AMMONIA AND SULFUR POISONING EFFECTS ON HYDROGENATION OF PHENYLACETYLENE OVER PD SUPPORTED CATALYSTS

The effect of palladium dispersion, on the selectivity for phenylacety lene hydrogenation was studied. Low dispersed palladium catalysts show ed to be more selective to partial hydrogenation than high dispersed o nes. The initial selectivity to styrene is increased with time on stre am. Carbonaceous deposits were assumed to be responsible for this phen omenon. Selectivity was also modified by ammonia and sulfur addition: ammonia increased the styrene selectivity while sulfur had a negative effect. The poisoning effects were explained through an electronic eff ect. Ammonia is an electron donor modifier whereas sulfur is an electr on acceptor modifier.