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Liquid phase hydrogenation of cinnamaldehyde was evaluated over SiO 2 supported Co-Pt and Cu-Pt bimetallic and Co, Cu, Pt monometallic catalysts in a batch reactor. H 2 -temperature-programmed reduction (H 2 -TPR) was utilized to characterize the reduction behavior and pulse CO chemisorption measurement was performed to characterize the number of active sites of the catalysts. Transmission electron microscopy (TEM) analysis was used to characterize metallic particle size distribution and extended X-ray absorption structure (EXAFS) measurements were performed to verify the bimetallic bond formation. The reactor evaluation results show that Co-Pt and Cu-Pt bimetallic catalysts exhibit much higher hydrogenation activity than the corresponding monometallic catalysts, and Co-Pt shows much higher selectivity toward C O bond hydrogenation than Cu-Pt. The trend of hydrogenation activity and selectivity is consistent with previous studies of the hydrogenation of unsaturated aldehydes on model bimetallic surfaces.

PtCo bimetallic and Co, Pt monometallic catalysts supported on γ-Al2O3, SiO2, TiO2 and activated carbon (AC) were prepared and evaluated for the hydrogenation of benzene at relatively low temperatures (343 K) and atmospheric pressure. Results from flow reactor studies showed that supports strongly affected the catalytic properties of different bimetallic catalysts. AC supported PtCo bimetallic catalysts exhibited significantly better performance than the other bimetallic catalysts, and all the bimetallic catalysts possessed higher activity than the corresponding monometallic catalysts. Results from CO chemisorption and H2-temperature-programmed reduction (H2-TPR) studies suggested that different catalysts possessed different properties in chemisorption capacity and reduction behavior, and AC supported PtCo catalysts possessed significantly higher CO chemisorption capacity compared to the other catalysts. Extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) analysis provided additional information regarding the formation of Pt–Co bimetallic bonds and metallic particle size distribution in the PtCo bimetallic catalysts on different supports.

Pd/Ni bimetallic catalysts were prepared by replacement reactions, characterized by X-ray diffraction, CO chemisorption and H2 temperature-programmed desorption, and evaluated for hydrogenation of cyclohexene, styrene and acetone. The results show that Pd atoms are monolayer-dispersed on the Ni surface in these Pd/Ni catalysts. Consequently, Pd/Ni catalysts are much more active than Pd/Ni and Pd/c-Al2O3 with the same Pd loading prepared by the conventional impregnation method.

Series of bimetallic systems were prepared by replacement reactions and characterized by XRD and XPS. The results suggest that the ad-metals are monolayer dispersed on the surface of sub-metal in Pd(Pt, Cu)/Co(Ni) systems, while in Pd(Pt, Au)/Cu systems surface solid solution is formed. In Ag(Au)/Co(Ni) and Ag/Cu systems no interaction between the metals is observed just as in the simple mixture of the respective crystallites. The outermost electronic configurations, the atomic radius of the metals, and the low-preparation temperature seem to be important factors for the different states of these bimetallic catalysts.

Several Pd-based bimetallic catalysts, Pd/Co, Pd/Ni and Pd/Cu, were synthesized by replacement reactions. The catalysts were characterized by XRD and CO chemisorption and their catalytic properties were evaluated using cyclohexene self-hydrogenation. The results suggest that the high catalytic activity of Pd/Ni is most likely due to the monolayer-dispersion of Pd on the Ni surface. The results also suggest that Pd is monolayer-dispersed on the Co surface in Pd/Co, whereas Pd forms surface alloy or solid solution with Cu in Pd/Cu.

The monolayer-dispersed Pt/Ni bimetallic catalyst was prepared through a simple replacement reaction, and its catalytic activity for the hydrogenation of cyclohexene, styrene, acetone, and butyl aldehyde was also tested. The Pt/Ni catalyst that was prepared by the replacement reaction showed much higher activity than Pt/Ni and Pt/Al 2 O 3 catalysts with the same Pt loading prepared by the conventional impregnation method.

The hydrogenation of propanal is used as a probe reaction to correlate the activity of CO 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 CC hydrogenation. Surface science studies using temperature programmed desorption (TPD) on Ni-modified polycrystalline Pt foil verify that different bimetallic surface structures exhibit distinct CO hydrogenation activity, with the Pt–Ni–Pt subsurface structure being much more active for propanal hydrogenation. Furthermore, γ-Al2O3 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/γ-Al2O3 bimetallic catalysts exhibit enhanced CO 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.