Year: 2026
Type: article
Abstract: A sustainable and scalable one-pot impregnation protocol, avoiding high-temperature calcination/activation, was employed to prepare Pd/Al2O3 (0.24 wt%), Pd/TiO2 (0.18 wt%), Pd/ZrO2 (0.21 wt%), Pd/SiO2 (0.37 wt%), Rh/Al2O3 (0.18 wt%), and Rh/TiO2 (0.15 wt%). Support effects on activity, selectivity, and recyclability of these low-metal content heterogeneous catalysts were investigated, using (E)-cinnamaldehyde and levulinic acid as probe molecules. In cinnamaldehyde hydrogenation, Pd catalysts were highly effective for chemoselective C=C reduction to 3-phenylpropanal under mild conditions, with Pd/TiO2 displaying the highest activity and robust performance over several recycles. However, the Lewis acidity of TiO2 promoted a solvent-involving side reaction in 2-propanol, with hemiacetal and ether formation, highlighting that apparent selectivity is strongly shaped by support acidity and product residence time. Rh/Al2O3 exhibited lower activity than Pd analogues but near-quantitative selectivity to the saturated aldehyde, whereas Rh/TiO2 again favored hemiacetal formation. In levulinic acid hydrogenation, Pd catalysts were essentially inactive toward ketone hydrogenation even at elevated temperature and H2 pressure, while Rh catalysts achieved high productivity with exclusive formation of γ-valerolactone, Rh/Al2O3 being the most active at comparatively mild pressures.
Source: Reactions
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,207
OpenAlex ID: W7166671484
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