共查询到20条相似文献,搜索用时 11 毫秒
1.
S. Cimino L. Lisi G. Mancino M. Musiani L. Vázquez-Gómez E. Verlato 《International Journal of Hydrogen Energy》2012
The catalytic partial oxidation (CPO) of methane–hydrogen mixtures in air, intended for the first stage of hybrid radiant catalytic burners, was investigated under self-sustained short contact time conditions on commercial Ni foam catalysts eventually modified with Rh and Pt. The modified catalysts were prepared by a simple novel method based on the spontaneous deposition of noble metals via metal exchange reactions onto those Ni foam substrates. SEM-EDS, electrochemical methods and H2-TPR analysis were integrated to characterize morphology, surface area of metal deposits and reducibility of foam catalysts before and after exposure to severe conditions in the CPO reactor. In particular Rh forms finely dispersed deposits that retain their high specific surface area at temperatures up ca. 1100 °C. Modification with noble metals enhances stability and reducibility of the Ni foam whereas the overall CPO performance is not significantly improved. Safe operation of the CPO reactor with up to 70% vol. H2 in the fuel mixture has been achieved by properly increasing the feed equivalence ratio to avoid catalyst overheating, while guaranteeing high methane conversions and a persistent net hydrogen production. 相似文献
2.
Esmaeil Habibi Elahe Bidad Alireza Feizbakhsh Maryam Fazli 《International Journal of Hydrogen Energy》2014
The comparative studies of methanol, ethanol, 2-propanol and 2-butanol electrooxidation were carried out on carbon-ceramic electrode (CCE) potentiostatically modified with Pd nano-particles. The Characterization of catalytic layer by Scanning electron microscope (SEM), Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) indicated that well-dispersed catalytic particles with high density have been formed on CC substrate. Voltammetry, Chronoamperometry (CA), Polarization study and electrochemical impedance spectroscopy (EIS) were used to investigate the alcohols oxidation reactions. The relevant parameters such as the Tafel slope and activation energy (Ea) were determined. This study upholds the fact that 2-propanol is a promising fuel candidate for a direct alkaline alcohol fuel cell. 相似文献
3.
Experiments were conducted to investigate the combustion and emission characteristics of a diesel engine with addition of hydrogen or methane for dual-fuel operation, and mixtures of hydrogen–methane for tri-fuel operation. The in-cylinder pressure and heat release rate change slightly at low to medium loads but increase dramatically at high load owing to the high combustion temperature and high quantity of pilot diesel fuel which contribute to better combustion of the gaseous fuels. The performance of the engine with tri-fuel operation at 30% load improves with the increase of hydrogen fraction in methane and is always higher than that with dual-fuel operations. Compared with ULSD–CH4 operation, hydrogen addition in methane contributes to a reduction of CO/CO2/HC emissions without penalty on NOx emission. Dual-fuel and tri-fuel operations suppress particle emission to the similar extent. All the gaseous fuels reduce the geometry mean diameter and total number concentration of diesel particulate. Tri-fuel operation with 30% hydrogen addition in methane is observed to be the best fuel in reducing particulate and NOx emissions at 70 and 90% loads. 相似文献
4.
Sufang He Hongmiao Wu Wanjin Yu Liuye Mo Hui Lou Xiaoming Zheng 《International Journal of Hydrogen Energy》2009
Ni/SiO2 and Ni–Al2O3/SiO2 catalysts were prepared by incipient wetness impregnation using citrate and nitrate precursors and tested with a reaction of combination of CO2 reforming and partial oxidation of methane to produce syngas (H2/CO). The catalytic activity of Ni/SiO2 and Ni–Al2O3/SiO2 greatly depended on interaction between NiO and support. NiO strongly interacted with support formed small nickel particles (about 4 nm for NiSC which is abbreviation of Ni/SiO2 prepared with Nickel citrate precursor) after reduction. The small nickel particles over NiSC catalysts exhibited a good catalytic performance. 相似文献
5.
This study has been implemented in two sections. At first, the turbulent jet flame of DLR-B is simulated by combining the k–ε turbulence model and a steady flamelet approach. The DLR-B flame under consideration has been experimentally investigated by Meier et al. who obtained velocity and scalar statistics. The fuel jet composition is 33.2% H2, 22.1% CH4 and 44.7% N2 by volume. The jet exit velocity is 63.2 m/s resulting in a Reynolds number of 22,800. Our focus in the first part is to validate the developed numerical code. Comparison with experiments showed good agreement for temperature and species distribution. At the second part, we exchanged methane with propane in the fuel composition whilst maintaining all other operating conditions unchanged. We investigated the effect of hydrogen concentration on C3H8–H2–N2 mixtures so that propane mole fraction extent is fixed. The hydrogen volume concentration rose from 33.2% up to 73.2%. The achieved consequences revealed that hydrogen addition produces elongated flame with increased levels of radiative heat flux and CO pollutant emission. The latter behavior might be due to quenching of CO oxidation process in the light of excessive cold air downstream of reaction zone. 相似文献
6.
