MAGNETIC-RESONANCE STUDIES OF ETHENE ADSORPTION ON ALUMINA-SUPPORTED PLATINUM SURFACES

Carbon-13 and deuterium magnetic resonance data for ethene adsorbed on high dispersion, alumina-supported platinum surfaces were obtained af ter adsorption at various temperatures and thermal treatments. Ethene is found to adsorb on 5% Pt/Al2O3 at low temperature in a pi-bonded fo rm that yields a single carbon line shape at 70 ppm. Upon warming to r oom temperature, this species is partially converted to ethylidene and a second adsorbate, which has two protonated carbons that yield a sin gle carbon line shape at 130 ppm. At 323 K, the predominant species on this catalyst is ethylidene, in contrast to observations reported for single-crystal and low dispersion metal-supported catalysts. Ethylide ne appears to decompose into methane gas and surface carbon.