On the mechanism of ion exchange in zirconium phosphates—XXII mixed zirconium titanium phosphates

α-Titanium phosphate, Ti(HPO₄)₂·H₂O, was found to form two sodium ion exchanged phases. A half exchanged phase of ideal composition TiNaH(PO₄)₂·4H₂O formed first. However, before all of the titanium phosphate was converted to this phase a second phase of higher Na⁺ content formed. Thus, a three phase solid existed until sufficient sodium ion uptake (∼ 5.5 meq/g) produced only the two exchanged phases. Finally, the half exchanged phase was converted to the more highly loaded one and this latter phase existed from 6–8 meq/g of Na⁺ uptake. Severe disordering of the crystal lattice during exchange is proposed to explain this unusual exchange behavior. A broad range of titanium phosphate-zirconium phosphate solid solutions was found to form. Their behavior towards Na⁺H⁺ exchange was determined and interpreted on the basis of the known behavior of the pure phases. Mixed TiZr solid solutions of their pyrophosphates were obtained at elevated temperatures.     

Activity of copper–cerium–zirconium catalysts in oxidation of hydrogen

We have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–1000 °C. We have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.     

Evaluation of thermal properties of zirconium–PHB composites

Journal of Thermal Analysis and Calorimetry - Most of the synthetic polymers that are used for packaging industry come from fossil fuel; thus, when their life cycle is complete, they normally...     

On the mechanism of ion exchange in zirconium phosphates—XXI Intercalation of amines by α-zirconium phosphate

The intercalation of n-propylamine, n-butylamine and ethylenediamine by the layered compound α-zirconium phosphate has been examined. Each of the amines forms a number of phases whose interlayer spacings are indicative of the orientation of the amines within the layers. At low uptakes of the n-alkyl amines, they appear to lie parallel to the layers. At higher contents a double layer forms with the carbon chain backbone roughly inclined at a 60° angle to the plane of the layer. A maximum of one n-alkyl amine molecule per phosphate group is intercalated. Half as much ethylenediamine is intercalated which constitutes the same number of amine-groups. The interlayer spacings indicate, however, that the ethylenediamine chain always lies parallel to the layer but in at least four different orientations, giving rise to as many phases.     

On the mechanism of ion exchange in zirconium phosphates—XIX exchange of alkaline earth cations using acetate salts

Zirconium phosphate was found to exchange alkaline earth cations in macro quantities from acetate solutions. Rates of exchange decrease with increasing crystallinity of the exchanger but increase appreciably with temperature. Magnesium ion exchange is very slow even at 100°C. Both Mg²⁺ and Ba²⁺ each form a single exchanged phase. Their respective compositions are close to ZrMg_0.75−1.0H_0.5−0(PO₄)₂·4H₂O and ZrBa_0.8−1.0H_0.4−0 (PO₄)₂·2H₂O. In contrast Ca²⁺ and Sr²⁺ each form phases with cation contents close to half-exchange, i.e. ZrCa_0.5−0.65H_1−0.7(PO₄)₂·3H₂O and ZrSr_0.45−0.55H_1.1−0.9(PO₄)₂·3.5H₂O. these phases are then converted to ZrCa_0.85−1H_0.3−0(PO₄)₂·4H₂O and ZrSr_0.65−1H_0.7−0(PO₄)₂·2.5H₂O, respectively at higher loadings. Apparently acetate ion is a sufficiently strong base to initiate exchange and then maintain pH values high enough to achieve high metal loadings.     

Study of temperature dependence of saturated vapour pressure of zirconium(IV) β-diketonates

By means of a tensiometric flow method and a static method with a silica-membrane zero gauge, the dependences of saturated vapour pressure on temperature were obtained for the complexes of zirconium(IV) with acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, dipivaloylmethane and pivaloyltrifluoroacetone. The thermodynamic characteristics of the evaporation and sublimation of these complexes were determined.     

