Co-production of high-purity hydrogen and value-added molecules from cellulose under alkaline environment: Mechanism and application

Herein, a NaOH-mediated facile process is proposed to directly co-produce high-quality H2 and value-added organic acids from cellulose, avoiding the necessity of complex catalyst. The H2 purity and total production of organic acids under optimized conditions are higher than 98 % and 410 g/kg of cellulose, respectively. Cellulose is first depolymerized to glucose, which simultaneously isomerizes to fructose under alkaline environment. Monosaccharides (multi-hydroxy aldehydes) form critical intermediates for H2 production via retro-aldol at C2-C3 bond. H2 is mainly derived from the dehydrogenation of glycolaldehyde and α-hydroxy-γ-butyrolactone, the latter of which also produces succinic acid. Glyceraldehyde and dihydroxyacetone produced by retro-aldol of fructose at C3-C4 bond is the source of lactic acid. The acetic acid is suggested to be derived from the 1, 2-isomerization of glycolaldehyde rather than lactic acid. KOH and NaOH exhibit excellent ability to facilitate the dehydrogenation of the cellulose, with H2 production higher than 390 L/kg cellulose for both. Alkali metal cations (K+ and Na+) can alter the conversion pathway of the intermediates. Most importantly, the ideal applicability to practical biomass, sustainable value of the products and alkali recycling concept endow the strategy with promising potential for industrial applications, exhibiting both environmental and economic benefits.