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1.
The hierarchy of the electron localization basins is a powerful tool of analysis of the bonding in molecules and solids within
the “elfological” framework. It is a generalization of the molecular isodensity contour analysis originally proposed by Mezey.
In this approach the basins are ordered with respect to the electron localization function values at the critical points which
determine the reduction of the reducible localization domains. The procedure enabling the corresponding tree diagrams to be
built is described and it is shown how the method can be used as a generator of mathematical definitions of chemical concepts.
The possibility offered by this simple tool is illustrated by a study of the VO
x
and VO
x
+ (x=1–4) oxides in their ground state and in some excited states.
Received: 20 July 2000 / Accepted: 20 October 2000 / Published online: 23 January 2001 相似文献
2.
NO Reduction Over Noble Metal Ionic Catalysts 总被引:1,自引:0,他引:1
In last 40 years, catalysis for NO
x
removal from exhaust gas has received much attention to achieve pollution free environment. CeO2 has been found to play a major role in the area of exhaust catalysis due to its unique redox properties. In last several
years, we have been exploring an entirely new approach of dispersing noble metal ions in CeO2 and TiO2 for redox catalysis. We have extensively studied Ce1−x
M
x
O2−δ (M = Pd, Pt, Rh), Ce1−x−y
A
x
M
y
O2−δ (A = Ti, Zr, Sn, Fe; M = Pd, Pt) and Ti1−x
M
x
O2−δ (M = Pd, Pt, Rh, Ru) catalysts for exhaust catalysis especially NO reduction and CO oxidation, structure–property relation
and mechanism of catalytic reactions. In these catalysts, lower valent noble metal ion substitution in CeO2 and TiO2 creates noble metal ionic sites and oxide ion vacancy. NO gets molecularly adsorbed on noble metal ion site and dissociatively
adsorbed on oxide ion vacancy site. Dissociative chemisorption of NO on oxide ion vacancy leads to preferential conversion
of NO to N2 instead of N2O over these catalysts. It has been demonstrated that these new generation noble metal ionic catalysts (NMIC) are much more
catalytically active than conventional nano crystalline noble metal catalysts especially for NO reduction. 相似文献
3.
A. Sárkány 《Reaction Kinetics and Catalysis Letters》1999,68(1):153-163
Formation of carbonaceous deposits from 1,3-butadiene has been investigated over a group of Pd catalysts. Hydrogen generated
in decomposition of diene at 473–523 K participates in diene hydrogenation, resulting in the formation ofn-butenes. XRD measurements have confirmed formation of dissolved carbon (PdCx) phase. DRIFT measurements over 0.06 wt.%Pd/γ-Al2O3 have revealed bands at 1575 and 1464 cm−1, suggesting formation of carboxylate structures. Selectivity of the competitive hydrogenation in 1,3-butadiene and propene
mixture R(BD)/R(Pr) has been measured on “fresh” and poisoned samples. Accumulation of deposits has decreased the R(BD)/R(Pr)
ratio. The results have been interpreted by transport hindrance and a greater prevalence of non-selective low coordination
sites on the poisoned surface. Measurements over Pd, Cu, Pt and Rh catalysts have shown that the highn-butane selectivity over Pt and Rh is also accompanied with low R(BD)/R(Pr) values, suggesting that thermodynamic and mechanistic
factors are not entirely separable.
Dedicated to Professor Pál Tétényi on the occasion of his 70th birthday 相似文献
4.
Surface interactions of CClF3 with polycrystalline samples of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Rh, Pd, Ag, Ta, W, Re, Ir, and Pt were investigated
by means of moderate dynamic SIMS. As observed with other reactant gases these transition metals in most cases appear to be
discernible into “dissociative” and (partial) “molecular” adsorbents. Small signals of oxidic secondary ions which are detectable
for residual gas conditions vanished under the action of CClF3. However, due to strong polarization by either of the halogens, the emission of Me2+ ions is enhanced for Ti, V, and Nb.
Received: 6 August 1997 / Revised: 22 December 1997 / Accepted: 29 December 1997 相似文献
5.
