共查询到20条相似文献,搜索用时 62 毫秒
1.
A study was carried out on the effect of noble metals (Pd, Pt, and Rh) on the activity and sulfur resistance of a Cu-Ni-Ce
oxide composite on yttrium-stabilized zirconium in the oxidation of methane by oxygen. The enhancement in activity in the
deep oxidation of methane, which is greatest for the pallaldium sample, is related to the oxidation-reduction properties of
the composites. The platinum catalyst displayed greatest sulfur resistance, which may be attributed to the mechanism for the
oxidation of SO2 on platinum-group metals.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 170–174, May–June, 2008. 相似文献
2.
A study was carried out on the properties of Ni/Al2O3 and Cu-ZnO/Al2O3 composites supported on ceramic honeycomb monoliths made from synthetic cordierite in the carbon dioxide conversion of methane
and the partial oxidation of methanol. The structured nickel-alumina catalysts are significantly more efficient than the conventional
granulated catalysts. The improved working stability of these catalysts was achieved by adjusting the acid-base properties
of the surface by introducing sodium and potassium oxides, which leads to inhibition of surface carbonization. The hydrogen
yield was close to 90% in the partial oxidation of methanol with a stoichiometric reagent ratio in the presence of the Cu-ZnO/Al2O3/cordierite catalyst. A synergistic effect was found, reducing the selectivity of CO formation in the presence of the Cu-ZnO
catalyst relative to samples derived from the individual components Cu and ZnO.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 299–306, September–October, 2007. 相似文献
3.
The effects of transition metal (Cu, Co, Ni) oxides and platinum-group metals (Pt, Pd, Rh) in composites based on Y(Sc)-stabilized zirconia on their catalytic properties (activity, selectivity, sulfur resistance) and service life characteristics (thermal stability, performance stability) in methane oxidation reactions have been investigated. The high activity of the composites (75–99% methane conversion at 600–800°C) correlates with the amount and mobility of surface oxygen in these materials. The promoting effect of the platinum-group metals depends on the composition of the reaction medium (on whether it corresponds to the partial or total methane oxidation and on whether it contains sulfur dioxide). 相似文献
4.
M. R. Kantserova T. K. Shashkova S. N. Orlik 《Theoretical and Experimental Chemistry》2006,42(3):197-201
The effect of the composition of composites based on Y-and Sc-stabilized zirconium dioxide doped with CeO2 and transition metal (Cu, Co, Ni) oxides on catalytic properties in the oxidative conversion of methane was studied. The
activity of the composites correlated with the quantity and mobility of oxygen in them.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 184–188, May–June, 2006. 相似文献
5.
A study was carried out on the composition and nature of the stabilizing additive on the activity of nickel-containing composites
based on zirconia in the methane steam conversion. The methane conversions were 91–99% on Ni/ZrO2(Y, Sc, Ce) at 700–800 °C. 相似文献
6.
S. V. Kolotilov K. S. Gavrilenko M. R. Kantserova A. V. Yakovenko N. N. Stepanenko N. V. Kas’yan A. V. Shvets 《Theoretical and Experimental Chemistry》2005,41(6):347-351
The effect of the composition of nanosized catalysts, produced by thermal decomposition of Co(II) and Cu(II) formates deposited
on ZrO2, SBA-15, and MCM-41, on their activity in the deep oxidation of methane was investigated. It was shown that the activity
of the catalyst depends on the nature of the support and on the Co/Cu ratio.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 331–335, November–December, 2005. 相似文献
7.
M. R. Kantserova S. N. Orlik V. P. Kazimirov 《Theoretical and Experimental Chemistry》2007,43(6):399-404
Alumina-and zirconia-manganese catalysts for the deep oxidation of methane were studied by X-ray phase analysis, temperature-programmed
hydrogen reduction, and IR spectroscopy. The most active catalyst has the optimal combination of dimensional, redox, and acid
characteristics. The zirconia-manganese catalysts formed on the surface of a kaolin-aerosil honeycomb matrix provides for
80–100% conversion of methane to CO2 at 690–750 °C.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 6, pp. 367–372, November–December, 2007. 相似文献
8.
Hydrotalcite-like compounds (HTlcs) can be used as the catalysts as it is since they contain various transition metal cations
as the catalytically active species well dispersed on the basic support materials. Moreover, increasing numbers of the applications
of HTlcs after the heat treatment have been found since the oxides with very small crystal size, stable to thermal treatments,
are obtained after the calcination. The oxides possess interesting properties such as high surface area, basic properties
and further form small and thermally stable metal crystallites by reduction. Moreover, the calcined oxides show a unique property,
i.e., “memory effect,” which allows the reconstitution of the original hydrotalcite structure. We have developed the catalytic
applications of hydrotalcites as it is and moreover the mixed oxides derived from hydrotalcites for various catalytic reactions,
i.e., oxidation, dehydrogenation and reforming of hydrocarbons, and even for the reforming of methanol and the CO shift reaction.
