Ionic Liquids as Solvents for Catalytic Conversion of Lignocellulosic Feedstocks (original) (raw)

The deconstruction and upgrading of lignocellulosic biomass dissolved in ionic liquids was studied as a potential alternative route to products traditionally synthesized from petroleum. While domestic biomass is a cheaper, lower carbon emission, alternative feedstock to petroleum, its utilization requires the selective deconstruction of the biopolymer to monomeric sugars and upgrading of the sugars to higher value products. Since biomass is soluble in ionic liquids, there is the opportunity to do both the deconstruction and secondary upgrading using "one-pot" homogeneous catalysis. The primary focus of this work was to understand the kinetics of both biomass deconstruction and secondary sugar chemistry in ionic liquids. Biomass is a complex collection of molecule that consists of three primary components, cellulose, hemicellulose, and lignin. Since cellulose is the primary component, accounting for roughly 45 wt% of the raw biomass on a dry basis, initial studies aimed to understand the hydrolysis of dissolved cellulose to its sugar residue glucose. Using microcrystalline Avicel cellulose as a model, the rate laws and activation energies of cellulose hydrolysis and glucose dehydration were determined in the ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]). No evidence of oligosaccharides was observed, suggesting that hydrolysis occurs preferentially at chain ends and is irreversible. Gradually adding water to the reaction solution, so as not to precipitate cellulose but also limit the secondary dehydration of the resulting glucose to 5-hydroxymethyl furfural (5-HMF), significantly increased glucose yield and limited production of degradation products (humins). Several mechanisms were proposed to explain the effects of water, and possible routes to humin formation. While understanding the reactivity of model compounds is important to the development of biomass conversion technologies, it is critical to understand how the components of biomass react in their native form. An investigation was carried out to compare the reactivity of cellulose and hemicellulose model compounds to both pretreated and miscanthus grass in 1-ethyl-3methylimidazolium chloride ([Emim][Cl]). Activation energies of model compounds were compared with the native component in raw biomass. Significant rate decreases in hydrolysis of the cellulosic and hemicellulosic Table of Contents List of Figures .

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