Abstract: The properties of the supported metal catalysts are largely determined by the size, morphology and electronic state of the metal particles, and the formation of these characteristics often depends on the processes occurring in the early stages of preparation. These include the precursor of the active component formation, the nature and strength of its interaction with the support and sequential transformation on the surface at various stages of synthesis. In the present work, the role of the nature of the active metal precursor and the interaction of the metal complex-support is demonstrated by examples of the formation of platinum catalysts using supports containing aluminum atoms: alumina, AlMg(M)Ox mixed oxides obtained from layered double hydroxides (LDH), and also alumina modified by synthesis of MgAl-LDH on its surface. Detailed study of the composition and properties of chloride Pt(IV) complexes adsorbed on gamma-alumina showed that two mechanisms of the metal complex – support interaction can occur: electrostatic adsorption with platinum fixation as outer-sphere complexes and coordination binding with the formation of inner-sphere platinum complexes. The realization of a certain mechanism makes it possible to form platinum particles with the necessary dispersion and electronic state and, consequently, to regulate their catalytic properties. Special methods are proposed that make it possible to realize selectively the required mechanism for platinum complexes fixing: by changing the composition of the Pt (IV) complexes and by changing the properties of the Al2O3 adsorption centers. The use of supports with spatially ordered structure is a promising way to control the characteristics of supported metal and obtain nanoparticles with uniform properties. Such supports can be represented by layered double hydroxides. LDHs have the composition (M2+1-х M3+x(OH)2)x+(An-)х/n nH2O, where M2+ and M3+ are bi- and trivalent metal cations, and comprise positively charged hydroxide layers and anions An– located in the interlayer space. The nature of interlayer anion is an essential parameter affecting the amount of anchored platinum, the composition of surface species, and their location in the structure of layered material. A low exchange capacity of carbonate LDH toward the double-charged anionic chloride complexes of platinum made it possible to anchor platinum selectively with participation of OH groups of the hydroxide layers and adsorption of hydrolyzed inner-sphere complexes on the surface. Their reduction led to the formation of isometric platinum particles of size 2-4 nm. When platinum complexes were anchored on aluminum-magnesium hydroxide with interlayer OH–anions, the precursor was located mainly in the interlayer space as outer-sphere complexes with subsequent formation of a plane morphology particles, length of 50 nm and thickness close to interlayer distance in LDH (0.75 nm). Structural features of oxide supports were studied by XRD (D8 Advance, Bruker). Adsorption–desorption isotherms of nitrogen at 77.4 К were measured using a static volume vacuum system ASAP-2020М (Micromeritics). Elemental analysis was made by ICP-AES on Varian 710-ES spectrometer. CO and H2 pulse chemisorption (AutoChem II 2920, Micromeritics) and transmission electron microscopy (JEM-2100, JEOL) were used to estimate the particle size of platinum. X-ray photoelectron spectroscopy was carried out on a spectrometer (SPECS, Germany). EXAFS spectra were measured at the ID26- beamline of the European Synchrotron Radiation Facility. Differences in the anchoring mechanism of metal complexes on Al2O3 and LDH were revealed by 195Pt MAS NMR (Avance-400, Bruker). Reactions of alkanes dehydrocyclization and dehydrogenation were employed for catalysts testing

Cite: Belskaya O.
The influence of the metal complex – support interaction on the formation of platinum centers in Pt/Al(Mg)O catalysts
In compilation Catalysis: from science to industry: proceedings of V International scientific school-conference for young scientists, September 25-29, 2018, Tomsk. – "Ivan Fedorov" publishing., 2018. – C.19. – ISBN 9785917011325. РИНЦ

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