INTERACTION OF CYCLOHEXADIENE WITH PT(111) STUDIED BY BPTDS AND HREELS

The interactions of 1,3- and 1,4-cyclohexadiene with Pt(1 1 1) have been studied with bismuth postdosing thermal desorption mass spectroscopy (BPTDS) and high-resolution electron energy loss spectroscopy (HREELS). Both species adsorb molecularly on Pt(1 1 1) at 100 K. Upon warming, both species dehydrogenate completely to produce adsorbed benzene. The reaction occurs at about 230-260 K with an activation energy of 14 +/- 2 kcal/mol. The adsorbed benzene thus produced either dehydrogenates, ultimately to graphitic carbon, or desorbs, both occurring above 450 K. When cyclohexadiene is coadsorbed with hydrogen adatoms, no significant amounts of hydrogenated products (<2%) are observed in normal TDS or in BPTDS.