Ru nanoparticles confined in Zr-containing spherical mesoporous silica containers for hydrogenation of levulinic acid and its esters into γ-valerolactone at ambient conditions

• Ru NPs confined in spherical mesoporous silica (SMS) were synthesized.
• Ultrasmall Ru NPs were obtained in the short mesopore channels of SMS.
• γ-Valerolactone (GVL) was produced from levulinic acid and its esters under ambient conditions.
• Zr addition afforded a catalyst with increased acidity, which gave an improved GVL selectivity.
• The catalytic activity far outperformed Ru particles supported on the conventional MCM-41.

Hydrogenation of levulinic acid and its esters to produce γ-valerolactone (GVL) was demonstrated over ruthenium nanoparticle (NP) catalyst supported on Zr-containing spherical mesoporous silicas as a bifunctional catalyst. The Ru NPs were found to be uniformly dispersed within the periodically ordered short mesopore channels with an average size of less than 1.5 nm without any agglomeration. They exhibited superior activity for the hydrogenation of both levulinic acid and its esters under mild reaction conditions (70 °C, 0.5 MPa H2) compared to those supported on the conventional silica owing to their ultrasmall particle size and the acidity of Zr sites. In the hydrogenation of levulinate ester, addition of heterogeneous acids could afford a faster reaction rate in GVL production by accelerating the following intramolecular dealcoholation step. The catalyst was reusable over repeated catalytic cycles without a significant loss of catalytic performance, demonstrating its potential as a heterogeneous catalyst for GVL production under ambient reaction conditions.

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