Catalytic hydrogenation of but-2-yne on palladium-gold alloys
Abstract
The hydrogenation of but-2-yne has been investigated on a series of alloys of palladium and gold in the form of wires in the temperature range 263–638 K. Wires rich in palladium were active at the lower end of the temperature range and those rich in gold at the higher end. No break in activity corresponding to the filling of the d-band in palladium was observed and the results have been interpreted by assuming that gold acts simply as a diluent, hydrogenation activity being centred on the palladium. It is suggested that active sites are islands of four adjacent palladium atoms.
The cis/trans ratio of but-2-enes produced fell from 99 : 1 for pure palladium to 4.2 : 1 for an alloy containing 97 atom % gold. At temperatures in excess of 628 K on pure gold products with less than four carbon atoms were observed in addition to butenes.