Degradation of cellulose polymorphs into glucose by HCl gas with simultaneous suppression of oxidative discoloration

As cellulose is the main polysaccharide in biomass, its degradation into glucose is a major undertaking in research concerning biofuels and bio-based platform chemicals. Here, we show that pressurized HCl gas is able to efficiently hydrolyze fibers of different crystalline forms (polymorphs) of cellulose when the water content of the fibers is increased to 30-50 wt%. Simultaneously, the harmful formation of strongly chromophoric humins can be suppressed by a simple addition of chlorite into the reaction system. 50-70 % glucose yields were obtained from cellulose I and II polymorphs while >90 % monosaccharide conversion was acquired from cellulose IIIII after a mild post-hydrolysis step. Purification of the products is relatively unproblematic from a gas-solid mixture, and a gaseous catalyst is easier to recycle than the aqueous counterpart. The results lay down a basis for future practical solutions in cellulose hydrolysis where side reactions are controlled, conversion rates are efficient, and the recovery of products and reagents is effortless.

Automated summary

In this study, pressurized HCl gas was used to efficiently hydrolyze different crystalline forms of cellulose, while suppression of harmful humin formation was achieved by adding chlorite. The cellulose I and II polymorphs yielded 50-70% glucose, and cellulose III and II showed >90% monosaccharide conversion. Purification of products from the gas-solid mixture was relatively easy, and the gaseous catalyst was easier to recycle than its aqueous counterpart. These results lay down the groundwork for practical solutions in cellulose hydrolysis, ensuring controlled side reactions, efficient conversion rates, and effortless recovery of products and reagents.