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1.
V. V. Lesnyak V. K. Yatsimirskii O. Yu. Boldyreva T. D. Kinder 《Theoretical and Experimental Chemistry》2008,44(3):189-194
The catalytic activity in the oxidation of hydrogen (in the gaseous state in the presence of excess oxygen) has been studied
for samples of Pt(Pd)/Ta2O5−x, formed by reduction with hydrogen. The samples obtained had greater activity than the traditional catalysts Pt(Pd)/Al2O3. According to X-ray diffraction analysis and electron microscopic studies, Ta2O5−x becomes amorphous with the formation of more reduced non-stoichiometric oxygen-deficient tantalum oxides with a surface layer
of catalyst.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 180–185, May–June, 2008. 相似文献
2.
V. V. Lesnyak V. K. Yatsimirskii I. N. Gut O. Yu. Boldyreva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(9):1456-1459
The influence of hydrogen-containing molybdenum and tungsten bronzes on the catalytic activity of palladium composite catalysts for the oxidation of H2, CO, and CH4 was studied. It was found that the composite catalysts containing H x MO3 phases (M = W or Mo), which were formed by the reduction of MoO3 and WO3 oxides with hydrogen in the presence of deposited Pd, showed higher catalytic activity in the oxidation of small molecules (H2, CO, and CH4) with excess oxygen than the traditional Pd/Al2O3 deposited catalyst with the same content of the deposited metal. It was shown that the thermal stability of the H x MO3 phases was the limiting factor influencing the activity of these composite catalysts. 相似文献
3.
V. V. Lesnyak V. K. Yatsimirskii T. D. Kinder O. Yu. Boldyreva 《Theoretical and Experimental Chemistry》2009,45(5):331-337
Catalysts prepared by the hydrogen reduction of Nb2O5 in the presence of Pt or Pd have specific surface much greater than for the starting oxide and their catalytic activity in
the oxidation of hydrogen is much greater than the activity of Pt/Al2O3 or Pd/Al2O3. X-ray phase analysis and X-ray photoelectron spectroscopy were used to establish the existence of Nb2O5–x
nonstoichiometric oxides in the catalyst, which enhances the catalytic activity of the surface. The kinetic behavior of the
oxidation of hydrogen on these catalysts is explained in the framework of the Eley–Riedel mechanism. 相似文献
4.
Yeon-Su Kim Sun Ju Lim Young Hun Kim Jin Ha Lee Ho-In Lee 《Research on Chemical Intermediates》2012,38(3-5):947-955
Supported Pt and Pd are most commonly used for oxidation catalysts. They have similar and different characteristics for deactivation factors. The catalytic activity of Pt and Pd catalysts supported on ??-Al2O3 was studied in the presence and absence of H2O and SO2 during CO oxidation under simulated conditions of diesel exhaust gas. Without the addition of H2O and SO2 to the feed gas, Pd/Al2O3 had a superior catalytic activity compared to Pt/Al2O3. The addition of H2O to the feed gas strongly and negligibly affected the activity of Pd and Pt, respectively, while the addition of SO2 to the feed gas had a strong poisoning effect on the catalytic activity of both Pt and Pd catalysts. Although being the most active, Pd catalysts exhibited a strong sensitivity to water and sulfur-containing compounds. Fe was added to the Pt and Pd catalysts to introduce sulfur resistance. The addition of Fe enhanced the activity of the catalysts by suppressing the phase transition of Al2O3 to Al2(SO4)3 and by hindering metal sintering. 相似文献
5.
Platinum electrocatalysts for fuel cells based on individual oxides Pt/SnO2 and Pt/TiO2 and their solid solutions Pt/Ti1−x
M
x
O2 (M = Ru, Nb) and Pt/Sn1−x
M′
x
O2−δ(M′ = Sb, Ru) were prepared. The influence of the composition of the oxide supports on the activity of the supported platinum
catalysts in electrooxidation of methanol and hydrogen in the presence of CO was studied. The prepared platinum catalysts
supported on solid solutions of tin dioxide Sn1−x
M
x
O2−δ(M = Sb, Ru; x = 0.4−0.9) and Ti1−x
M
x
O2 (M = Ru, Nb; x = 0.7) exhibited higher tolerance to CO poisoning and higher activities for methanol electrooxidation than commercial Pt,Ru
catalysts on carbon support. The use of the proposed oxide supported catalysts in hydrogen and direct methanol fuel cells
improved their performances in comparison with that for the fuel cells with traditional Pt,Ru catalysts on carbon support. 相似文献
6.