Cyclomagnesation of cycloalkynes with the use of RMgR’ catalyzed by zirconium complexes

The intermolecular cyclomagnesation of cycloalkynes and joint cyclomagnesation of cycloalkynes and disubstituted acetylenes was carried out by treating with RMgR′ (R, R′ = Et, Bu, Hlg) in the presence of Cp₂ZrCl₂ as a catalyst. As a result new unsaturated bi-and tricyclic organomagnesium compounds were obtained in high yields.     

X-ray structural study of fluorinated β-diketonate complexes of zirconium(IV)

Three novel complexes of zirconium(IV) are prepared and characterized by single crystal X-ray diffraction: zirconium(IV) pivaloyltrifluoroacetonate Zr(ptac)₄, zirconium(IV) trifluoroacetylacetonate Zr(tfac)₄, and zirconium(IV) hexafluoroacetylacetonate Zr(hfac)₄. Crystal data for C₃₂H₄₀F₁₂ZrO₈: a = 19.9842(6) Å, b = 11.8417(3) Å, c = 16.4831(5) Å; β = 95.2880(10)°, monoclinic, space group Cc, Z = 4, d _calc = 1.491 g/cm³, R = 0.061. Crystal data for C₂₀H₁₆F₁₂ZrO₈: a = 21.5063(15) Å, b = 7.9511(5) Å, c = 16.0510(10) Å; β = 113.736(4)°, monoclinic, space group C2/c, Z = 4, d _calc = 1.860 g/cm³, R = 0.047. Crystal data for C₂₀H₄F₂₄ZrO₈: a = 15.3533(13) Å, b = 20.2613(15) Å, c = 19.6984(17) Å; β = 95.828(2)°, monoclinic, space group P2₁/c, Z = 2, d _calc = 2.004 g/cm³, R = 0.078. All the structures are molecular and include isolated mononuclear Zr(β-dik)₄ complex molecules. Coordination environment of zirconium atom is made by eight oxygen atoms of four β-diketonates; the coordination polyhedron is an almost regular square antiprism. The Zr-O distances fall within 2.14–2.23 Å. Complexes in the structures are joined by van der Waals interactions. Using the structural data, the van der Waals energies of crystal lattices of the studied compounds are calculated by the atom-atom potential method.     

A new method of immobilizing ionic liquids into layered zirconium phosphates

In this work, a new method of a series of ion liquids (ILs) 1-alkyl-3-methylimidazolium chloride [Cnmim]Cl (n = 2, 4, 6, 8) intercalation into layered zirconium phosphates was investigated. It was found that theα-ZrP-2BA (i.e. pre-intercalated BA was arranged in a bilayer mode in the galleries ofα-ZrP) was a suitable host for intercalation ILs: ILs was inserted through exchanging pre-intercalated BA. And the intercalation orientation was investigated by use of X-ray diffraction (XRD) experiments and molecular modeling calculation.     

FT-IR studies on intercalates and organic derivatives of crystalline (α- and γ-forms) zirconium phosphate and zirconium phosphate-phosphite

FT-IR studies were carried out for various α- and γ-crystalline intercalates of zirconium phosphate (ZrP) and also for zirconium phosphatephosphite (ZrPP). The characteristic peaks of n-alkanols, n-alkylamines, benzylalcohol and benzylamine, diethyleneglycol and also some amino acid intercalates/derivatives were determined. Based on the data assumptions are made about the type of bonding between the layers and also the variety of intercalates of various crystalline form zirconium phosphates was determined.     

Crystal structures of layered zirconium pentafluorides of methylammonium,glycinium, and β-alanine

For the first time, new hybrid organic-inorganic layered zirconium pentafluorides of methylammonium, glycinium, and β-alanine with the composition (CH₃NH₃)ZrF₅·0.5H₂O, (H₃NCH₂COOH)ZrF₅·2H₂O, and (H₃N(CH₂)₂COOH)ZrF₅ are synthesized and their structures are analyzed. In the studied compounds, CN of the Zr atom is 8, and its coordination polyhedron represents a dodecahedron sharing its 6 vertex with three neighboring Zr polyhedra. The Zr dodecahedra are joined with each other in planar netlike anion layers of the composition _∞²[ZrF₅]⁻. The anion layers are hydrogen bonded into a three-dimensional structure by H₂O cations and molecules.     

