Excellent Selectivity with High Conversion in the Semihydrogenation of Alkynes using Palladium‐Based Bimetallic Catalysts

Abstract

A series of active‐carbon‐supported PdPb and PdCu bimetal catalysts were prepared for the selective semihydrogenation of alkynes in the liquid phase. The Pd0.33Pb0.67/C catalyst showed the best performance for various alkynes under mild reaction conditions (room temperature and ambient H2 pressure) and achieved 100 % conversion with 98 % selectivity to alkenes. In particular, over‐hydrogenation was avoided at complete alkyne conversion.

A General One‐Pot Methodology for the Preparation of Mono‐ and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi‐hydrogenation of Alkynes and Acetylene

“…[20] Kiwi-Minsker and co-workerss tudied the range between Pd 0.6 Cu 0.4 to Pd 0.16 Cu 0.84 for the semi-hydrogenation of dehydroisophytol (DIP). For both substrates, the Pd 0.5 Cu 0.5 provided excellent alkene selectivity at full conversion.…”

“…[20] The authors claimed that under the tested conditions the activity of this catalyst was remarkably low that reaction times above 30 hw ere requiredt oapproachthe full conversion.The low activity was attributed to the excess of the promoter,s ince formulations with less coppers uch as Pd 0.67 Cu 0.33 /C, converted9 9% of the substrate in 4hwith a9 0% of alkene selectivity. Very recently,L iu et al reportedt he hydrogenation of this substrate by an activated carbon supported bimetallic catalyst (Pd 0.5 Cu 0.5 /C) at room temperaturea nd atmosphericp ressure.…”

“…The inactivity of pure copper catalysts in the semihydrogenation of alkynes wasa lso observed by other authors and mainly associated to the low activity of copper in the activation of the hydrogen molecule. [20] In contrast, Pd/CNTs easily isomerize 4-octyne under very mild reaction conditions (0.1 mol %P d, 3bar H 2 ,3 0 8C, 3h; entry 3), showing the high activity of this metal and the associated selectivity issues. Using the bimetallic catalysts, the first observation when testing NiCu/CNTs was the remarkably lower activityw hen compared to the monometallic Ni/CNTs (entries 4vs.…”

“…In line with our observations, the authors observed ar emarkable lowering of the reaction rate for the catalysts with copper molar fractionsh igher to Pd 0.50 Cu 0.50 . [20] Kiwi-Minsker and co-workerss tudied the range between Pd 0.6 Cu 0.4 to Pd 0.16 Cu 0.84 for the semi-hydrogenation of dehydroisophytol (DIP). In their study,t he alkene selectivity was not affected by the amount of modifier for the studied range.…”

“…Very recently,L iu et al reportedt he hydrogenation of this substrate by an activated carbon supported bimetallic catalyst (Pd 0.5 Cu 0.5 /C) at room temperaturea nd atmosphericp ressure. [20] The authors claimed that under the tested conditions the activity of this catalyst was remarkably low that reaction times above 30 hw ere requiredt oapproachthe full conversion.The low activity was attributed to the excess of the promoter,s ince formulations with less coppers uch as Pd 0.67 Cu 0.33 /C, converted9 9% of the substrate in 4hwith a9 0% of alkene selectivity.…”