共查询到20条相似文献,搜索用时 15 毫秒
1.
Aitor Gual Jorge A. Delgado Cyril Godard Sergio Castillón Daniel Curulla-Ferré Carmen Claver 《Topics in Catalysis》2013,56(13-14):1208-1219
Small water soluble Ru-nanoparticles (ca. 2–5 nm) stabilized by lignins were synthesized by reduction of RuCl3 using H2. For comparison purposes, small Ru-NPs (ca. 2.0 nm) with narrow size distribution were also synthesized using polyvinylpyrrolidone (PVP) as stabilizer and H2 and NaBH4 as reducing agents. All these Ru-NPs were active catalysts in Fischer–Tropsch reaction. Interestingly, CO2 was detected as by-product demonstrating that the water gas shift reaction is taking place under these conditions. The Ru-NPs stabilized by lignins were less active (up to 0.49 molCO mol Ru ?1 h?1) that those stabilized by PVP (up to 3.35 molCO mol Ru ?1 h?1), exhibiting also higher CO2 production. Several reaction parameters were optimized such as the stirring rate, reducing method, polymer/Ru ratio and size of the Ru-NPs. 相似文献
2.
Johannes Z. Mbese 《Journal of Sulfur Chemistry》2017,38(2):173-187
Tris(N-phenyldithiocarbamato) ruthenium(III) complexes, [Ru(L1)3] (1); tris(N-(4-methylphenyl)dithiocarbamato)) ruthenium(III), [Ru(L2)3] (2); and tris(N-(4-methoxyphenyl)dithiocarbamato)) ruthenium(III), [Ru(L3)3] (3) were synthesized and characterized by elemental analysis, thermogravimetric analysis, FTIR, UV–VIS and NMR spectroscopy. TGA analyses show major degradation of all complexes in the range 120–350°C, leading to the formation of residual weight corresponding to ruthenium (III) sulfides. The 1H-NMR spectra of the ligands and complexes are in agreement with the proposed structures. FTIR studies confirmed that the ligands coordinate the Ru3+ ion in a bidentate chelating mode. The complexes were thermolysed at 180°C to prepare hexadecylamine-capped Ru2S3 nanoparticles. Powder X-ray diffraction patterns revealed the formation of hexagonal-phase Ru2S3 nanoparticles with average crystallite sizes ranging from 8.3 to 9.5?nm. TEM images showed the crystalline clusters with shapes ranging from square to hexagonal, while SEM images elucidated that the particles were agglomerated. Energy-dispersive X-ray spectra confirmed the presents of Ru2S3 nanoparticles. 相似文献
3.
Xiaojun Luo Rong Wang Jun Ni Jianxin Lin Bingyu Lin Xianming Xu Kemei Wei 《Catalysis Letters》2009,133(3-4):382-387
A series of CeO2-La2O3 supported ruthenium catalysts were prepared by co-precipitation method and the as-obtained samples were characterized by N2 physisorption, X-ray diffraction, CO chemisorption, H2-TPR, H2-TPD and XPS. The activity test shows that ammonia concentration of the catalyst with 10% La is 13.9% at 10 MPa, 10,000 h?1, 450 °C, which is 17% higher than that of Ru/CeO2. La doping can improve the activity of Ru-ceria catalyst for ammonia synthesis by facilitating the reduction of oxygen which subsists in the cerium oxide surface. In addition, it can be realized that the test of catalyst stability proves the stability performance of Ru/CeO2-La2O3 catalyst within the reaction time of 55 h. 相似文献
4.
The desire to explain the origin(s) of the unexpected catalytic activity of oxide-supported Au nanoparticles for CO oxidation discovered by Haruta and coworkers has stimulated numerous experimental and theoretical studies of Au nanoclusters in the gas phase and on metal oxide supports, and on Au single-crystal surfaces. In order to explore further the reactivity of low-coordination Au step sites, we have performed transient kinetics studies of CO oxidation on an O-precovered, stepped Au(211) single crystal surface. We found behavior similar to that observed previously on flat Au(111) and (110) surfaces; i.e., there is no evidence in these transient kinetics for any special reactivity associated with this stepped Au surface. The CO oxidation reaction rate was highly dependent on the initial oxygen coverage, and we determined an apparent activation energy for CO oxidation of ?7.0 kJ mol?1 for θ O init = 0.9 ML. Within the Langmuir-Hinschelwood (LH) reaction scheme, we estimate an activation energy of E LH = 20–43 kJ mol?1 on this surface for CO oxidation via this pathway. This is somewhat below the value of 67 kJ mol?1 predicted by recent theoretical calculations. 相似文献
5.
