共查询到20条相似文献,搜索用时 15 毫秒
1.
G. A. Kovalenko L. G. Tomashevskaya T. V. Chuenko N. A. Rudina L. V. Perminova A. N. Reshetilov 《Kinetics and Catalysis》2011,52(4):564-572
The carbon-carbon composite materials obtained via the synthesis of catalytic filamentous carbon (CFC) on a Ni/graphite supported
catalyst in the process of the pyrolysis of C3–C4 alkanes in the presence of hydrogen were systematically studied. The effects of the following conditions on the catalytic
activity expressed as the yield of carbon (g CFC)/(g Ni) and on the character of CFC synthesis on graphite rods were studied:
procedures for supporting Ni(II) compounds (impregnation and homogeneous precipitation), the concentrations of impregnating
compouds (nickel nitrate, urea, and ethyl alcohol) in solution, graphite treatment (oxidation) conditions before supporting
Ni(II) compounds, and the pyrolysis temperature of C3–C4 alkanes in the range of 400–600°C. Optimum conditions for preparing CFC/graphite composite materials, which are promising
for use as electrodes in microbial fuel cells (MFCs), were chosen. The electrochemical characteristics of an MFC designed
with the use of a CFC/graphite electrode (anode) and Gluconobacter oxydans glycerol-oxidizing bacteria were studied. The morphology of the surfaces of graphite, synthesized CFC, and also bacterial
cells adhered to the anode was studied by scanning electron microscopy. 相似文献
2.
G. Veera Babu M. Palaniappa M. Jayalakshmi K. Balasubramanian 《Journal of Solid State Electrochemistry》2007,11(12):1705-1712
Graphite particles were coated with Ni–P by electroless deposition using a conventional bath consisting of a nickel salt and
hypophosphite. After 15 min of electroless deposition, the graphite particles were covered with 10 wt% nickel and 0.7–1.0 wt%
phosphorus as analysed by wet chemical method. Surface morphology was studied by scanning electron microscopy (SEM). Electrochemical
characterisation for the catalytic activity was done by cyclic voltammetry. Pure Ni powder and electroless Ni–P coated on
graphite were used as catalysts for the electro-oxidation of dextrose (1.8 × 10−3 to 4.5 × 10−3 M) in 0.1 M KOH solution. Comparative studies revealed that electroless Ni–P coated on graphite particles acted as a better
catalyst than pure Ni powder for catalytic reaction. 相似文献
3.
Yu. M. Mikhailov L. M. Kustov V. V. Aleshin A. L. Tarasov L. V. Zhemchugova 《Kinetics and Catalysis》2011,52(2):277-281
The hydrogenation of 1,3-pentadiene into pentenes over the commercial 0.5% Pd/Al2O3 catalyst and over a new catalyst containing 1.0% Pd and 3.7% Ag (μ-catalyst) has been investigated. The new catalyst has
been prepared via the flameless wave conversion of cyclotrimethylenetrinitramine in a porous composite. The catalytic properties
of the new composite in the hydrogenation reaction depend on the hydrogen/1,3-pentadiene ratio and on the catalyst activation
temperature. The reaction conditions for selective 1,3-pentadiene hydrogenation have been optimized. The pentenes yield as
a function of temperature passes through a maximum at any H2/C5H8 ratio between 1 and 2. The 2-pentene/1-pentene ratio in the reaction products increases as the temperature is raised. 相似文献
4.
Reza Ojani Jahan-Bakhsh Raoof Shahla Fathi Sharife Alami-Valikchali 《Journal of Solid State Electrochemistry》2011,15(9):1935-1941
Nickel ions were incorporated in NaY zeolite according to cation exchange mechanism. Then NiY zeolite was used as modifier
for preparation of modified carbon paste electrode. The electrochemical behavior of NiY-modified carbon paste electrode (NiY/CPE)
was studied in alkaline solution using cyclic voltammetry method. Ability of different electrodes containing NiY/CPE, Ni-NiY/CPE,
Ni-NaY/CPE, and Ni/CPE for electrocatalytic oxidation of methanol was compared (three last electrodes prepared by open circuit
accumulation of Ni(II) ions on the surface of NiY/CPE, NaY/CPE, and bare CPE, respectively). Results show that Ni-NiY/CPE
is best catalyst for the electrochemical oxidation of methanol in alkaline solution and both process of earlier Ni ion incorporation
through cation exchange in NaY zeolite and open circuit accumulation of Ni ion on the surface of electrode are essential to
have good catalyst. Effect of graphite–zeolite ratio on electrocatalytic current was studied and 3:1 ratio of graphite–zeolite
was selected as optimum ratio for preparing electrode. Ni-NiY/CPE has very good stability toward the methanol oxidation in
concentration range of 0.005 to 0.5 M. Finally, using chronoamperometric method, the catalytic rate constant (k) for methanol was found to be 1.56 × 104 cm3 mol−1 s−1. 相似文献
5.
