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1.
简要分析各种储氢材料和技术的基础上,重点介绍了高比表面积活性炭的制备方法,目前最常用的活化方法是以氢氧化钾为活化剂的化学活化法;并总结了近年来前人在高比表面积活性炭储氢方面的研究结果,同时简要分析了高比表面积活性炭储氢机理方面的研究进展. 相似文献
2.
Back CK Sandí G Prakash J Hranisavljevic J 《The journal of physical chemistry. B》2006,110(33):16225-16231
The hydrogen sorption behavior of novel Pd-doped sepiolite-derived carbon nanofibers (SDCNs) was investigated. Two chemical doping methods of ethanol/toluene reduction and a polyol process were applied to control Pd(0) formation in the SDCNs at different Pd doping levels. Hydrogen storage capacity was observed to vary depending on the Pd particle size and doping amount as the Pd particle surface area and the carbon Brunauer-Emmett-Teller (BET) surface area change with them, suggesting the existence of an optimum Pd doping level at each doping method for the best hydrogen storage capacity. Among the samples prepared using the polyol method at different Pd amounts, the maximum hydrogen uptake of about 0.41 wt % was obtained at 298 K and 90 bar for the 5 wt % Pd-doped SDCN that has a relatively high Pd particle surface area and carbon BET surface area. Samples prepared using the ethanol/toluene reduction method exhibited a higher hydrogen uptake of about 0.59 wt % at lower Pd doping levels (3 wt % Pd) due to a smaller Pd particle size and relatively high carbon BET surface area. The hydrogen desorption behavior investigated by differential scanning calorimeter exhibited that a higher amount of hydrogen desorbed at around 860 K from the Pd-doped SDCNs compared to that from the undoped SDCN. Fourier transform infrared (FTIR) spectroscopic analysis suggested that some of the weak chemisorbed hydrogen changes to a normal covalent bond during the heating and effuses at around 860 K. 相似文献
3.
Hashizume T. Terayama K. Shimazaki T. Itoh H. Okuno Y. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):1045-1050
We succeeded in studying the mechanism of hydrogen added carbothermic reduction process of iron-manganese oxide by means of
the new technique, simultaneous measurement of evolved gas analysis (EGA) and humidity sensor (HS). Water vapor evolved by
the reduction with hydrogen can be detected by HS. Other gas was detected by TCD. Without carbon, the hydrogen reduction process
was followed to the formation of the intermediate product between MnO and FeO and finally reduction to the mixture of MnO
and Fe. With carbon, the intermediate products between MnO and FeO was formed at about 780 K. The methane was formed in higher
temperature than 1073 K and the reduction with carbon proceeded mainly. At higher temperatures, methane decomposed to yield
nascent carbon that tended to result in the acceleration of the reduction rate with carbon. The study is concerned with the
mechanism of the hydrogen reduction of MnFe2O4 and the effect of without and with carbon on this reduction by means of combining EGA and HS.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
使用模型化合物在微型反应釜中研究了载体炭黑对渣油内部氢转移反应的影响。结果表明,炭黑可以明显地促进四氢萘到蒽的氢转移反应。使用等体积浸渍法制备了Fe/炭黑、Ni/炭黑催化剂并对Fe/炭黑催化剂进行了XRD、SEM表征,结果表明,金属硫化物附着在炭黑颗粒的表面,直径为1μm左右。在高压反应釜中研究了载体炭黑和以炭黑为载体的催化剂对克拉玛依常压渣油430℃加氢反应的影响,并于传统的水溶性分散型催化剂的抑焦性能进行了对比。 结果表明,Fe/炭黑、Ni/炭黑催化剂可以明显地抑制渣油加氢反应的生焦,水洗后的催化剂效果比未经水洗的催化剂抑制生焦的效果好;Ni/炭黑催化剂抑焦效果比Fe/炭黑催化剂好;Fe/炭黑催化剂比同等浓度的水溶性Fe催化剂抑焦效果好。对反应产物馏分的分析表明,Fe/炭黑催化剂可以有效地抑制渣油缩合生焦,同时在一定程度上抑制裂化反应。 相似文献
5.
