Hydrodechlorination of 1,2-dichloroethane catalyzed by dendrimer-derived Pt–Cu/SiO2 catalysts

Dendrimer-metal-nanocomposites (DMNs) were used as precursors to prepare SiO2-supported monometallic Pt, Cu, and bimetallic Pt–Cu catalysts with Pt/Cu atomic ratios of 1:1 (Pt50Cu50) and 1:3 (Pt25Cu75). After impregnation of these DMNs onto the support, the catalysts were thermally treated and activated following an optimized protocol. Scanning transmission electron microscopy (STEM) showed that the metal nanoparticles in the dendrimer-derived SiO2-supported catalysts were smaller and had a narrower size distribution compared with those in conventional catalysts prepared using corresponding metal salts via the wet-impregnation method. Slow deactivation was observed for hydrodechlorination of 1,2-dichloroethane over monometallic Cu catalysts, which showed an activity about one to two orders of magnitude lower than that of the Pt-containing catalysts. Hydrodechlorination of 1,2-dichloroethane over the Pt and Pt50Cu50 catalysts produced mainly ethane, and the selectivity toward ethane increased with temperature. For the Pt25Cu75 catalyst, the selectivity toward ethane decreased in favor of that of ethylene. The overall activity decreased with increasing Cu loading in the catalysts. Activity based on surface Pt sites suggests the formation of bifunctional surfaces in Pt25Cu75 catalyst favoring CCl bond scission on Cu sites and hydrogenation of intermediate ⋅CH2CH2⋅ on Pt sites. In addition, kinetic analyses suggest different reaction mechanisms for hydrodechlorination of 1,2-dichloroethane over Pt and Cu-enriched surfaces in the Pt–Cu bimetallic catalysts.