LAUSR

In the present work we report the valorization of hemicellulose isolated from lignocellulosic biomass (wheat straw, rice husk and bagasse) to furfural by pH controlled acid catalysed valorization using few choline based Bronsted acidic (BA) and natural acidic (NA) deep eutectic solvents (DES) serving both as catalyst and solvent. The effect of pH variation on the catalytic activity of various BADES and NADES prepared in 1:1 molar ratio was observed and ChCl:p-TSA among all the DESs was found to be the best with lower pH value of 1.0. The yield of furfural decreases from 85 to 51% with increase in the pH value from 1.0 to 3.0. The molar ratio of HBD (hydrogen bond donor) to HBA (hydrogen bond acceptor) components was varied from 1:1 to 1:9 to achieve the lowest possible pH values of the DESs and to increase the furfural yield. Further optimization of reaction conditions were also done in terms of DES loading, time of reaction and temperature using the model DES to achieve higher furfural yield. The best results were obtained using 5 mmol DES having pH 1.0 in 1.5 h at 120oC. ChCl:p-TSA (Choline Chloride:p-Toluene sulfonic acid), ChCl:oxalic acid (Choline chloride:oxalic acid) among BADES and ChCl:LevA (Choline chloride:Levulinic acid) among NADES investigated in this work yielding 85% furfural were found to be most efficient. The reported methodology is advantageous in terms of using bio-based green solvent, milder reaction conditions and efficient up scaling of reaction. The DESs were found to be efficiently recyclable up to five consecutive runs for the process.