Camino Trobajo

Intercalation of n-alkylamines by lamellar materials of the α-zirconium phosphate type

Abstract n-Alkylamines have been intercalated by α-titanium phosphate by exposing the solid to the vapour of the amines. The formula of the intercalation compounds is Ti(OPO 3 ) 2 .2C n H 2n+1 NH 3 .H 2 O (n=1–9). X-ray diffraction patterns and information on the disposition of the guests within the interlayer region have been derived. The n-alkylamines form a bimolecular film in which the carbon chains incline at roughly 59° to the titanium phosphate layers. The terminal amino groups are protonated by the -POH groups of the host. The results obtained are discussed together with the extracted from literature referring to the n-alkylamines intercalation in α-zirconium phosphate and α-tin phosphate.

Intercalation of α,ω-Alkyldiamines into Layered α-Titanium Phosphate from Aqueous Solutions

Abstract This paper reports a study on the mechanism of intercalation of α,ω-alkyldiamines, NH 2 (CH 2 ) n NH 2 (n = 2–9), into layered α-titanium phosphate, α-Ti(HPO 4 ) 2 ·H 2 O. The intercalates synthesis was performed by titrating the host with aqueous solutions of alkyldiamine at 25%C. Crystalline phases showing a general formula α-Ti(HPO 4 ) 2 ·xNH 2 (CH 2 ) n NH 2 ·H 2 O (x ≤ 1) have been obtained. In every case, a monolayered arrangement of α,ω-alkyldiamine molecules into the host layers is formed. The average inclination angle of the alkyldiamine molecules to the phosphate layer and the intercalates packing density have been determined.

Intercalation ofn-alkylamines into α-titanium phosphate from aqueous solutions

The intercalation reactions betweenn-alkylamines and α-titanium phosphate in aqueous media have been investigated. The compounds with the maximum intercalation have the formula α-Ti(HOPO3)2 · 2 CnH2n+1NH2 · H2O (n=1–10). Defined crystalline phases with lower amine content are described, the general formula being α-Ti(HOPO3)2 ·mCnH2n+1NH2 ·pH2O (m=1.0 1.3, 1.5, 1.7). Whenm=1.0 then-alkylamines form a monomolecular layer. Whenm>1.0 the layer is bimolecular. The inclination angle and the packing density of then-alkylamines in the interlayer space is determined.

Double magnetic phase transition inND4Fe(DPO4)2andNH4Fe(HPO4)2

B. F. Alfonso,1 C. Pique,1 C. Trobajo,2 J. R. Garcia,2 E. Kampert,3 U. Zeitler,3 J. Rodriguez Fernandez,4 M. T. Fernandez-Diaz,5 and J. A. Blanco6 1Departamento de Fisica, Universidad de Oviedo, E-33204 Gijon, Spain 2Departamento de Quimica Organica e Inorganica, Universidad de Oviedo, E-33006 Oviedo, Spain 3Institute for Molecules and Materials, High Field Magnet Laboratory, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands 4CITIMAC, Facultad de Ciencias, Universidad de Cantabria, E-39005 Santander, Spain 5Institute Laue-Langevin, BP 156X, F-38042 Grenoble, France 6Departamento de Fisica, Universidad de Oviedo, E-33007 Oviedo, Spain Received 3 June 2010; revised manuscript received 14 September 2010; published 20 October 2010

Synthesis and crystal structure of thorium bis(hydrogenphosphate) monohydrate.

Microcrystals of Th(HPO 4) 2.H 2O were hydrothermally obtained from a Th(NO 3) 4-CO(NH 2) 2-H 3PO 3-H 2O system ( T = 180 masculineC). The structure [orthorhombic, Pbca, a = 9.1968(2) A, b = 18.6382(2) A, c = 8.7871(2) A], unlike alpha-Zr(HPO 4) 2.H 2O-type layered compounds, consists of a three-dimensional framework with PO 4 tetrahedra coordinated to Th atoms. The water molecule is also coordinated to the Th atom and projected toward small channels running along the directions of the a and c axes. The ThO 6O(w) environment could be described as a highly distorted pentagonal bipyramid.

Hydrothermal synthesis and characterization of alkali metal titanium silicates

Preparation of granulated alkali metal titanium silicates is described in which the desired silicon to titanium ratio is controlled via a sol-gel route, using hexamethylenetetramine as an inner gelation reagent. The amorphous precursors are treated hydrothermally in the presence of NaOH or KOH solution under mild conditions (150-250°C). By varying the Si:Ti molar ratio in the precursor, concentration of alkali, temperature and duration of treatment, six granular sodium titanium silicates (Na 2 Ti 2 O 3 SiO 4 ·2H 2 O, Na 2 TiSi 2 O 7 ·2H 2 O, Na 2 TiOSiO 4 and three novel phases characterized by the first reflection in the XRD at 10.8, 7.2 and 5.4 A, respectively) and two potassium titanium silicates [K 3 H(TiO) 4 (SiO 4 ) 3 ·8H 2 O, K 2 TiSi 3 O 9 ·H 2 O] were synthesized. All compounds were characterized by elemental analysis, TGA, powder XRD, SEM and 29 Si MAS NMR spectroscopy. Some of the titanium silicates are thermally stable, possessing unique ion exchange properties for alkali, alkaline earth, and some toxic heavy metal cations.

