Hydrogenation of ethylene over platinum (111) single-crystal surfaces

The hydrogenation of ethylene with both hydrogen and deuterium was studied over (111) platinum single crystal surfaces under a total pressure of 110 torr and a temperature range of 300-370K.An activation energy (Ea) of 10.8 t 0.1 Kcal/mole, and kinetic orders with respect to hydrogen and ethylene partial pressure of 1.31 0.05 and -0.60 0.05 respectively were observed.The deuterium atom distribution in the product from the reaction with D2 peaks at 1-2 deuterium atoms per ethane molecule produced, similar to what has been reported for supported catalysts.The reaction takes place on a partially ordered carbon covered surface, where the carbonaceous deposits have a morphology similar to that of ethylidyne.However, this ethylidyne does not directly participate in the hydrogenation of ethylene , since both its hydrogenation and its deuterium exchange are much slower than the ethane production.A mechanism is proposed to explain the experimental results.