Abstract: A ¹H resonance peak of the adsorbed hydrogen in palladium-carbon catalysts was observed at the high field side about 20 ppm away from the resonance peak of the dissolved hydrogen in the palladium sponge. Its position varies with the species of the carbon support, and is related to the activity of the palladium-carbon catalyst in hydrogenation reactions. While, the spin lattice relaxation time of the resonance peak does not show any dependency on the activity of the catalyst. It seems to be dependent on the amount of surface acid groups of the support. This resonance implies a special state of the adsorbed hydrogen and can be attributed to the spilled over hydrogen. The activity of the catalyst is discussed with respect to the hydrophobic property of the support by the NMR parameters of water adsorbed on the support.

Key words: palladium-carbon catalyst, NMR of hydrogen spilled over