A series of ZrO2 catalysts supported on mesoporous SBA-15 silica were synthesized and examined as catalysts in the production of γ-valerolactone (GVL) from biomass-derived levulinic acid and its esters via a catalytic transfer hydrogenation (CTH) using several alcohols as hydrogen donors. Among the catalysts examined, ZrO2 supported on high-surface-area SBA-15 silica bearing highly-dispersed zirconium species exhibited the highest catalytic activity. Zr K-edge XAFS analysis revealed that Zr4+-oxide species with a low-coordination state anchored on silica surface is the dominant active species. Such a Zr species efficiently converted levulinic acid and its esters to GVL (∼95% yields) under mild reaction conditions (150°C,1.0 MPa Ar). The sulfonic acid-functionalized UiO-66, a microporous zirconium-based metal organic framework (Zr-MOF), is also reported herein. UiO-66 bearing a 60 mol % fraction of sulfonic acid-containing benzene dicarboxylate (BDC) linker and retaining a high surface area exhibits the highest catalytic activity in the CTH reaction of levulinic acid and its esters to give GVL. The high catalytic activity is provided by the cooperative effect between Lewis-basic Zr6O4(OH)4 clusters and Brönsted-acidic−SO3H sites arranged in a confined nanospace adjacently with each other.

Catalytic transfer hydrogenation of biomass-derived levulinic acid and its esters to γ-valerolactone over ZrO2 catalyst supported on nanoporous materials

ACS Spring 2022

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