Cellulose obtained from banana plant waste for catalytic production of 5-HMF: Effect of grinding on the cellulose properties

Cellulose fibers from "Banana Tabasco" plant rachis, were isolated using a combination of soft chemical treatments, and were mechanically comminuted with a high energy ball mill at different milling timings. Infrared spectroscopy (FTIR-ATR) and nuclear magnetic resonance (H-1 NMR) were used to study the effects of grinding on the molecular structure and depolymerization of the comminuted cellulose. Changes in morphology, crystallinity index, particle size, thermal properties, and solubility, were also studied using different characterization techniques. Previously reported catalyst (Al2O3-TiO2-W with 5 wt% of W) which was successfully probed in the production of hydroxymethylfurfural (5-HMF) from glucose, was employed for the transformation of the comminuted cellulose into 5-HMF. The reactivity of the Al2O3-TiO2-W catalyst in the conversion of cellulose into 5-HMF, was successful for all comminuted cellulose samples; whereas for commercial cellulose, the catalyst did not work, possibly due to the high polymerization degree. For most of the samples the highest 5-HMF concentration obtained was between 43 and 50 mg/mL at 60 min of reaction. At 120 min, the sample comminuted for 1.5 h grinding showed the highest 5-HMF concentration of 46 mg/mL; this result was associated to the transformation of cellulose oligomers with the most appropriate chain size. The cellulose extracted from Tabasco Banana rachis by means of the methodology established in this study, presented favorable features for the conversion into 5-HMF.