Nearly 100% Selective Hydrolysis of Pyrolytic Sugar Over Sustainable Carbon Catalysts Enables Highly Efficient Production of Bioethanol

Abstract

The hydrolysis of levoglucosan (LG)–the major component of biomass pyrolysis oil–is the crucial step to bridge pyrolysis and fermentation. This study reports a series of sulfonated carbon catalysts (SCCs) as sustainable Brønsted acids for LG hydrolysis, which exhibit a nearly 100% glucose selectivity over other hydration products (e.g. 5-furans and light oxygenates). Notably, SCCs maintain a LG conversion rate of 95% and a glucose yield of 90% after five cycles of batch operation. Time-of-flight mass spectrometry and theoretical calculations further clarify the hydrolysis mechanism, as water-derived protons are activated by sulfonate groups of SCCs and hydrolyse LG through C–O bond cleavage and hydration. Moreover, SCC-catalysed hydrolysate is used in fermentation to produce bioethanol, enabling an ethanol yield of ~99%, which is comparable to pure glucose commodity and much efficient than that of the aqueous acid hydrolysate. This study provides a sustainable alternative to mitigate the demand on homogenous hydrolysis for pyrolysis oil upgrading towards net-zero biorefineries.

Keywords: Levoglucosan, Glucose, acid hydrolysis, carbon catalyst, Bioethanol