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1.
An approach for significantly suppressing N2O formation in reduction of NO by NH3 over V2O5–WO3/TiO2 (VWT) catalyst has been studied by coating different amounts of a Fe-exchanged zeolite (FeZ) onto the catalyst. FeZ-promoted VWT samples were characterized using N2 sorption, X-ray diffraction (XRD) analysis, and NH3 adsorption/desorption techniques to understand the primary role of FeZ in lowering N2O production levels. At high temperatures (≥450 °C), VWT gave N2O production with high concentrations, while N2O formation was noticeably reduced when using FeZ-promoted catalysts, which also showed somewhat lower NO removal activities (<5 %) at all temperatures. N2 sorption and XRD measurements revealed no perceptible physical or chemical alterations of each constituent, even in VWT catalysts after FeZ coating following high-temperature calcination. Adsorption of NH3 on unpromoted and FeZ-promoted catalysts and subsequent desorption yielded very complicated spectra for N2O that might primarily come from NH3 oxidation, and the interaction between V–NO species at temperatures >580 °C. NO on neighboring sites seems to be produced via decomposition of N2O generated at lower temperatures. The FeZ in the promoted VWT catalysts could be responsible for N2O decomposition and N2O reduction with unreacted NH3 at temperatures >400 °C, thereby significantly lowering N2O emission levels. This promotional effect bodes well for use in many industrial deNO x applications. 相似文献
2.
A. V. Fetisov S. Kh. Estemirova G. A. Kozhina R. I. Gulyaeva G. A. Dorogina L. B. Vedmid’ L. A. Cherepanova 《Doklady Physical Chemistry》2016,470(2):168-172
Physicochemical features of the YBa2Cu3O6 + δ superconductor synthesized via ceramic route and subjected to a kind of modification by long-term exposure to an atmosphere with low pH2O have been studied by X-ray diffraction, thermal analysis, and magnetometry. The resulting material had a high degree of saturation with air components at room temperature and 30% humidity, up to 1.5 wt % in 30 days, which is not inherent in YBa2Cu3O6 + δ. 相似文献
3.
A. I. Klyndyuk E. A. Tugova O. N. Karpov E. A. Chizhova M. V. Tomkovich V. M. Kononovich 《Russian Journal of General Chemistry》2016,86(10):2282-2287
The sequence of phases appearance during the formation of Bi1–xNdxFeO3 solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO3 or NdFeO3) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi1–xNdxFeO3 as the final product, due to the prevalence of various interphase contacts in the starting reaction zone. 相似文献
4.
L. A. Dunyushkina 《Russian Journal of Electrochemistry》2018,54(3):243-250
Information on the across-plane conductivity of films of solid-oxide electrolytes SrZr0.95Y0.05O3–δ and CaZr0.9Y0.1O3–δ deposited on ion-conducting supports is acquired by the impedance method. It is shown that the support/film interface and the intergrain boundaries considerably affect the across-plane charge transfer in the film. The effect of the crystallographic orientation of the YSZ support on the microstructure and conductivity of the CaZr0.9Y0.1O3–δ electrolyte film is demonstrated. 相似文献
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6.
A new composite, Li2MnO3·LiNi0.5Co0.45Fe0.05O2, can be synthesized by a solid-state method and preconditioned with 5 wt% HCl, H2SO4, or H3PO4 solution to achieve H+/Li+ exchange. The effects of acid treatment on the structure, morphology, and electrochemical properties of Li2MnO3·LiNi0.5Co0.45Fe0.05O2 cathode materials are analyzed. The X-ray powder diffraction patterns imply that the hexagonal α-NaFeO2 structure (space group R\(\bar{3}\)m) of the materials is not changed by the acid treatment. The scanning electron microscope images show that particles become spherical with smooth surfaces after acid treatment, and the Brunauer–Emmett–Teller analysis reveals that the specific surface area increases. The charge–discharge test demonstrates that acid-treated Li2MnO3·LiNi0.5Co0.45Fe0.05O2 cathode materials deliver higher initial coulombic efficiencies than untreated material, owing to the improvement of the catalytic reduction activity of oxygen released during the initial charge process. Furthermore, Li2MnO3·LiNi0.5Co0.45Fe0.05O2 treated with HCl displays the best electrochemical performance, with the acid treatment improving the initial coulombic efficiency from 66.0 to 82.2%. Thus, acid treatment can effectively improve the electrochemical performance of electrode materials in Li-ion batteries. 相似文献
7.
