ACTIVE-SITES AND REACTION-MECHANISMS FOR DEUTERATION OF ACROLEIN ON TIO2-SUPPORTED, Y2O3-SUPPORTED, ZRO2-SUPPORTED, CEO2-SUPPORTED AND NA/SIO2-SUPPORTED PLATINUM CATALYSTS

Acrolein-deuterium reactions on low- and high-temperature-reduced Pt/TiO2, Pt/Y2O3, Pt/ZrO2 and Pt/CeO2 in comparison with Pt/SiO2 and Na/Pt/SiO2 have been investigated in order to understand promotion in supported-metal catalysis by isotope tracing and infrared studies. The products on Pt/TiO2, Pt/Y2O3, Pt/ZrO2 and Pt/CeO2 were propanal and allyl alcohol but only propanal was formed over Pt/SiO2 and Na/Pt/SiO2. The similarity of the d-electron density of platinum in high-temperature-reduced Pt/TiO2, Pt/Y2O3, Pt/ZrO2 and Pt/CeO2, and Na/Pt/SiO2 was not reflected in the reaction profiles, suggesting the contribution of the periphery of suboxides on Pt particles and/or the boundary/interface of Pt particles on support. eta(4)-Adsorbate was suggested to be an intermediate for allyl alcohol formation on Pt/TiO2 and Pt/Y2O3 by IR spectra and isotope distributions in the products. On Pt/TiO2, Pt/Y2O3, Pt/ZrO2 and Pt/CeO2 reduced at both low and high temperatures, the active sites and reaction environments (surface D/H ratio) for the formations of propanal and allyl alcohol were different for the two products. The reaction mechanisms are discussed in connection with the promoting effects and the SMSI state of catalysts.