B. Das M. V. Reddy G. V. Subba Rao B. V. R. Chowdari 《Journal of Solid State Electrochemistry》2011,15(2):259-268
Nano-composites of SnO(V2O3)
x
(x = 0, 0.25, and 0.5) and SnO(VO)0.5 are prepared from SnO and V2O3/VO by high-energy ball milling (HEB) and are characterized by X-ray diffraction (XRD), scanning electron microscopy, and
high-resolution transmission electron microscopy techniques. Interestingly, SnO and SnO(VO)0.5 are unstable to HEB and disproportionate to Sn and SnO2, whereas HEB of SnO(V2O3)
x
gives rise to SnO2.VO
x
. Galvanostatic cycling of the phases is carried out at 60 mA g−1 (0.12 C) in the voltage range 0.005–0.8 V vs. Li. The nano-SnO(V2O3)0.5 showed a first-charge capacity of 435 (±5) mAh g−1 which stabilized to 380 (±5) mAh g−1 with no noticeable fading in the range of 10–60 cycles. Under similar cycling conditions, nano-SnO (x = 0), nano-SnO(V2O3)0.25, and nano-SnO(VO)0.5 showed initial reversible capacities between 630 and 390 (±5) mAh g−1. Between 10 and 50 cycles, nano-SnO showed a capacity fade as high as 59%, whereas the above two VO
x
-containing composites showed capacity fade ranging from 10% to 28%. In all the nano-composites, the average discharge potential
is 0.2–0.3 V and average charge potential is 0.5–0.6 V vs. Li, and the coulombic efficiency is 96–98% after 10 cycles. The
observed galvanostatic cycling, cyclic voltammetry, and ex situ XRD data are interpreted in terms of the alloying–de-alloying
reaction of Sn in the nano-composite “Sn-VO
x
-Li2O” with VO
x
acting as an electronically conducting matrix. 相似文献
6.
A. S. Ivanova 《Kinetics and Catalysis》2009,50(6):797-815
The effect of synthesis conditions, the nature of components, and the ratio between the components on the phase composition,
the texture, and the redox and catalytic properties of the Ce-Zr-O, Ce-Zr-M1-O (M1 = Mn, Ni, Cu, Y, La, Pr, or Nd), N/Ce-Zr-O (N = Rh, Pd, or Pt), and Pd/Ce-Zr-M2-O/Al2O3 (M2 = Mg, Ca, Sr, Ba, Y, La, Pr, Nd, or Sm) was considered. A cubic solid solution with the fluorite structure was formed on
the introduction of <50 mol % zirconium into CeO2, and the stability of this solid solution depended on preparation procedure and treatment conditions. The presence of transition
or rare earth elements in certain concentrations extended the range of compositions with the retained fluorite structure.
The texture of the Ce-Zr-O system mainly depended on treatment temperature. An increase in this temperature resulted in a
decrease in the specific surface area of the samples. The total pore volume varied over the range of 0.2–0.3 cm3/g and depended on the Ce/Zr ratio. The presence of transition or rare earth elements either increased the specific surface
area of the system or made it more stable to thermal treatment. The introduction of the isovalent cation Zr4+ into CeO2 increased the number of lattice defects both on the surface and in the bulk to increase the mobility of oxygen and facilitate
its diffusion in the Ce1 − x
Zr
x
O2 lattice. The catalytic properties of the Ce-Zr-M1-O or N/Ce-Zr-M2-O systems were due to the presence of anion vacancies and the easy transitions Ce4+ ai Ce3+, M12n+ ai M1
n+, and N
δ+ → N
0 in the case of noble metals. 相似文献
7.
V. Ya. Kavun A. V. Gerasimenko A. B. Slobodyuk N. A. Didenko N. F. Uvarov V. I. Sergienko 《Russian Journal of Electrochemistry》2007,43(5):537-544
The ionic mobility in the temperature interval 180 to 480 K, structure, and electrophysical properties of rubidium-ammonium
hexafluorozirconates Rb2−x
(NH4)
x
ZrF6 (1.5 ≤ x ≤ 2.0) are studied by methods of the 19F, 1H NMR spectroscopy, x-ray structure analysis, differential thermal analysis, and impedance spectroscopy. Correlations between
the composition of the cationic sublattice, the character of ionic motions, and the phase transition temperature (of the type
order-disorder) are established in these compounds. The salient feature of the high-temperature modifications of these fluorozirconates
with x ≥ 1.5 is the translation diffusion of ions inside the fluoride and ammonium sublattices and the 19F NMR spectra are characterized by monoaxial anisotropy of the magnetic shielding tensor of the fluorine nuclei. Fluorozirconates
with x > 1.5 are shown to belong with the structural type (NH4)2ZrF6. The rubidium cations isomorphically replace the ammonium cations. The electrophysical characteristics of the compounds are
examined in the temperature interval 300 to 480 K. It is established that the electroconductivity of these compounds increases
with x.
