Deuteration study to elucidate hydrogenolysis of benzylic alcohols over supported palladium catalysts

Deuteration in combination with multinuclear NMR spectroscopy was applied to elucidate the pathway of the C-O bond scission of 1-(4-isobutylphenyl) ethanol (4-IBPE) to 4-isobutylethylbenzene (4-IBEB) over Pd/SiO2, Pd/C, and unsupported Pd black. Information about the pathway was obtained by determining the positions at which deuterium was incorporated by means of H-1, H-2, and C-13 NMR spectroscopy. The C-O bond scission of 4-IBPE over Pd/SiO2 and Pd black occurred exclusively by direct hydrogenolysis, whereas both hydrogenolysis and the dehydration-hydrogenation route were observed over Pd/C. The latter was attributed to the acidic nature of the carbon support. Spillover of dissociatively adsorbed hydrogen from the metal surface to the support does not play an important role in the direct hydrogenolysis of 4-IBPE over Pd. (c) 2007 Elsevier Inc. All rights reserved.