Yu. A. Mirgorod 《Journal of Structural Chemistry》2009,50(3):456-460
Thermodynamic cycles including the increments \(\Delta G_{CH_2 }^0 , \Delta H_{CH_2 }^0 \), and \(T\Delta S_{CH_2 }^0 \) were constructed for dissolution, evaporation, hydrophobic hydration of C5–C9 hydrocarbons, and transfer from vapor (\(\Delta G_{CH_2 }^0 \) = ?0.7 kJ·mol?1, \(\Delta H_{CH_2 }^0 \) = 2.9 kJ·mol?1, \(T\Delta S_{CH_2 }^0 \) = 3.6 kJ·mol?1) and water (\(\Delta G_{CH_2 }^0 \) = ?1.4 kJ·mol?1, \(\Delta H_{CH_2 }^0 \) = 5.8 kJ·mol?1, \(T\Delta S_{CH_2 }^0 \) = 7.2 kJ·mol?1) to micelles of C12–C18 hydrocarbons. The formation of bistable hydrated micelles of C12–C18 is explained by a transition between the order-disorder states in an assembly of small (nano) systems of water. The extensive parameters of small systems and critical phenomena predicted by fluctuation theory are discussed. 相似文献
8.
9.
Crystal structure of α-Ag<Subscript>8</Subscript>S<Subscript>3</Subscript>SO<Subscript>4</Subscript>
T. A. Shestimerova A. S. Mityaev D. I. Davlyatshin A. V. Shevel’kov 《Moscow University Chemistry Bulletin》2012,67(1):13-18
The crystal structure of silver sulfide-sulfate α-Ag8S3SO4 was determined by X-ray powder diffraction data. The substance crystallizes in the tetragonal system and the space group P-4 with the unit cell parameters of α = 7.2032(4) Å, c = 5.1043(5) Å, Z = 1, R f = 5.55%, χ2 = 3.45. The layers in the structure of the compound formed by trigonal prisms of Ag6S connected to each other through the vertices are connected by the additional atoms of sulfur into a three-dimensional framework. Distorted tetrahedral anions of SO 4 2? are located in the cavities of the framework, the symmetry (D 2d ) of which was confirmed by the data of IR spectroscopy. 相似文献
10.
Bismuth titanate (Bi4Ti3O12) and bismuth titanium niobate (Bi3TiNbO9) c-axis textured thin films were fabricated using the sol–gel processing technique. Chemical modification of precursor solutions was performed using a proprietary photosensitive chemical (photoresist). Increases in crystallinity and texture of resulting films were seen over films that were made from unmodified solutions. Analysis by X-ray diffraction (XRD) revealed c-axis orientation factors for Bi4Ti3O12 near 88% and Bi3TiNbO9 near 63% in “modified” films. Atomic force microscopy images of films show microstructural improvement between “modified” and “unmodified” films. Images generally show smaller randomly oriented grains in “unmodified” films, and larger oriented platelet structures related to growth due to crystal habit in “modified” films. Light scattering experiments show the addition of photoresist to the precursor solution initiates accelerated particle growth. AFM imaging of soft-baked films also suggests an enhancement of texture. 相似文献
11.
The compositionally graded Ba1−xCaxZr0.05Ti0.95O3 (x = 0, 0.05, 0.10) (BCZT) thin films with compositional gradient from BaZr0.05Ti0.95O3 to Ba0.90Ca0.10Zr0.05Ti0.95O3 were deposited on Pt/Ti/SiO2/Si substrates by sol-gel processing. The crystal structure of the thin films was determined by X-ray diffraction. Field emission
scanning electron microscopy (FESEM) was used to examine crystallite size and morphology of compositionally graded thin films.
The dielectric properties of compositionally graded thin films were characterized by measuring the dielectric constant and
dielectric loss as a function of temperature, applied electric field and frequency. As a result, compositionally graded thin
films with weak temperature dependence were realized. Dielectric constant peaks, common to a ferroelectric transition, were
not observed in the temperature range from 298 to 413 K. The compositionally graded BCZT thin films with weak temperature
dependence of tunability could be attractive materials for frequency and phase agile tunable microwave components such as
tunable filters, tunable oscillators, and phase shifters for application in phased array antennas. 相似文献
12.