On the mechanism of ion exchange in zirconium phosphates—XXIII exchange of first row divalent transition elements on γ-zirconium phosphate

The exchange of transition metal (M²⁺) ions from manganese to zinc with γ-zirconium phosphate was examined. By using acetate salts the hydrogen ion concentration is kept low enough to achieve high loadings. The fully loaded solids have the composition ZrM(PO₄)₂·4H₂O. Near quantitative uptakes are achieved at 100°C. The interlayer spacings change very little with loading indicating that γ-zirconium phosphate is able to accomodate cations and water molecules without appreciable increase in volume. The copper exchanged phase readily forms an acetylacetonate when shaken with 2,4-pentanedione.     

Synthesis and spectral studies of β-diketone and β-ketoester derivatives of aluminium zirconium isopropoxide

The reactions of aluminium zirconium heptaisopropoxide [AlZr(OPrⁱ)₇] with some β-diketones and β-ketoesters, resulting in the formation of derivatives of type ZrAl(OPrⁱ)_(7−x)L_x (where L = acetylacetone, benzoylacetone, methylacetoacetate or ethylacetoacetate; x = 1 or 2) have been carried out. These newly synthesized compounds have been characterized by elemental analyses, and IR and NMR (²⁷Al, ¹H and ¹³C) spectral studies.     

Copper-catalyzed addition reaction of γ,γ-dialkoxyallylic zirconium species with imines

In the presence of CuCN, reaction of γ,γ-dialkoxyallylic zirconium species 1 with imines proceeded at the γ-position of 1 to give gem-dialkoxyhomoallylic amines 3 in high yield. In this reaction, γ,γ-dialkoxyallylic zirconium species 1 acts as an α,β-unsaturated acyl anion equivalent.     

Interaction of metallic zirconium and its alloys Zry-2 and E110 with molten eutectic salt of LiF—NaF—KF containing zirconium fluoride components

The interactions of selected zirconium alloys used as special construction materials (Zr-pure, Zry-2, E-110) with the molten system of (LiF—NaF—KF)_(eut.) with additions of K₂ZrF₆ or Na₇Zr₆F₃₁ were studied. Corrosion losses of pure zirconium decrease sharply with 5 mole% addition of K₂ZrF₆ to (LiF—NaF—KF)_(eut.). The presence of alloying additives (Sn, Nb) has a positive influence on corrosion resistance in the eutectic mixture — up to 60% increase in corrosion resistance in comparison with pure zirconium. The mass losses of pure zirconium indicate an increasing corrosion attack with increasing Na₇Zr₆F₃₁ content in (LiF—NaF—KF)_(eut.) mixtures.     

Nonclassical β-hydrogen elimination of hydrosilazido zirconium compounds via direct hydrogen transfer

Salt metathesis reactions of Cp(2)(NR(2))ZrX (X = Cl, I, OTf) and lithium hydrosilazides ultimately afford hydride products Cp(2)(NR(2))ZrH that suggest unusual β-hydrogen elimination processes. A likely intermediate in one of these reactions, Cp(2)Zr[N(SiHMe(2))t-Bu][N(SiHMe(2))(2)], is isolated under controlled synthetic conditions. Addition of alkali metal salts to this zirconium hydrosilazide compound produces the corresponding zirconium hydride. However as conditions are varied, a number of other pathways are also accessible, including C-H/Si-H dehydrocoupling, γ-abstraction of a CH, and β-abstraction of a SiH. Our observations suggest that the conversion of (hydrosilazido)zirconocene to zirconium hydride and silanimine does not follow the classical four-center mechanism for β-elimination.     

