Metal Nanoparticle/Ionic Liquid/Cellulose: New Catalytically Active Membrane Materials for Hydrogenation Reactions

Transition metal-containing membrane films of 10, 20, and 40 mu m thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 +/- 1.1 nm (Rh(0)) and 3.0 +/- 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI center dot (NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 mu m, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and better formability of the cellulose material. The nanoparticle/IL/CA combinations exhibit an excellent synergistic effect that enhances the activity and durability of the catalyst for the hydrogenation of cyclohexene. The nanoparticle/IL/cellulose acetate film membranes display higher catalytic activity (up to 7353 h(-1) for the 20 mu m film of CA/IL/Pt(0)) and stability than the nanoparticles dispersed only in the IL.