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1.
Walker GS Abbas M Grant DM Udeh C 《Chemical communications (Cambridge, England)》2011,47(28):8001-8003
MgH(2) has too high an operating temperature for many hydrogen storage applications. However, MgH(2) ball-milled with Ge leads to a thermodynamic destabilisation of >50 kJ mol(-1)(H(2)). This has dramatically reduced the temperature of dehydrogenation to 130 °C, opening up the potential for Mg-based multicomponent systems as hydrogen stores for a range of applications. 相似文献
2.
A new Li-Al-N-H system for reversible hydrogen storage 总被引:2,自引:0,他引:2
Complex metal hydrides are considered as a class of candidate materials for hydrogen storage. Lithium-based complex hydrides including lithium alanates (LiAlH(4) and Li(3)AlH(6)) are among the most promising materials owing to its high hydrogen content. In the present work, we investigated dehydrogenation/rehydrogenation reactions of a combined system of Li(3)AlH(6) and LiNH(2). Thermogravimetric analysis (TGA) of Li(3)AlH(6)/3LiNH(2)/4 wt % TiCl(3)-(1)/(3)AlCl(3) mixtures indicated that a large amount of hydrogen (approximately 7.1 wt %) can be released between 150 degrees C and 300 degrees C under a heating rate of 5 degrees C/min in two dehydrogenation reaction steps. The results also show that the dehydrogenation reaction of the new material system is nearly 100% reversible under 2000 psi pressure hydrogen at 300 degrees C. Further, a short-cycle experiment has demonstrated that the new combined material system of alanates and amides can maintain its hydrogen storage capacity upon cycling of the dehydrogenation/rehydrogenation reactions. 相似文献
3.
An Li-Mg-N-H system has been synthesized from Mg(NH2)2 and LiH in the ratio 3:8 by a ball-milling process and its dehydrogenation/rehydrogenation properties at around 190°C were
investigated. XRD, FTIR and TG results showed that the system was composed of an LiH phase and an amorphous Mg(NH2)2 phase with a purity of 90%. A reversible hydrogen storage capacity of 4.7% was observed during the first cycle and more than
90% of the stored hydrogen was desorbed within 100 min for each cycle. However, only 4.2% and 2.9%, respectively, of hydrogen
was observed during two subsequent dehydrogenation cycles. In situ GC results showed that no NH3 could be observed during the dehydrogenation process. On the basis of the SEM and XRD results,
the loss in hydrogen storage capacity can be mainly attributed to agglomeration, oxidation and crystallization of the materials. 相似文献
4.
The hydrogen desorption mechanism in the reaction from LiH + LiNH2 to Li2NH + H2 was examined by thermal desorption mass spectrometry, thermogravimetric analysis, and Fourier transform IR analyses for the products replaced by LiD or LiND2 for LiH or LiNH2, respectively. The results obtained indicate that the hydrogen desorption reaction proceeds through the following two-step elementary reactions mediated by ammonia: 2LiNH2 --> Li2NH + NH3 and LiH + NH3 --> LiNH2 + H2, where hydrogen molecules are randomly formed from four equivalent hydrogen atoms in a hypothetical LiNH4 produced by the reaction between LiH and NH3 according to the laws of probability. 相似文献
5.
Huaiyu Shao 《Journal of solid state chemistry》2004,177(10):3626-3632
There are few reports on the hydrogen storage behavior study of Mg-Co-H system in the literature, although Mg2CoH5 has a much higher hydrogen capacity than Mg2NiH4. This is due to the great difficulty in the synthesis of Mg2CoH5 and Mg2Co in convenient conditions. Here we successfully synthesized the nanostructured Mg2CoH5 and Mg2Co from Mg and Co nanoparticles prepared by hydrogen plasma-metal reaction method. The reaction mechanism of the synthesis of the Mg-Co-H system was studied. The morphology of the Mg-Co-H system in nanometer scale was observed. The hydrogen absorption curves and the pressure-composition isotherm (P-C-T) properties of the Mg-Co-H system were studied. The van’t Hoff equations and the formation enthalpies and entropies of the produced Mg2CoH5 and Mg3CoH5 were obtained. The results were discussed by comparing with the corresponding ones of Mg-Co-H system by other groups and the ones of nanostructured Mg-H and Mg-Ni-H systems by our group. 相似文献
6.
