Ionic Liquid-based Biomass Deconstruction And Utilization Process

Now with the depletion of petroleum resources, combined with increasing demand for fossil fuels by emerging economies, and political and environmental concerns about fossil fuels, it is essential to develop cost-competitive and energy-efficient processes for the sustainable production of fuels and chemicals. In this respect, lignocellulosic biomass is the only current sustainable source of organic carbon and biofuels. Fortunately, it is the most abundant and renewable resource of carbon on the earth. It mainly consists of three structural polymers, namely, the carbohydrates cellulose, hemicelluloses and lignin. Lignocellulosic biomass is naturally resistant to deconstruction from many microbes and enzymes, so it is essential to deconstruct the biomass firstly. IL-based pretreatment technology is believed to be a nascent technology with great promise. In the dissolution process, ILs with the anion of acetate and chloride are most widely studied. However, this process suffers from the cost of ILs, for instance,1-ethyl-3-methylimidazolium acetate ([C2C1im][OAc]), which is the most effective ILs for the dissolution process found to date, but a cost of$50/kg would represent approximately half the cost of converting lignocellulosic biomass to ethanol. In order to make the cost-competitive IL-based biomass pretreatment process a practical reality, it is imperative to develop affordable ILs to deconstruct biomass.In the present contribution, ILs synthesis methodology was investigated, and various ILs were syntheised in the Lab. Moreover, ILs ([HNEt3][HSO4] and IL1([HC1im][HSO4], IL2) preparation process models were implemented for the first time using ASPEN software. Then the economic assessment of ILs production plants was performed based on the simulation models. The results showed that some ILs can be as cheap as conventional organic solvents. The cost prices of IL1and IL2are$1.24/kg and$2.96-5.88/kg, respectively.The reactions occurring behind the Ionosolv process was also illustrated through the study of the plant cell walls of Miscanthus giganteus and Ionosolv lignin. The result suggested that the lignin structure was altered and S/G ratio was also changed during the Ionosolv process. It also showed that lignin underwent depolymersation at the first stage of the process through the cleavage of β-O-4aryl ether linkages, confirmed by the ether bond signal in HSQC and lignin hydroxyl groups concentration changes. However, as the pretreatment time increased which means the severity of the process enhanced, repolymersation (condensation) process took place, which was supported by the lignin molecular weight determination and aromatic CH correlation detect results. During the Ionosolv process, IL disrupted the linkages among cellulose, hemicelluloses and lignin, meanwhile, dissolved and removed hemicelluloses and lignin, resulting in the disruption of the hydrogen bond networking in crystalline cellulose, as evidenced by the CPMAS13C NMR, ATR-IR and ToF-SIMS. The CrI value of recovered cellulose varied largely, depending on its measurements techniques. However, it was generally increased by removing the amorphous fractions after the Ionosolv process. These results suggested that CrI was not a key substrate characteristic impacting enzymatic cellulose hydrolysis and relating to pretreatment efficacy. In addition, based upon the EDX results, the ILs left on biomass after pretreatment can be recycled through soxhlet extraction, which also facilitated enzymatic hydrolysis process.The pretreatemtn effect of the low-cost ILs [HNEt3][HSO4] on biomass was also investigated. After24hours pretreatment, the glucose yield reached to90.6%based on the enzymatic sacchrification test, and the composition analysis indicated that91%of the treated biomass was glucan. Moreover, the structure elucidation of recovered lignin and cellulose was also conducted, suggesting that this process had similar mechanism with Ionosolv process.Solvents intensification for lignin model compound aromatic alcohols oxidation was performed by experimentally screening. A co-solvent mixture of1-octyl-3-methylimidazolium chloride ([Omim]Cl) and toluene was found to significantly intensify this class of reactions with high conversion of alcohols (>90%) and high selectivity to their aldehydes (>90%). Moreover,[Omim]Cl was also found to effectively intensify cyclohexanol oxidation.