共查询到20条相似文献,搜索用时 15 毫秒
1.
Low-temperature catalytic combustion of methanol and its decomposed derivatives over supported gold catalysts 总被引:2,自引:0,他引:2
Gold can be compared favorably with Pd and Pt in the catalytic combustion of CH3OH, HCHO and HCOOH when it is deposited on some reducible metal oxides (-Fe2O3, TiO2, etc.). While the supported gold catalysts are less active in H2 oxidation, they exhibit much higher activities in CO oxidation. For Au/TiO2, the effect of catalyst preparation was further investigated. Since the activity for CO oxidation of the gold catalysts is not depressed but enhanced by moisture, they are practically applicable to CO removal from air at room temperature. Gold supported on manganese oxide is especially effective in the selective CO removal from hydrogen, indicating its potential applicability to polymer electrolyte fuel cells using the reformed gas of methanol. 相似文献
2.
3.
4.
Zhen Yan Sivadinarayana Chinta Ahmed A. Mohamed John P. Fackler Jr. D. Wayne Goodman 《Catalysis Letters》2006,111(1-2):15-18
A series of Au/TiO2 catalysts has been prepared from precursors of various metal-organic gold complexes (Au
n
, n = 2–4) and their catalytic activity for CO oxidation studied. The Au/TiO2 catalyst synthesized from a tetranuclear gold complex shows the best performance for CO oxidation with transmission electron
microscopy of this catalyst indicating an average gold particle size of 3.1 nm. 相似文献
5.
Nanoporous gold (NPG), a novel unsupported gold catalyst prepared by dealloying, exhibits exceptional catalytic activity for CO oxidation. Systematic studies were carried out on this new catalytic system, including the active sites of catalysts, the reaction kinetics, and activity dependence as functions of space velocity and temperature. Our results show strong evidence that metallic gold atoms on NPG are the intrinsic active sites at which the reaction of CO with O2 occurs. The kinetic study found that the reaction rate of CO oxidation on unsupported NPG depends significantly on CO concentration but only slightly on O2 concentration. We suggest that CO adsorption plays a decisive role in CO oxidation on NPG as the rate-limiting step. By completely ruling out the support influence, our findings provide considerable insight into the role of gold catalysts. 相似文献
6.
7.
A number of oxide-supported gold catalysts have been prepared by deposition–precipitation, with variation of the pH over a wide range, the optimum pH for high activity being 9 for TiO2, 7.5 for Fe2O3, and 7 for SnO2 and CeO2. Whereas the activity shown by Au/TiO2 and Au/Fe2O3 decreased linearly with time, Au/CeO2 and Au/SnO2 underwent an initial major deactivation. Addition of iron in the preparation lowered the rate of deactivation when TiO2, SnO2 and CeO2 were used as supports, and imparted activity when as with Bi2O3 it was previously lacking. XPS revealed the existence of a broad multi-state iron-containing region, and TEM and STEM/EDX indicated that small gold particles (1.5–4 nm) were partly in contact with it. Improved stability is therefore due to gold particles being in contact with an iron phase such as FeO(OH); calcination removed the stabilisation. 相似文献
8.
A spatially resolved infrared (IR) imaging technique to monitor the linear adsorbed CO coverage on supported catalyst surface combining an IR bandpass filter and an IR thermography camera has been developed. Images acquired during the CO adsorption/desorption and ignition indicate that the technique provides an excellent method to image the change of surface coverage with a spatial resolution. It is expected that the combination of infrared thermography with spatially resolved imaging of surface coverage will provide a deeper insight in the dynamics of spatio-temporal patterns on heterogeneous catalysts. 相似文献
9.
Massimiliano Comotti Claudia Weidenthaler Wen-Cui Li Ferdi Schüth 《Topics in Catalysis》2007,44(1-2):275-284
Gold catalysts were prepared on different allotropic phases of TiO2 using the colloidal deposition method. The supports were chosen in order to study the influence of the support structure
on the catalytic activity of the final material. Furthermore, for the same allotropic modification of titania, materials with
a different particle size distributions have been used to study the influence of the grain size of the support on the deposition
of the colloid. Our results indicate that the activity of the final catalyst is not much affected by the variation of the
titania structure, though the situation becomes different when the catalyst is calcined at different temperatures. In this
case, pure anatase and rutile supported catalysts showed a lower thermostability than the one prepared using P25 titanium
oxide (Degussa). Concerning the colloid immobilization on the support it was found that the most important parameter is the
grain size of the support. In particular, the deposition of the colloidal gold particles is greatly enhanced in the case of
supports composed of particles of few nanometers in size. 相似文献
10.