Raúl A. Sánchez-Moreno M. Jesús Gismera M. Teresa Sevilla Jesús R. Procopio 《Analytical and bioanalytical chemistry》2010,397(1):331-338
A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis.
The carbon screen-printed electrode was modified with a graphite–epoxy composite. The optimal graphite–epoxy matrix contains
37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal
analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed
sensor exhibits a response time of 20 ± 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour
using 0.1 M NaNO3 solution at pH 3 as the carrier, a flow rate of 2.5 mL·min−1, and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI)
ions and optimal detection limits in both static mode (2.1 × 10−7 M) and online analysis (9.4 × 10−7 M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river
waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful
results in leachates from municipal solid waste landfills. 相似文献
6.
Roozbeh Javad Kalbasi Majid Kolahdoozan Sedigheh Mozafari Vanani 《Journal of solid state chemistry》2011,184(8):2009-2016
In this work, Al2O3 was mixed with SiO2 and poly 4-vinylpyridine by the sol-gel method in order to make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation reaction. The physical and chemical properties of the composite catalyst were investigated by XRD, FT-IR, TG, BET and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compound and malononitrile. The reactions were performed in solvent-free conditions and the product was obtained in high yield and purity after a simple work-up. The effects of the amount of catalyst, amount of monomer for the synthesis of composite and recyclability of the heterogeneous composite were investigated. The composite catalyst used for this synthetically useful transformation showed considerable level of reusability besides very good activity. 相似文献
7.
J. Agrisuelas J. J. García-Jareño D. Gimenez-Romero F. Negrete F. Vicente 《Journal of Solid State Electrochemistry》2009,13(10):1599-1603
Electrochemical techniques are applied to estimate the fractal dimension value of electroactive surface structures. However,
the fractal dimension value is an abstract concept, which sometimes is hard to understand. Herein, this abstract concept is
used to calculate the fractional content of the nickel/graphite–polypropylene hybrid composite material, putting into practice
this concept in the study of composite materials. 相似文献
8.
Tanţa Spătaru Maria Marcu Loredana Preda Petre Osiceanu Jose Maria Calderon Moreno Nicolae Spătaru 《Journal of Solid State Electrochemistry》2011,15(6):1149-1157
Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell
electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine
on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward
method exhibited, for platinum loadings as low as ca. 0.12 mg cm−2, a specific electrochemically active surface area of the electrocatalyst of ca. 54 m2 g−1, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of
Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the
results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH3OH oxidation. 相似文献
9.
V. Rodríguez-González R. Gómez M. Moscosa-Santillan J. Amouroux 《Journal of Sol-Gel Science and Technology》2007,42(2):165-171
Platinum catalysts supported on indium-doped alumina were prepared by the sol–gel method. The method allows the incorporation
of In3+ in the alumina network. The indium-doped alumina supports showed narrow pore size distribution (5.4–4.0 nm) and high specific
surface areas (258–280 m2/g). The 27Al NMR-MAS spectroscopy identified aluminum in tetrahedral, pentahedral, and octahedral coordination; however, the intensity
of the signal assigned to aluminum in pentahedral coordination diminishes with the increase of the content of indium. Total
acidity determined by ammonia thermodesorption diminishes strongly in Pt/In–Al2O3 catalysts, suggesting a selective deposit of platinum over the acid sites of the support. The effect of the support in the
platinum catalytic activity was evaluated in the n-heptane dehydrocyclization reaction. The selectivity patterns for such reaction were modified substantially in the doped
Pt/In–Al2O3 catalysts, in comparison with the Pt-In/Al2O3–I coimpregnated reference catalyst. As an important result, the formation of benzene was suppressed totally over the indium-doped
alumina sol–gel supports with a high content (3 wt%) of indium. 相似文献
10.
