Facile depolymerization of microcrystalline cellulose in ionic liquid medium catalyzed by carbon materials as catalysts

Abstract

This study highlights novel approach for complete utilization of cellulose using metal immobilized modified activated carbon M-ACS and metal immobilized cellulose composite M ​− ​C in ionic liquid medium. Catalytic activity of the system was improved using metal immobilized modified activated carbon with varying impregnation ratios (0.5–25 ​wt%) respectively. Maximum yield of Total reducing sugars (TRS) was 64.68% and 5-Hydroxymethylfurfural (5-HMF) was 54.76% using Chromium immobilized modified activated carbon catalyst (15 ​wt%) in a reaction time of 60 ​min ​at 120 ​°C. Also, Chromium immobilized cellulose composite i.e. Cr–C: 20 ​wt% gave maximum 48.78% (TRS) and 39.67% (5-HMF) yield under similar operating conditions. Results revealed that metal immobilized cellulose composite M ​− ​C also gave appreciable product yield but at a lower rate than M-ACS. Also, the efficacy of cellulose pretreatment was evaluated using acids and results were found to be significant and effective. To understand hydrolysis rate during isomerization and dehydration steps, synthetic glucose and fructose solutions of varying concentration (3–45 ​wt%) were used. Complete utilization of cellulose with suitable acidity of the process has been proposed i.e cellulose solubilization without compromising with 5-HMF yield. Recyclability of catalyst, composite and ionic liquid at 1 ​atm pressure facilitate the economical and feasible production of TRS and 5-HMF. Development of environment friendly and economical ionic liquid/catalyst system can be considered as a potential alternative for the conversion of cellulose to bio-based products.