A RAIRS AND HREELS STUDY OF ISOPROPYL-ALCOHOL ON PT(111)

RAIRS, HREELS and TDS were used to characterize isopropyl alcohol (IPA) adsorbed on Pt(111). Little or no decomposition occurs during adsorption at 85 K, but during thermal desorption of monolayer and submonolayer coverages, all the IPA decomposes to acetone and hydrogen below 200 K. No CO or CH4 was detected. TDS of multilayer coverages produce a strong IPA peak at 153 K and less intense peaks at 173 and 217 K along with acetone peaks between 190 and 230 K. The desorption energy of the multilayer species is 10.6 kcal/mol. Preadsorbed hydrogen (0.75 ML) markedly reduces IPA decomposition and allows the monolayer species to desorb at 208 K, which corresponds to a desorption energy of 13.2 kcal/mol. RAIRS and HREELS spectra gave sharp bands for multilayer IPA that are in excellent agreement with liquid-phase reference spectra. Vibrational bands associated with acetone after decomposition, and flashing to 200 K removes IPA but leaves strongly bound acetone with bands between 1510 and 1610 cm-1 which are similar to those associated with an eta-2 acetone species on this Pt surface.