Structure of Zirconia Nanoparticles used for Pillaring of Clay
- PDF / 64,525 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 47 Downloads / 179 Views
STRUCTURE OF ZIRCONIA NANOPARTICLES USED FOR PILLARING OF CLAY V. A. Sadykov, T. G. Kuznetsova, V. P. Doronin, T. P. Sorokina, D. I. Kochubei, B. N. Novgorodov, V. N. Kolomiichuk, E. M. Moroz, D. A. Zyuzin, E. A. Paukshtis, V. B. Fenelonov, A. Ya. Derevyankin, S. A. Beloshapkin, V. A. Matyshak*, G. A. Konin*, J. R. H. Ross** Boreskov Institute of Catalysis, Lavrentieva, 5, Novosibirsk 630090, Russia, [email protected] * - Semenov Institute of Chemical Physics, Moscow, Russia ** - Limerick University, Limerick, Ireland 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 Zr4 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. INTRODUCTION
Сlays pillared by nanosize zirconia particles (Zr PILC) are promising supports and catalysts for different petrochemical processes [1-2] and selective catalytic reduction of NOx by hydrocarbons in excess oxygen [3]. Their performance strongly depends upon the size, shape and structure of nanosized zirconia pillars propping the alumosilicate layers, which are in turn determined by the properties of zirconium hydroxy polycations in pillaring solutions. The majority of published data on pillared clays synthesis mainly concerns studies of the effects of preparation procedures and properties of starting clays, while little attention has been paid to the shape and structure of pillaring species formed in solutions. In this work, to cover this gap, SAXS and EXAFS were applied for investigation of the early stages of zirconium salts (zirconyl chloride and acetate, concentration 0.1-0.3 M) hydrolysis during aging at temperatures in the range from 25 to 80 oC. In addition, the effect of the alkaline-earth cations (Ca, Sr and Ba) on this process was considered as well. The Xray structural analysis, UV-Vis and FTIRS of adsorbed CO were used to further characterize the zirconia nanoparticles in the calcined pillared montmorillonite clays. EXPERIMENTAL Zr-containing solutions (Zr concentration 0.1-0.3 M) were prepared from recrystallized ZrOCl2 8 H2O and zirconium acetate (Aldrich 41 380-1, solution in diluted acetic acid). Those solutions were modified by adding chlorides of Ca, Sr and Ba with V13.21.1
variation of the Zr:Me ratio in the range of 3.3-9.0. Next series of solutions were prepared and studied: I. Zirconium salt or its mechanical mixture with Ca, Sr or Ba chlorides was dissolved in the distille
Data Loading...
