Solid-State NMR Study of Acetylene Adsorbed to Platinum on Alumina as Followed by Direct Observation Using CP MAS Methods. Differentiation Between Acetylene Adsorbed to Alumina and Platinum.

In a recent series of papers Slichter and co-workers have reported solid-state {sup 13}C and {sup 195}Pt NMR investigations of small molecules, e.g., acetylene and ethylene, adsorbed to platinum on {eta}-alumina. Of particular interest to us is the work involving the adsorption of acetylene. This work is significant because it verified that the principal species on the surface was not the ethylidyne, {triple bond}CCH{sub 3}, species proposed by Somorjai et al. The authors confirm that ethylidyne species are not present on Pt/{gamma}-Al{sub 2}O{sub 3} surfaces. However, we also prove that acetylene does chemisorb to alumina in the presence and absence of platinum metal. Finally, we conclude the principal species bound to the platinum is such that the bonding between the carbon atoms is intermediate between double and triple bonds. This latter conclusion is supported by IR experiments on the Pt/{gamma}-alumina surface.