Well-dispersed graphene supported Ru@Co core–shell nanoparticles were synthesized by one-step in situ co-reduction of aqueous solution of ruthenium(III) chloride hydrate, cobalt(II) chloride hexahydrate and graphite oxide (GO) with ammonia borane under ambient condition. The as-synthesized nanoparticles exert excellent catalytic activities, with the turnover frequency (TOF) value of 344 mol H2 min− 1 (mol Ru)− 1 for catalytic hydrolysis of ammonia borane, which is the second highest value ever reported. The as-synthesized catalysts exert superior catalytic activities than the monometallic (Ru/graphene), alloy (RuCo/graphene), and graphene-free Ru@Co counterparts towards the hydrolytic dehydrogenation of AB. Moreover, the catalytic hydrolysis of MeAB at room temperature was also studied. These Ru@Co NPs are a promising catalyst for amine-borane hydrolysis and for developing a highly efficient hydrogen storage system for fuel cell applications. 相似文献
6.
The decomposition of FeS2, both as a single phase and as it exists in coal, has been studied between 250 and 350 °C, in hydrogen and nitrogen atmospheres, and in the presence of a coal-derived solvent. The first-order rate constant for decomposition of FeS2 at 350 °C with H2 alone is 6.7 × 10?1min?1; with H2 and coal-derived solvent, it is 5.5 × 10?2min?1; for FeS2 contained within coal, solvent and H2, it is 8.6 × 10?3min?1. Although the rate constant for decomposition is dependent upon temperature and the system, the activation energy in each case has been calculated to be 88 kJ mol?1. A mechanism consistent with these data is the thermal decomposition of FeS2 to produce Fe1?xS and S, followed by reaction of the sulphur with available hydrogen (from H2, solvent or coal) to form H2S. 相似文献
7.
《分离科学与技术》2012,47(12):1698-1708
Hybrid organic-inorganic H2-selective membranes consisting of single-layer or dual-layers of silica incorporating aromatic groups are deposited on a porous alumina support by chemical vapor deposition (CVD) in an inert atmosphere at high temperature. The single-layer silica membranes, which are made by the simultaneous decomposition of phenyltriethoxysilane (PTES) and tetraethylorthosilicate (TEOS), have good hydrothermal stability at high temperature and a high permeance for hydrogen in the order of 10?7 mol m?2 s?1 Pa?1 at 873 K, while preventing the passage of other larger molecular gases such as CH4 and CO2. The dual-layer silica membranes, which are obtained from the sequential decomposition of PTES and TEOS, exhibit an extremely high permeance for hydrogen of 3.6 × 10?6 mol m?2 s?1 Pa?1 at 873 K with a permselectivity of hydrogen over methane of 30. A normalized Knudsen based permeance method is applied to measure the pore size of PTES-derived silica membrane on the dual-layer silica membrane before treatment with TEOS. The method indicates that the pore size of the silica network is approximately in the range of 0.50–0.85 nm, which is higher than the characteristic length of pure silica membranes of 0.3 nm, accounting for the high permeance of the hybrid membranes. 相似文献
8.
Zifeng Wang Xing Zhang Yan Sun Hui Zhang Congliang Wang Anjian Xie 《Ceramics International》2018,44(6):5848-5854
Economy and efficiency are two important indexes of lithium-ion batteries (LIBs) materials. In this work, nitrogen doped hollow porous coaxial carbon fiber/Co3O4 composite (N-PHCCF/Co3O4) is fabricated using the fibers of waste bamboo leaves as the template and carbon resource by soaking and thermal treatment, respectively. The N-PHCCF/Co3O4 exhibits an outstanding electrochemical performance as anode material for lithium ion batteries, due to the nitrogen doping, coaxial configuration and porous structure. Specifically, it delivers a high discharge reversible specific capacity of 887 mA h g?1 after 100 cycles at the current density of 100 mA g?1. Furthermore a high capability of 415 mA h g?1 even at 1 A g?1 is exhibited. Most impressively, the whole process is facile and scalable,exhibiting recycling of resource and turning waste into treasure in an eco-friendly way. 相似文献
9.
