Hydrothermal processing of cellulose: A comparison between oxidative and non-oxidative processes

Area of Science:

• Biomass Conversion
• Thermochemical Processing
• Cellulose Chemistry

Background:

• Hydrothermal processing is a key method for biomass conversion.
• Understanding the mechanisms of cellulose degradation under oxidative and non-oxidative conditions is crucial.
• Limited data exists on simultaneous hydrogen peroxide formation and its impact on degradation products.

Purpose of the Study:

• To investigate and compare oxidative and non-oxidative hydrothermal processing of cellulose.
• To quantify volatile fatty acids (VFAs), total suspended solid (TSS) degradation, dissolved organic carbon (DOC), and chemical oxygen demand (COD).
• To experimentally confirm and analyze hydrogen peroxide (H₂O₂) formation in both processes across varying temperatures.

Main Methods:

• Cellulose samples were subjected to hydrothermal processing at temperatures ranging from 180°C to 260°C.
• Oxidative and non-oxidative conditions were employed.
• Key parameters including VFAs, TSS, DOC, and COD were measured.
• Hydrogen peroxide presence was experimentally verified.

Main Results:

• Hydrogen peroxide (H₂O₂) production was confirmed in both oxidative and non-oxidative processes.
• H₂O₂ yield was significantly higher in oxidative processing below 220°C, but higher in non-oxidative processing above 240°C.
• Volatile fatty acids (VFAs) concentration was substantially lower (<10%) under non-oxidative conditions.
• Soluble chemical oxygen demand (COD) generally increased with time and temperature, with a decrease at 260°C due to further conversion.

Conclusions:

• Hydrothermal processing of cellulose yields hydrogen peroxide, with its production influenced by temperature and process conditions.
• Non-oxidative processing offers a pathway to significantly reduce volatile fatty acids formation.
• Understanding these degradation pathways is vital for optimizing biomass conversion strategies.