Na Song Yang Teng Jiawei Wang Zhao Liu William Orndorff Wei-Ping Pan 《Journal of Thermal Analysis and Calorimetry》2014,116(3):1189-1195
Mercury is one of the most hazardous trace elements produced by coal-fired power plants. Mercury in the flue gas is predominately present as three different species: particulate mercury (Hgp), oxidized mercury (Hg2+), and elemental mercury (Hg0). Of these three, elemental mercury is the most difficult to remove from flue gas streams due to its low reactivity and low solubility in water. With increasing production costs associated with activated carbon materials, and increasing restrictions on mercury emissions, the development of an alternative low cost absorbent to capture elemental mercury by using fly ash modified with bromide compounds is highly desirable. Modified fly ash is usually injected into the flue gas stream after the air pre-heater system of a coal-fired power plant to oxidize and subsequently absorb elemental mercury. Research on the quantity and method of modifying the bromide amended fly ash is needed to obtain the most efficient mercury capture rate. This study utilized the impregnation method to prepare three different fly ashes with hydrogen bromide (HBr). Adsorption capabilities of the modified fly ashes were then examined using a fixed bed reactor. Thermogravimetric (TG) analysis was employed to quantify the amount of hydrogen bromide in the modified fly ash, which was subsequently compared to the water extraction method using ion chromatography. TG-MS was also utilized to evaluate the release of HBr from the modified fly ash and elucidate the mechanism for mercury capture. 相似文献
7.
John R. Moody 《Trends in analytical chemistry : TRAC》1983,2(5):116-118
Accurate analysis depends upon a valid, representative and uncontaminated analytical sample. For many trace metals, contamination overwhelms the sample, leading to inaccurate analytical data. Methods of controlling contamination and their implications for better methods of sampling and storage are discussed here. 相似文献
8.
Liu Y Li B Tu F Liang C Gao M Pan H Wang Q 《Dalton transactions (Cambridge, England : 2003)》2011,40(32):8179-8186
Hydrogen storage performances of a Li(2)NH-xMgNH combination system (x = 0, 0.5, 1 and 2) are investigated for the first time. It is found that the hydrogenated samples with MgNH exhibit a significant reduction in the dehydrogenation temperatures. Mechanistic investigations reveal that there is a strong dependence of the hydrogen storage reaction process on the molar ratio between MgNH and Li(2)NH. As a consequence, tuning of thermodynamics is achieved for hydrogen storage in the Li(2)NH-xMgNH system by changing the reaction routes, which is ascertained to be the primary reason for the reduction in the operating temperature for hydrogen desorption. Specifically, it is found that under 105 atm hydrogen (140-280 °C) 5.6 wt% hydrogen is reversibly stored in the Li(2)NH-0.5MgNH combination system, which is greater than in the well-investigated Mg(NH(2))(2)-2LiH system. 相似文献
9.
The results obtained when a laser microprobe is adapted to imaging detectors for multiwavelength detection are described. Detectors evaluated are a silicon-intensified target vidicon and a second-generation photodiode array. Data are presented to illustrate how the combined system can be used to monitor both surface and depth profiles of elemental content of a variety of sample types including a ruby rod and ceramic material with blemishes, electrical capacitors, integrated circuits, and surface-coated electrical conductors. It is also shown how the gating capability of the intensified vidicon can be used to monitor time-dependent changes in the several nanosecond range during the laser microprobe excitation process. Detection limits obtained with both detectors are in the range 2–500 ppm depending on the element, the wavelength used, the matrix, and other variables. The uncertainty associated with the measurement step can be improved by a factor of 2–3 by using ratios of spectral lines. Principal limitations of the laser microprobe method are the nonlinear response of intensity vs. concentration and the resulting need for reference materials with matrices similar to samples for calibration purposes. 相似文献
10.
Amine-borane adducts are promising compounds for use in hydrogen storage applications, and the efficient catalytic release of hydrogen from these systems has been recently demonstrated. However, if hydrogen storage is to be of practical use, it is necessary that, once hydrogen has been removed from the material, it can be put back into the system to recharge the appliance. In order to develop such systems, we computationally screened a range of amine-borane adducts for their thermodynamic dehydrogenation properties. Structural trends, which lay the foundation for the possible design of amine-borane systems that exhibit reversible dihydrogen uptake, are established. We found that it is mainly the strengths of the dative bonds in both starting materials and products that govern the thermodynamic parameters of the dehydrogenation reactions. Thus, in general, electron-donating groups on nitrogen and electron-withdrawing groups on boron lead to more favorable systems. It is also possible to design promising systems whose thermodynamic parameters are a consequence of different steric strain in starting materials and products. 相似文献
11.