Aerobic oxidation of alcohols, Baeyer−Villiger oxidation of ketones and O3 oxidation of oxalic acid have been successfully carried out with the Mg−Al hydrotalcites containing Ni, Fe and Cu, respectively,
as the catalysts in liquid phase. In the O3 oxidation of oxalic acid, the catalytic activity was enhanced by the “memory effect,” i.e., Mg(Cu)–Al hydrotaclite was reconstituted
on the surface of Mg(Cu,Al)O periclase particles and oxalic acid was incorporated as anions in the hydrotalcite layer, resulting
in an enhanced oxidation of oxalic acid. As the catalysts in the vapor phase reactions, Mg/Fe/Al mixed oxides prepared from
Mg–Al(Fe) hydrotalcites and effectively catalyzed the dehydrogenation of ethylbenzene. Supported Ni metal catalysts have been
prepared from Mg(Ni)–Al hydrotalcites and successfully used in the steam reforming and the oxidative reforming of methane
and propane. Moreover, the Ni catalysts have been improved by combining a trace amount of noble metals by adopting the “memory
effect” and used in the production of hydrogen for the PEFC under the daily startup and shutdown operation. Also starting
from aurichalcite or hydrotalcite precursor as the precursor, Cu/Zn/Al catalysts with high Cu metal surface area have been
prepared and successfully applied in the steam reforming of methanol and dimethyl ether, and moreover in the CO shift reaction. 相似文献
9.
K. Opoku-Gyamfi Zahra M. Tafreshi A. A. Adesina 《Reaction Kinetics and Catalysis Letters》1998,64(2):229-238
The methane oxidation activities of Pt−NiO and Co−NiO bimetallic catalysts have been investigated as part of a larger research
program on the autothermal reforming of methane (combined methane oxidation and steam reforming) in a fluidized bed reactor.
Experiments at atmospheric pressure and 783–1023 K for both catalysts showed that the reaction was more selective towards
H2 production at CH4∶O2 ratios greater than unity. Light-off temperature increased with decreasing CH4∶O2 ratios, but increase in gas velocity (beyond minimum fluidization) increased the light-off temperature. Co−NiO was as promising
as the more expensive Pt−NiO catalyst for the oxidation. 相似文献
10.
N. I. Il'chenko Yu. I. Pyatnitskii N. V. Pavlenko 《Theoretical and Experimental Chemistry》1998,34(5):239-256
It was shown that the carbides of transition metals are effective catalysts of oxidation reactions on account of their metal-like
nature, combined with their high chemical and thermal stability. The results from systematic investigations into the catalytic
characteristics of the carbides in the oxidation of hydrogen, carbon monoxide, and ammonia and in the oxidative coupling of
methane (OCM) are examined. The first two reactions are total oxidation processes, and the oxidation of ammonia is a selective
oxidation process. The oxidative coupling of methane is a heterogeneous-homogeneous process and represents a prospective method
for the direct transformation of methane into higher hydrocarbons.
L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039,
Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 265–281, September–October, 1998. 相似文献
11.
In this review, a summary of our published results, completed with new unpublished data are considered together with some
of other authors’ publications, making an attempt to reveal the mechanism of the third element co-deposition in electroless
Ni–P plating and to define its influence on the ternary coatings’ properties. A model explaining the triple role of Cu added
to the solution for electroless (EL) Ni–P plating is described: as a stabilizer [Cu(I)]; as an accelerator; and as a stability-affecting
agent, forming a dispersed solid phase in the solution. The disproportionation reaction of Cu(I) has been taken into account.
A planned experiment was performed using full-effect factorial design with two levels of three process variables, and the
response surfaces were constructed. The interaction between the factors was revealed. The results are in harmony with the
aforementioned model. In low-tin Ni–Sn–P coatings, the alloy components are uniformly distributed both on the surface and
through the thickness. In contrast, high-tin coatings exhibit three-dimensional areas enriched in Sn and impoverished in Ni
and P. As the reason for their formation, the disproportionation reaction of Sn(II) is suggested, supposed to be locally predominant
over the hypophosphite oxidation. EL deposition of pure Sn onto Ni–Sn–P substrates is shown. The inclusion of Cu or Sn in
EL Ni–P increases the thermal stability of amorphous state, ensures the preservation of a paramagnetic behavior and improves
the corrosion resistance.
Dedicated to the 70th birthday of Professor A. Vaskelis. 相似文献
12.
