Modification Of Lignocellulose In Ionic Liquids

One of the major current challenges to the sustainable society is the efficient utilization ofrenewable resources for the production of performance materials, platform chemicals, andbiofuels. During the past few decades, much effort had been devoted to increasing theutilization of lignocellulosic biomass to create biofuels, biochemicals, biocomposites, and ahost of other bioproducts to replace fossil-based products. Recently, ionic liquids with stronghydrogen-bond-destroying ability had been developed for the processing of lignocellulosicbiomass. Homogeneous acetylation, benzoylation, and carbanilation reaction of wood-basedlignocellulosic materials was accomplished to produce the highly substituted lignocellulosicesters under mild conditions.In this study,the dissolution and modification of bagasse in ionicliquid were investigated.The primary results were described as follow:1The homogeneous succinoylation of sugarcane bagasse(SCB) with succinic anhydridein ionic liquid1-butyl-3-methylimidazolium chloride ([C4mim]Cl) without any catalyst wasinvestigated. Parameters including reaction temperature, reaction duration, and SA/SCB ratiowere discussed. The results showed that the yield of succinylated sugarcane bagasse was highat100oC of reaction temperature,3:1of the SA/SCB ratio and90min of reaction time. Thederivatives were also characterized by FT-TR, DTG/TGA and NMR spectroscopies as well asXRD. It was found that both were succinylated. The succinoylation at C-6, C-2, and C-3incellulose were all occurred. The thermal stability of SCB decreased after succinoylation.2Bagasse acetate butyrates were prepared homogeneously in [C4mim]Cl ionic liquidfrom ball-milled sugarcane bagasse by acylation with acetic anhydride and butyric anhydride.The parameters, including reaction temperature, reaction time, feeding method of addinganhydrides, the dosage of total anhydrides to SCB, and the molar ratio of acetic anhydride tobutyric anhydride, were discussed, and the extent of acylation was measured by weightpercent gain (WPG). The results showed the positive effects of reaction duration and totalanhydride dosage on WPG and the negative effects of reaction temperature and molar ratio ofAA/BA on WPG. The feeding method of acetylation after butyrylation resulted in theincreased WPG compared with acetylation before butyrylation. FT-IR and1H–13Ccorrelation2D NMR (HSQC) studies provided evidences for acylation. The bagasse acetatebutyrates showed increased thermal stability after acylation. This study provides a new wayfor high-value-added utilization of renewable lignocellulosic biomass. 3In present study, homogeneous acylation of ball-milled SCB with pentanoic acid wasintroduced with in situ activation with N,N’-carbonyldiimidazole (CDI) in ionic liquid[C4mim]Cl. The effects of the parameters, including reaction temperature, reaction time, andthe dosage of pentanoic acid to SCB, on the extent of acylation, measured by weight percentgain (WPG), were investigated. This method was facile for the preparation of bagasse esterdirectly using carboxylic acid in ionic liquid. The products were characterized by the meansof FT-IR and2D1H–13C correlation (HSQC) NMR for more detailed evidences of acylation.4The increased dissolution of ball-milled lignocellulosic biomass including SCB,Eucalyptus, and Masson pine was investigated in ionic liquid [C4mim]Cl at relatively hightemperature. The dissolution of bagasse in [C4mim]Cl decreased from13.5h at90oC to2.0hat140oC, and further decreased to0.5h at170oC,0.33h at180oC, and0.28h at190oC.Similarly, the dissolution of ball-milled Eucalyptus and Masson pine in [C4mim]Cl achievedunder same conditions within0.75h and0.25h, respectively. The order of the dissolution ofthe ball-milled lignocellulosics in [C4mim]Cl at170oC was Masson pine <bagasse <Eucalyptus, which probably related to the more compact and complicated cell wall structureof Eucalyptus than bagasse and Masson pine. The physicochemical properties of theregenerated lignocellulosics was characterizated with FT-IR, CP/MAS13C-NMR andwide-angle XRD diffraction as well as thermal analysis. The results indicated that noderivatization occurred in dissolution in ionic liquid even at high dissolution time. Thecrystalline structure in native bagasse was destroyed and converted from cellulose I toamorphous structure at low dissolution temperature and to cellulose II at high dissolutiontemperature after regeneration. Thermal stability of lignocellulosics was slightly decreasedafter dissolution and regeneration in [C4mim]Cl.