Separation of zirconium and hafnium from early actinides and rare earth elements with eichrom’s pb resin in HCl

The separation of zirconium and hafnium isotopes from the early actinides and rare earth elements (REE) with Eichrom’s Pb resin has been studied. Batch studies were performed to characterize the behavior of actinium, thorium, zirconium, hafnium, lutetium, and yttrium on Pb resin from HCl solutions (0.001 M to 11 M). The early actinides and REE had no affinity for the resin at any concentration of HCl, but zirconium and hafnium showed a moderate uptake at high concentrations of HCl with a maximum extraction at 11 M HCl. Several column separations were tested, including with only tracer isotopes and with mass. Rapid, simple separations of zirconium from actinium, thorium, protactinium, and the REE with high yields and low elution volumes are presented with applications for tracer isotope production and fission product separations. The resin is less suitable for hafnium separations as hafnium tends to bleed off the resin even at high concentrations of HCl.

     

Efficient dehydration of carbohydrates to 5-hydroxymethylfurfural in ionic liquids catalyzed by tin(Ⅳ) phosphonate and zirconium phosphonate

In this work,we synthesized tin(IV)phosphonate(SnBPMA)and zirconium phosphonate(ZrBPMA)by the reaction of SnCl4·5H2O or ZrOCl2·8H2O with N,N-bis(phosphonomethyl)aminoacetic acid,which was synthesized from a biomaterial glycine through a Mannich-type reaction.The SnBPMA and ZrBPMA were very efficient heterogeneous catalysts for the dehydration of fructose to produce 5-hydroxymethylfurfural(HMF),and the SnBPMA had higher activity than the ZrBPMA.The effects of solvents,temperature,reaction time,and reactant/solvent weight ratio on the reaction catalyzed by SnBPMA were investigated.It was demonstrated that the yield of HMF could reach 86.5%with 1-ethyl-3-methylimidazolium bromide([Emim]Br)as solvent,and the SnBPMA and SnBPMA/[Emim]Br catalytic system could be reused five times without considerable reduction in catalytic efficiency.Further study indicated that the SnBPMA and ZrBPMA in[Emim]Br were also effective for the dehydration of sucrose and inulin to produce HMF with satisfactory yields.     

Synthesis of submicrometer zirconium carbide formed from inorganic–organic hybrid precursor pyrolysis

Zirconium carbide (ZrC) was synthesized from inorganic–organic hybrid precursor’s pyrolysis by solution-based processing. Zirconium-containing complexes, which were obtained by chelation of oxide bidentate ligands to zirconium, were used to combine with phenolic resin to form precursors for ZrC. The precursors using specific ligands including acetylacetone, ethyleneglycol, and salicylic acid transformed into pure ZrC at a relatively low temperature (1,550 °C) in addition to that using lactic acid. As a comparison, synthesis of ZrC only using zirconium oxychloride octahydrate (ZrOCl₂·8H₂O) and phenolic resin was also conducted. The synthesized powders had a small average crystallite size (~300 nm), and a low oxygen content (~2.5 at.%). The conversions from as-synthesized preceramic precursors to ceramics were studied by means of FTIR, SEM, EDS, XRD, and XPS. The oxidation behavior of the synthesized ZrC in air was studied by DSC-TG analysis.     

Electrolytic production of niobium powder from chloride—fluoride melts containing compounds of niobium and zirconium

Electroreduction of niobium is studied in a chloride-fluoride electrolyte used for obtaining zirconium powder. Limiting densities of cathodic diffusion currents of the niobium discharge and diffusion coefficients for fluoride complexes of Nb(V) and Nb(IV) are determined as functions of temperature. Optimum electrolysis parameters are determined by studying how the cathodic current density, niobium concentration, and temperature affect the cathodic electrodeposition current efficiency. The morphology and granulometric composition of powdered niobium are investigated as functions of the electrolysis parameters. Effect of zirconium, as a melt component, on the electrolytic niobium production is discussed