Water as solvent in the liquid-phase selective hydrogenation of crotonaldehyde to crotyl alcohol over Pt/ZnO: A factorial design approach

• Crotonaldehyde selective reduction was optimized through factorial design.
• Solvent was found to be the most influential parameter.
• Water weakens CO bond, thus favoring selective reduction.
• XPS revealed that ZnOxCly species close to Pt act as Lewis sites favoring selectivity.

The liquid-phase selective reduction of crotonaldehyde to crotyl alcohol was studied on Pt/ZnO. Optimization through factorial design of experiments led to a 75% increase in the yield to crotyl alcohol and solvent was found to be the most influential parameter. The yield to the unsaturated alcohol was found to increase with the water content in water/dioxane mixtures. FT-Raman spectroscopy evidenced the progressive weakening of CO bond as the water content was increased thus accounting for the catalytic results. A study of catalyst reutilization showed an increase in both conversion and selectivity up to the third use, subsequent reuses leading to a drop in both parameters. The data obtained by XRD, XPS, and HAADF showed that the evolution of chlorinated species in the catalytic system were the plausible cause of this behavior.

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