S. A. Solov’ev E. V. Gubareni Ya. P. Kurilets 《Theoretical and Experimental Chemistry》2008,44(6):368-373
It has been established that oxides of the rare-earth elements with moderate redox potentials (La2O3, CeO2) increased the activity and working stability of Ni-Al2O3/cordierite catalysts in the reactions of deep and partial oxidation of methane. In the presence of the (NiO + La2O3 + Al2O3)/cordierite catalyst the process of carbon dioxide conversion of methane can be intensified by introduction of oxygen into
the reaction gas mixture which decreases the temperature to achieve high conversion to 75–100 °C and has practically no effect
on selectivity with respect to H2.
Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 359–364, November–December, 2008. 相似文献
13.
Mullite–Zirconia–Zircon composites have proved to be suitable for high-temperature structural applications, with good mechanical
and fracture properties and good thermal shock resistance. In this paper, the special dilatometric behavior of a series of
Mullite–Zirconia–Zircon (3–40 vol.% ZrO2) composites is evaluated and compared with that of a pure Zircon material and explained in terms of the high Zirconia linear
thermal expansion coefficient (α) and Zirconia martensitic transformation. Linear thermal expansion (α) up to 1273 K is studied
and correlated with the phase composition of the composites; a linear correlation was found with the m-ZrO2 content evaluated with the Rietveld method. Zirconia (m-ZrO2) dispersed grains containing ceramics material showed a hysteresis in a reversible dilatometric curve (DC). The martensitic
transformation temperatures could be evaluated and then compared with the endothermic and exothermic peaks temperatures obtained
from the differential thermal analysis (DTA). Furthermore, the hysteresis area was correlated with m-ZrO2 content, where composites with less than 10 vol.% ZrO2 did not show this behavior, and from this content up to 40 vol.% of ZrO2 a linear increase of the hysteresis area was found. 相似文献
14.
N. M. Popova R. Kh. Salakhova K. Dosumov S. A. Tungatarova A. S. Sass Z. T. Zheksenbaeva L. V. Komashko V. P. Grigor’eva A. A. Shapovalov 《Kinetics and Catalysis》2009,50(4):567-576
Data on the selective oxidation of methane to synthesis gas on a 9% NiCuCr/2% Ce/(ϑ + α)-Al2O3 catalyst in dilute mixtures with Ar at short residence times (2–3 ms) are presented. The composition, structure, morphology,
and adsorption properties of the catalyst with respect to oxygen and hydrogen before and after reaction were studied using
XRD, BET, electron microscopy with electron microdiffraction, TPR, TPO, and TPD of oxygen and hydrogen. The following optimum
conditions for the preparation and pretreatment of the catalyst for selective methane reduction were found: the incipient
wetness impregnation of a support with aqueous nitrate solutions; drying; and heating in air at 873 and then at 1173 K (for
1 h at either temperature) followed by reduction with an H2-Ar mixture at 1173 K for 1 h. At a residence time of 2–3 ms (space velocity to 1.5 × 106 h−1) and 1073–1173 K, the resulting catalyst afforded an 80–100% CH4 conversion in mixtures with O2 (CH4/O2 = 2: 1) diluted with argon (97.2–98.0%) to synthesis gas with H2/CO = 2: 1. The selectivity of CO and H2 formation was 99.6–100 and 99–100%, respectively; CO2 was almost absent from the reaction products. The catalyst activity did not decrease for 56 h; carbon deposition was not
observed. A possible mechanism of the direct oxidation of CH4 to synthesis gas is considered. 相似文献
15.
Victor L. Kozhevnikov Ilia A. Leonidov Mikhail V. Patrakeev Alexey A. Markov Yakov N. Blinovskov 《Journal of Solid State Electrochemistry》2009,13(3):391-395
Dense planar and tubular oxygen separation membranes of La0.5Sr0.5FeO3 −
δ
were studied in the partial oxidation of methane to syngas process. The oxygen permeation properties were obtained from the
analysis of the outlet gas and compared with the data calculated from conductivity measurements. For the planar reactor, the
selectivity achieved 95% and the CH4 conversion was 95–99% at 900 °C with pure methane. For the tubular reactor, the CO selectivity and CH4 conversion were 90% and 100%, respectively, under the same conditions. In both cases, the H2/CO ratio was 1.6–1.9. No degradation of membranes was observed after 250 h of operation. 相似文献
16.
The thermal stability of the solid solutions of Fe2Mo1–xTixO4 for x=0.0 to 1.0 in air, had been investigated in the temperature range 303–1173 K using differential thermal analysis and thermogravimetry
(DTA and TG). The products obtained by heating the sample in air, at different temperatures, have been characterized by X-ray
diffraction and IR-studies. The results show that all the ferrite samples undergo surface oxidation during initial heating.
On heating to 823 K, the samples undergo oxidation of the octahedral site cations only and forma cation deficient spinel phase.
