共查询到20条相似文献,搜索用时 46 毫秒
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Guopeng Wu Tao Chen Weiguang Su Guohua Zhou Xu Zong Zhibin Lei Can Li 《International Journal of Hydrogen Energy》2008
H2 with ultra-low CO concentration was produced via photocatalytic reforming of methanol on Au/TiO2 catalyst. The rate of H2 production is greatly increased when the gold particle size is reduced from 10 to smaller than 3 nm. The concentration of CO in H2 decreases with reducing the gold particle size of the catalyst. It is suggested that the by-product CO is mostly produced via decomposition of the intermediate formic acid species derived from methanol. The smaller gold particles possibly switch the HCOOH decomposition reaction mainly to H2 and CO2 products while suppress the CO and H2O products. In addition, some CO may be oxidized to CO2 by photogenerated oxidizing species at the perimeter interface between the small gold particles and TiO2 under photocatalytic condition. 相似文献
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F. Gallucci F. Chiaravalloti S. Tosti E. Drioli A. Basile 《International Journal of Hydrogen Energy》2007
Hydrogen permeation through a palladium membrane has been measured in the presence of several gases, such as CO, N2, CO2, and Ar, both in the feed side and in the shell side of the (membrane) module. It has been found that CO molecules, remarkably inhibit hydrogen permeation. In particular, in the presence of carbon monoxide the permeation decreases with two different slopes: (I) for low CO concentrations, the hydrogen permeation decreases quickly (surface effects), whereas (II) for higher ones it decreases smoothly (dilute effect). Permeation of hydrogen, in the presence of the other gases, i.e. N2, CO2 and Ar, always decreases with the same slope (dilute effect). In order to describe the CO inhibition, a theoretical investigation has been proposed. In particular, the framework of the Density Functional Theory has been used. CO and N2 Density Functional full optimisations on palladium clusters show that CO and N2 molecules present two minima on the cluster surfaces with bond lengths of 2.0 and 3.8 Å, respectively. The CO minima are much stable than N2 minima, resulting in a surface effect on the hydrogen permeation through the membrane. 相似文献
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Hydrogen generation by hydrolysis of Mg and MgH2 has been investigated in pure water and 1 M KCl. It has been found that hydrolysis reaction of Mg and Mg–Ni composite, both obtained by high-energy ball milling, is faster and extensive when they are immersed in 1 M KCl. In contrast, milled Mg and Mg–Ni composite in pure water, MgH2 and MgH2–Ni composites in pure water and in 1 M KCl show low yield and reactivity. Hydrolysis kinetics and yield are maximum with Mg–10 at% Ni composite milled for 30 min, so reaction is fully completed within an hour in the presence of chloride ions. It is related to the creation of micro-galvanic cells between Mg and dispersed Ni elements, accentuating greatly Mg corrosion in highly conductive aqueous media. A significant increase of the H2 production is also observed with 30 min milled Mg sample, likely because of the accentuation in the pitting corrosion resulting from the creation of numerous defects and fresh surfaces through the milling process. On the other hand, intensive ball milling of pure magnesium has no effect on the Mg reactivity in pure water. Ball milling effect is likely masked by the significant Mg passivation in pure water. A correlation is established between the conversion yield of ball-milled MgH2 powder in pure water and its effective surface area, which is increased by the milling process. Ni addition has no effect on the hydrolysis reaction in nonconductive media (i.e. pure water) and with nonconductive material (i.e. MgH2). 相似文献
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Tatyana V. Laurinavichene Alexander S. Fedorov Maria L. Ghirardi Michael Seibert Anatoly A. Tsygankov 《International Journal of Hydrogen Energy》2006
It was demonstrated that immobilized, sulfur-deprived algal cultures can photoproduce H2. After identifying the optimal material and procedures for immobilization of Chlamyodomonas reinhardtii at high cell density, we examined the effect of liquid mixing, sulfate content, acetate levels and light intensity on the H2-production activity of the culture. Our results indicate that (a) liquid mixing is important to provide homogeneous conditions for the immobilized culture; (b) sulfur deprivation is necessary for hydrogen production by immobilized cultures; and (c) high light intensity decreases H2 production. The maximum total volume of H2 produced by the system (160 ml of reactor volume) was 380 ml over 23 days, and the highest rate of H2 production observed was 45 ml day-1. Cell immobilization significantly increased the duration of the H2-photoproduction phase (up to 4 weeks), maintained specific rates of H2 photoproduction similar to those of suspension cultures and showed potential for large increases in H2 production. 相似文献
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Sodium borohydride is attracting considerable interests as a hydrogen storage medium. In this paper, we investigated the effects of hydrogen pressure, reaction temperature and transition metal addition on sodium borohydride synthesis by the reaction of sodium meta-borate with Mg and H2. It was found that higher H2 pressure was beneficial to NaBH4 formation. The increase in reaction temperature first improved NaBH4 formation kinetics but then impeded it when the temperature was raised to near the melting point of Mg. It was also found that some additions of transition metals such as Ni, Fe and Co in the NaBO2+Mg+H2 system promoted the NaBH4 formation, but Cu addition showed little effect. The activation energy of the NaBH4 formation from Mg, NaBO2 and H2 was estimated to be 156.3 kJ/mol NaBH4 according to Ozawa analysis method. 相似文献