B. Li Y. Y. Wang W. Q. Luo Y. H. Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(3):1619-1625
Radiation-induced degradation of the weakly and strongly 4-vinylpyridine basic ion exchange resins by gamma radiolysis was investigated in the presence of air and liquid water. This study is focused on evaluating the radiolytic gases (H2, CO, CO2 and CH4) and liquid products (water-solute TOC and NH4 +). The weakly basic resin yielded lower amounts of H2 and CO and higher amounts of CO2 than those of the strongly basic resin. Moreover, the strong basic resin tended to yield greater amounts of NH4 +. Resins were characterized by the FTIR spectroscopy technique and the results showed that the resins structures are relatively stable. 相似文献
13.
The Ba0.5Sr0.5Co0.8–xWxFe0.2O3–δ (х = 0–0.1) materials prepaMIECred by partial substitution of cobalt in BSCF with tungsten were studied. The tungsten solubility limit in the structure of cubic perovskite BSCF was shown to be ~2%. The doping with the highly charged W6+ (2%) cation improved the functional properties of BSCF: it increased the oxygen permeability and membrane stability in the CO2-containing atmosphere and suppressed the cubic–hexagonal perovskite polymorphic transition. This stabilizes high oxygen fluxes during long-term stability tests. 相似文献
14.
Xuehang Wu Wenwei Wu Shushu Li Xuemin Cui Sen Liao 《Journal of Thermal Analysis and Calorimetry》2011,103(3):805-812
The single phase NH4NiPO4·6H2O was synthesized by solid-state reaction at room temperature using NiSO4·6H2O and (NH4)3PO4·3H2O as raw materials. XRD analysis showed that NH4NiPO4·6H2O was a compound with orthorhombic structure. The thermal process of NH4NiPO4·6H2O experienced three steps, which involves the dehydration of the five crystal water molecules at first, and then deamination,
dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization
of Ni2P2O7. In the DTA curve, the two endothermic peaks and an exothermic peak, respectively, corresponding to the first two steps’
mass loss of NH4NiPO4·6H2O and crystallization of Ni2P2O7. Based on Flynn–Wall–Ozawa equation, and Kissinger equation, the average values of the activation energies associated with
the thermal decomposition of NH4NiPO4·6H2O, and crystallization of Ni2P2O7 were determined to be 47.81, 90.18, and 640.09 kJ mol−1, respectively. Dehydration of the five crystal water molecules of NH4NiPO4·6H2O, and deamination, dehydration of the crystal water of NH4NiPO4·H2O, intramolecular dehydration of the protonated phosphate group from NiHPO4 together could be multi-step reaction mechanisms. Besides, the thermodynamic parameters (ΔH
≠, ΔG
≠, and ΔS
≠) of the decomposition reaction of NH4NiPO4·6H2O were determined. 相似文献
15.
A series of MoO3/ZrO2–Al2O3 catalysts was prepared and investigated in the sulfur-resistant methanation aimed at production of synthetic natural gas. Different methods including impregnation, deposition precipitation, and co-precipitation were used for preparing ZrO2–Al2O3 composite supports. These composite supports and their corresponding Mo-based catalysts were investigated in the sulfur-resistant methanation, and characterized by N2 adsorption–desorption, XRD and H2-TPR. The results indicated that adding ZrO2 promoted MoO3dispersion and decreased the interaction between Mo species and support in the MoO3/ZrO2–Al2O3 catalysts. The co-precipitation method was favorable for obtaining smaller ZrO2 particle size and improving textural properties of support, such as better MoO3 dispersion and increased concentration of Mo6+ species in octahedral coordination to oxygen. It was found that the MoO3/ZrO2–Al2O3 catalyst with ZrO2Al2O3 composite support prepared by co-precipitation method exhibited the best catalytic activity. The ZrO2 content in the ZrO2Al2O3 composite support was further optimized. The MoO3/ZrO2–Al2O3 with 15 wt % ZrO2 loading exhibited the highest sulfur-resistant CO methanation activity, and excess ZrO2 reduced the specific surface area and enhanced the interaction between Mo species and support. The N2 adsorption-desorption results indicated that the presence of ZrO2 in excessive amounts decreased the specific surface area since some amounts of ZrO2 form aggregates on the surface of the support. The XRD and H2-TPR results showed that with the increasing ZrO2 content, ZrO2 particle size increased. These led to the formation of coordinated tetrahedrally Mo6+(T) species and crystalline MoO3, and this development was unfavorable for improving the sulfur-resistant methanation performance of MoO3/ZrO2–Al2O3 catalyst. 相似文献
16.
