Pt-WOx/C Catalysts for α, β-Unsaturated Aldehydes Hydrogenation: An NMR Study of the Effect of the Reactant Adsorption on Activity and Selectivity

The selective hydrogenation of alpha,beta-unsaturated aldehydes is an ideal case for studying the structure-activity relationships in heterogeneous catalysis. In particular, cinnamaldehyde can be used as probe molecule for revealing the competition between hydrogenation of C=C and C=O bond. Here, we investigated the effect of the modification of some Pt supported on carbon catalysts by WOx species in cinnamaldehyde hydrogenation, as WOx species are reported to increase the adsorption and activation of the C=O group of alpha, beta-unsaturated aldehydes. Classical techniques used for correlating the catalyst activity and the selectivity to the characteristic of the materials (XRD, HAADF-STEM, XEDS mapping and XPS) have been coupled with NMR relaxometry, as innovative application, to disclose how the molecule approaches the catalyst surface. This indeed constitutes a crucial aspect that rule the catalytic activity. Therefore, an innovative, holistic approach has been used to consider the whole catalytic system

Exploring the Effect of Sn Addition to Supported Au Nanoparticles on Reducible/Non-Reducible Metal Oxides Supports for Alkane Oxidation

Acetone-stabilized Au- and Sn-solvated metal atoms (SMAs) were used as to obtain Au- and AuSn-supported catalysts by simple impregnation on a reducible (TiO2) and a non-reducible (Al2O3) metal-oxide. Their catalytic behaviour was investigated for cyclohexane oxidation to cyclohexanol and cyclohexanone (KA oil), and their morphological and physical properties were studied by TEM, STEM-EDS and 119Sn-Mössbauer spectroscopy. The catalytic results firstly demonstrated that the bare supports played a role on the reaction mechanism, slowing down the formation of the oxidation products and directing the radical formation. Hereinafter, the comparison between the monometallic Au-supported catalysts and the corresponding bimetallic Au-Sn catalysts allowed for the understanding of the potential role of Sn. 119Sn-Mössbauer characterization analyses showed the presence of SnO2, which was recognized to favour the electrons’ exchange to form radicals, interacting with oxygen. Such interaction, in particular, could be favoured by the co-presence of Au. Moreover, the same metal composition on the catalyst surface resulted in a different catalytic behaviour depending on the support