A. P. Soldatov A. N. Kirichenko E. V. Tat’yanin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(7):1419-1426
A comparative analysis of hydrogen absorption capability is performed for the first time for three types of carbon nanostructures: graphenes, oriented carbon nanotubes with graphene walls (OCNTGs), and pyrocarbon nanocrystallites (PCNs) synthesized in the pores of TRUMEM ultrafiltration membranes with mean diameters (Dm) of 50 and 90 nm, using methane as the pyrolized gas. The morphology of the carbon nanostructures is studied by means of powder X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). Hydrogen adsorption is investigated via thermogravimetric analysis (TGA) in combination with mass-spectrometry. It is shown that only OCNTGs can adsorb and store hydrogen, the desorption of which under atmospheric pressure occurs at a temperature of around 175°C. Hydrogen adsorption by OCNTGs is quantitatively determined and found to be about 1.5% of their mass. Applying certain assumptions, the relationship between the mass of carbon required for the formation of single-wall OCNTGs in membrane pores and the surface area of pores is established. Numerical factor Ψ = mdep/mcalc, where mdep is the actual mass of carbon deposited upon the formation of OCNTGs and mcalc is the calculated mass of carbon necessary for the formation of OCNTGs is introduced. It is found that the dependence of specific hydrogen adsorption on the magnitude of the factor has a maximum at Ψ = 1.2, and OCNTGs can adsorb and store hydrogen in the interval 0.4 to 0.6 < Ψ < 1.5 to 1.7. Possible mechanisms of hydrogen adsorption and its relationship to the structure of carbon nanoformations are examined. 相似文献
6.
Dr. Shunsuke Kato Dr. Santhosh Kumar Matam Philipp Kerger Dr. Laetitia Bernard Dr. Corsin Battaglia Dirk Vogel Dr. Michael Rohwerder Prof. Dr. Andreas Züttel 《Angewandte Chemie (International ed. in English)》2016,55(20):6028-6032
Atomic hydrogen on the surface of a metal with high hydrogen solubility is of particular interest for the hydrogenation of carbon dioxide. In a mixture of hydrogen and carbon dioxide, methane was markedly formed on the metal hydride ZrCoHx in the course of the hydrogen desorption and not on the pristine intermetallic. The surface analysis was performed by means of time‐of‐flight secondary ion mass spectroscopy and near‐ambient pressure X‐ray photoelectron spectroscopy, for the in situ analysis. The aim was to elucidate the origin of the catalytic activity of the metal hydride. Since at the initial stage the dissociation of impinging hydrogen molecules is hindered by a high activation barrier of the oxidised surface, the atomic hydrogen flux from the metal hydride is crucial for the reduction of carbon dioxide and surface oxides at interfacial sites. 相似文献
7.
H.-P. Martin G. Irmer G. Schuster E. Müller 《Fresenius' Journal of Analytical Chemistry》1994,349(1-3):160-161
The combination of combustion analysis, IR-spectroscopy and Raman spectroscopy yields information about the chemical state of carbon in polycarbosilanes or silicon carbide. A stable polycarbosilane can be found where carbon is bonded in a network of silicon, carbon and hydrogen. In the temperature range between 700 and 800°C, the polycarbosilane is transformed into an amorphous silicon carbide with a small excess of carbon. During the crystallisation of the amorphous silicon carbide, which takes place at temperatures above 1100°C, glassy carbon is found by Raman-spectroscopy and combustion analysis. Finally after pyrolysis temperatures above 1500°C only silicon carbide exists; this may be caused by the reaction of free carbon with oxygen impurities in the samples. 相似文献
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9.
Density-functional calculations of the adsorption of molecular hydrogen on a planar graphene layer and on the external surface of a (4,4) carbon nanotube, undoped and doped with lithium, have been carried out. Hydrogen molecules are physisorbed on pure graphene and on the nanotube with binding energies about 80-90 meV/molecule. However, the binding energies increase to 160-180 meV/molecule for many adsorption configurations of the molecule near a Li atom in the doped systems. A charge-density analysis shows that the origin of the increase in binding energy is the electronic charge transfer from the Li atom to graphene and the nanotube. The results support and explain qualitatively the enhancement of the hydrogen storage capacity observed in some experiments of hydrogen adsorption on carbon nanotubes doped with alkali atoms. 相似文献
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11.
