Modification of the catalytic behaviour of platinum by zinc in crotonaldehyde hydrogenation and iso-butane dehydrogenation

The effect of the presence of zinc on the catalytic behaviour of platinum in the vapour phase hydrogenation of crotonaldehyde (2-butenal) and in iso-butane dehydrogenation has been determined in activated carbon-supported catalysts prepared using H2PtCl6 and Zn(NO3)2 as the metal precursors. The catalysts have been characterised by temperature-programmed reduction (TPR), adsorption microcalorimetry of CO at room temperature and X-ray photoelectron spectroscopy after in situ reduction at 773 K. The bimetallic catalyst, with a bulk Zn/Pt atomic ratio of 13.7, showed a much higher initial activity in crotonaldehyde hydrogenation, although it deactivated more strongly with time on stream. Lower activation energy for this reaction was also obtained, as well as a higher selectivity towards the unsaturated alcohol. On the other hand, the catalytic behaviour for iso-butane dehydrogenation was greatly improved by the presence of zinc, the bimetallic catalyst being more active than its monometallic counterpart and showing 100% selectivity to iso-butene.