Xiao-Ying Wang Shu-Ping Wang Shu-Rong Wang Ying-Qiang Zhao Jing Huang Shou-Min Zhang Wei-Ping Huang Shi-Hua Wu 《Catalysis Letters》2006,112(1-2):115-119
Au/CeO2 catalysts prepared by co-precipitation (CP) and deposition-precipitation (DP) methods were tested for low temperature CO
oxidation reaction. The structural characters and redox features of the catalysts were investigated by XRD, XPS and H2-TPR. Their catalytic performances for low temperature CO oxidation were studied by means of a microreactor -GC system. It
showed that the catalytic activities of Au/CeO2 catalysts greatly depended on the preparation method. The catalysts prepared by DP method exhibited a surprisingly higher
activity towards CO oxidation than that prepared by CP method. This may arise from the differences in the particle sizes of
Au and redox properties of the catalysts. The low Au loading and the resistance to high temperature of DP-prepared catalyst
made it more applicable. 相似文献
11.
埃洛石纳米管(HNTs)是一类具有独特物理结构和化学性质的天然黏土化合物,本文以经过提纯和聚二烯丙基二甲基氯化铵溶液(PDDA)改性的埃洛石为载体,将预先制备的粒径可控的金溶胶负载到改性埃洛石(PHNTs)表面得到负载型的纳米金颗粒,通过调节氯金酸前体的浓度和用量,实现了对负载型纳米金尺寸的有效调控,透射电镜表征结果显示,埃洛石负载的纳米金分散性良好,平均粒径分别处于2nm以下、2~5nm和5nm以上。以环己烷的液相选择性氧化为模型反应,评价了所制备的不同尺度负载型纳米金粒子的活性和对环己醇和环己酮的选择性。结果表明:纳米金颗粒的平均粒径处于2~5nm时,表现出最好的催化活性和选择性,在170℃和2.0MPa下反应2h,环己烷的转化率可达10.29%,环己醇和环己酮的选择性达85.75%,优于该反应体系使用的工业催化剂对活性和选择性的指标要求。此外,X射线光电子能谱仪表征结果显示,当埃洛石负载的纳米金平均粒径处于2~5nm时,金元素主要以Au0 的形式存在。 相似文献
12.
In situ X-ray diffraction experiments have been conducted during rate oscillations of catalytic CO oxidation on a supported Pt catalyst, EuroPt-1. The measurements which were carried out at atmospheric pressure with flow rates of 200 ml/min showed that the non-isothermal oscillations in the reaction rate were accompanied by periodic intensity variations of a Bragg peak. A Debye function analysis of beam profiles recorded at the two extrema of the oscillations revealed that the Pt catalyst undergoes a periodic oxidation and reduction during rate oscillations. The diffraction experiments are therefore considered to be the first experimental proof that the oxide model proposed originally by Sales, Turner and Maple to explain rate oscillations in the CO + O2 reaction at atmospheric pressure is in fact correct. 相似文献
13.
TAP (temporal analysis of products) technique was used to clarify the controversial mechanism for low-temperature CO oxidation
on supported Au catalysts involving unidentified moisture effects on the performances. The unique TAP transient technique,
along the use of a specially prepared, highly active Au/Ti(OH)
4
*
catalyst, provided the information and characterization of each elementary step involving weak and reversible CO adsorption,
strong and molecular O2 adsorption, and their surface reaction, which are suppressed by the coexistence of water vapor. 相似文献
14.
Carbon supported platinum catalysts for catalytic wet air oxidation of refractory carboxylic acids 总被引:3,自引:0,他引:3
Carbon supported platinum (1% wt) catalysts were prepared by the incipient wetness impregnation method and by organometallic chemical vapor deposition. Catalyst characterization was carried out by means of adsorption and thermogravimetric techniques, and by electron microscopy. The catalyst with higher metal dispersion was produced by incipient wetness impregnation. The catalysts were tested in the catalytic wet air oxidation (200°C and 6.9 bar of oxygen partial pressure) of aqueous solutions containing low molecular weight (C2 to C4) carboxylic acids. Significant conversions (greater than 60% over 2 h) and 100% selectivity towards water and non-carboxylic acid products were observed for both systems. The initial reaction rate was used to compare the performance of the two catalytic materials and direct correspondence to the metal dispersion was found. No metal leaching was observed during reaction and no significant deactivation occurred in three successive catalytic oxidation runs. A kinetic model based on the Langmuir–Hinshelwood formulation was applied and the results were analyzed in terms of a heterogeneously catalyzed free radical mechanism. 相似文献
15.