On the adsorption/oxidation of hydrogen sulfide on activated carbons at ambient temperatures 总被引:27,自引:0,他引:27
Bandosz TJ 《Journal of colloid and interface science》2002,246(1):1-20
Activated carbons of various origins (bituminous coal, wood, coconut shells, and peat) were studied as adsorbents of hydrogen sulfide. Before the experiments the surface of the adsorbents was characterized by using the sorption of nitrogen, Boehm and potentiometric titrations, thermal analysis, and FTIR. The adsorbents were chosen to differ in their surface areas, pore volumes, and surface acidities. To broaden the spectrum of surface acidity, carbons were oxidized by using nitric acid and ammonium persulfate. After hydrogen sulfide adsorption the species present on the surface were analyzed using thermal analysis, ion chromatography, and elemental analysis. The H(2)S breakthrough capacity tests showed that the performances of different carbons differ significantly. For a good performance of carbons as hydrogen sulfide adsorbents a proper combination of surface chemistry of carbon and porosity is needed. It was demonstrated that a more acidic environment promotes the formation of sulfur oxides and sulfuric acid despite yielding small H(2)S removal capacities. On the other hand, a basic environment favors the formation of elemental sulfur (sulfur radicals) and yields high capacities. The presence of a sufficient amount of water preadsorbed on the carbon surface to facilitate dissociation also plays an important role in the process of H(2)S adsorption/oxidation. The results showed that there is a critical value in carbon surface acidity, which when exceeded results in a negligible hydrogen sulfide breakthrough capacity. This is consistent with the mechanism of H(2)S adsorption on unmodified carbons, where the rate-limiting step is the reaction of adsorbed hydrogen sulfide ion with dissociatively adsorbed oxygen. When the acidity is expressed as pH, its value should be higher than 5 to ensure the effective removal of hydrogen sulfide from the gas phase. Study of carbon regeneration using water washing and heat treatment showed that the adsorbents can be regenerated to about 40% of their initial capacity. 相似文献
12.
在推导出适应于甲烷化反应体系非线性动态分析不同吸附物种动力学参数模型的基础上,采用计算优化出工业镍铝甲烷化催化剂上可逆吸附氢和可逆吸附一氧化碳的吸附速率常数和吸附平衡常数。结果表明,镍铝催化剂上吸附可逆氢要比吸附一氧化碳快2.2倍左右。该结果为镍铝催化剂上甲烷化产物的生成主要依赖于一氧化碳的吸附这一判断提供了理论依据。由于镍铝催化剂上甲烷化是可逆吸附氢与不可逆吸附一氧化碳共同作用的结果,且不可逆吸 相似文献
13.
The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated. 相似文献
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15.
由于某些有机金属化合物很不稳定,制取困难,获得量甚少,因此迫切需要建立相应的快速分析方法,并尽可能利用一份样品测出多种元素含量,以判断化合物的组成或纯度。虽然有机金属化合物(包括原子簇化合物)中碳、氢和金属的同时快速测定法已有报道,但是,某些有机钼(锌)化合物在高温燃烧氧化过程中,能生成挥发性的金属氧化物,并随着载气吹离样品舟,故不能简单地以高温氧化分解和称样品舟中残渣的方法来进行快速同时测定。本文对Gawargious等人建 相似文献
16.
S. N. Shilobreeva 《Journal of Analytical Chemistry》2017,72(14):1355-1368
Based on a review of recent domestic and international literature, examples of using secondary ion mass spectrometry (SIMS) for the determination of carbon and hydrogen in solving particular problems of geochemistry and space chemistry are presented. Special attention is paid to problems arising in calibration procedures for the quantitative determination of carbon and hydrogen by SIMS. A summary of equipment currently used for SIMS analysis is given. Mass spectral imaging method based on mathematical processing of the recorded secondary ion currents of carbon and hydrogen for visualizing 3D distributions of elements is considered in detail. 相似文献
17.
