Solvent-free catalytic depolymerization of cellulose to water-soluble oligosaccharides

Area of Science:

• Biomass conversion
• Green chemistry
• Biorefinery technology

Background:

• Cellulose utilization is limited by challenges in depolymerizing this biopolymer into soluble forms.
• Mechanically assisted, solid-state reactions often face contact problems, hindering efficient cellulose breakdown.

Purpose of the Study:

• To develop a highly effective strategy for minimizing contact problems in solid-state cellulose reactions.
• To investigate the conversion of cellulosic substrates into water-soluble products using acid impregnation and milling.

Main Methods:

• Impregnation of cellulosic substrates with catalytic amounts of strong acids (sulfuric acid, hydrochloric acid).
• Mechanically assisted solid-state reaction (milling) of acid-impregnated cellulose.
• Liquid-phase hydrolysis of the resulting water-soluble oligosaccharides.

Main Results:

• Milling acid-impregnated cellulose fully converted the substrate into water-soluble oligosaccharides within 2 hours.
• Liquid-phase hydrolysis yielded 91% conversion of α-cellulose to glucose and 96% of xylans to xylose.
• Practical feedstocks like wood and sugarcane bagasse also yielded water-soluble oligosaccharides and lignin fragments.

Conclusions:

• Acid impregnation is a highly effective strategy for overcoming contact problems in solid-state cellulose reactions.
• The integrated approach of solid-state depolymerization followed by liquid-phase hydrolysis is a promising "entry process" for biorefineries.
• This method efficiently converts various cellulosic materials into valuable sugars and lignin fragments.