S. Parres-Esclapez F. E. López-Suárez A. Bueno-López M. J. Illán-Gómez B. Ura J. Trawczynski 《Topics in Catalysis》2009,52(13-20):1832-1836
The improving effect of Sr in the catalytic activity of Rh for N2O decomposition has been studied under 1,000 ppm N2O/He and 1,000 ppm N2O/5% O2/He (GHSV = 10,000 h?1). Different techniques have been used for catalysts characterization: TEM, SEM-EDX, XRD, N2 adsorption at ?196 °C and in situ XPS. Sr favours the Rh dispersion and reduction under reaction conditions, and allows the low temperature removal of N2O in the presence of O2 (100% decomposition at 350 °C). 相似文献
10.
Lionel Fabre Guy Flèche Patrick Fuertes Pierre Gallezot Alain Perrard 《Catalysis Letters》2000,68(1-2):41-44
Water solutions of glucono-δ-lactone and glucono-γ-lactone in equilibrium with gluconic acid were hydrogenated with molecular
hydrogen in the presence of a commercial carbon-supported ruthenium catalyst (5% Ru/C, Engelhard Escat 40). Reactions were
conducted batchwise on 20 wt% solutions under 100 bar pressure in the temperature range 80–140°C. Reaction rates were unexpectedly
high at moderate temperatures (e.g., 0.58 mol h-1 g
Ru
-1
at 100°C) because lactones were probably the reactive species. The selectivity to sorbitol at total conversion was larger
than 99% at temperatures lower than 100°C. Kinetic study was done at different temperatures, pressures and concentrations.
Modelling of the reaction kinetics showed that the reaction followed a rate law corresponding either to the Langmuir–Hinshelwood
mechanism without H2 dissociation, or to the Horiuti–Polanyi mechanism.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
The catalytic ammonia decomposition over iron and iron nitride, Fe4N, under the atmosphere of ammonia–hydrogen mixtures of different amounts of ammonia in the temperature range of 400–550 °C by means of thermogravimetry has been studied. A differential tubular reactor with mixing has been used. The ammonia concentration in the gas phase during all the process was analysed. The balance between the inlet and outlet ammonia quantity has been used to determine a degree of ammonia conversion and the values of decomposition reaction rate. The activation energy of ammonia decomposition reaction over Fe and Fe4N was found to be 68 and 143 kJ/mol, respectively. 相似文献
12.
K. Mech P. Żabiński R. Kowalik T. Tokarski K. Fitzner 《Journal of Applied Electrochemistry》2014,44(1):97-103
Investigations of the influence of electrolysis parameters such as the concentration of metal ammonia complexes, working electrode potential and temperature on the composition, structure and catalytic activity of synthesized alloys for water molecule reduction reaction in 2 M NaOH (T = 25 °C) were conducted. The alloys were deposited under potentiostatic conditions within potential range from ?0.7 to ?1.1 V in electrolytes of pH 9.5, containing ammonia complexes of cobalt(III) and palladium(II), [Co(NH3)6]3+ and [Pd(NH3)4]2+, of different concentration ratio. Structural changes in electrodeposited alloys were discussed based on results of X-ray diffraction measurements. An elemental analysis was performed using the energy-dispersive X-ray spectroscopy technique. Finally, based on results of galvanostatic measurements, the Tafel slope within the range of activation control for hydrogen evolution reaction was determined and mechanism of the process was discussed. The alloys presented low Tafel slope value, from 25.4 to 88.7 mV dec?1. The alloy of the highest activity for hydrogen evolution reaction contained 31.2 at.% of Pd. 相似文献
13.
Colloidal 5.1 wt% Ru/γ-Al2O3 catalyst was prepared by a microwave assisted, solvothermal reduction of RuCl3 in ethylene glycol in the presence of γ-Al2O3. The catalyst subjected to heat-treatment in hydrogen up to 700 °C, was characterized by BET, XRD, TEM and H2 chemisorption. As-prepared catalyst contained Ru nanoparticles with mean size of 1.5 nm and narrow size distribution uniformly distributed over the support. The nanoparticles were stable on the alumina to 500 °C, but treatment at 600–700 °C caused some sintering of Ru due to migration and coalescence of a part of smallest ruthenium nanoparticles. However, even after H2 treatment at 700 °C, large amount of Ru nanoparticles with sizes of 1–3 nm remained in the catalyst. H2 chemisorption data revealed decrease of Ru dispersion from 0.28 to 0.19 by hydrogen treatment at 700 °C and were in good correspondence with TEM results. On the contrary, mean crystallite sizes obtained from XRD were strongly overestimated. 相似文献
14.
