Easy Fabrication of Highly Thermal-Stable Cellulose Nanocrystals Using Cr(NO₃)₃ Catalytic Hydrolysis System: A Feasibility Study from Macro- to Nano-Dimensions.

This study reported on the feasibility and practicability of Cr(NO₃)₃ hydrolysis to isolate cellulose nanocrystals (CNC) from native cellulosic feedstock. The physicochemical properties of CNC were compared with nanocellulose isolated using sulfuric acid hydrolysis (CNC). In optimum hydrolysis conditions, 80 °C, 1.5 h, 0.8 M Cr(NO₃)₃ metal salt and solid-liquid ratio of 1:30, the CNC exhibited a network-like long fibrous structure with the aspect ratio of 15.7, while the CNC showed rice-shape structure with an aspect ratio of 3.5. Additionally, Cr(NO₃)₃-treated CNC rendered a higher crystallinity (86.5% ± 0.3%) with high yield (83.6% ± 0.6%) as compared to the H₂SO₄-treated CNC (81.4% ± 0.1% and 54.7% ± 0.3%, respectively). Furthermore, better thermal stability of CNC (344 °C) compared to CNC (273 °C) rendered a high potential for nanocomposite application. This comparable effectiveness of Cr(NO₃)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.