CeO2 promoted palladium catalysts supported on Al2O3 were prepared using the impregnation (IM) and the deposition-precipitation (DP) methods. The activities and sulfur tolerance
of the catalysts for hydrodesulfurization (HDS) were detected with thiophene HDS as probe reaction. H2 adsorption, XRD, FTIR, NH3-TPD, XPS were used to characterize the catalysts. The Pd-CeO2/Al2O3 (IM) catalyst was highly active for the HDS reaction, and it had much stronger sulfur tolerance than the Pd/Al2O3 catalyst. Pd-CeO2/Al2O3 (DP) showed excellent sulfur tolerance while its initial activity decreased. It was observed that with the chlorine bridge,
the interfacial structure of Pd-Cl−1-Ce3+ was responsible for the high activity of the Pd-CeO2/Al2O3 (IM) catalyst, at the same time the interaction of Pd with Ce was weakened by Cl−1 ions. The enhanced sulfur tolerance over the Pd-CeO2/Al2O3 (IM) catalyst was attributed to the weakened Pd-S bond caused by the competitive adsorption of H2S on Ce3+ ions. As to the Pd-CeO2/Al2O3 (DP) catalyst, a strong interaction of Pd with Ce put Pd at an electron-deficient state, the creation of sulfided palladium
was therefore inhibited. 相似文献
7.
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
8.
V. K. Yatsimirskii N. A. Boldyreva E. V. Ishchenko A. I. Senkevich G. G. Tsapyuk 《Theoretical and Experimental Chemistry》1998,34(2):108-110
We have studied the catalytic activity of TiN0.65, TiO2, Al2O3, and palladium catalysts supported on them in the oxidation of carbon monoxide. The order in which the activities of the
supported catalysts vary, Pd/Al2O3>Pd/TiO2>Pd/TiN0.65, is the reverse of the activity series for the supports. This is explained by the effect of transfer of electron density
from the palladium to the substrate.
Taras Shevchenko Kiev University, 64 Vladimirskaya ul., Kiev 252033, Ukraine, G. V. Kurdyumov Institute of the Physics of
Metals, National Academy of Sciences of Ukraine, 36 Akademika Vernadskogo bul’var, Kiev-142 252642, Ukraine. Translated from
Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 118–121, March–April, 1998. 相似文献
9.
Xiaohuin Liu Yong Guo Wenjie Xu Yanqin Wang Xueqing Gong Yanglong Guo Yun Guo Guanzhong Lu 《Kinetics and Catalysis》2011,52(6):817-822
The influence of the alumina support on the catalytic activity of Pt/Al2O3 catalysts in aqueous phase reforming of ethylene glycol to hydrogen was studied. The catalysts were prepared by impregnation
of γ-, δ-, and α-alumina with H2PtCl6. The highest rate of hydrogen production (452 μmol min−1 g−1) obtained with the Pt/α-Al2O3 catalyst can be related to the highest extent of dispersion of Pt on α-Al2O3. XPS, TEM-EDX and TPR-H2 measurements showed the absence of chloride-containing surface complexes in the Pt/α-Al2O3 catalyst. However, chloride-containing entities were found on the surface of Pt/γ-Al2O3 and Pr/δ-Al2O3 catalysts. When chloride ions are removed chlorinated Pt species facilitate the sintering of Pt crystallites and in this
way affect the extent of Pt dispersion. Moreover, depending upon the particular crystalline form, alumina atoms have different
coordination and alumina surfaces contain varying amounts of OH groups of different nature which affect the interaction between
Pt and the support. 相似文献
10.
Huimei Duan Rui You Shutao Xu Zhaorui Li Kun Qian Tian Cao Weixin Huang Xinhe Bao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12171-12176
Supported Pd catalysts are active in catalyzing the highly exothermic methane combustion reaction but tend to be deactivated owing to local hyperthermal environments. Herein we report an effective approach to stabilize Pd/SiO2 catalysts with porous Al2O3 overlayers coated by atomic layer deposition (ALD). 27Al magic angle spinning NMR analysis showed that Al2O3 overlayers on Pd particles coated by the ALD method are rich in pentacoordinated Al3+ sites capable of strongly interacting with adjacent surface PdOx phases on supported Pd particles. Consequently, Al2O3‐decorated Pd/SiO2 catalysts exhibit active and stable PdOx and Pd–PdOx structures to efficiently catalyze methane combustion between 200 and 850 °C. These results reveal the unique structural characteristics of Al2O3 overlayers on metal surfaces coated by the ALD method and provide a practical strategy to explore stable and efficient supported Pd catalysts for methane combustion. 相似文献
11.
