Effect of Hydrotalcites Interlayer Water in Pt-Catalyzed Aqueous-Phase Selective Hydrogenation of Cinnamaldehyde

The heterogeneous hydrogenation of α, β-unsaturated compounds requires understanding of structure-activity relationship of metallic catalysts in consideration of solvent-mediated processes. In this work, CoAl-hydrotalcites (CoAl-HTs)-supported Pt nanoparticle catalyst is employed to study the effect of solvent water and HTs interlayer water in aqueous-phase selective hydrogenation of cinnamaldehyde (CALD). Pt/CoAl-HTs catalyst displays 5075 h-1 of specific reaction rate and 89% of C=O hydrogenation selectivity at 80 oC under 20 bar of H2. Combined results of isotope-labeling experiments and theoretical DFT calculations demonstrate that the water-mediated hydrogen-exchange pathway exists in the reaction with a relatively lower energy barrier compared to the direct H2-dissociated hydrogenation pathway. The results also reveal that the interlayer water species of HTs support participate in the hydrogen-exchange reaction. Based on the H2-D2 exchange results, these HTs interlayer water species can promote H2 a...