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Experiments on synthesis gas preparation from dry reforming of methane by carbon dioxide with thermal plasma only and cooperation of thermal plasma with commercial catalysts have been performed. In all experiments, nitrogen gas was used as the plasma gas to form a high-temperature jet injected into a tube reactor. A mixture of CH4 and CO2 was fed vertically into the jet. Both kinds of experiments were conducted in the same conditions, such as total flux of feed gases, the molar ratio of CH4/CO2, and the plasma power except with or without catalysts in the tube reactor. Higher conversion of CH4 and CO2, higher selectivity of H2 and CO, and higher specific energy of the process were achieved by thermal plasma with catalysts. For example, the conversions of CH4 and CO2 were high to 96.33% and 84.63%, and the selectivies of CO and H2 were also high to 91.99% and 74.23%, respectively. Both were 10–20% higher than those by thermal plasma only. 相似文献
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Composite nickel coated steel cathodes were fabricated for hydrogen evolution reaction. TiO2-supported RuO2 particles of varying size were incorporated in the electroless coating. The electrodes exhibited high catalytic activity which was dependent on the size of RuO2 particles incorporated. The smaller the size at nano-level, the higher the catalytic activity. There was enhanced hydrogen adsorption due to high surface roughness and abundant active sites. 相似文献
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Effect of hydrogen introduction into some metal oxide and nitride thin films was examined. Modification of electrical and optical properties by hydrogen introduction was examined on SnO2, Sn–GeO2, Ge–CdO2, ZnO. Electrical resistance could be reduced in some films without loosing their transparence to the visible light. Hydrogen introduction to Cu3N changed the film an electrical conductor. Films of AlN and TiN were rather insensitive to the hydrogen introduction; the hydrogen effect was only observed when the nitrides contain some imperfection in the compounds. 相似文献
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The nonisothermal dehydrogenation of TiH2 powders was studied using thermogravimetry and differential scanning calorimetry. The reaction model was established by estimating the activation energy. The results show the nonisothermal dehydrogenation occurred in a four-step process. The hydrogen released from the TiH1.5∼2 phase in the first step, which led to the decrease of activation energy. The second step was derived from the formation of βH in δ phase and the reaction model was Phase boundary reaction. In the third step, the hydrogen started to release from the βH phase, and then the βH→αH phase transformation happened. So the activation energy Eα underwent a decrease followed by a quick increase. The fourth step corresponded to the formation of αH in βH phase, and the slight oxidation resulted in the small fluctuation of activation energy. 相似文献
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Though hydrogen fueled spark ignition engine can operate at high thermal efficiency with almost zero emission of HC and CO, the high level of NOx poses problems. The high combustion temperature and lean mixtures used are the reasons. In this work, the effect of N2, CO2 and hot EGR gas as diluents in the intake charge to suppress NO emission in a manifold injected hydrogen fueled SI engine was studied. Nitrogen as a diluent is not so effective at low loads while inducting smaller amounts, but very effective at higher loads where the mixture becomes richer and the dilution effect (oxygen depletion) is significant. On other hand, carbon dioxide is a good diluent with relatively better thermal effect and diluent effect and effectively controls NO emission at all output regions. However this is at the expense of thermal efficiency. Recirculating hot exhaust gas which contains both N2 and steam comes in between N2 and CO2 in terms of its effectiveness. On the whole N2 is the most effective as it has minimum impact on thermal efficiency for a given level of permissible NO emission. Thus it is felt that cold EGR could be a good option. In all cases, a good control system is necessary to supply correct quantity of diluent. 相似文献
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Heiner Schwarz Michael Geske C. Franklin Goldsmith Robert Schlögl Raimund Horn 《Combustion and Flame》2014
A versatile flow-reactor design is presented that permits multi-species profile measurements under industrially relevant temperatures and pressures. The reactor combines a capillary sampling technique with a novel fiber-optic Laser-Induced Fluorescence (LIF) method. The gas sampling provides quantitative analysis of stable species by means of gas chromatography (i.e. CH4, O2,CO,CO2, H2O,H2, C2H6, C2H4), and the fiber-optic probe enables in situ detection of transient LIF-active species, demonstrated here for CH2O. A thorough analysis of the LIF correction terms for the temperature-dependent Boltzmann fraction and collisional quenching are presented. The laminar flow reactor is modeled by solving the two-dimensional Navier–Stokes equations in conjunction with a detailed kinetic mechanism. Experimental and simulated profiles are compared. The experimental profiles provide much needed data for the continued validation of the kinetic mechanism with respect to C1 and C2 chemistry; additionally, the results provide mechanistic insight into the reaction network of fuel-rich gas-phase methane oxidation, thus allowing optimization of the industrial process. 相似文献