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1.
The variations in the structure of deep-level calcinated NH4Na-Y zeolite (68 % NH4 +, Si/Al = 2.56) at 873 K (stage I of the hydrothermal dealumination) as a result of ammonation and subsequent calcination in water vapor at 973 and 1023 K (stageII) were studied using the IR spectra of zeolite framework vibrations. It was shown that ammonation of the product of stageI promotes the formation of linear disiloxane bonds and extra-framework =AlVI-OH species identified by absorption at 482, 1196 cm–1, and 524, 612, 829 cm–1. The ammonation is also accompanied by an increase in the excessive negative framework charge (ENFC), which is manifested in the high-frequency (HF) shift of the bands that have maxima in thev as (TO4) region and equals 10 cm–1, and also by a decrease in the unit cell parameter (a 0) by 0.14 Å. The decrease in both the ENFC anda 0 for the products of stageII, v as (TO4) = 10–20 cm–1 and a 0 = 0.07–0.14 Å, is due to the formation of nonlinear disiloxane bonds and non-framework aluminum hydroxide species identified by the absorption bands at 478, 1173 cm–1 and 530, 615, 835 cm–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 660–664, April, 1993.  相似文献   

2.
The effect of alkaline modification on the structure of highly dealuminated zeolite Y, prepared by steaming (at 973 K) the ammoniation product of NH4-Y zeolite (53% NH4 +, Si/Al=2.37) pretreated at 873 K in a humid atmosphere, was studied by means of IR spectra of the zeolite lattice vibrations. Treatment of the sample with 0.25 N KOH at 293 K causes the dissolution of the non-framework aluminum hydroxide species with formation of basic aluminate, and the cleavage of linear siloxane bridges at the dealuminated sites. At 353 K the cleavage involves the non-linear disiloxane bonds, while the interaction of potassium aluminate with the terminal Si-O(H,K) bonds thus formed brings about the regeneration of normal Al-O-Si bridges; however, parallel amorphization of the zeolite structure takes place due to pronounced depolymerization of the high-siliceous framework.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 797–799, April, 1993.The author is grateful to V.Lutz (ZIPhCh, Germany) who kindly submitted samples1,2, and4, and to N. N. Feoktistova (IChS of the RAS), for the samples of silicaalumogel.  相似文献   

3.
29Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O)4/2 and CH3Si(O)3/2 units, (CH3) n Si8O 20 – n /(8 – n) – (n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that 29Si NMR peaks due to Si(OSi)3(O) units shift to lower frequencies by replacement of the adjacent Si(O)4/2 units by CH3Si(O)3/2 units, in other words, with increasing m value in Si[OSi(O)3]3 – m [OSi(CH3) (O)2] m (O) (m=0–2). Peaks from CH3 Si(OSi)3 units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH3Si(O)3/2 units in the cubic octameric siloxane framework of (CH3) n Si8O 20 – n /(8 – n) – (n=2, 3), for both of which three isomers are present, have been estimated.  相似文献   

4.
The substitution of silicon by germanium in the AST zeolite framework type, [SinGe40−nO80]*4(SDA+F) expressed as unit cell content in its cubic F-centered symmetry, has been studied. Three different kinds of templates, dimethyldiethylammonium, dimethyldiisopropylammonium and isopropyltrimethylammonium cations, were used in the hydrothermal synthesis process in fluoride medium. The products were identified with XRD, MAS NMR, SEM and thermal analysis. The analysis of the X-ray powder diagrams shows that AST crystallizes in different space group symmetries depending on the nature of the SDA and the degree of Ge-substitution. The resonance signals of 19F in MAS NMR experiments for the pure Si- and Ge-end members are at −38.2 and −15 ppm, respectively, indicating that the F-anion is located as co-template in the double-four-ring (D4R) of the tetrahedral framework. This is confirmed by Rietveld analysis of powder diffraction data of the pure Ge-end member. The peak splitting of the 19F NMR signal in pure GeO2AST-type material is related to the displacement of F location inside the D4R. Two more distinct signals at −8 and −19 ppm, respectively, are observed for X-ray pure AST-samples of intermediate compositions and assigned to fluoride in D4R built of 4[GeO4]- and 4[SiO4]-tetrahedra (4Ge, 4Si) and to (2Ge, 6Si)-D4R, respectively. An ordered distribution of Ge in the AST-framework is proposed for cubic AST with compositions around Si/Ge=1.5–1 by correlating the intensities of 19F NMR signals and the results from chemical analysis. This model is further confirmed by the quantitative analyses of the corresponding 29Si MAS NMR spectra.  相似文献   

