Selective Hydrogenation of 1,3-Butadiene to 1-Butene by Pd(0) Nanoparticles Embedded in Imidazolium Ionic Liquids

The reduction of Pd(acac)2 (acac=acetylacetonate), dissolved in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI⋅PF6) or tetrafluoroborate (BMI⋅BF4) ionic liquids, by molecular hydrogen (4 atm) at 75 °C affords stable, nanoscale Pd(0) particles with sizes of 4.9±0.8 nm. Inasmuch as 1,3-butadiene is at least four times more soluble in the BMI⋅BF4 than butenes, the selective partial hydrogenation could be performed by Pd(0) nanoparticles embedded in the ionic liquid. Thus, the isolated nanoparticles promote the hydrogenation of 1,3-butadiene to butenes under solventless or multiphase conditions. Selectivities up to 97% in butenes were observed in the hydrogenation of 1,3-butadiene by Pd…