Modulation of Ru and Cu nanoparticle contents over CuAlPO-5 for synergistic enhancement in the selective reduction and oxidation of biomass-derived furan based alcohols and carbonyls

Abstract

Furfural (FAL) and 5-hydroxymethylfurfural (HMF) are important and sustainable platform chemicals. They are produced from lignocellulose biomass and attract significant attention as precursors for producing value-added chemicals and fuels. The selective conversion of these chemicals requires precise modulation of reaction parameters, solvent, and catalyst. In this study, FAL is selectively reduced to furfuryl alcohol (FOL), and HMF is selectively oxidized to 2,5-diformylfuran (DFF) over a Cu and Ru decorated copper aluminophosphate (CuAlPO-5) catalyst. A high FAL conversion (99.5%) and FOL selectivity (99.6%) are obtained in water under mild reaction conditions of 353 K and 1 MPa H₂ pressure. On the other hand, 94.0% HMF conversion and 99.9% DFF selectivity are obtained at 1 atm O₂ flow at 413 K. Both these processes are efficiently conducted over Cu and Ru nanoparticles supported CuAlPO-5 at optimized Cu and Ru contents and under different reaction conditions. The calculated activation energies for these processes are 21.5 kJ mol⁻¹ (for FAL hydrogenation) and 34.5 kJ mol⁻¹ (for HMF oxidation). The temperature-programmed reduction/oxidation (TPR/TPO) and adsorption results suggest the synergy between Cu and Ru, resulting in higher catalytic activity. Systematic and precise modulation of active metal contents and minimizing the Ru content in the Cu–Ru bimetallic catalyst system would be desirable from the industrial and academic perspective, especially for achieving oxidation/reduction capabilities in biomass conversion using a single catalyst.