Hydrogenation of 1-Butene and 1,3-Butadiene Mixtures over Pd/ZnO Catalysts

Selective catalytic low pressure hydrogenation of acetophenone on Pd/ZnO/ZnAl2O4

“…Nevertheless we can suppose the presence of a substantial amount of Palladium and zinc are known to be very miscible and can easily form an alloy when a mixture of the two metals is thermally treated in a reducing atmosphere [2] or if an intimate mixture of zinc oxide and palladium is reduced at high temperature in hydrogen flow. The tendency of the two metals to form an alloy increases with the increasing reduction temperature as reported by other authors [7][8][9][10][11][12][13].…”

“…The same authors [36] demonstrated that, due to the stronger Pd-Zn bonding, compared to the homonuclear Pd-Pd and Zn-Zn bonds, surface segregation of neither Zn nor Pd is favored. In the methanol steam reforming and related reactions [8][9][10][11][12][13] the catalytic behavior of systems, the active phase of which was found to be the PdZn alloy, further encourages the idea of a close structural and chemical similarity of the 1:1 tetragonal PdZn alloy and Cu. It was recently found [38] that the heterogeneous hydrogenation of aryl ketones occurs with a very high selectivity to the corresponding alcohols in batch conditions on a Cu/Al 2 O 3 (Cu 8% w/w) catalyst.…”

“…Various authors have observed that the catalytic behavior of Pd in a reductive atmosphere is significantly modified when ZnO is used as a support and the catalyst is pretreated at high temperature in hydrogen flow before use [5][6][7][8][9][10]. In fact, when a Pd/ZnO catalyst is reduced in hydrogen flow above 553 K a significant reduction of ZnO is observed, along with the formation of PdZn intermetallic alloys generated by the interaction of reduced Zn with metallic Pd [8][9][10][11][12][13]. The temperature of the reduction process influences the amount of metallic alloys [8][9][10][11][12][13] and consequently the Pd/PdZn ratio.…”

“…In fact, when a Pd/ZnO catalyst is reduced in hydrogen flow above 553 K a significant reduction of ZnO is observed, along with the formation of PdZn intermetallic alloys generated by the interaction of reduced Zn with metallic Pd [8][9][10][11][12][13]. The temperature of the reduction process influences the amount of metallic alloys [8][9][10][11][12][13] and consequently the Pd/PdZn ratio.…”

Kinetics of the solvent-free hydrogenation of 2-methyl-3-butyn-2-ol over a structured Pd-based catalyst

“…The rate of the semi-hydrogenation of MBY to MBE was found to be an order of magnitude higher than that found for the catalyst in water-assisted conditions. Nevertheless, the over-hydrogenation rate of MBE to MBA was much slower than that reported for Pd and PdPb catalysts [24], but yet not zero, as was the case in the water-assisted reaction [15]. These two findings could be attributed to the presence of the PdZn phase in the latter since Pd/Al 2 O 3 and Pd/ZnO powdered catalysts were previously compared in our group showing the presence of the PdZn phase in the latter even when no hightemperature treatment had been applied.…”