ABSTRACT The incorporation of Zr 4+ ions into the beta zeolite framework creates Lewis acid sites that can facilitate catalytic transfer hydrogenation of furfural in the presence of alcohols. Hydrogenation of furfural in the presence of acid sites and alcohols is known to proceed in a cascade manner, leading to the formation of furfuryl alcohol, furfuryl acetal, furfuryl ether, levulinate ester and γ‐valerolactone. Controlling this cascade reaction and selectively obtaining a desirable product are challenging, and this work addresses them. Different precursors, namely zirconyl chloride, zirconium (IV) isopropoxide, and zirconium (IV) ethoxide, were used to load Zr onto beta zeolite post‐synthetically and were found to incorporate zirconium into different locations. Zirconyl chloride (ZrO‐beta) preferably incorporates Zr 4+ ions into the zeolite's tetrahedral framework. Zirconium (IV) isopropoxide (ZrP‐beta) incorporated the majority of the Zr 4+ ions into the tetrahedral framework, but some Zr also ended up in forming extra‐framework ZrO 2 clusters. While zirconium (IV) ethoxide (ZrE‐beta) was employed, the loaded Zr predominantly formed extra‐framework ZrO 2 clusters. The prepared Zr–Al‐beta zeolites showed distinctly different product selectivities during catalytic transfer hydrogenation of furfural with isopropyl alcohol. ZrO‐beta preferentially transformed furfural to isopropyl levulinate (selectivity = 90% at 82% conversion). In contrast, ZrP‐beta and ZrE‐beta selectively converted furfural to isopropyl furfuryl ether (selectivity: ZrP‐beta = 74% at 59% conversion, ZrE‐beta = 88% at 63% conversion). The difference in product selectivity of the catalysts is also confirmed at similar furfural conversions. The variations observed in the reaction pathways and product selectivity are correlated with the catalysts' acidic and basic properties.
Periyasamy et al. (Thu,) studied this question.