4,4′‐Diisocyanato diphenylmethane (MDI)‐based polyurethanes melt and start to burn at 150–200 °C. Mainly H2O, CO2, CO, HCN, and N2 are formed. The new modified polyurethane shows a different pyrolysis behavior. GAP‐diol (glycidyl azide polymer), which was used as a modifying agent, is a well‐known energetic binder with a high burning velocity and a very low adiabatic flame temperature. The modified polyurethane starts to burn at approximately 190 °C because of the emitted burnable gases, but it does not melt. The PU foam shrinks slightly and a black, solid, carbon‐rich hybrid foam remains. TGA and EGA‐FTIR revealed a three‐step decomposition mechanism of pure GAP‐diol, the isocyanate‐GAP‐diol, and PU‐GAP‐diol formulations. The first decomposition step is caused by an exothermic reaction of the azido group of the GAP‐diol. This decomposition reaction is independent of the oxygen content in the atmosphere. In the range of 190–240 °C the azido group spontaneously decomposes to nitrogen and ammonia. This decomposition is assumed to take place partly via the intermediate hydrogen azide that decomposes spontaneously to nitrogen and ammonia in the range of 190–240 °C. The second decomposition step was attributed to the depolymerization of the urethane and bisubstituted urea groups. The third decomposition step in the range of 500–750 °C was attributed to the carbonization process of the polymer backbone, which yielded solid, carbon‐rich hybrid foams at 900 °C. In air, the second and the third decomposition step shifted to lower temperatures while no solid carbon hybrid foam was left. Samples of PU‐GAP‐diol, which were not heated by a temperature program but ignited by a bunsen burner, formed a similar carbon‐rich hybrid foam. It was therefore concluded that the decomposition products of the hydrogen azide, ammonia and mainly nitrogen act as an inert atmosphere. FTIR, solid‐state 13C‐NMR, XRD, and heat conductivity measurements revealed a high content of sp2‐hybridized, aromatic structures in the hybrid foam. The carbon‐rich foam shows a considerable hardness coupled with high temperature resistance and large specific surface area of 2.1 m2⋅g−1. 相似文献
15.
The supported Ru clusters with mean sizes ranging from 1.9 to 4.6 nm showed a high activity towards the NH3 decomposition reaction. The structural properties of catalysts were characterized by N2 adsorption/desorption, X-ray diffraction (XRD) and transmission electron micrograph (TEM). Steady-state reaction kinetics
revealed that the apparent activation energy increased with a decrease in Ru particle size and ranged from 79 kJ mol−1 to 122 kJ mol−1. The decomposition rate over Ru nanoparticles showed a strong dependency on mean crystallite size and the optimum appeared
at d
Ru = 2.2 nm. The dependencies of reaction rate on partial pressures of NH3 and H2 were also sensitive to the varying Ru particle size. Experimental data could be well fitted by the Temkin–Pyzhev equation,
indicating that the recombinative desorption of surface nitrogen atom acts as the rate-determining step. A compensation effect
between the pre-exponential factor (k
0) and activation energy (E
a
) was quantified. 相似文献
16.
Bimetallic Ru-Fe Nanoparticles Supported on Carbon Nanotubes for Ammonia Decomposition and Synthesis
Cai Chen Yiwen Chen Arshid M. Ali Wenjia Luo Jie Wen Lianhong Zhang Hui Zhang 《化学工程与技术》2020,43(4):719-730
Alloy catalysts can achieve superior performance to single metal while reducing the cost by fine-tuning the composition and morphology. Bimetallic Ru-Fe nanoparticles were synthesized via liquid-phase reduction method followed by impregnation with multiwall carbon nanotubes (CNTs) to prepare Ru-Fe/CNTs catalysts. The Ru3Fe/CNTs catalyst yields a superior catalytic stability for ammonia decomposition compared to the Ru/CNTs catalyst. Hence, the ammonia synthesis rate of the Ru3Fe/CNTs catalyst was significantly higher than that of Ru/CNTs catalyst. The potential of bimetallic catalysts with reasonable composition and proportion will expand the research of efficient catalysts for ammonia decomposition and synthesis. 相似文献
17.
