Time-release catalysis for cascade hydrolytic hydrogenation of cellulose

Abstract

Valorization of cellulosic biomass into chemicals and fuels via a multi-step reaction is necessary for achieving a sustainable industry. However, the one-pot direct transformation of cellulose into value-added chemicals like sorbitol via a glucose intermediate through cascade pathways remains challenging due to the interplay between multiple catalytic sites and the kinetics of different reaction pathways. Herein, inspired by time-release mechanisms used in medicines and fertilizers, carbon-encapsulated nickel phosphide (NiP@C) catalysts exhibiting time-release properties were synthesized through sequential chemical precipitation, hydrothermal treatment and thermal reduction using nickel nitrate, fulvic acid and (NH₄)₂HPO₄ as precursors. The as-synthesized NiP@C served as a time-release catalyst for the one-pot hydrolytic hydrogenation of cellulose to sorbitol by providing a continuous and adequate supply of H⁺ for cellulose hydrolysis via a time-release mechanism, coupled with abundant Ni^δ+ sites for sequential hydrogenation, thus achieving a balanced hydrolysis and hydrogenation process that afforded a high sorbitol yield of 84.5% at 200 °C within 3 h. The NiP@C catalyst demonstrated good recyclability due to its anti-oxidation capacity in air. The time-release catalysis strategy proposed in this work should have broad applications in one-pot cascade reaction schemes requiring balanced multiple catalytic sites for converting renewable resources.