Novel Waste-Derived Cu–Zn/Zeolite A Catalyst for Ethanol Dehydrogenation to Highly Selective Acetaldehyde

A sustainable and highly selective catalyst for ethanol dehydrogenation, Cu–Zn/Zeolite A derived from sugarcane bagasse ash (ZA-SBA), was developed using silica-rich agricultural waste as a low-cost precursor for zeolite A synthesis. Zeolite A was crystallized via hydrothermal treatment of SBA-derived precursors and subsequently modified with 15 wt % Cu and 15 wt % Zn using the incipient wetness impregnation method. Comprehensive characterization (XRF, XRD, SEM-EDX, TEM, FTIR, BET, XPS, NH3-TPD, NH3–FTIR, and CO2-TPD) confirmed the successful formation of zeolite A with enhanced crystallinity, surface area, and basicity. CO2-TPD analysis revealed a notable increase in medium-to-strong basic sites (32.76 μmol of CO2 /g), over three times higher than that of the unmodified support. These basic sites, in synergy with highly dispersed Cu and Zn species, facilitated ethanol activation and hydride elimination while suppressing dehydration and etherification side reactions. In gas-phase ethanol dehydrogenation, the Cu–Zn/ZA-SBA catalyst exhibited outstanding performance, achieving 56.5% ethanol conversion and 99.7% selectivity toward acetaldehyde at 350 °C. This superior activity is attributed to the cooperative interaction between Cu and Zn species and the tailored acid–base surface properties of the SBA-derived zeolite A support. The present work demonstrates the valorization of sugarcane bagasse ash into functional zeolitic materials, providing a green, low-cost, and efficient strategy for developing sustainable catalysts for bioethanol upgrading into value-added acetaldehyde.