Metal-support effects on the intramolecular selectivity of crotonaldehyde hydrogenation over platinum

摘要: The vapor-phase hydrogenation of crotonaldehyde (CROALD) was studied at low temperature and conversions over Pt powder dispersed on SiO2, η)-Al2O3, TiO2 after either a high or low-temperature reduction, HTR LTR, respectively. butyraldehyde (BUTALD) crotyl alcohol (CROALC) to butanol (BUTNOL) the isomerization CROALC BUTALD were also investigated obtain additional information about this network reactions. typical catalysts produced 100% BUTALD, as expected from previous studies CROALD awareness activity for CC double bonds. However, TiO2-supported both BUTNOL, best catalyst, sol(HTR) PtTiO2, gave selectivity 37% with no BUTNOL formation. In addition marked enhancement in selectivity, turnover frequencies PtTiO2 samples, based sites counted by hydrogen chemisorption near reaction temperatures, more than an order magnitude higher displaying normal adsorption behavior. Activation energies somewhat solPtTiO2 catalysts, however. This behavior is very similar that observed previously CO acetone these same it consistent proposal created Pt-titania interface are responsible activation carbonyl Previous liquid-phase other molecules conjugated CO bonds support model indicate 1,4 diadsorbed species, rather 1,2 3,4 species (counting oxygen atom 1), formed polar solvents. By analogy, defect titania metal-support may interact O atom, polarize bond, favor intermediate which can react give CROALC.