Homogeneous modification of sugarcane bagasse with maleic anhydride in 1-butyl-3-methylimidazolium chloride without any catalysts

During the past few decades, much effort has been devoted to increasing the utilization of lignocellulosic biomass to create biofuels, biochemicals, biocomposites, and a host of other bioproducts to replace fossil-based products. Recently, the utilization of lignocellulosic biomass received much more attention in ionic liquids with strong hydrogen-bond-destroying ability to produce lignocellulosic derivatives containing new functionality. In present study, carboxyl groups were attached onto sugarcane bagasse (SCB) by the homogenous modification of SCB with maleic anhydride in ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) without any catalysts. The parameters optimized included maleic anhydride concentration, reaction temperature and reaction time required in the process. The extent of maleation of SCB was measured by the weight percent gain (WPG), which increased with an increment of maleic anhydride concentration between 1:1 and 5:1 (g/g, maleic anhydride/SCB). It should be noted that WPG decreased at wild conditions, including long reaction duration (>60 min) and high temperature (>110 °C). The results from FT-IR and solid-state CP/MAS 13C NMR spectroscopies indicated that the maleation of hydroxyl groups in lignin, cellulose and hemicelluloses all occurred. XRD, SEM and TGA/DTG analyses of the native and modified SCB showed that the cellulose crystalline structure of SCB was significantly destroyed after dissolution, maleation, and regeneration in IL. However, the remained cellulose crystalline structure did not change except remarkable decrystallization. The thermal stability of the maleated SCB decreased at low temperature (lower than 300 °C), and increased at high temperature (above 300 °C) compared with that of native ball-milled SCB.

► Homogeneous maleation of SCB was performed in BMIMCl without catalysts.
► Effects of maleic anhydride dosage, temperature and time were investigated.
► Maleation of hydroxyl groups in lignin, cellulose and hemicelluloses all occur.
► Remained crystalline structure does not change except significant decrystallization.
► SCB shows differential thermal stability after homogeneous maleation in IL.