Changes in the zirconium local surrounding on ligand substitution in solutions

Abstract

EXAFS and SAXS methods have been used to examine zirconium hydroxide and oxychloride aqueous solutions in the presence of sulfuric acid in a wide range of concentrations, as well as a zirconium sulfate aqueous solution. The structure of the complexes and their transformation regularities were determined. Structures of the given complexes and structures of zirconium hydroxide and zirconium oxychloride and hydroxide complexes in aqueous solutions were compared. Complexes in zirconium hydroxide and oxychloride aqueous solutions have identical structures in the presence of sulfuric acid. When the concentration ratio of sulfuric acid and the initial compound is low (20-30), the complex is an open trimer with zirconium atoms bonded by sulfate groups. Bridge sulfate groups form Zr-O-S-O-Zr bonds. Apart from the bridge sulfate groups, there are three terminal sulfate groups and three terminal hydroxyl groups for each zirconium atom. When the concentration of sulfuric acid is increased (up to a ratio of 40-100), closed trimers are observed in the solution. Keywords: zirconium hydroxide, zirconium oxychloride, zirconium sulfate, aqueous solutions of zirconium salts, sulphate solutions of zirconium salts, zirconium complexes, small-angle X-ray scattering, EXAFS.

Corrigendum to “Zircon solubility and zirconium complexation in H2O+Na2O+SiO2±Al2O3 fluids at high pressure and temperature” [Earth Planet. Sci. Lett. 349–350 (2012) 15–25]

“…It reproduces the pre-edge feature as well as the fine structure at the main edge with a very good match in the relative energy positions compared to the experiment. In this ZrO 8 -cluster, the oxygen ligands form an irregular polyhedron with Zr-O distances ranging from 2.110 to 2.338Å (Mak, 1968), which is consistent with the results of Hagfeldt et al (2004) and Kanazhevskii et al (2006).…”

“…Armstrongite (CaZrSi 6 O 15 Á 3H 2 O, Kabalov et al, 2000), elpidite (Na 2 ZrSi 6 O 15 Á 3H 2 O, Cannillo et al, 1973), eudialyte (Na 12 Ca 6 Fe 3 Zr 3 Si 24 O 66 (OH) 5 Cl, Golyshov et al, 1972), and wadeite (K 2 ZrSi 3 O 9 , Blinov et al, 1972) represent examples of alkali and alkaline-earth zircono-silicate minerals with Zr in 6-fold coordination. Zirconium is 8-coordinated in ZrOCl 2 Á 8H 2 O, zircon, and the standard solution (5000 ppm Zr) (Mak, 1968;Finger, 1974;Kanazhevskii et al, 2006;Hagfeldt et al, 2004). Seven-fold coordinated Zr is found in monoclinic ZrO 2 (baddeleyite, Smith and Newkirk, 1965).…”

n-Pentane Isomerization Over Pt- and Ni–Pt-Promoted Sulfated Zirconia Catalysts Supported on Alumina

“…The strength of the acid sites depends on a series of features such as: metal electronegativity [35], the number of d-electrons [37], the nature of the binder material [23], the intrinsic sulfate group content and the coordination state of oxygen and sulfur in the catalyst. The active surface sites consists in: (1) polysulfate species with mainly three or four S atoms and two ionic bonds of S-O-Zr in addition to S=O coordination bonds with Zr, the active site being Lewis sites on the S atoms [16,38]; (2) a complex mixture of open trimer with zirconium atoms bonded by sulfate groups while bridge sulfate groups form Zr-O-S-O-Zr bonds; and three terminal sulfate groups and three terminal hydroxyl groups for each zirconium atom [39]. Moreover, Yamaguchi [40] concluded that the generation of high acidity was accompanied by the formation of S 6?…”

1-Hexene Double Bond Isomerization Reaction Over SO 4 = Promoted NiO, Al2O3 and ZrO2 Acid Catalysts

“…Recent studies describe different operating mechanism for sulfated zirconia samples: (i) the active surface sites consists in polysulfate species with mainly three or four S atoms and two ionic bonds of S-O-Zr in addition to S=O coordination bonds with Zr, the active site being Lewis sites on the S atoms [30]; (ii) the active sites are a complex mixture of open trimer with zirconium atoms bonded by sulfate groups while bridge sulfate groups form Zr-O-S-O-Zr bonds; and three terminal sulfate groups and three terminal hydroxyl groups for each zirconium atom [31]. Moreover, Yamaguchi [32] concluded that the generation of high acidity was accompanied by the formation of S 6?…”