Selective dehydrolinalool hydrogenation with poly(ethylene oxide)-block-poly-2-vinylpyridine micelles filled with Pd nanoparticles

Abstract Selective dehydrolinalool (3,7-dimethyloct-6-ene-1-yne-3-ol, DHL) hydrogenation to linalool (3,7-dimethylocta-1,6-diene-3-ol, LN, a fragrant substance) was studied with Pd nanoparticles formed in poly(ethylene oxide)- block -poly-2-vinylpyridine (PEO- b -P2VP) micelles with varying solvent composition (‘isopropanol ( i -PrOH):water’ ratio) and the pH of the reaction medium. According to transmission electron microscopy (TEM) and atomic force microscopy (AFM), isopropanol fraction and KOH loading control the micellar characteristics governing catalytic properties. The larger and denser the micelles, the slower the reaction due to internal diffusion limitations within the micelles. Denser micelle cores provide better modification of the Pd nanoparticle surface with pyridine units and higher selectivity. The highest selectivity (99.4%) was obtained at pH of 9.4 and 95 vol.% of isopropanol. The highest observed TOF value was found to be 24.4 s −1 at pH of 13.0 and 70 vol.% of isopropanol. KOH and isopropanol were shown both to affect the micelle characteristics and act as modifiers of the catalyst surface. The hydrogenation kinetics was studied and zero order with respect to dehydrolinalool was found.