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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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This paper presents experimental study on catalytic autothermal reforming (ATR) of natural gas (NG) for hydrogen (H2) production over sulfide nickel catalyst supported on gamma alumina. The experiments are conducted on a cylindrical reactor of 30 mm in diameter and 200 mm in length with “simulated” NG of different composition under thermal-neutral conditions and fed with different molar air to fuel ratio (A/F) and molar water to fuel ratio (W/F). The results showed that reforming performance is significantly dependent on A/F, W/F and concentration of C2+ hydrocarbons in inlet fuel. Fuels containing higher C2+ hydrocarbons concentration have optimum performance in terms of more H2 at higher A/F and W/F but lower conversion efficiency. Good performance for ATR of fuel containing 15%–20% C2H6 can be achieved at A/F=5–7 and W/F=4–6, much higher than that for optimum performance of ATR of methane (A/F=3,W/F=2–2.5). CO2 in the inlet fuel does not have significant effect on the reversed water–gas shift reaction. Its effect on reforming performance is mainly due to the dilution of inlet fuel and products. 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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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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Measurements on ignition delay times of propane/hydrogen mixtures in argon diluted oxygen were conducted for hydrogen fractions in the fuel mixtures (XH2) from 0 to 100%, pressures of 1.2, 4.0 and 10 atm, and temperatures from 1000 to 1600 K using the shock-tube. Results show that for XH2 less than 70%, ignition delay time shows a strong Arrhenius temperature dependence and it decreases with the increase of pressure, while for XH2 larger than 90%, there is a crossover pressure dependence of the ignition delay time with increasing temperature. Numerical studies were made using the selected kinetic mechanisms and results show that the predicted ignition delay time gives a reasonable agreement with the measurements. Both measurements and predictions show that for XH2 less than 70%, the ignition delay time is only moderately decreased with the increase of XH2, indicating that hydrogen addition has weak effect on ignition enhancement. Sensitivity analysis reveals the key reactions that control the simulation of ignition delay time. Kinetic study is made to interpret the ignition delay time dependence on pressure and XH2. 相似文献
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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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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
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Myung Geun Jung Young Jin KimYeon-Gil Jung Hyung-Tae Lim 《International Journal of Hydrogen Energy》2014
Yttria doped barium cerate (BCY) electrolyte, Ni + BCY anode supported protonic ceramic fuel cells were fabricated with Pt reference electrodes embedded in a thin (∼40 microns) electrolyte layer. The embedded electrodes function as selective probes exchanging only electrons with the BCY so that the voltage measurements (ΔV) using the embedded probes through the electrolyte correspond to a change in the reduced negative electrochemical potential of electrons (Δφ ). Using this method, the corresponding change in hydrogen and oxygen chemical potential (ΔμH2, ΔμO2) or partial pressure of hydrogen and oxygen (ΔpH2, ΔpO2) were determined on the basis of the local equilibrium assumption, allowing us to investigate ionic and electronic transport properties through the BCY electrolyte. The results indicate that the pH2 and pO2 change mainly occurs across the middle electrolyte region while the electrolyte regions close to the anode and the cathode showed very small variation. The present work revealed that the BCY electrolyte consists of three major parts with different transport properties; 1) mixed ionic-electronic conduction in the electrolyte close to the anode side (reducing atmosphere), 2) predominantly ionic conduction in the middle region, 3) mixed ionic-hole conduction in the electrolyte close to the cathode side (oxidizing atmosphere). 相似文献
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Possibility of hydrogen production from biogas using hot slag has been studied, in which decomposition rate of CO2–CH4 in a packed bed of granulated slag was measured at constant flow-rate and pressure. The molten slag, discharged at high temperature over 1700 K from smelting industries such as steelmaking or municipal waste incineration. It has enough potential for replacing energy required for hydrogen production due to the catalytic steam reforming or carbon decomposition of hydrocarbon. However, heat recovery of hot slag has never been established. Therefore, the objective of this work is to generate hydrogen from methane using heated slag particles as catalyst, in which the effect of temperature on the hydrogen generation was mainly investigated at range from 973 to 1273 K. In the experiments a mixed gas of CH4 and CO2 was continuously introduced into the packed bed of hot slag at constant flow-rate and atmospheric pressure and then the outlet gas was monitored by gas chromatography. The results indicate that slag acted as not only thermal media but also good catalyst, for promoting decomposition. The product gases were mainly hydrogen and carbon monoxide with/without solid carbon deposition on the surface of slag, depending on the reaction temperature. Increasing temperature led to large hydrogen generation with decreasing un-reacted methane in the outlet gas, at when the largest methane conversion was about 96%. The results suggested a new energy-saving process of hydrogen production, in which the waste heat from molten slag can replace the energy required for hydrogen production, reducing carbon dioxide emission. 相似文献
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Yang-huan Zhang Dong-liang Zhao Bao-wei Li Xiao-long Zhao Zhong-wang Wu Xin-lin Wang 《International Journal of Hydrogen Energy》2008
In order to investigate the influences of the stoichiometric ratios of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structure and the electrochemical performances of the AB2.5–3.5-type electrode alloys, the La–Mg–Ni–Co system La0.75Mg0.25Ni2.5Mx (M=Ni, Co; x=0, 0.2, 0.4, 0.6, 0.8, 1.0) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The obtained results show that the structures and electrochemical performances of the alloys are closely relevant to the M content. All the alloys exhibit a multiphase structure, including LaNi2, (La,Mg)Ni3 and LaNi5 phases, and the major phase in the alloys changes from LaNi2 to (La,Mg)Ni3+LaNi5 with the variety of M content. The electrochemical performances of the alloys, involving the discharge capacity, the high rate discharge (HRD) ability, the activation capability and the discharge potential characteristics, significantly improve with increasing M content. When M content x increases from 0 to 1.0, the discharge capacity rises from 177.7 to 343.62 mAh/g for the alloy (M=Ni), and from 177.7 to 388.7 mAh/g for the alloy (M=Co). The cycle stability of the alloy first mounts up then declines with growing M content. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed M content (x=1.0), the substitution of Co for Ni enhances the discharge capacity from 343.62 to 388.7 mAh/g, and the capacity retention ratio (S100) after 100 charging–discharging cycles from 51.45% to 61.1%. 相似文献