Structure of Zirconia Nanoparticles used for Pillaring of Clay

Abstract

SAXS and EXAFS were applied to study genesis of polynuclear zirconium hydroxyspecies in pillaring solutions as dependent upon the zirconium concentration, addition of alkaline-earth chlorides and aging. After the montmorillonite clay pillaring, the structure of zirconium nanopillars was characterized by applying X-ray structural analysis, UV-Vis, FTIRS of adsorbed CO and nitrogen adsorption isotherms. Main pillaring species appear to be nanorods comprised of several Zr 4 tetramers. Basic structural features of the tetramers are preserved in zirconia nanoparticles fixed between alumosilicate layers in pillared clays. In calcined samples, those nanoparticles contain only bridging hydroxyls and/or oxygen anions responsible for bonding within pillars and between pillars and clay sheets.

Molecular design and characterization of catalysts for NO x selective reduction by hydrocarbons in the oxygen excess based upon ultramicroporous zirconia pillared clays

“…The properties of catalysts in the NO x HC-SCR reactions were tested in flow microreactors following procedures described previously [5,[10][11][12] and using, mainly, mixtures with standard compositions 0.1% C 3 H 8 +0.1% NO +1% O 2 in He (feed 1, GHSV 12 000h )1 ), 0.2% C 3 H 6 + 0.2% NO + 2.5% O 2 in N 2 (feed 2, GHSV 18 000h )1 ), 0.05% C 10 H 22 + 0.15% NO in air (feed 3, GHSV 13 000h )1 ). Reaction mixtures were analyzed by GC + chemiluminescence methods.…”

Ceria-based fluorite-like oxide solid solutions as catalysts of methane selective oxidation into syngas by the lattice oxygen: synthesis, characterization and performance

“…The unit cell parameter of doped ceria samples was determined from the position of 3 1 1 diffraction peak. To obtain the curves of the electronic density radial distribution (RED), synchrotron radiation with λ = 0.703 Å (Siberian Synchrotron Radiation Center) was applied for measurements in the 2θ range 5-135 • with a step of 0.1 • [8].…”

“…The surface properties were probed by the IR spectroscopy of adsorbed CO test molecule (a Fourier-transform IFS 113 V Bruker spectrometer) [7,8].…”

“…The radial distribution function (RDF) was calculated from the EXAFS spectra in k 3 χ(K) as modulus of Fourier-transform [7,8].…”

“…Since this method is not sensitive to the nature of a scattering element [8], and at a low Sm content the intensity of corresponding peak is determined mainly by Ce cations, this result implies that anion vacancies are located in the coordination sphere of Ce cation. This conclusion agrees with the EXAFS results of Yamazaki et al [16] for ceria doped with lanthanides.…”