Combined steam and CO2 reforming of ethanol over Ni–Cu/ZrO2 catalyst: Experimental and statistical optimization for sustainable syngas and hydrogen production

The combined steam and CO 2 reforming of ethanol (CSCRE) is a promising route for sustainable syngas and hydrogen production, enabling simultaneous utilization of renewable ethanol and CO 2 . In this study, a bimetallic Ni–Cu/ZrO 2 catalyst was synthesized and evaluated for the CSCRE reaction through an integrated approach combining catalyst characterization, long-term stability testing, and statistical process optimization. Structural and redox characterization (XRD, BET, H 2 -TPR, TEM, Raman, and TGA) revealed that Cu incorporation enhances Ni dispersion, improves reducibility, and suppresses sintering and carbon deposition. Response surface methodology (RSM) was employed to investigate the effects of temperature, CO 2 /H 2 O ratio, and (CO 2 + H 2 O)/ethanol ratio on ethanol and CO 2 conversions, syngas yields, and H 2 /CO ratio. Reaction temperature was identified as the dominant parameter influencing conversions and product yields, while the CO 2 /H 2 O ratio effectively tuned syngas composition. Under the optimized conditions (900 °C, CO 2 /H 2 O = 2, (CO 2 + H 2 O)/ethanol = 2), the Ni–Cu/ZrO 2 catalyst exhibited high ethanol and CO 2 conversions (>90%) and maintained stable activity for approximately 950 min, followed by only moderate deactivation during prolonged operation. The stability tests demonstrated that Ni–Cu/ZrO 2 consistently outperforming monometallic Ni/ZrO 2 under the different operating conditions. These results highlight the importance of both catalyst design and operating condition optimization in achieving high performance and sustained stability in CSCRE processes.