Hydrolysis of microcrystalline cellulose using functionalized Bronsted acidic ionic liquids – A comparative study

• Bronsted acidic functionalized ionic liquids were synthesized and characterized.
• Microcrystalline cellulose hydrolysis was conducted using synthesized ionic liquid.
• Maximum %TRS yield obtained with SO3H functionalized ionic liquid.
• Acidity trend was compared using both Hammett function values and DFT results.

Cellulose conversion to platform chemicals is required to meet the demands of increasing population and modernization of the world. Hydrolysis of microcrystalline cellulose was studied with SO3H, COOH and OH functionalized imidazole based ionic liquid using 1-butyl-3-methylimidazolium chloride [BMIM]Cl as a solvent. The influence of temperature, time, acidity of ionic liquids and catalyst loading was studied on hydrolysis reaction. The maximum %TRS yield 85%, was obtained at 100 °C and 90 min with 0.2 g of SO3H functionalized ionic liquid. UV–vis spectroscopy using 4-nitro aniline as an indicator was performed to find out the Hammett function of ionic liquid and acidity trends are as follows: SO3H > COOH > OH. Density functional theory (DFT) calculations were performed to optimize the ionic liquid and their conjugate bases at B3LYP 6-311G++ (d, p) level using Gaussian 09 program. Theoretical findings are in agreement with the experimental results.