Original Russian Text ? V.Ya. Kavun, A.V. Gerasimenko, A.B. Slobodyuk, N.A. Didenko, N.F. Uvarov, V.I. Sergienko, 2007, published
in Elektrokhimiya, 2007, Vol. 43, No. 5, pp. 563–570.
Based on the paper delivered at the 8th Meeting “Fundamental Problems of Solid-State Ionics”, Chernogolovka (Russia), 2006. 相似文献
8.
V. V. Lesnyak V. K. Yatsimirskii T. D. Kinder O. Yu. Boldyreva 《Theoretical and Experimental Chemistry》2010,46(2):126-131
The Pt/V2O5 and Pd/V2O5 systems formed upon hydrogen reduction have catalytic activity in the oxidation of carbon monoxide exceeding the activity
of Pt/Al2O3 and Pd/Al2O3. The transition from the low-activity to high-activity state on the Pt/V2O5 and Pd/V2O5 catalysts is characterized by temperature hysteresis and change in the kinetic equation. X-ray phase analysis (XPA), X-ray
photoelectron spectroscopy (XPES), and X-ray spectral microanalysis were used to establish that prior reduction of V2O5 by hydrogen gives VO2, V6O13, a-H
x
V2O5, and b-H
x
V2O5, which facilitates the formation of an active catalyst surface. 相似文献
9.
T. G. Nikiforova 《Russian Journal of Electrochemistry》2010,46(12):1378-1382
Reduction of palladium(II) glycinate complexes in strongly acid 0.5 M NaClO4 solutions (pH 0.6 and 1.0) with variable palladium(II) complex and free glycine concentration was studied by the taking of
cyclic voltammograms at palladium rotating disc electrode. It is shown that it was a chelate monoglycinate palladium(II) complex
that was present in all studied solutions and underwent the reduction. The diffusion coefficient of the chelate monoglycinate
palladium(II) complex D = (6.5 ± 0.5) × 10−6 cm2/s was determined from the limiting diffusion current of the complex reduction. The monoglycinate palladium(II) complex reduction
occurred in the double-layer segment of the palladium charging curve; it was not complicated by hydrogen adsorption at electrodes.
The palladium(II) complex reduction half-wave potential was determined (E
1/2 = ∼0.300 to 0.330 V (SCE)). It is shown that the decreasing of the number of ligands coordinated by palladium via nitrogen
atom facilitates the complex reduction process. In particular, the reduction potentials of palladium(II) complexes with different
ligand number at palladium electrode shifted markedly toward negative potentials in the series: Pdgly+ < Pd(gly)2 < Pd(gly)42−. 相似文献
10.
V. M. Uvarov D. A. de Vekki V. P. Reshetilovskii N. K. Skvortsov 《Russian Journal of General Chemistry》2010,80(1):35-46
New chiral rhodium complexes cis-[Rh(CO)2(RNH2)Cl] [RNH2 = (R)-(−)-cis-MyrtNH2, (R)-(−)-MenthylNH2, (R)-(+)-BornylNH2] were synthesized and their catalytic properties in reactions of hydrosilylation of acetophenone with diphenylsilane were
studied. It was shown that the reaction products were diphenyl-1-phenylethoxysilane, diphenyl-1-phenylvinyloxysilane and 1,1,3,3-tetraphenyldisiloxane.
The best catalytic activity displayed (−)-cis-[Rh(CO)2(MenthNH2)Cl]. The hydrosilylation of acetophenone with diphenylsilane in the presence of [Rh(CO)2(μ-Cl)]2 and [Rh(cod)Cl]2 and amines in situ was studied. The best ratio amine:complex = 5:1 was established. With the catalytic systems based on [Rh(cod)Cl]2 or [Rh(CO)2(μ-Cl)]2 the activity increased in the series of amines: (R)-(−)-cis-MyrtNH2 < (R)-(−)-MenthylNH2 < (R)-(+)-BornylNH2, and (R)-(−)-MenthylNH2 < (R)-(+)-BornylNH2 < (R)-(−)-cis-MyrtNH2, respectively. The chemoselectivity maximum was observed in the presence of [Rh(cod)Cl]2 with (R)-(−)-MenthylNH2 and [Rh (CO)2(μ-Cl)]2 with (R)-(+)-BornylNH2; maximum asymmetric induction was 43.5% ee at the use of [Rh(CO)2 (μ-Cl)]2 and (R)-(+)-BornylNH2. 相似文献
11.
