The Pt-Enriched PtNi Alloy Surface and its Excellent Catalytic Performance in Hydrolytic Hydrogenation of Cellulose

Ni‐based catalysts are currently a subject of intense research in the hydrolytic hydrogenation of cellulose. We previously reported that Ni/ZSM‐5 catalyst gave high yield of hexitols. However, Ni‐based catalysts suffered fast deactivation in hot‐compressed water. In this follow‐up study we designed highly active Ni‐based bimetallic catalysts with excellent hydrothermal stability for the hydrolytic hydrogenation of microcrystalline cellulose. PtNi/ZSM‐5 shows a 76.9 % yield of hexitols, which is the best obtained so far in the hydrolytic hydrogenation of microcrystalline cellulose over Ni‐based catalysts. Furthermore, the yield of hexitols remained greater than 55 % after the catalyst was reused for 4 times. The results showed that PtNi nanoparticles were formed with a Pt‐enriched alloy surface as confirmed by XRD, H2‐TPR (temperature‐programmed H2 reduction), XPS (X‐ray photoelectron spectroscopy), and H2‐TPD (temperature‐programmed H2 desorption). The surface features of these nano‐particles were characterized by CO‐TPD (temperature‐programmed CO desorption), CO‐FTIR (CO adsorption FTIR spectroscopy), HRTEM (high resolution TEM), and O2‐TPO (temperature programmed oxidation) and this special surface structure may be responsible for the high activity, selectivity, and stability in the hydrolytic hydrogenation of cellulose in hot‐compressed water. Put a Pt on it: ZSM‐5‐supported PtNi alloy particles with Pt‐enriched alloy surface are prepared and characterized. The Pt‐enriched alloy surface enhances hydrogenation activity but suppresses hydrogenolysis activity, thus resulting in high yield of hexitols. The decoration with an alloy surface offers a new approach to prevent the rapid deactivation of Ni‐based catalysts in hot‐compressed water.