Palladium-based alloy and monometallic catalysts for gas phase hydrogenation of crotonaldehyde: effects of alloying and alloy crystallite size

Gas phase hydrogenation of crotonaldehyde has been investigated with supported Pd catalysts using different supports. The overall conversion and product distribution significantly depend on the supports used. Crotyl alcohol is formed along with butyraldehyde as the chief products in comparable quantities with Pd/ZnO, while little crotyl alcohol is formed with such catalysts as Pd/Al2O3 and Pd/SiO2. The difference in the product distribution is due to the difference in the active species, which is PdZn alloy in Pd/ZnO but is Pd in the other catalysts. The activity of Pd/ZnO decreases slightly with the size of PdZn alloy crystallites, but the selectivity to crotyl alcohol increases and that to butyraldehyde decreases.