The catalytic properties of supported mono- and bimetallic catalysts of the Tc/support, M/support, and M-Tc/support types
(M=Pt, Pd, Rh, Ru, Ni, Re, Co; supports are γ-Al2O3, MgO, SiO2) were investigated in the acetone hydrogenation. The main products of this reaction are isopropyl alcohol and propane. The
catalytic activity in the acetone hydrogenation of the metals studied decreases in the consequence Pt>Tc≈Rh>Pd>Ru >Ni≈Re>Co
(with γ-Al2O3 as the support). The influence of support nature on the catalytic activity was investigated for the Rh−Tc system as an example.
A nonadditive increase in the catalytic activity of Rh−Tc/γ-Al2O3 in comparison with monometallic catalysts was found. The state of the surface of the catalysts was characterized by the UV-VIS
diffuse reflectance spectra.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 414–417, March, 1998. 相似文献
12.
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
13.
Xu-hua Zou Feng Li Shi-xue Qib Li-dun An Xue Duan 《Reaction Kinetics and Catalysis Letters》2006,88(1):97-103
Summary A new facile single-step synthetic route is reported for the preparation of Au/MOx/Al2O3 catalysts. The preparation method has the merit of facility but leads to not only the simultaneous load of both gold source
and MOx precursor on Al2O3 support, but also the formation of Au/MOx/Al2O3 with high gold loading ratio, high dispersion and high activity for CO oxidation. 相似文献
14.
N. I. Sorokin 《Russian Journal of Electrochemistry》2009,45(8):946-948
The ionic conductivity of Na,Zr and Na,Sn silicates of the lovozerite family (Na8 − x
H
x
ZrSi6O18 structural type, space group R
$
\bar 3
$
\bar 3
m) was studied in the temperature range of 293–800 K using the impedance spectroscopy method (5−5 × 105 Hz). The compositions of the studied compounds were obtained using the method of hydrothermal synthesis in the MO2-SiO2-NaOH-H2O and MO2-SiO2-CaO-NaOH-H2O (M = Zr, Sn) systems at 573–823 K. The samples for electrophysical studies were prepared according to the ceramic technology.
It was found that isovalent cation substitutions of Sn4+ → Zr4+ in Na8M4+Si6O18 and Na6CaM4+Si6O18 and H+ → Na+ in Na8 − x
H
x
ZrSi6O18 result in an increase in the ionic conductivity by 2–3 orders of magnitude, without affecting the ionic transport activation
energy (0.6–0.7 eV). The best electrolytic characteristics are typical for the Na5H3ZrSi6O18 compound, for which the ionic conductivity value is 5 × 10−4 S/cm at 573 K. 相似文献
15.
A. M. Gololobov I. E. Bekk G. O. Bragina V. I. Zaikovskii A. B. Ayupov N. S. Telegina V. I. Bukhtiyarov A. Yu. Stakheev 《Kinetics and Catalysis》2009,50(6):830-836
The specific activity of 0.8% Pt/Al2O3 catalysts in the deep oxidation of C1–C6
n-alkanes increases with an increase in the Pt particle size from 1 to 3–4 nm. Further coarsening of the particles insignificantly
changes the specific activity. The size effect was studied for a series of catalysts containing platinum nanoparticles 1 to
11 nm in diameter. The specific catalytic activity variation range depends on the size of the reacting hydrocarbon molecules.
As the platinum particle size increases, the specific catalytic activity increases 3–4 times for the oxidation of CH4 and C2H6 and by a factor of 20–30 for the oxidation of n-C4H10 and n-C6H14. 相似文献
16.
Au–Pd catalysts supported on SBA-16, SBA-16-CeO2, and CeO2 had been studied for partial oxidation of methanol to produce H2. The physicochemical characteristics of the catalysts prepared by deposition–precipitation using urea hydrolysis were examined
by inductively coupled plasma atomic emission spectroscopy (ICP-AES), Brunauer-Emmett-Teller (BET), X-ray powder diffraction
(XRD), Temperature-programmed reduction (TPR), and H2 temperature-programmed desorption (H2-TPD) analyses. The results show that AuxPdy alloys are observed in Au–Pd/SBA-16 and Au–Pd/SBA-16-CeO2 catalysts. The catalytic results demonstrate that both Au–Pd/SBA-16 and Au–Pd/SBA-16-CeO2 catalysts exhibit higher activity and lower CO selectivity than the Au–Pd/CeO2 catalyst. This could be ascribed to the formation of AuxPdy alloys. The comparison of the Au–Pd/SBA-16 and Au–Pd/SBA-16-CeO2 catalysts reveals that the Au–Pd/SBA-16-CeO2 shows the lower CO selectivity, probably due to the presence of CeO2. 相似文献
17.