5.
The structural transformations of ammonium-exchanged forms of Na-Y zeolite during thermal evacuation and acid treatment were studied using IR spectroscopy. The formation of the zeolite H-forms by shallow-bed evacuation of NH4N-Y at 570 K is accompanied by a high-frequency shift of the bands in the IR lattice vibration spectra. In the formation of the H+-forms resulting from the decationization of zeolite by treatment with an aqueous HCl solution, no shifts of the bands are observed. During deep-bed calcination in air the H+-form, is transformed into the H-form completed by the formation of a highly-crystalline stabilized zeolite at 623 K. A rapid increase in the shallow-bed calcination temperature results in a collapse of the structure of the H- and H+-forms followed by the formation of amorphous SiO2.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 236–240, February, 1995.  相似文献   

6.
The zeolite water arrangement in laumontite Ca3.85Na0.23K0.06Al7.96Si16.03O48·nH2O (n=16–18) and leonhardite (n=12–14.4) has been studied from1H and27Al-NMR data at temperatures of 200–390 K. Close agreement is found between NMR data obtained for samplesn=12 andn=18 and previous X-ray and neutron diffraction data. The H2O arrangement in the powder sample withn=14.4 and in a laumontite single crystal is represented by a combination of the H2O arrangements in samples withn=12 andn=18 with increased orientational H2O disordering. Concentration-type phase transitions are found in the single crystal and then=16 andn=18 samples at 226 and 230 K, and orientational-type phase transitions are found in the sample withn=14.4 at 230 K, and in the sample withn=18 at 293 K. The smooth transformations into an orientationally disordered glassy state arrangement of H2O in the zeolite channels is found in smaples withn=14.4, 16, and 18 at 300–330 and 305–315 K.  相似文献   

7.
Using aqueous GaCl3 and chloride containing Ga(ClO4)3 solutions measurements have been carried out to investigate the formation of complexes with mixed ligands beside the [GaCl4] ion. In contrast to the Raman spectra, which contain only the signals of the [GaCl 4 ] and the [Ga(H2O)6]3+ ion, the71Ga-NMR spectra give clear evidence for the existence of complexes with mixed ligands. Investigations at low temperatures showed their coordination to be octahedral resulting in species [GaCln(H2O)6–n ](3–n)+.  相似文献   

8.
Sols for the synthesis of hybrid organic-inorganic materials have been prepared by mixing zirconium n-propoxide and methacryloxypropyltrimethoxysilane (MPS). The synthesis was done in two steps: a 15 minute hydrolysis of a MPS : H2O : EtOH 1 : 1 : 2 mixture and then addition of 0.5 molar equivalent of zirconium alkoxide. All the experimental parameters—hydrolysis ratio, pH, dilution, pre-hydrolysis time—have been optimized through a detailed 29 Si and 17O NMR analysis. Immediately after the addition, 94% of the initial water was consumed for the formation of Si–O–Zr bridges. Cleavage of these bonds, associated with formation of Si–O–Si and Zr–O–Zr bridges are then observed during the aging time.  相似文献   

9.
The reaction of hexafluoro-cyclo-triphosphazene P3N3F6 with ammonia in acetonitrile has been studied. New compounds, (2-imino-2,4,4,6,6-pentafluoro-2λ5,4λ5,6λ5-cyclo-triphosphaza-1,3,5-trienyl)-2-amino-4,4,6,6-tetrafluoro-2λ5,4λ5,6λ5-cyclo-triphosphaza-1,3,5-triene, P3N3F5–NH–P3N3F4NH2 (2) and cis and trans isomers of non-gem-2,4-diamino-2,4,6,6-tetrafluoro-2λ5,4λ5,6λ5-cyclo-triphosphaza-1,3,5-triene, P3N3F4(NH2)2 (4, 5), were detected by GC/MS, and 31P NMR spectroscopy in reaction mixtures. X-ray diffraction analysis of P3N3F5–NH–P3N3F4NH2 (2) revealed two conformational polymorphs, 2A and 2B, the latter being built up of two different conformers that were further denoted as 2Ba (the same as the single conformer in 2A) and 2Bb. The compound 2 was characterized by spectroscopic methods and its 2D potential energy surface (PES) was described by density functional theory computations depending on two dihedral angles. The calculated PES spans over 30 kJ/mol in energy including 8 local minima and all first and second order saddle points. The occurrence of the two experimentally observed conformers 2Ba and 2Bb seems to be governed by crystal packing effects.  相似文献   