S. P. Khranenko I. A. Baidina N. V. Kuratieva S. A. Gromilov 《Journal of Structural Chemistry》2009,50(1):166-169
A new Pd nitrate complex KCs[Pd(NO3)4]·0.5H2O is synthetized. Its crystal structure contains isolated complex anions [Pd(NO3)4]2−, cations K+, Cs+, and crystallization water. Square-planar coordination around Pd is achieved by oxygen atoms of monodentate nitrate ligands.
The coordinated nitrate ligands are all oriented in the same way, in a “basket”-like arrangement. The coordination around
Pd is completed to 4+1 by forming Pd...Pd contacts of 3.564 ?.
Original Russian Text Copyright ? 2009 by S. P. Khranenko, I. A. Baidina, N. V. Kuratieva, and S. A. Gromilov
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 1, pp. 173–176, January–February, 2009. 相似文献
12.
V. Sauchuk S. Megel E. Girdauskaite N. Trofimenko M. Kusnezoff A. Michaelis 《Russian Journal of Electrochemistry》2011,47(5):522-530
Corrosion kinetics of ferritic alloys/steels (Crofer22APU, ITMLC, ZMG232L) were studied at high temperature. An extent of
corrosion was evaluated by measuring the oxide scale thickness and the weight gain as a function of heating time. It is shown
that even porous layer applied to interconnect can significantly reduce the rate of the steel oxidation. Contribution of the
“oxide component” into the total degradation of the SOFC stack performance is estimated. Different protection materials and
combinations were tested to analyze their influence on the processes of high temperature oxidation and long-term degradation
of Fe-Cr steels. It has been shown that “more soft” materials on the basis of spinels (Mn(Co1 − x
Fe
x
)2O4, Cu1 − x
Ni
x
Mn2O4) are most suitable materials for the use as protective layers in comparison to perovskites. The efficiency of different protective
materials was also tested in the real SOFC stacks designed in cooperation with company Staxera GmbH. It has been shown that
applied spinel materials can effectively increase the long-term stability of the SOFC stacks. 相似文献
13.
Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the
fusion enthalpy and temperature determination of the biuret (NH2CO)2NH (synthesis by-product of the urea fertilizer (NH2)2CO). Recommended values are Δm
H = (26.1 ± 0.5) kJ mol−1, T
m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems
to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature
of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested. 相似文献
14.
Electrochemistry of hydrofullerene C60H36 was studied by cyclic voltammetry in THF and CH2Cl2 in the −47–14 °C temperature range. Hydrofullerene undergoes reversible one-electron reduction to form a radical anion in
THF (E
0=−3.18 V (Fc0/Fc+), Fc=ferrocene) and irreversible one-electron oxidation in CH2Cl2 (E
p
a
=1.22 V (Fc0/Fc+)). The reduction potential was used to estimate electron affinity of hydrofullerene as EA=−0.33 eV. It was suggested that
C60H36 is an isomer withT-symmetry in which 12 double bonds form four isolated benzenoid rings located in vertices of an imaginary inscribed tetrahedron
on the molecular surface. For hydrofullerene, the “electrochemical gap” is an analog of the energy gap (HOMO−LUMO), equal
to (E
Ox−E
Red)=4.4 V, and indicates that C60H36 is a sufficiently “hard” molecule with a low reactivity in redox reactions.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2083–2087, November, 1999. 相似文献
15.
Violeta D. Kassabova-Zhetcheva Lilyana P. Pavlova Bisserka I. Samuneva Zara P. Cherkezova-Zheleva Ivan G. Mitov Mikhail T. Mikhov 《Central European Journal of Chemistry》2007,5(1):107-117
Structural and magnetic properties of Mg
x
Zn1−x
Fe2O4 powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg
x
Zn1−x
Fe2O4 (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns
of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes
from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely
small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to
explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts
remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.
相似文献
16.
