Deep eutectic solvent-functionalized biochar derived tobacco stalks: A novel heterogeneous catalyst for solketal synthesis

This study investigates the synthesis of catalyst by the impregnation of acidic deep eutectic solvent into biochar obtained from tobacco stalk. And also, the catalytic activity of the synthesized catalyst was tested in the acetalization reaction of glycerol and acetone to synthesize solketal, a versatile bioadditive of fuel. Deep eutectic solvent containing choline chloride and para toluene sulfonic acid has been used to alter the surface functionality of biochar. The changes in textural features, surface chemistry and morphology of activated biochar (A-BC) and DES-impregnated biochar (B-DES@A-BC) were characterized. The characterization methods highlighted change in properties after DES impregnation; surface area and pore volume decreased significantly, more acidic functional groups added and developed on the surface and also pore size increased. Under the optimized conditions (T = 50 °C, molar ratio of acetone to glycerol = 15:1, catalyst loading = 8 wt%, reaction time = 60 min), B-DES@A-BC showed excellent reusability and catalytic activity; 93.9 % of glycerol conversion and 97.4 % of solketal selectivity. B-DES@A-BC catalyst was found to be efficient, economical, sustainable and efficient. So, preparing heterogeneous catalyst from biomass by carbonization and following DES impregnation could be proposed as a promising method. DES containing choline chloride and para toluene sulfonic acid was found to be effective agent to improve catalytic activity introducing functionalities. • Low-cost and waste tobacco stalk was utilized as a carbon source. • Tobacco stalk which is a sustainable source was transformed to biochar having a surface area of 800 m 2 /g. • Deep eutectic solvent, which provides green functionalization, enhanced pore size, and acidity of biochar. • DES-impregnated biochar showed excellent activity and reusability.