Rhenium Based Mono And Bi Metallic Nanoparticles

Download or read book Rhenium Based Mono- and Bi-metallic Nanoparticles written by Tugçe Ayvali and published by . This book was released on 2015 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this PhD thesis, the synthesis, characterization and preliminary catalytic application of rhenium based mono- and bi-metallic nanoparticles are reported. Rhenium has been chosen as a primary metal given the knowledge of its positive contribution in terms of catalytic activity and selectivity in the hydrogenation of difficult functional groups. Mono-metallic rhenium nanoparticles were prepared by decomposition of [Re2(C3H5)4]. Rhenium-based bimetallic nanoparticles were synthesized by co-decompositions or two-step decomposition of two different rhenium complexes, namely [Re2(CO)10] and [Re2(C3H5)4], with other organometallic complexes such as [Ru(COD)(COT)], [Ru(Me-Allyl)2(COD)], [Pt(CH3)2(COD)] and [Pt(C7H10)3]. By tuning the nature of organometallic complexes and the reaction conditions, rhenium-based bimetallic nanoparticles displaying different morphologies could be quantitatively prepared. The synthesis was carried out in solution under mild pressure of dihydrogen (3 bar) and in the presence of either a polymer (polyvinylpyrolidone) or a weakly coordinating ligand (hexadecylamine) as stabilizing agents. The precise characterization of the so-obtained nanoparticles was performed by using a combination of state-of-the art techniques (WAXS, EXAFS, TEM, HRTEM, STEM-EDX, STEM-HAADF, EA). Surface reactivity studies (norbornene hydrogenation, oxidation and CO adsorption reactions) were also carried out and followed by spectroscopic techniques (NMR, FT-IR) to determine their surface state and apprehend better their interest in catalysis. By this way, useful information could be obtained on their surface chemistry, as following: 1) Hydrides are present on the metallic surface and are very strongly coordinated to rhenium in agreement with rhenium molecular chemistry; 2) CO can substitute hydrides and is also strongly coordinated to the surface of Re but can react further to be substituted, oxidized or dissociated, where the latter is easier on alloy type Re-based bimetallic nanoparticles. 3) Oxidation of pure rhenium and alloy bimetallic ruthenium-rhenium nanoparticles display a zero state core and an oxide shell while core-shell type bimetallic nanoparticles result in amorphous structure. The originality of this work lies on the development of a systematic approach for the preparation of rhenium-based nanoparticles for the first time in the team and in the literature, by applying the organometallic approach largely experienced in the group for other metal systems. This method is well-known as an efficient way to obtain well-controlled nanostructures with clean surfaces, important mainly in catalysis.