DTA and XRD studies of the Fe2V4O13–Cr2V4 O13 system have shown that continuous solid solutions of a Fe2–xCrxV4O13 type, bearing a Fe2 V4 O13 structure, are formed in the system. With the increasing degree of the Cr3+ ion incorporation into the Fe2 V4 O13 structure, a contraction of the solid solution crystal lattice develops. Solid solutions of a Fe2–x Crx V4 O13 type melt incongruently, their melting temperature increasing from 953 to 1003 K with increase in the degree of the Cr3+ ion incorporation. The solid product of melting Fe2–x Crx V4 O13 solid solutions for 0.2<x >1.2 is the Fe1–x Crx VO4 solution phase, and for x ≤0.2 and x ≥1.4 – the Fe1–x Crx VO4 phase as well as FeVO4 or CrVO4 , respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Tatiana Nedoseykina Pavel Plyusnin Yuri Shubin Sergey Korenev 《Journal of Thermal Analysis and Calorimetry》2010,102(2):703-708
Thermolysis of double complex salt [Pd(NH3)4][AuCl4]2 has been studied in helium atmosphere from ambient to 350 °C. The XAFS of Pd K and Au L3 edges and thermogravimetry measurements have been carried out to characterize the intermediates and the final product. In
the temperature range 115–160 °C the complex is decomposed to form Pd(NH3)2Cl2 and AuCl4−x
N
x
species with x ranging from 2 to 3. Subsequent heating of the intermediate up to 300 °C leads to the total loss of NH3. The Au–Cl and Au–Au bonds form the local environment of Au at the stage of decomposition while only four chlorine atoms
are around Pd. At the temperature of 330 °C the Au and Pd nanoparticles as well as residues of palladium chloride are detected.
The final product consists of separated Au and Pd nanoparticles. 相似文献
18.
M.L.F. Bayard T.G. ReynoldsM. Vlasse H.L. McKinzieR.J. Arnott A. Wold 《Journal of solid state chemistry》1971
Partial substitution of fluorine for oxygen in VO2 and V2O5 was achieved by reacting V and V2O5 under 1.33 kb pressure in the presence of concentrated or dilute solutions of HF. Two new phases having the composition V2O5−xFx (0 < x < 0.025) and VO2−xFx (0 < x < 0.2) were prepared. X-Ray diffraction studies have been carried out on both phases and show the structure of V2O5−xFx to be orthorhombic and isostructural to V2O5, while VO2−xFx has a tetragonal structure of the rutile type (for x ? 0.03). Single-crystal-resistivity data show V2O5−xFx to be a semiconductor, whereas VO2−xFx undergoes a metallic to semiconductor transition at a temperature solely dependent upon the value of x. 相似文献
19.
E. V. Fesik V. I. Zarazhevskii V. V. Grebnev G. D. Mal’chikov 《Kinetics and Catalysis》2013,54(5):626-631
The rhenium- and ruthenium-containing catalysts are active in the oxidation of CH x and CO and in the reduction of NO x . Comparative testing of catalyst samples under laboratory conditions and on an engine stand demonstrated that these catalysts outperform the known commercial catalysts in the neutralization of exhaust gas from automotive gasoline engines. It is, therefore, possible to completely replace expensive Rh and partially replace Pt and Pd with cheaper components—Re and Rh—in the manufacturing of catalytic converters. 相似文献
20.
Isupova L. A. Yakovleva I. S. Rogov V. A. Alikina G. M. Sadykov V. A. 《Kinetics and Catalysis》2004,45(3):446-453
Oxygen states in the La1 – x
Ca
x
FeO3 – y
perovskites prepared using different procedures are studied by temperature-programmed reduction (TPR). Results are compared to data on the catalytic activity in the oxidation of methane and carbon monoxide. The activity of the samples in the CO and CH4 oxidation over a wide temperature range (200–600°C) is shown to correlate with the amount of reactive surface and subsurface oxygen removable during TPR below 420°C. These oxygen states in the samples of the La1 – x
Ca
x
FeO3 – y
series can be associated with the domain or intergrain boundaries. No correlation is found between the amount of lattice oxygen removable during TPR and the activity of the La1 – x
Ca
x
FeO3 – y
samples in the complete oxidation of methane at temperatures of 450–600°C. It is suggested that catalytic complete oxidation is determined by the most reactive surface and subsurface oxygen states located at the interphase boundaries, whereas the lattice oxygen does not participate in these reactions. 相似文献