A flow-through reaction cell for in situ X-ray diffraction and absorption studies of heterogeneous powder–liquid reactions and phase transformations

A portable powder-liquid high-corrosion-resistant reaction cell has been designed to follow in situ reactions by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine-BM25 beamline at the European Synchrotron Radiation Facility. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X-ray pathway by a porous membrane, under forced liquid reflux circulation. Owing to the short pathway of the X-ray beam through the cell, XRD and XAS measurements can be carried out in transmission configuration/mode. In the case of the diffraction technique, data can be collected with either a point detector or a two-dimensional CCD detector, depending on specific experimental requirements in terms of space or time resolution. Crystallization processes, heterogeneous catalytic processes and several varieties of experiments can be followed by these techniques with this cell. Two experiments were carried out to demonstrate the cell feasibility: the phase transformations of layered titanium phosphates in boiling aqueous solutions of phosphoric acid, and the reaction of copper carbonate and L-isoleucine amino acid powders in boiling aqueous solution. In this last case the shrinking of the solid reactants and the formation of Cu(isoleucine)(2) is observed. The crystallization processes and several phase transitions have been observed during the experiments, as well as an unexpected reaction pathway.

Structural and magnetic phases of Fe(ND3)2PO4

Polycrystalline samples of Fe(ND3)2PO4 were prepared by means of a hydrothermal route and characterized using powder x-ray diffraction, scanning electron microscopy, chemical and thermal analysis, magnetic measurements, specific heat and neutron diffraction experiments. This material orders within an orthorhombic (Pnma space group) crystal structure at room temperature, but below 220 K the crystal structure changes towards a monoclinic P 21/n structure through a phase transition with almost no latent heat. Furthermore, the magnetic cell at 2 K is twice the size of the crystallographic cell observed at 80 K. The magnetic structure associated with the Fe(III) ions is thus commensurate with the crystal lattice having a propagation vector , the magnetic moments lying in the yz plane of the crystallographic cell.

Phosphorous Acid and Urea: Valuable Sources of Phosphorus and Nitrogen in the Hydrothermal Synthesis of Ammonium-Thorium Phosphates

Microcrystals of the first ammonium-thorium phosphates, (NH 4) 2Th(PO 4) 2.H 2O (tetragonal, I4 1/ amd, a = 7.0192(4) A, c = 17.9403(8) A) and NH 4Th 2(PO 4) 3 (monoclinic, C2/ c, a = 17.880(6) A, b = 6.906(1) A, c = 8.152(2) A, beta = 104.39(2) degrees ) were hydrothermally obtained from a Th(NO 3) 4-CO(NH 2) 2-H 3PO 3-H 2O system ( T = 180 degrees C). In both cases, the structure consists of a three-dimensional framework with PO 4 tetrahedra coordinated to Th atoms (ThO n polyhedra, where n = 8 or 9, for the tetragonal or monoclinic phase, respectively). The ammonium ions (and water molecules) are located in the tunnels.

HYDROTHERMAL SYNTHESIS AND ION EXCHANGE PROPERTIES OF THE NOVEL FRAMEWORK SODIUM AND POTASSIUM NIOBIUM SILICATES

ABSTRACT Two novel metastable sodium niobium silicates of the empirical formula: Nal+x−yHy(Nb1−xSix)O3 nH2O, where x=0.33−0.38, y<l+x, n=0,7-l.l (NbSi-Na, 6.0 A phase), and Na3-x HxNb3Si2O13 nH2O, where x<1.5, n=2.5−3.5 (NbSi-Na, 12.6 A phase), and two novel potassium niobium silicates: K4−xHxNb4SijO22nH2O, where x<l, n=3.5-4.0 (NbSi-K., 10.0 A phase), and K1−xHxNbSi4O11nH2O, where x<0.2, n=0.4-0.5 (NbSi-K, 6.05 A phase), were synthesized in the homogeneous alkaline reaction system NbCl5 - SiO2 - NaOH (KOH) -H2O2 - H2O under mild hydrothermal conditions. The compounds were characterized by elemental analysis, FTIR, TGA, MAS 29Si NMR and X-ray diffraction. It was found that alkali metal niobium silicates have open framework structures. Their ion exchange affinity towards alkali, alkaline earth and some transition metal ions was studied. All alkali metal niobium silicates are moderately acidic ion exchangers. Both sodium niobium silicates show a distinct affinity for Cs+ ion among alkali metal ions, whereas...