《Applied catalysis》1981,1(5):291-302
A great part of the high catalytic activity of ruthenium in the synthesis of ammonia is not immediately evident because of the strong inhibition by hydrogen. Decreasing the hydrogen content of the reactant mixture results in a lowering of the temperature at which the reaction becomes detectable, but does not allow the attainment of high ammonia production rates due to the interference of thermodynamic constraints. This difficulty can be avoided if the catalyst is subjected to alternate feeds of nitrogen and hydrogen. A detailed study of the nitrogen adsorption process taking place during this periodic procedure, and that of the reaction of the chemisorbed layer with hydrogen, makes it possible to optimize the operation with a view to obtaining the highest production rate of ammonia. The improvement due to the cyclic procedure is higher the larger the catalyst area. With a sample of 1 m2 active area the average rate of production is eight times higher than the best steady rate of production. The factor of enhancement is of the order of 103 at 200°C, if the average rate is compared with the steady state rate corresponding to the stoichiometric mixture. A reasonable extrapolation to a catalyst which would be made of dispersed ruthenium shows that the industrial performance obtained on usual iron catalysts could be attained at 300°C and atmospheric pressure. 相似文献
18.
O. Pitkänen N. Halonen A.-R. Leino J. Mäklin Á. Dombovári J. H. Lin G. Tóth K. Kordás 《Topics in Catalysis》2013,56(9-10):522-526
Low temperature growth process of carbon nanotubes (CNTs) over bi-metallic (Co–Fe) and tri-metallic (Ni–Co–Fe) catalysts on Si/Al/Al2O3 substrates is carried out from acetylene precursor using hydrogen, ammonia or nitrogen as a carrier in a low pressure chemical vapor deposition system. Using the tri-metallic Ni–Co–Fe catalyst template, vertically aligned CNTs of ~700 nm length could be grown already at 450 °C within 10 min using ammonia as a carrier. Within the same period of time, on bi-metallic Co–Fe catalyst templates, ~250 nm long aligned nanotubes emerged already at 400 °C in nitrogen carrier. At low temperatures most of the catalyst materials were elevated from the support by the grown nanotubes indicating tip growth mechanism. The structure of catalyst layers and nanotube films was studied using scanning and transmission electron microscopy and atomic force microscopy. 相似文献
19.
Bojan Janković Željko Čupić Dušan Jovanović Miroslav Stanković 《Chemical Engineering Communications》2016,203(2):182-199
A series of silica-supported nickel catalyst precursors was synthesized with different SiO2/Ni molar ratios. Reduction of Ni catalyst precursors with different SiO2/Ni molar ratios under a hydrogen atmosphere was investigated at different heating rates. Kinetic parameters were determined using Kissinger–Akahira–Sunose isoconversional and invariant kinetic parameter methods. It was found that for all molar ratios, the apparent activation energy (Ea) is practically constant in the conversion range of 0.20 ≤ α ≤ 0.80. In the considered conversion range, following values of Ea were found: 134.5 kJ mol?1 (SiO2/Ni = 0.20), 139.6 kJ mol?1 (SiO2/Ni = 0.80), and 128.3 kJ mol?1 (SiO2/Ni = 1.15). It was established that the reduction of Ni catalyst precursors with different SiO2/Ni molar ratios is a complex process and can be described by the ?esták–Berggren autocatalytic model. It was found that the reaction is more Langmuir–Hinshelwood type, as hydrogen dissociates rapidly on surface nuclei and the dissociated hydrogen reacts with the Ni–O active system. It was concluded that the reduction process proceeds through bulk nucleation, which is a dominant mechanism, where three-dimensional growth of crystals with polyhedron-like morphology exists. It was found that the Ni/Si ratio decreases after the reduction process. This has been explained by low Ni and higher Si surface concentrations. It has been disclosed that Ni dispersion decreases. 相似文献
20.
Nanosized Na2Ti3O7, K2Ti6O13 and Cs2Ti6O13 materials were prepared and used as supports of ruthenium nanoparticles for catalytic ammonia decomposition. It is shown that these catalysts exhibit higher catalytic activity than ruthenium supported on TiO2 nanoparticles promoted with cesium. The difference is attributed to the use of nanostructured materials with incorporated alkali metals in the crystal lattice, which apparently gives a higher effect of the promoter. All samples were characterized by X-ray powder diffraction, transmission electron microscopy and N2 physisorption measurements. Furthermore, the effect of ruthenium loading on the catalytic decomposition of ammonia was investigated. 相似文献