Two types of organic–inorganic hybrid base catalysts are prepared. Organic-functionalized molecular sieves (OFMSs); in particular,
“amine-immobilized porous silicates” are designed based on common idea to immobilize catalytic active sites on silicate surface.
Silicate–organic composite materials (SOCMs), such as “ordered porous silicate–quaternary ammonium composite materials”, are
the precursors of ordered porous silicates obtained during the synthesis. Both the OFMS and the SOCM are used as the catalysts
for Knoevenagel condensation and Michael addition reactions. Among the OFMSs, there is clear tendency that the use of molecular
sieve with larger pore volume and/or surface area gives the product in higher yield. Aminopropylsilyl (AP)-tethered mesoporous
silicate such as AP-MCM-41 gives the Knoevenagel condensation product in high yield under mild conditions. No loss of activity
is observed after repeated use for three times. The SOCMs are also active for the same reaction. The OFMSs are effective when
the supports have large pore volume and/or surface area and the reaction is carried out in polar solvents ethanol and DMF.
However, the activity of the OFMSs is considerably low in a non-polar solvent such as benzene. In contrast, the SOCMs are
remarkably active in benzene. The organic cation–MCM-41 composite is more active than the composite of an organic cation and
a microporous silicate such as zeolite beta and ZSM-12. In the SOCM catalysts, (SiO)3SiO−(+NR4) moieties located at the accessible sites are considered to play some important roles. The active species are absent in the
liquid phase after the reaction. The recycle of the catalyst was possible without significant loss of activity when the substrates
are enough reactive. The mechanism of the reaction over SOCM catalyst is discussed. 相似文献
11.
Hydrogenation of crotonaldehyde in a gas phase over Pt/α-GeO2 catalysts was investigated. The systems were characterized by BET, XRD, TPR, TEM, ToF-SIMS, and FTIR methods. The optimum
pretreatment parameters were studied. The best catalytic performance shows the catalyst 5 wt % Pt/α-GeO2 (69% selectivity to crotyl alcohol at 200 μmol s−1 g
Pt
−1
activity and 10% conversion of crotonaldehyde). Lower loaded catalysts (2 and 1 wt % Pt) show lower, but also promising activity
and selectivity. This good catalytic performance was related to the physicochemical properties of the catalyst. GeO2 in the presence of Pt undergoes a partial surface reduction at temperatures higher than 100°C probably leading to the creation
of the active Pt-Ge centers responsible for high selectivity to crotyl alcohol. Reduction at a temperature≥200°C deactivates
the catalytic systems due to the formation of inactive PtGe alloys.
Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 4, pp. 600–605.
This article was submitted by the authors in English. 相似文献
12.
N. V. Bausk S. B. Érenburg N. F. Yudanov L. N. Mazalov 《Journal of Structural Chemistry》1995,36(6):932-940
Synchrotron radiation was used to measure the EXAFS and XANES polarization dependences for intercalation compounds of graphite
fluoride. An approach is developed which allows one to analyze the orientation of molecules of arbitrary shapes using XANES
and EXAFS data. Analyzing the orientation dependences of BrK XANES spectra for the T-shaped BrF3 molecules, we determined possible combinations and admissible ranges of angles between the normal to the graphite fluoride
matrix planes and the Br−F bond directions (α=52–90°, β=27–82°) and between the normal to the matrix planes and the molecular
planes (γ=27–53°). The average orientation angles obtained by the combined analysis of the EXAFS and XANES data are as follows:
α=62±1.5°, β=58±1.5°, γ=45±1.5°. The interatomic distances Br−F, Br−Br, and Fe−Br are determined. It is established that thermal
treatment, which recovers the X-ray diffraction pattern from the unfilled matrix, does not affect the predominant orientation
of the BrF3 molecules. This suggests that the thermally treated graphite fluoride matrix contains thin layers of ordered molecules. The
absence of the polarization dependence of the spectra of FeBr3 in graphite fluoride allows the assumption that the molecular planes are oriented with respect to the normal to the matrix
planes at a “magic” angle of 35°.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1020–1029, November–December, 1995.
Translated by I. Izvekova 相似文献
13.