Lueking AD Gutierrez HR Fonseca DA Narayanan DL Van Essendelft D Jain P Clifford CE 《Journal of the American Chemical Society》2006,128(24):7758-7760
We provide evidence of low-temperature hydrogen evolution and possible hydrogen trapping in an anthracite coal derivative, formed via reactive ball milling with cyclohexene. No molecular hydrogen is added to the process. Raman-active molecular hydrogen vibrations are apparent in samples at atmospheric conditions (300 K, 1 bar) for samples prepared 1 year previously and stored in ambient air. Hydrogen evolves slowly at room temperature and is accelerated upon sample heating, with a first increase in hydrogen evolution occurring at approximately 60 degrees C. Subsequent chemical modification leads to the observation of crystalline carbons, including nanocrystalline diamond surrounded by graphene ribbons, other sp2-sp3 transition regions, purely graphitic regions, and a previously unidentified crystalline carbon form surrounded by amorphous carbon. The combined evidence for hydrogen trapping and carbon crystallization suggests hydrogen-induced crystallization of the amorphous carbon materials, as metastable hydrogenated carbons formed via the high-energy milling process rearrange into more thermodynamically stable carbon forms and molecular hydrogen. 相似文献
12.
Hino S Ichikawa T Ogita N Udagawa M Fujii H 《Chemical communications (Cambridge, England)》2005,(24):3038-3040
The partial pressure of NH3 gas estimated by Raman spectroscopy indicates that approximately 0.1% NH3 inevitably contaminates the H2 desorbed from a hydrogen storage material composed of LiH and LiNH2 at any temperature up to 400 degrees C in a closed system. 相似文献
13.
14.
Development of amidoboranes for hydrogen storage 总被引:1,自引:0,他引:1
With high hydrogen content and moderate dehydrogenation conditions, metal amidoboranes have been regarded as potential hydrogen storage candidates and have attracted increasing attention recently. In this review we provide a practical introduction to the recent progress on the syntheses, crystal structures and dehydrogenation properties of metal amidoboranes and their derivatives. 相似文献
15.
Lifang Song Shuang Wang Chengli Jiao Xiaoliang Si Zhibao Li Shuang Liu Shusheng Liu Chunhong Jiang Fen Li Jian Zhang Lixian Sun Fen Xu Fenglei Huang 《The Journal of chemical thermodynamics》2012
The growing use of conventional energy such as fossil fuels results in problems degrading our environment. Hydrogen is frequently discussed as a clean energy in the future without pollution. However, efficient and safe storage of hydrogen constitute a key challenge and unresolved problem. One of the main options is solid-state storage technology. A successful solid-state reversible storage material should meet the requirements of high storage capacity, suitable thermodynamic properties, reversibility and fast adsorption and desorption kinetics. This feature article focuses mainly on the development of thermodynamic improvement of hydrogen storage materials in the past few years including the complex hydride, ammonia borane, and metal-organic frameworks. 相似文献
16.
Deshmane Vinay Lee Cheng-Ming Sublette Kerry L. 《Applied biochemistry and biotechnology》1993,(1):739-752
It has been demonstrated that heat- and alkali-pretreated sewage sludge may serve as an electron donor and carbon source for
SO2 reduction byDesulfovibrio desulfuricans. A continuousD. desulfuricans culture was operated for 6 mo with complete reduction of SO2 to H2S. The culture required only minor amounts of mineral nutrients in addition to pretreated sewage sludge. It has also been
shown that the sulfate-reducing bacteriumDesulfotomaculum orientis can be grown on H2 as an energy source, CO2 as a carbon source, and SO2 as a terminal electron acceptor. Complete reduction of SO2 to H2S was observed. 相似文献
17.
Nitrogen in organic samples may be determined on a routine basis after combustion in elemental analyzer instruments. If elementary copper is used in the reduction column, it will be oxidized to copper(II) oxide by passing oxygen and nitrogen oxides. Instead of changing the reduction column it is possible to regenerate the copper(II) oxide to elemental copper with hydrogen gas without removing the column from the oven. A modification of the original instrument and procedure is described. In this method, the capacity of the column will decrease after regeneration, but time and chemical costs will be saved. 相似文献
18.
19.
Three silica gel sample systems, modified with 3-amino-propyltriethoxy silane (APTS), were prepared by sequentially sampling
the reaction mixture at various time intervals. The concentrations of 3-aminopropylsilyl groups (APS) bound on the silica
surface were determined by elemental analysis. For the same sample systems, 29Si NMR intensities of an (–O)4Si species belonging only to the silica gel particles and corrected by a cross-polarization correction factor were also measured.
Both the APS-concentrations and the correc-ted 29Si NMR intensities depended upon reaction time, reflecting the rate of the APTS–silica gel reaction. Kinetic analysis of these
data was made by use of the Gauss–Newton method, and the overall reaction was found to consist of three reaction processes
(an initial fast reaction, a slower second reaction and a much slower third reaction). In particular, the conversion of (–O)3SiOH to (–O)4Si is predominant in the second reaction process and the pore size of a silica gel particle affects the reaction mechanism.
Received: 1 November 1996 Accepted: 24 January 1997 相似文献