion efficiency of 35% after 72 h.