Structural changes in microcrystalline cellulose in subcritical water treatment

Area of Science:

• Green Chemistry
• Biomass Conversion
• Materials Science

Background:

• Subcritical water offers a sustainable approach for cellulose hydrolysis.
• Understanding structural changes is crucial for optimizing cellulose processing.

Purpose of the Study:

• To investigate the structural modifications of microcrystalline cellulose treated with subcritical water.
• To analyze changes in particle size, morphology, degree of polymerization, crystallinity, and crystallite dimensions.

Main Methods:

• Scanning Electron Microscopy (SEM) for morphology and particle size.
• Gel Permeation Chromatography (GPC) for molecular weight distribution.
• Wide-Angle X-ray Scattering (WAXS) and solid-state Carbon-13 Nuclear Magnetic Resonance ((13)C NMR) for crystallinity and crystallite analysis.

Main Results:

• Cellulose crystallinity remained largely unchanged, while crystallite size increased.
• Significant depolymerization occurred, eventually plateauing at a high degree of polymerization.
• Molar mass distributions exhibited a bimodal pattern, suggesting limited dissolution until extensive depolymerization.

Conclusions:

• Subcritical water treatment induces depolymerization and alters crystallite size in cellulose.
• Cellulose dissolution in subcritical water is a post-depolymerization phenomenon.