This paper concerns thermodesorption analysis of the interaction of ammonia, hydrogen, carbon dioxide and a mixture of H(2) + CO(2) with GaAs and ZnSe surfaces, to determine the strength and concentration of acid surface centres. The mechanism of interaction of the gases and surfaces has been examined. This work was aimed at differentiating between the strengths of acid centres on GaAs and ZnSe semiconductor surfaces to obtain more information about the quantity of hydrogen and carbon dioxide adsorbed, their energy characteristics, the presence or absence of dissociation, and the nature of the CO(2) hydration.(1). 相似文献
18.
Production of Hydrogen from Bio-oil Using Low-temperature Electrochemical Catalytic Reforming Approach over CoZnAl Catalyst
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High-efficient production of hydrogen from bio-oil was performed by electrochemical catalytic reforming method over the CoZnAl catalyst. The influence of current on the hydrogen yield, carbon conversion, and products distribution were investigated. Both the hydrogen yield and carbon conversion were remarkably enhanced by the current through the catalyst, reaching hydrogen yield of 70% and carbon conversion of 85% at a lower reforming temperature of 500 oC. The influence of current on the properties of the CoZnAl catalyst was also characterized by X-ray diffraction, X-ray photoelectron spectroscopy, thermal gravimetric analysis, and Brunauer-Emmett-Teller measurements. The thermal electrons would play an important role in promoting the reforming reactions of the oxygenated-organic compounds in the bio-oil. 相似文献
19.
Roussel T Pellenq RJ Bienfait M Vix-Guterl C Gadiou R Béguin F Johnson M 《Langmuir : the ACS journal of surfaces and colloids》2006,22(10):4614-4619
Two mesoporous ordered carbon materials (MOCs) have been synthesized from silica templates by using sucrose as the carbon precursor. The textural characterization using Ar, N2, and CO2 adsorption combined with neutron diffraction showed that the two samples exhibit a significant microporous volume close to 0.5 cm3/g and an ordered network of mesopores. For both MCM48 and SBA15 templated carbons, adsorption first proceeds with the filling of micropores and then by the filling of mesopores with an adsorption energy close to the enthalpy of vaporization of bulk hydrogen. The hydrogen isosteric heat of adsorption in the micropores (6-8 kJ/mol) is significantly larger than that on the graphite surface (approximately 4 kJ/mol) but still too small for a reasonable use of these MOCs as hydrogen adsorbents for storage at room temperature. The neutron scattering study showed that the structure at 10 K of the adsorbed deuterium phase is poorly organized; it exhibits short and medium range orders of about 13 angstroms in micropores and about 20 angstroms in mesopores, respectively. The average distance between adsorbed molecules decreases with coverage by about 10%. In the mesopores, the diffracted line is consistent with a pseudohexagonal packing. 相似文献
20.
煤焦表面官能团对甲烷裂解的影响 《燃料化学学报》2016,44(6):661-667
采用石英管固定床反应器,考察了1 123 K,CH_4/N_2=1∶4的状态下,煤焦表面官能团对甲烷裂解的影响。煤焦表面主要含有羟基、羰基和醚键等官能团,分别通过氢氧化钡、苯肼和碘化氢溶液对煤焦表面进行化学处理,除去煤焦表面相应的官能团,研究处理后煤焦的催化活性,得出煤焦中官能团对甲烷裂解的影响。氢氧化钡处理煤焦后,煤焦中部分羟基被氢氧化钡消耗,甲烷初始转化率和氢气初始收率分别为90.5%和65.2%,说明煤焦中的羟基不利于甲烷的裂解。通过苯肼处理煤焦中羰基并使之转化,甲烷初始转化率和氢气初始收率分别为55.4%和42.9%,说明煤焦中的羰基对甲烷裂解有利。碘化氢处理煤焦后,煤焦中的醚键转化成羟基,甲烷的转化率和氢气收率都明显下降,说明醚键的存在对甲烷裂解同样有利。随着反应时间的延长,甲烷的转化率和氢气的收率降低,催化剂逐渐失活。反应前后煤焦电镜扫描照片表明,甲烷裂解生成的积炭沉积在煤焦表面,堵塞煤焦的孔道,煤焦的比表面积减小,催化活性降低。 相似文献