We have been exploring the utilization of supported ceria and ceria–zirconia nano-oxides for different catalytic applications.
In this comprehensive investigation, a series of Ce
x
Zr1−x
O2/Al2O3, Ce
x
Zr1−x
O2/SiO2 and Ce
x
Zr1−x
O2/TiO2 composite oxide catalysts were synthesized and subjected to thermal treatments from 773 to 1073 K to examine the influence
of support on thermal stability, textural properties and catalytic activity of the ceria–zirconia solid solutions. The physicochemical
characterization studies were performed using X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron spectroscopy
(XPS), and high-resolution transmission electron microscopy (HREM), thermogravimetry and BET surface area methods. To evaluate
the catalytic properties, oxygen storage/release capacity (OSC) and CO oxidation activity measurements were carried out. The
XRD analyses revealed the formation of Ce0.75Zr0.25O2, Ce0.6Zr0.4O2, Ce0.16Zr0.84O2 and Ce0.5Zr0.5O2 phases depending on the nature of support and calcination temperature employed. Raman spectroscopy measurements in corroboration
with XRD results suggested enrichment of zirconium in the Ce
x
Zr1−x
O2 solid solutions with increasing calcination temperature thereby resulting in the formation of oxygen vacancies, lattice defects
and oxygen ion displacement from the ideal cubic lattice positions. The HREM results indicated a well-dispersed cubic Ce
x
Zr1−x
O2 phase of the size around 5 nm over all supports at 773 K and there was no appreciable increase in the size after treatment
at 1073 K. The XPS studies revealed the presence of cerium in both Ce4+ and Ce3+ oxidation states in different proportions depending on the nature of support and the treatment temperature applied. All characterization
techniques indicated absence of pure ZrO2 and crystalline inactive phases between Ce–Al, Ce–Si and Ce–Ti oxides. Among the three supports employed, silica was found
to stabilize more effectively the nanosized Ce
x
Zr1−x
O2 oxides by retarding the sintering phenomenon during high temperature treatments, followed by alumina and titania. Interestingly,
the alumina supported samples exhibited highest OSC and CO oxidation activity followed by titania and silica. Details of these
findings are consolidated in this review. 相似文献
18.
V. K. Yatsimirskii V. V. Lesnyak I. N. Gut O. Yu. Boldyreva 《Theoretical and Experimental Chemistry》2005,41(5):329-333
We have shown that WO3 and MoO3 with Pt or Pd additives exhibit high catalytic activity in the reaction of H2 oxidation. In the temperature range 313 K to 353 K, we have studied the kinetic behavior of the reaction on 0.1 mass % Pt(Pd)/WO3 and Pt(Pd)/MoO3 samples. We have established that the kinetics of H2 oxidation on these catalysts correspond to an Eley - Rideal mechanism.
__________
Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 313–316, September–October, 2005. 相似文献
19.
A. K. Khudorozhkov A. V. Bukhtiyarov E. Yu. Gerasimov I. P. Prosvirin V. I. Bukhtiyarov 《Russian Chemical Bulletin》2015,64(12):2802-2805
Alumina-supported bimetallic Pt—Pd catalysts proved to be more active in the complete oxidation of methane than monometallic systems (Pt/Al2O3, Pd/Al2O3). The maximum activity of the bimetallic catalysts was achieved at ~40 at.% Pt in Pd on the catalyst surface. After the oxidation reaction, redistribution of platinum and palladium was observed in the active component of the catalysts with the degree of redistribution depending on the initial Pt: Pd ratio. 相似文献
20.
Phenylacetylene hydrogenation on Pd, Pt and Pd–Pt/Al2O3 catalysts has been studied. In all catalysts activity was found not to depend on particle size. However, selectivity to styrene was found to depend on Pd/Al2O3 catalysts. Carbon deposition in both metal and support explains such a behavior. Nevertheless, in small Pd particles a longer residence time of styrene may control the selectivity. 相似文献