KINETICS OF DISSOCIATIVE CHEMISORPTION OF METHANE AND ETHANE ON PT(110)-(1X2)

The initial probability of dissociative chemisorption Prof methane and ethane on the highly corrugated, reconstructed Pt(110)-(1X2) surface has been measured in a microreactor by counting the number of carbon atoms on the surface following the reaction of methane and ethane on the surface which was held at various constant temperatures between 450 and 900 K during the reaction. Methane dissociatively chemisorbs on the Pt(110)-(1x2) surface with an apparent activation energy of 14.4 kcal/mol and an apparent preexponential factor of 0.6. Ethane chemisorbs dissociatively with an apparent activation energy of 2.8 kcal/mol and an apparent preexponential factor of 4.7 × 10−3. Kinetic isotope effects were observed for both reactions. The fact that Pris a strong function of surface temperature implies that the dissociation reactions proceed via a trapping-mediated mechanism. A model based on a trapping-mediated mechanism is used to explain the observed kinetic behavior. Kinetic parameters for C H bond dissociation of the thermally accommodated methane and ethane are extracted from the model. © 1990, American Vacuum Society. All rights reserved.