Wenxuan Zhang Zhanpeng Liu Chengjian Xu Wenzhi He Guangming Li Juwen Huang Haochen Zhu 《Research on Chemical Intermediates》2018,44(9):5075-5089
The wide use of lithium ion batteries (LIBs) has created much waste, which has become a global issue. It is vital to recycle waste LIBs considering their environmental risks and resource characteristics. Anode graphite from spent LIBs still possess a complete layer structure and contain some oxygen-containing groups between layers, which can be reused to prepare high value-added products. Given the intrinsic defect structure of anode graphite, copper foils in LIB anode electrodes, and excellent properties of graphene, graphene oxide–copper composite material was prepared in this work. Anode graphite was firstly purified to remove organic impurities by calcination and remove lithium. Purified graphite was used to prepare graphene oxide–copper composite material after oxidation to graphite oxide, ultrasonic exfoliation to graphene oxide (GO), and Cu2+ adsorption. Compared with natural graphite, preparing graphite oxide using anode graphite consumed 40% less concentrated H2SO4 and 28.6% less KMnO4. Cu2+ was well adsorbed by 1.0 mg L?1 stable GO suspension at pH 5.3 for 120 min. Graphene oxide–copper composite material could be successfully obtained after 6 h absorption, 3 h bonding between GO and Cu2+ with 3/100 of GO/CuSO4 mass ratio. Compared to CuO, graphene oxide–copper composite material had better catalytic photodegradation performance on methylene blue, and the electric field further improved the photodegradation efficiency of the composite material. 相似文献
14.
Ibrahim M. EI-Mehasseb Abd El-Motaleb M. Ramadan Raafat M. Issa 《Transition Metal Chemistry》2006,31(6):730-739
The oxidation of catechol by molecular oxygen in the presence of a catalytic amount of copper(II) complex with 2-methyl-3-amino-(3H)quinazoline-4-one (MAQ) and various anions (Cl−, Br−, ClO
4
−
, SCN−, NO
3
−
and SO
4
–
) was studied. The catecholase biomimetic catalytic activity of the copper(II) complexes has been determined spectrophotometrically
by monitoring the oxidative transformation of catechol to the corresponding light absorbing o-quinone (Q). The rate of the catalytic oxidation reaction was investigated and correlated with the catalyst structure, time,
concentration of catalyst and substrate and finally solvent effects. Addition of pyridine or Et3N showed a dramatic effect on the rate of oxidation reaction. Kinetic investigations demonstrate that the rate of oxidation
reaction has a first order dependence with respect to the catalyst and catechol concentration and obeying Michaelis–Menten
Kinetics. It was shown that the catalytic activity depends on the coordination environment of the catalyst created by the
nature of counter anions bound to copper(II) ion in the complex molecule and follows the order: Cl− > NO
3
−
> Br− > SO
4
–
> SCN− > ClO
4
−
. To further elucidate the catalytic activity of the complexes, their electrochemical properties were investigated and the
catecholase mimetic activity has been correlated with the redox potential of the Cu2+/Cu+ couple in the complexes. 相似文献
15.
Mingshi Jin Jung-Nam Park Jeong Kuk Shon Zhenghua Li Min Young Yoon Hyun Jung Na Young-Kwon Park Ji Man Kim 《Research on Chemical Intermediates》2011,37(9):1181-1192
Highly ordered mesoporous cerium dioxide (meso-CeO2) was successfully synthesized using a facile solvent-free infiltration method from a mesoporous silica template, KIT-6. The
meso-CeO2 material, thus obtained, exhibited well-defined mesostructure and high surface area (153 m2 g−1). The physicochemical properties of meso-CeO2 material and Pd-supported on meso-CeO2 (Pd/meso-CeO2) were characterized by electron microscopy, X-ray diffraction, N2 adsorption–desorption, and temperature-programmed experiments. The Pd/meso-CeO2 catalyst exhibited excellent catalytic activity for CO oxidation compared with those of other Pd/CeO2 catalysts which were prepared using nanocrystalline CeO2 and bulk-CeO2 as the supports. Moreover, a hydrogen pretreatment of the Pd/meso-CeO2 catalyst resulted in a remarkable increase of catalytic activity (T
100 = 52 °C). 相似文献
16.
