Small gold nanoparticles (1-5 nm) supported on metal oxides are extremely active catalysts for C-C coupling, aerobic oxidations and selective hydrogenations. The interaction of gold nanoparticles with hydrogen has remained elusive to be studied, due to the opacity of the material to most of the IR region. There are evidences showing that gold hydrides are extremely instable and even their existence is controversial. Forthe present proposal we have prepared a large batch (25 g) of titania supported gold nanoparticles and we aim to study by neutron spectroscopy the interaction of the catalyst with hydrogen. Gold nanoparticles on titania is currently the most selective catalyst for the hydrogenation of nitro groups to oximes in the presence of C=C that remain unaltered in the hydrogenation. The information obtained with the proposed experiments will serve to propose a reasonable mechanism.