On further heating in air, the ferrites undergo complete oxidation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Elena L. Gubanova Vladislav A. Sadykov Andre C. van Veen Claude Mirodatos 《Reaction Kinetics and Catalysis Letters》2009,97(2):349-354
The temporal analysis of products (TAP) technique coupled with the oxygen TPD was used to elucidate the effects of the Pt-supported
fluorite-like doped ceria–zirconia oxide chemical composition and the type of pretreatment on their oxygen bonding strength,
mobility, and reactivity as related to catalytic properties in the partial oxidation of methane into synthesis gas. A rapid
evolution of hydrogen under CH4 pulse observed for oxidized catalysts agrees with the direct route of the methane selective oxidation into syngas. This route
is favored by the Pt-support interaction and a moderate bonding strength of surface oxygen species along with a high lattice
oxygen mobility. 相似文献
18.
Sorption of copper on filter-paper with chemically attached hexamethylenediamino-groups (HMDA-filter) allows to obtain the
sorbent (Cu/HMDA-filter) stable in respect to desorption of copper. A nitrogen-containing herbicide imazapyr (imaz) is retained on Cu/HMDA-filters at pH 5.5–7.0 forming a relatively stable complex. Imazapyr is determined directly on the
sorbent by its activating effect in the oxidation of hydroquinone with H2O2 catalyzed by Cu(II) with the formation of a product absorbing at 490 nm. The copper ions serve both to preconcentrate imazapyr
and to catalyze the indicator reaction. The use of 1-μL sample aliquots pipetted onto the Cu/HMDA-filters allows to determine
1 × 10−3–0.03 μmol of imazapyr, whereas preconcentration of the analyte by pumping of its solution through the same sorbent expands
the linear range to 1 × 10−4–1 × 10−1 μmol of imazapyr. When the indicator reaction is carried out in solution, the range of activating action of imazapyr is narrower
(0.06–0.1 μmol a for a solution volume of 10 mL). The determination is selective: 5–100-fold amounts of amines, aminoacids,
carboxylic acid derivatives and other model compounds do not interfere. Soil extracts and carrot juice samples spiked with
imazapyr have been analyzed.
Received January 10, 2000. Revision July 28, 2000. 相似文献
19.
A set of all-electron scalar relativistic calculations on Au
n
Cu (n = 1–12) clusters has been performed using density functional theory with the generalized gradient approximation at PW91 level.
The lowest energy geometries of Au
n
Cu clusters may be considered as assemblies of triangular Au3 moieties substituted with one Cu atom at the highest coordinated site. All these lowest energy geometries of the Au
n
Cu clusters are slightly distorted but retain the planar structures of the Au
n+1 clusters due to the strong scalar relativistic effects. The Au–Cu bonds are stronger, and a few Au–Au bonds far from the
Cu atom are weaker, than the corresponding Au–Au bonds in pure Au
n+1 clusters. After doping with a Cu atom, the thermodynamic stability and chemical reactivity are enhanced to some extent. The
odd-numbered Au
n
Cu clusters with even numbers of valence electrons are more stable than the neighboring even-numbered Au
n
Cu clusters with odd numbers of valence electrons. Odd–even alternations of magnetic moments and electronic configurations
for the Au
n
Cu clusters can be observed clearly and may be understood in terms of the electron pairing effect. 相似文献
20.
L. A. Isupova I. S. Yakovleva G. M. Alikina V. A. Rogov V. A. Sadykov 《Kinetics and Catalysis》2005,46(5):729-735
Oxygen species and their reactivity in La1 − x
Sr
x
FeO3 − y
perovskites prepared using mechanochemical activation were studied by temperature-programmed reduction (TPR) with hydrogen
and methane. The experimental data were compared with data on the catalytic activity in oxidation reactions. It was found
that the rates of CO and methane oxidation on the perovskites in the presence of gas-phase oxygen correlated (k = 0.8) with the amount of reactive surface oxygen species that were removed by TPR with hydrogen up to 250°C. Maximum amounts
of this oxygen species were released from two-phase samples (x = 0.3, 0.4, and 0.8), which exhibited an enhanced activity in the reaction of CO oxidation. In the absence of oxygen in the
gas phase, methane is oxidized by lattice oxygen. In this case, the process activity and selectivity depend on the mobility
of lattice oxygen, which is determined by the temperature, the degree of substitution, the degree of reduction, and the microstructure
of the oxide. Thus, the high mobility of oxygen, which is reached at high concentrations of point defects or interphase/domain
boundaries, is of importance for the process of deep oxidation. However, the process of partial oxidation occurs in single-phase
samples at low degrees of substitution (x = 0.1–0.2).
__________
Translated from Kinetika i Kataliz, Vol. 46, No. 5, 2005, pp. 773–779.
Original Russian Text Copyright ? 2005 by Isupova, Yakovleva, Alikina, Rogov, Sadykov. 相似文献