Low-temperature hydrogenation of the C=O bond of propanal over Ni-Pt bimetallic catalysts: from model surfaces to supported catalysts

The hydrogenation of propanal is used as a probe reaction to correlate the activity of C=O bond hydrogenation over Ni-Pt bimetallic surfaces and catalysts. Density functional theory (DFT) calculations predict that propanal is more weakly bonded on the Pt-Ni-Pt(111) subsurface structure than on either Ni or Pt, suggesting a possible novel low-temperature hydrogenation pathway based on a previous trend predicted for C=C hydrogenation. Surface science studies using temperature programmed desorption (TPD) on Ni-modified polycrystalline Pt foil verify that different bimetallic surface structures exhibit distinct C=O hydrogenation activity, with the Pt-Ni-Pt subsurface structure being much more active for propanal hydrogenation. Furthermore, gamma-Al(2)O(3) supported Ni-Pt bimetallic catalysts have been prepared to extend the surface science studies to real world catalysis. In the gas phase hydrogenation of propanal, both batch and flow reactor studies show that Ni-Pt/gamma-Al(2)O(3) bimetallic catalysts exhibit enhanced C=O hydrogenation activity compared to the corresponding monometallic catalysts. The excellent correlation between theoretical predictions, surface science studies on model surfaces, and catalytic evaluation of supported catalysts demonstrates the feasibility to rationally design bimetallic catalysts with enhanced hydrogenation activity.