Investigating acid/peroxide-alkali pretreatment of sugarcane bagasse to isolate high accessibility cellulose applied in acetylation reactions

Sugarcane bagasse was selected as residual feedstock to investigate the effects of an acid/peroxide-alkali (APA) combined pretreatment on the extraction of cellulose and on its applicability for producing cellulose acetate. The pretreatment was effective in disrupting the recalcitrant lignocellulose structure and isolating cellulose (SBC), which reached 85.67% purity. High performance liquid chromatography, 1 H and 13 C nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetry, calorimetry, X-ray diffractometry (XRD), scanning electron microscopy and elemental analysis were applied to characterize the materials. Crystallinity and accessibility were evaluated by Segal and deconvolution crystallinity indexes, full-width at half maximum, crystallite size (L), total crystalline index and lateral order index parameters. SBC cellulose presented lower crystallinity and was classified after XRD peak deconvolution as a mixture of cellulose II polymorph with considerable amorphicity and some features of remaining cellulose Iβ from sugarcane bagasse, while CC was labeled type Iβ, indicating that the sustainable material is more susceptible to chemical modifications. The degrees of substitution of acetylation products showed that both celluloses have satisfactory reactivity and reached mono, di and triacetylation in different reaction conditions. SBC cellulose is presented as an efficient and renewable alternative to commercial cellulose for producing chemicals, and it is proposed that the APA pretreatment had a significant influence on the low crystallinity and high accessibility of this material. Graphical abstract