Bifunctionalization of MCM-22 zeolite with Cu and Zr species for the one-pot conversion of furfural to γ-valerolactone

The conversion of biomass-derived compounds into high-value chemicals is a cornerstone of sustainable industrial development. This study reports the synthesis and application of bifunctional catalysts based on MCM-22 zeolite (MWW topology) containing Zr and Cu species for the one-pot conversion of furfural into γ-valerolactone (GVL). Catalysts were prepared via incipient wetness and wet impregnation with varying loadings of Zr and Cu (0.8 to 10 wt%). Comprehensive characterization (XRD, FEG-SEM, HAADF-STEM/EDS, Py-FTIR, and XPS) confirmed the preservation of the 2D lamellar MWW topology and the formation of metal oxide clusters on the zeolite surface. Catalytic tests in a batch reactor at 170 °C using isopropanol as a hydrogen donor revealed that pure MCM-22 exhibits negligible activity (2.4% conversion), while bifunctionalization significantly enhances performance. The Zr-containing catalyst achieved 76.7% conversion with 24.8% selectivity for GVL, outperforming Cu-based systems which primarily accumulated isopropyl levulinate (IPL). XPS and catalytic investigations on unreduced systems confirmed that reduced copper is essential to initiate the transfer hydrogenation of FF, whereas Zr 4+ Lewis sites govern the cascade steps. To overcome the reaction limiting step in the conversion of IPL to GVL, physical mixtures with Zr(OH) 4 were evaluated. The 10Zr/M+Zr(OH) 4 system demonstrated a synergistic effect, reaching 100% furfural (FF) conversion and a GVL yield of 52%. However, deactivation studies via TGA and nitrogen physisorption of spent catalysts indicated that pore blockage by condensed humins remains the primary challenge for catalyst stability. These results highlight the importance of balancing Lewis and Brønsted acidity for efficient cascade reactions in biomass valorization.