from first principles PP-I-1

PP-III-10Selectivity Control of Pairwise Hydrogen Addition over CatalyticHydrogenation of C 4 Hydrocarbons on Supported Pt and Pd CatalystsBarskiy D.A. 1,2 , Kovtunov K.V. 1,2 , Khudorozhkov A.K. 3 , Bukhtiyarov V.I. 3 , Koptyug I.V. 1,21 International Tomography Center SB RAS, Novosibirsk, Russia2 Novosibirsk State University, Novosibirsk, Russia3 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russiabarskiy@tomo.nsc.ruIn the last few years, parahydrogen-induced polarization (PHIP) became a tool forinvestigating hydrogenation reactions in heterogeneous catalysis [1,2]. Information extractedfrom the nuclear magnetic resonance (NMR) spectra of hydrogenation products allows towatch the position of hydrogen atoms which came to the substrate from the same hydrogenmolecule. This distinctive feature of PHIP makes possible to explore reaction mechanisms ofheterogeneous catalytic reactions. The fact that supported metal catalysts exhibit PHIP effectsconfirms that pairwise addition of H 2 to unsaturated compounds does contribute to thereaction in some extent even when the reaction occurs at the surface of a metal particle andthe dissociation of H 2 on the metal surface with the subsequent addition of random hydrogenatoms to a substrate is expected to dominate.In this work, the PHIP technique was applied to study the selectivity and the degree of pairwiseH 2 addition in 1,3-butadiene, 1- and 2-butynes hydrogenation over supported Pt and Pd catalysts.Series of catalysts with different particle size distribution supported on Al 2 O 3 , SiO 2 , ZrO 2 , TiO 2and carbon were examined. It was found that Pd and Pt catalysts behave differently in pairwisehydrogenation. If Pt catalysts were used in hydrogenation of 1,3-butadiene, all reaction productscontained correlated hydrogen atoms, while the same reaction carried out on Pd catalysts led tothe observation of polarization only for 1-butene. This selectivity disagreement towards pairwisehydrogen addition can be explained by different structure of active sites and not by the relaxationtime differences of product molecules.Work is supported by the RFBR 11-03-93995-CSIC_a, RFBR 11-03-00248-а, 12-03-00403-a,RAS (5.1.1), SB RAS (160, 61, 57, 122), NSh-2429.2012.3 and program of the RussianGovernment to support leading scientists (11.G34.31.0045).References:[1] K. V. Kovtunov, I. E. Beck, V. I. Bukhtiyarov, I. V. Koptyug, Angew. Chem. Int. Ed. 2008, 47,1492.[2] V. V. Zhivonitko, K. V. Kovtunov, I. E. Beck, A. B. Ayupov, V. I. Bukhtiyarov, I. V. Koptyug, J.Phys. Chem. C, 2011, 115 (27), 13386–13391161