Mitsutaka Okumura Shyunichi Nakamura Susumu Tsubota Toshiko Nakamura Masashi Azuma Masatake Haruta 《Catalysis Letters》1998,51(1-2):53-58
In order to clarify the effect of metal oxide support on the catalytic activity of gold for CO oxidation, gold has been deposited
on SiO2 with high dispersion by chemical vapor deposition (CVD) of an organo-gold complex. Comparison of Au/SiO2 with Au/Al2O3 and Au/TiO2, which were prepared by both CVD and liquid phase methods, showed that there were no appreciable differences in their catalytic
activities as far as gold is deposited as nanoparticles with strong interaction. The perimeter interface around gold particles
in contact with the metal oxide supports appears to be essential for the genesis of high catalytic activities at low temperatures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Zhiming Liu Zhengping Hao Huiping Zhang Yahui Zhuang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(7):800-804
A series of perovskite‐type oxides and derived Ag catalysts were prepared, and characterized by N2‐adsorption, X‐ray diffraction and X‐ray photoelectron spectroscopy. The influences of pretreatment and Ag loading on catalytic activity for diesel soot oxidation were also investigated. Prereduction resulted in a decrease in catalytic activity. An increase in activity with Ag addition was observed, especially with more than 5% Ag loading. This catalyst could be a promising candidate for the catalytic elimination of diesel soot. © 2002 Society of Chemical Industry 相似文献
17.
Chaos and synchronisation in heterogeneous catalytic systems: CO oxidation over Pd zeolite catalysts 总被引:3,自引:0,他引:3
The influence of experimental parameters on the structure of global reaction rate oscillations and the coupling of local oscillators on a catalyst bed in a continuous stirred tank reactor is studied for the oxidation of CO on zeolite supported palladium catalysts. Global coupling can be achieved via mass transfer through the gas phase or via heat transfer in the case of a support of high heat conductivity. Characteristic differences in the activity of catalysts as well as in the period and the amplitude of the oscillations are related to the size of the palladium clusters and can be simulated by adding the state of the oxidation of the metal surface as a parameter to a common kinetic model. The analysis of observed chaotic behaviour leads to the conclusion that diffusional chaos characteristic of a distributed system is observed on the level of the zeolite crystallite that supports the palladium clusters. 相似文献
18.
Y. Hasegawa K. Fukumoto T. Ishima H. Yamamoto M. Sano T. Miyake 《Applied catalysis. B, Environmental》2009,89(3-4):420-424
Copper-containing mesoporous manganese oxides were prepared by the sol–gel method. The samples obtained were characterized by XRD, N2 adsorption–desorption, ICP, CO-TPD, redox measurement and XPS. After calcination at 300 °C, amorphous structure was shown by XRD for all the samples. All the samples had mesopores of about 6 nm and high surface areas of 170–230 m2 g−1. Using these samples as catalysts, CO oxidation was carried out as a model reaction. Copper-containing mesoporous manganese oxide prepared by the sol–gel method showed a very high activity. On the other hand, copper-supported manganese oxide prepared by the impregnation method using copper sulfate showed a low activity. Differences in activities were correlated with the mobility of lattice oxygen. 相似文献
19.
The kinetics of the glycerol oxidation using a carbon supported gold catalyst was studied experimentally in a batch reactor
at oxygen pressures up to 10 bar and at temperatures from 25 to 100 °C. The influence of the mass transfer on the reaction
was estimated and confirmed with theoretical calculations. A kinetic model has been proposed on the basis of a Langmuir-Hinshelwood
mechanism for the experiments carried out in the kinetic regime and the kinetic parameters (reaction rate and adsorption constants
as well as activation energies) were calculated. 相似文献
20.
活性炭负载催化剂臭氧催化氧化处理印染废水研究 总被引:8,自引:2,他引:8
以堇青石蜂窝陶瓷、硅藻土、活性氧化铝和活性炭作为载体、金属氧化物(FexOy、CuO、NiO、MnxOy、BaO)作为催化活性组分,对臭氧催化氧化印染废水进行了试验对比,并对影响载铁型活性炭催化剂臭氧催化氧化印染废水的因素进行了研究。结果表明,载铁型的催化剂活性相对较高,当焙烧温度为750℃时,催化性能最好。利用载铁型活性炭催化剂,在臭氧质量浓度为10mg/L、pH值为6、反应时间为60min的条件下,催化氧化具有最佳的效果,COD去除率达86%;催化剂的重复利用性好,连续使用12次,COD的去除率仍可达64%。 相似文献