Supported palladium–copper catalysts: Preparation and catalytic behavior in hydrogen-related reactions

• Pd–Cu/AlF3 catalysts prepared by co-gelation were probed in n-pentane isomerization.
• Pd–Cu/C catalysts prepared by coimpregnation were probed in CCl4 hydrodechlorination.
• XRD, TEM and catalytic probes indicate good metal dispersion and alloy homogeneity.
• During CCl4 hydrodechlorination carbon incorporates into bulk of Pd75Cu25/C catalyst.

Two series of highly dispersed supported Pd–Cu catalysts were prepared using different supports: highly acidic aluminum fluoride HS-AlF3, characterized by high surface area, and active carbon, both prepared by different preparation methods (fluorolytic sol–gel method and co-impregnation). A variety of techniques: chemisorption of hydrogen, XRD, TEM, and catalytic performance in two hydrogen-related probe reactions (in n-pentane hydroisomerization and CCl4 hydrodechlorination) were employed to probe metal dispersion and the extent of interaction between two metal components. A reasonable degree of bimetal intermixing in Pd–Cu/HS-AlF3 catalysts synthesized by fluorolytic co-gelation was recognized by the catalytic behavior in bifunctional hydroisomerization of n-pentane. A significantly decreased, compared to pure palladium, hydrogenation–dehydrogenation potential of Pd–Cu alloys led to a weaker performance of bimetallic catalysts. Similarly, it was found that incipient wetness co-impregnation of active carbon resulted in the formation of catalysts characterized by good metal dispersion and significant extent of Pd–Cu alloying. Although the monometallic 2 wt% Cu/carbon catalyst is nearly inactive in CCl4 hydrodechlorination, copper addition to palladium in the co-impregnated catalysts had very pronounced effect, vastly increasing the selectivity toward longer than methane hydrocarbons.

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