Preparation and properties of a new composite photocatalyst based on nanosized titanium dioxide 总被引:1,自引:0,他引:1
The use of photocatalysts supported on adsorbents is receiving substantial attention. Supporting TiO2 with zeolites is found to be one of the best solutions to increase the efficiency of TiO2-based photocatalysts. This work was focused on simple preparation of a TiO2/Na-ZSM-5 composite catalyst by the solid state dispersion (SSD) method and its modification with an organic photosensitizer
— polythiophene (PT). Using the XRD diffractometry, structure of the new composite catalyst was proved. Beside this composite
catalyst, mechanical mixtures of TiO2-based catalysts with Na-ZSM-5 zeolite were prepared. The efficiency of all five available photocatalysts (TiO2, TiO2-PT, mechanical mixture of TiO2 + Na-ZSM-5, mechanical mixture of TiO2-PT + Na-ZSM-5, and the modified SSD-PT composite) on photodegradation of 4-chlorophenol was compared. By measuring the formation
of chloride ions and decreasing the 4-chlorophenol concentration at two different initial concentrations of 4-chlorophenol
in the basic aqueous solution, the photoefficiency and adsorption properties of our photocatalysts were determined.
Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May
2008. 相似文献
17.
Various Pt catalysts (Pt/ZrO2, Pt/CeO2, Pt/CeZrO, Pt/WO3/ZrO2 and Pt/WO3/CeZrO) were prepared and characterized, and their catalytic reduction reactions of NO by CO, with or without the presence
of excess oxygen, were investigated. The results of temperature-programmed experiments showed that CO could be easily oxidized
over Pt/CeO2 and Pt/CeZrO while the introduction of WO3 into the catalyst (Pt/WO3/CeZrO) inhibited the reduction of catalyst surface; NO could not dissociate over those catalysts in oxidized state but after
CO reduction at a low temperature, NO dissociation took place only over Pt/CeO2 and Pt/CeZrO catalysts. For NO + CO reaction, those easily reduced catalysts Pt/CeO2 and Pt/CeZrO exhibited better catalytic performances, and NO could be rapidly converted below 350 °C. For the reaction with
the presence of excess O2, the NO conversions were significantly inhibited, but better NO conversions were obtained over the tungstate-contained catalysts
when compared with Pt/CeO2 and Pt/CeZrO. The higher activities of Pt/W–Ce–Zr catalysts were attributed to their high acidities. 相似文献
18.
Vesela Rashkova Snejana Kitova Todor Vitanov 《Journal of Solid State Electrochemistry》2010,14(6):1073-1078
The influence of nickel addition in Co–Te–O catalytic films, obtained by vacuum co-evaporation of Co, Ni, and TeO2 on electrocatalytic activity toward oxygen reactions in alkaline media has been investigated. Bifunctional gas-diffusion
oxygen electrodes were prepared by direct deposition of catalyst films on gas-diffusion membranes consisting of hydrophobized
carbon blacks. The method used allows the deposition of nanostructured films consisting of intertwined nanowires with high
surface area. Thus, obtained electrodes with different atomic ratio R
(Co+Ni)/Te of the catalyst, fresh and thermally treated at 100 °C temperatures were electrochemically tested by means of cyclic voltammetry
and steady-state voltammetry. It has been shown that the partial replacement of Co with about 30 at.% Ni leads to the increase
in the film catalytic activity toward oxygen evolution reaction. 相似文献
19.
Liming He Xiaochun Chen Jingsheng Ma Hailong He Wei Wang 《Journal of Sol-Gel Science and Technology》2010,55(3):285-292
A series of Cu/SiO2 catalysts with copper loadings ranging from 17.8 to 42.2 wt% were prepared by the sol–gel method and evaluated for the hydrogenolysis
of diethyl oxalate to ethylene glycol. The physicochemical properties of these catalysts were systematically characterized
by means of different techniques. It is found that copper loadings have great influence on the catalytic performance; the
catalyst with a copper loading of 37.8 wt% exhibited the best activity and ethyl glycol selectivity. The sol–gel derived catalyst
was superior in catalytic performance to the catalyst prepared by the deposition precipitation method, a result due to the
presence of finely dispersed copper phyllosilicate. 相似文献
20.
Electroless and electroplated nickel electrodes are extensively used for hydrogen evolution reaction (HER). In the present
work, TiO2-supported IrO2 mixed oxide composite was prepared and used to reinforce Ni–P electroless plates to be used as catalytic electrodes for HER.
The electrodes exhibited high electrocatalytic activity when the electrodes were used for HER. All the parameters including
particle size of the catalyst, surface roughness, and surface active sites were studied. The particle size of the IrO2 catalyst in the mixed oxide was found to have high influence on the catalytic activity of the electrodes. Low overpotential
as low as 70 mV at a current density of 200 mA cm−2 was achieved with the mixed oxide-reinforced Ni–P electrodes. 相似文献