Boron nitride supported PtFe catalysts for selective hydrogenation of crotonaldehyde

The selective hydrogenation of crotonaldehyde was studied using boron nitride (BN) supported PtFe catalyst. A higher selectivity of crotyl alcohol than butyraldehyde was obtained, although butyraldehyde is thermodynamic favorable in the hydrogenation. The catalyst, PtFe/BN, was prepared by co-incipient wetness method. The metal loadings were 1.1 wt.% Pt and Fe ranging 0.1–0.6 wt.%. Commercial catalyst supports, graphite and γ-Al2O3, were also used to compare with BN. The higher iron content, the higher the crotyl alcohol selectivity was, while the activity was depressed. PtFe/γ-Al2O3 gave the lowest selectivity of crotyl alcohol. PtFe/graphite had the product selectivities similar to PtFe/BN, but its activity was lower than that of PtFe/BN. A maximum yield of crotyl alcohol was found at 0.2 wt.% Fe (molar ratio Fe/Pt = 0.64) on PtFe/BN catalysts at 100 °C. XRD revealed that PtFe alloy was formed on PtFe/BN during H2 reduction at 300 °C. The improvement of selectivity toward crotyl alcohol was attributed to the easier formation of PtFe alloy particle on BN surface than on γ-Al2O3. The Fe2+ on PtFe alloy polarizes the CO bond of crotonaldehyde and the nearby Pto supplies the absorbed hydrogen to conduct the hydrogenation of the CO bond, instead of the CC bond. Therefore, both activity and the selectivity toward crotyl alcohol were enhanced appreciably.