Wenwei Wu Xuehang Wu Shuibin Lai Sen Liao 《Journal of Thermal Analysis and Calorimetry》2011,104(2):685-691
Nanocrystalline NH4ZrH(PO4)2·H2O was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O and (NH4)2HPO4 as raw materials. X-ray powder diffraction analysis showed that NH4ZrH(PO4)2·H2O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH4ZrH(PO4)2·H2O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration
of the protonated phosphate groups, and the formation of orthorhombic ZrP2O7. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps'
mass losses of NH4ZrH(PO4)2·H2O and crystallization of ZrP2O7 were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated
with the NH4ZrH(PO4)2·H2O thermal decomposition and crystallization of ZrP2O7 were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol−1, respectively. Dehydration of the crystal water of NH4ZrH(PO4)2·H2O could be due to multi-step reaction mechanisms: deamination of NH4ZrH(PO4)2 and intramolecular dehydration of the protonated phosphate groups from Zr(HPO4)2 are simple reaction mechanisms. 相似文献
17.
Single crystal X-ray diffraction study of glycine phosphite C2H5NO2·H3PO3 was performed (monoclinic, space group P21/c, a = 7.401(3) Å, b = 8.465(3) Å, c = 9.737(3) Å; β = 100.73(5)°, Z = 4). It has been found that one of hydrogen atoms is located at the centre of symmetry forming two strong hydrogen bonds to yield H4P2O 6 ?2 dimers, while another hydrogen atom is statistically disordered over two positions and organizes the dimers into an infinite corrugated chain. The ordering of this hydrogen atom position and/or displacement of the other one from the centre of symmetry will lead to the loss of symmetry centre and lowering of the point group symmetry from C2h to piezo-active group C2 or C s . 相似文献
18.
G. V. Avdeev T. I. Milenov A. V. Egorysheva K. P. Petrov V. M. Skorikov R. Kh. Titorenkova P. M. Rafailov 《Russian Journal of Inorganic Chemistry》2011,56(6):913-918
A compound with the general formula Bi36MgP2O60 ? δ was obtained by a solid-state reaction method. Its composition was confirmed using EDAX. The compound belongs to the cubic crystal system (space group I23, no. 197) and has a sillenite-type structure. The lattice parameter a o is 10.15704(12) Å. The Rietveld refinement of the crystallographic data revealed mixed tetrahedral sites (2a) occupied by Mg, P, and Bi in a ratio of 32: 63: 5. The resulting lattice strains are compensated by vacancies in the cationic (2a) and anionic sites (24f) and by distortion of the Bi-O framework detected by IR and Raman spectroscopy. 相似文献
19.
R. Taherzadeh Mousavian S. Sharafi M. R. Roshan M. H. Shariat 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1063-1070
A powder mixture of Al/TiO2/H3BO3 = 10/3/6 in molar ratio was used in this study to form the Al2O3–TiB2 ceramic composite via thermite reactions (combustion synthesis). As no combustion synthesis occurred for an unmilled sample
in a furnace, the mixture was milled in a planetary ball-mill for various milling times, and the as-milled samples were in
situ synthesized in the furnace at a heating rate of 10 °C/min. The differential scanning calorimetry (DSC) measurements were
performed with the same heating rate on the unmilled and the as-milled samples to evaluate the influences of the milling on
the mechanisms and efficiencies of reactions. Although no combustion synthesis occurred for the unmilled sample in the furnace,
two exothermic peaks were detected in its DSC curve after the melting of the Al. For the as-milled samples, significant changes
revealed in the DSC curves, suggest that the milling process before the combustion synthesis changed the mechanisms and efficiencies
of reactions. In addition, the intensity and the temperature of the exothermic peaks in the DSC curves changed by increasing
the milling time. According to the XRD analyses, by enhancing the milling time, the purity of the final products would increase,
confirming that the efficiency of the reactions increased. Finally, the microstructures of the as-milled and as-synthesized
samples were examined by a SEM, and it was shown that the morphology of the reactant powders was altered by increasing the
milling time. 相似文献
20.
N. V. Vlasenko Yu. N. Kochkin P. E. Strizhak 《Theoretical and Experimental Chemistry》2009,45(4):271-275
We have established that the calcination temperature for ZrO2–Y2O3 catalysts changes their acid–base spectrum, which determines the direction of the conversions in the mixture MeOH + CO2. For samples with predominance of acid sites, the major product is dimethyl ether. As the content of base sites increases,
methyl formate is formed. Activity in dimethyl carbonate synthesis is exhibited only by samples in which the basicity is higher
than the acidity or close to it. 相似文献