Easy Fabrication of Highly Thermal-Stable Cellulose Nanocrystals Using Cr(NO(3))(3) Catalytic Hydrolysis System: A Feasibility Study from Macro- to Nano-Dimensions

This study reported on the feasibility and practicability of Cr(NO(3))(3) hydrolysis to isolate cellulose nanocrystals (CNC(Cr(NO3)3)) from native cellulosic feedstock. The physicochemical properties of CNC(Cr(NO3)3) were compared with nanocellulose isolated using sulfuric acid hydrolysis (CNC(H2SO4)). In optimum hydrolysis conditions, 80 °C, 1.5 h, 0.8 M Cr(NO(3))(3) metal salt and solid–liquid ratio of 1:30, the CNC(Cr(NO3)3) exhibited a network-like long fibrous structure with the aspect ratio of 15.7, while the CNC(H2SO4) showed rice-shape structure with an aspect ratio of 3.5. Additionally, Cr(NO(3))(3)-treated CNC rendered a higher crystallinity (86.5% ± 0.3%) with high yield (83.6% ± 0.6%) as compared to the H(2)SO(4)-treated CNC (81.4% ± 0.1% and 54.7% ± 0.3%, respectively). Furthermore, better thermal stability of CNC(Cr(NO3)3) (344 °C) compared to CNC(H2SO4) (273 °C) rendered a high potential for nanocomposite application. This comparable effectiveness of Cr(NO(3))(3) metal salt provides milder hydrolysis conditions for highly selective depolymerization of cellulosic fiber into value-added cellulose nanomaterial, or useful chemicals and fuels in the future.