Adsorption of propylene oxide on Pt(111) surfaces and its reactions with gaseous and adsorbed H atoms

Adsorption of propylene oxide (PO) on Pt(111) surfaces and its reactions wi th gaseous and coadsorbed hydrogen atoms was studied using TDS and HREELS m ethods. PO adsorbs molecularly and desorbs from the multilayer and monolaye r states near 130 and 180 K, respectively. Monolayer PO is bound through th e O atom to the Pt surface. Approximately 50% of the monolayer PO molecules dissociate near 180 K leading to desorption of CO and H-2 above 250 K. The initial step of the PO dissociation is cleavage of the C-O-C ring. Reactio ns of gaseous H atoms with PO monolayers on Pt(111) lead to the formation o f acetone, n-propanol, and isopropanol. The branching of the reactions towa rd the products changes with the H atom exposure as the coadsorption of hyd rogen weakens the PO/Pt(111) interaction, illustrating the influence of the metallic substrate on the reaction paths in atom/adsorbate reactions. Coad sorbed PO and hydrogen react toward a strongly bound acetone species, proba bly eta(2)-acetone, with a selectivity of 100%. (C) 2000 Elsevier Science B .V. All rights reserved.