Two series of Pd–Pt/Al₂O₃ catalysts, characterized by high metal dispersions were prepared and investigated in the reaction of n-hexane conversion at the temperature < 300 °C. Incipient wetness co-impregnation of γ-alumina with the solutions of Pd(acac)₂ and Pt(acac)₂ led to relatively good Pd–Pt alloying. However, a similar catalyst preparation using solutions of PdCl₂ and H₂PtCl₆ resulted in unsatisfactory homogenization; furthermore, significant amounts of chlorine were retained in the catalysts. The Pd–Pt alloy homogeneity has a significant effect on the relations of catalytic activities and product selectivities with Pd–Pt alloy composition. The relationship between the catalytic activity of chlorine-free Pd–Pt/Al₂O₃ catalysts and bulk Pd–Pt composition matches the accepted relation between the surface composition and bulk composition of Pd–Pt, reflecting a high surface enrichment in palladium. In contrast, for the chloride series of Pd–Pt/Al₂O₃, variations of the turnover frequency are directly correlated with the bulk composition, indicating that unalloyed, more active, Pt particles decide about the catalytic behavior. Pd/Al₂O₃ shows better than Pt/Al₂O₃ selectivity for isomerization, especially after reduction at higher temperatures, ≥ 500 °C. On alloying with Pt, for the Cl-free series the isomerization selectivity was very high for nearly all bimetallic catalysts and showed a synergistic effect for 20 at.% Pt. In contrast, for the Cl-containing series, the isomerization selectivity was proportional to the palladium content. The effect of reduction temperature on the isomerization propensity of Cl-containing Pd–Pt/Al₂O₃ catalysts was rather small, suggesting that possible variations in support acidity associated with chloride presence do not have large catalytic consequences, confirming the metal-only catalytic action in alkane isomerization carried out at the temperatures below 300 °C.

Commercial activated carbon, pretreated in helium at 1600 °C and largely free of micropores, was used as a support for two series of 2 wt.% Pd–Pt catalysts, prepared by impregnating the support with metal acetylacetonates or metal chlorides. The catalysts were characterized by temperature-programmed methods, H₂ chemisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) with energy dispersive spectroscopy (EDS). Overall, the results confirmed the existence of well-dispersed Pd–Pt nanoparticles in the bimetallic catalysts, ranging in size from 2 to 3 nm. The catalysts were investigated in the gas phase hydrodechlorination of chlorodifluoromethane (HCFC-22). In this environmentally relevant reaction, both the ex-chloride and ex-acetylacetonate Pd–Pt/C catalysts exhibited better hydrodechlorination activity than the monometallic catalysts, which is consistent with the previous results of hydrodechlorination for other chlorine-containing compounds. This synergistic effect can be attributed to the electron charge transfer from platinum to palladium. In general, product selectivity changes regularly with Pd–Pt alloy composition, from high in CH₂F₂ for Pd/C (70–80%) to the selective formation of CH₄ for Pt/C (60–70%).

Pd/MgO, Pd/MgF₂ and Pd/MgO-MgF₂ catalysts were investigated in the reaction of CCl₄ hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF₂-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C₂-C₅ hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF₂ is beneficial for shaping high activity of palladium catalysts. The MgO-MgF₂ support characterized by stronger Lewis acidity than MgF₂ contributes to very good catalytic activity for a relatively long reaction period (~5 h) but subsequent neutralization of stronger acid centers (by coking) eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO) are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.

The behavior of alumina-supported palladium-platinum catalysts in the reaction of n-hexane hydrogenolysis was analyzed. The monometallic Pt/Al₂O₃ catalyst showed much higher activity than the rest of catalysts. The relationship between the catalytic activity of Pd–Pt/Al₂O₃ catalysts and bulk Pd–Pt composition matched the accepted relation between the surface composition and bulk composition of Pd–Pt, confirming a high surface enrichment in palladium. A linear relation between the apparent activation energy and preexponential factor (compensation effect) suggests that the reaction mechanism is similar for all Pd–Pt catalysts. However, after very high temperature of catalyst reduction (at 600 °C), the behavior of monometallic Pd/Al₂O₃ catalyst exhibited a considerable departure from the compensation plot, and drastic variations in C₁–C₅ products distribution. Such big changes are rationalized by assuming the transformation of Pd/Al₂O₃ into Pd–Al alloy, occurring at very high temperature of reduction. Product distribution of n-hexane hydrogenolysis for Pt/Al₂O₃ differs from that of Pd/Al₂O₃, showing more internal bond splitting than a terminal demethylation. However, bimetallic Pd–Pt/Al₂O₃ catalysts showed even more ‘internal bond splitting’ character than the Pt/Al₂O₃. Reasons for this synergism and changes in the behavior of Pd/Al₂O₃ catalysts are analyzed in terms of an electronic interaction between metals and alumina support.