10.
Trisilylphosphanes of the type PSi3 Me x Ph 9–x are formed when sodium/potassiumphosphide reacts with methylphenylchlorosilanesMe n Ph 3–n SiCl or with mixtures of methylphenylchlorosilanes. The phosphanes (SiMe 3) n P (SiMe m Ph 3–m )3–n (n, m=0, 1, 2, 3) were separated and purified by destillation or crystallization and their29Si as well as31P-NMR-spectra were recorded.
  相似文献   

11.
Antimony(m) chlorofluoride complexes M2SbCl3F2 (M = Rb, Cs, or NH4) were studied by the121,123Sb NQR method. A temperature range (77–285 K) with anomalous change in the NQR parameters and a second-order phase transition at 250–280 K for (NH4)2SbCl3F2 were found.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 382–385, February, 1996  相似文献   

12.
The variations in the structure of Na-Y zeolite after its dealumination with ethylenediaminetetraacetic acid at 293 and 373 K were studied by IR spectra of lattice vibrations. The resulting deformation of the terminal [O3SiO](H,Na) tetrahedra is accompanied by the closure of the terminal Si-O(H,Na) groups with the formation of bridge bonds. The saturation of samples dealuminated at 373 K with water decreases the deformation of the terminal tetrahedra which recovers on heating. Long-term exposure to water vapor results in an irreversible decrease in local deformations and in lowering the excessive negative charge of the skeleton, which manifests itself in a general high-frequency shift of the bands by 5–7 cm–1. These changes are more pronounced when the samples are heated in air at 873 K. The local structure deformations of the samples dealuminated at 293 K are irreversible. Heating them at 873 K causes the reorganization of the structure with the formation of a silica phase.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 655–659, April, 1993.  相似文献   

13.
The mononuclear Au(III)-complex ([Au(C18H18N2O4)Cl]) and hydrogensquarate ([C22H21N2O8]) of dipeptide phenylalanyltyrosine (H–Phe–Tyr–OH) have been synthezised, characterized spectroscopically and structurally by means of solid-state linear-polarized IR-spectroscopy, 1H- and 13C-NMR, ESI-MS, HPLC-MS–MS, FAB-MS, TGS and DSC methods. The structure of the Au(III)-complex has been predicted theoretically by DFT calculations. The dipeptide coordinated in a tridentate manner via –NH2, –COO and N-groups. One Cl ion is attached to the metal centre as a terminal ligand, yielding a planar AuN2OCl chromophor. The hydrogensquarate consists in positive charged dipeptide moiety and negative one hydrogensquarate (HSq) anion stabilizing by strong intermolecular hydrogen bonds.  相似文献   

14.
A systematic investigation on glass formation in the ternary system InF3–BaF2–Sc(PO3)3n has been carried out. Scandium polyphosphate Sc(PO3)3n has been used as a third component in order to investigate the possibilities of obtaining new stable glasses. The above long-chain polyphosphate has been prepared using a specially elaborated cryo-technique, which allowed the preparation of high-purity product. Stable ternary compositions have been obtained within the compositions range (in mol%): 5–75 InF3, 0–80% BaF2, 0–50% Sc(PO3)3n. Glasses were characterized by Differential Scanning Calorimetry, vibrational spectroscopy (Raman) and 31P NMR. Structural features for the glass were put forward. Isolated P(O,F)4 groups or fluoroindated metaphosphate units could be identified depending on glass compositions.  相似文献   

15.
The effect of alkaline modification on the structure of the products of heat treatment of NH4Na-Y zeolite (53% NH 4 + , Si/Al - 2.37) in a vacuum at 573 K and in water vapors at 873 K was investigated with the IR spectrum of vibrations of the zeolite framework in the 400–1200 cm–1 region. It was shown that the high-frequency shift of the bands in the spectra of the products obtained, the stretching vibration of vas(TO4) tetrahedrons in particular (T=Si, Al) at 1023 cm–1 by 6 and 19 cm–1, is determined by a decrease in the excess negative charge of the framework due to weakening and hydrolytic splitting of Al-O bonds of the deammoniated units with the formation of bridging Si-O(H)...Al and terminal Si-OHHO-Al hydroxyl groups. Treatment of these samples with an aqueous solution of KOH (pH 13.4) at 293 and 353 K restores the normal framework Si-O-Al bonds at the sites of formation of bridging and terminal hydroxyl groups. In the second case, restoration is hindered by substitution of H+ by K+ with some silanol groups.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. I. V. Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, 199164 St. Petersburg. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1733–1739, August, 1992.  相似文献   

16.
The spectra of copper(II)–ammonia solutions in 2 mol-kg–1 NH4NO3(aq) were recorded as a function of pH with a new UV–visible flow cell, capable of operating at conditions up to 325°C and 300 bars. Equilibrium constants for the formation of copper(II)–ammonia complexes Cu(NH3)n 2+, 1 n 4, from 30 to 150°C were determined by evolving factor analysis and nonlinear least-squares regression. Measurements at higher temperatures were limited by thermal decomposition of NH4NO3(aq). The formation constants of Cu(NH3)n 2+ decrease with temperature, consistent with extrapolations of literature data from measurements below 100°C. Measurements above 150°C were carried out in 0.5 mol-kg–1 CF3SO3H (aq), at the very high ammonia concentrations required to avoid the precipitation of CuO(s). The spectra are consistent with Cu(NH3)4 2+ as the predominant species, based on extrapolations of peak maxima and molar absorptivities from lower temperatures. Shifts in the spectra of Cu2+ and the Cu(NH3)n 2+ species to higher wavelength and increases in molar absorbance with increasing temperature are discussed in terms of the structure of the complexes.  相似文献   

17.
The temperature dependence of the frequencies of121Sb nuclear quadrupole resonance in the spectra of M2Sb2SO4F6 (M = K, Rb, NH4) was studied in the temperature range from 77 to 340 K. A secondary phase transition was found above 320 K for (NH4)2SO4F6.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1831–1833, October, 1994.This study was sponsored by the Russian Foundation for Basic Research (Grant No. 93-03-4394).  相似文献   

18.
Tetracethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) have been co-hydrolyzed in methanolic solutions containing tetramethylammonium ions that only affect polymerization of silicate species (hydrolysis products of TEOS) to form the Si8O 20 8– cubic octameric silicate species. The effects of water content and TEOS-to-MTEOS molar ratio on the distribution of species formed in the solutions have been investigated with the trimethylsilylation technique and 29Si n.m.r. spectroscopy. Formation of Si8O 20 8– and the cubic octameric species consisting of both Si(O)4 and CH3Si(O)3 units, (CH3)nSi8O 20–n (8–n)– (n=1–5), is found in the solutions. The increase of water content in the solutions solely results in increasing yield of Si8O 20 8– in spite of the presence of hydrolysis products of MTEOS together with those of TEOS, suggesting that water in the solutions plays an important role in the formation of Si8O 20 8– with the aid of tetramethylammonium ions. The TEOS-to-MTEOS molar ratio varies the distribution that is kept under control by the water content, increasing yields of (CH3)nSi8O 20–n (8–n)– (n=1, 2). It is found that the water content and TEOS-to-MTEOS molar ratio determine the reaction conditions effective for the formation of CH3Si(O)3 unit-containing cubic octameric species.  相似文献   

19.
The15N NMR chemical shifts and15N-1H SSCCs are presented for substituted N-methylpyrazoles with substituents such as CH3, NO2, Br, Cl, NH2, O=CNH2, O=CPh, and COOH at the carbon atoms. The15N chemical shifts of the cyclic atoms of nitrogen and the nitro groups are discussed as well as the geminal and vicinal SSCCs of the ring nitrogen atoms with the hydrogen atoms of the CH and CH3 fragments.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117334 Moscow. D. I. Mendeleev Chemico-Technological Institute, Moscow, Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2554–2561, November, 1992.  相似文献   

20.
Microcrystalline samples of Zn(NH3)2Br2 and Ni(NH3)2X2 (X is Cl and Br) have been investigated from 100 to 293 K using X-ray diffraction and IR spectroscopy measurements (range 400–4000 cm) performed with isotopically dilute (5% deuterated) samples. Values of Δν(ND)/ΔT for all compounds hint at the existence of hydrogen bonds. Zn(NH3)2Br2 shows The dynamics of ammonia molecules even at 100 K, and no indications are apparent that dynamic disorder of ammonia molecules takes place in Ni(NH3)2X2 (X is Cl and Br). A comparison between octahedrally coordinated ammoniates [Ni(NH3)6]Br2, Ni(NH3)2Br2 and [Zn(NH3)6]Br2 with tetrahedrally coordinated ones [Zn(NH3)2Br2] leads to the conclusion that the lower coordination number increases the strength of the hydrogen bonds. Because this effect is small, it is not possible to separate the influence of the type of coordinating ions for one coordination number from the influence of the coordination number itself.  相似文献   

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