Yongfeng Liu Fenghuai WangYanhui Cao Mingxia GaoHongge Pan 《International Journal of Hydrogen Energy》2010
Complex hydrides and Metal–N–H-based materials have attracted considerable attention due to their high hydrogen content. In this paper, a novel amide–hydride combined system was prepared by ball milling a mixture of Na2LiAlH6–Mg(NH2)2 in a molar ratio of 1:1.5. The hydrogen storage performances of the Na2LiAlH6–1.5Mg(NH2)2 system were systematically investigated by a series of dehydrogenation/hydrogenation evaluation and structural analyses. It was found that a total of ∼5.08 wt% of hydrogen, equivalent to 8.65 moles of H atoms, was desorbed from the Na2LiAlH6–1.5Mg(NH2)2 combined system. In-depth investigations revealed that the variable milling treatments resulted in the different dehydrogenation reaction pathways due to the combination of Al and N caused by the energetic milling. Hydrogen uptake experiment indicated that only ∼4 moles of H atoms could be reversibly stored in the Na2LiAlH6–1.5Mg(NH2)2 system perhaps due to the formation of AlN and Mg3N2 after dehydrogenation. 相似文献
7.
Hujun Cao Yongshen Chua Yao Zhang Zhitao Xiong Guotao Wu Jieshan Qiu Ping Chen 《International Journal of Hydrogen Energy》2013
Ball milling the mixture of Mg(NH2)2, LiH and NH3BH3 in a molar ratio of 1:3:1 results in the direct liberation of 9.6 wt% H2 (11 equiv. H), which is superior to binary systems such as LiH–AB (6 equiv. H), AB–Mg(NH2)2 (No H2 release) and LiH–Mg(NH2)2 (4 equiv. H), respectively. The overall dehydrogenation is a three-step process in which LiH firstly reacts with AB to yield LiNH2BH3 and LiNH2BH3 further reacts with Mg(NH2)2 to form LiMgBN3H3. LiMgBN3H3 subsequently interacts with additional 2 equivalents of LiH to form Li3BN2 and MgNH as well as hydrogen. 相似文献
8.
Bjorn Hasa Evangelos Kalamaras Evangelos I. Papaioannou Labrini Sygellou Alexandros Katsaounis 《International Journal of Hydrogen Energy》2013
In this study Pt–TiO2 binary electrodes were prepared by means of thermal decomposition of chloride precursors on Ti substrates, characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), electrochemical techniques and CO stripping and used as anodes for alcohol oxidation. The minimization of the Pt loading without electrocatalytic activity losses was also explored. TiO2 was chosen due to its chemical stability, low cost and excellent properties as substrate for Pt dispersion. It was found that TiO2 loading up to 50% results in Electrochemically Active Surface (EAS) increase. The EAS of Pt(50%)-TiO2(50%) was found to be almost one order of magnitude higher than that of pure Pt while the EAS of samples with Pt loading lower than 30% was negligible. The above conclusion has been confirmed both by following the charge of the reduction peak of platinum oxide and by CO stripping experiments. All samples have been evaluated during the electrochemical oxidation of methanol and ethanol. In both cases the Pt(50%)-TiO2(50%) electrode had better electrocatalytic activity than the pure Pt anode. The observed higher performance of the binary electrodes was mainly attributed to the enhanced Pt dispersion as well as the formation of smaller Pt particles by the addition of TiO2. 相似文献
9.
Won-Jun Jang Dae-Woon Jeong Jae-Oh Shim Hyun-Seog Roh In Hyuk Son Seung Jae Lee 《International Journal of Hydrogen Energy》2013
Ni–Ce0.8Zr0.2O2 and Ni–MgO–Ce0.8Zr0.2O2 catalysts were investigated for H2 production from CO2 reforming of CH4 reaction at a very high gas hourly space velocity of 480,000 h−1. Ni–MgO–Ce0.8Zr0.2O2 exhibited higher catalytic activity and stability (CH4 conversion >95% at 800 °C for 200 h). The outstanding catalytic performance is mainly due to the basic nature of MgO and an intimate interaction between Ni and MgO. 相似文献
10.
A series of gold catalysts supported on ZnO–TiO2 with various ZnO contents were prepared. ZnO–TiO2 was prepared by incipient-wetness impregnation using aqueous solution of Zn(NO3)2 onto TiO2. Gold catalysts with nominal gold loading of 1 wt. % were prepared by deposition-precipitation (DP) method. Various preparation parameters, such as pH value and Zn/Ti ratio on the characteristics of the catalysts were investigated. The catalysts were characterized by inductively-coupled plasma–mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The preferential oxidation of CO in H2 stream (PROX) on these catalysts was carried out in a fixed bed micro-reactor with a feed of CO: O2: H2: He = 1: 1: 49: 49 (volume ratios) and a space velocity of 30,000 ml/g h. Limited amount of oxygen was used in the feed. A high gold dispersion and narrow gold particle size distribution was obtained. Au/ZnO–TiO2 with Zn/Ti atomic ratio of 5/95 showed the highest CO conversion at room temperature. The conversion increased with increasing temperature even in the presence of limited amount of oxygen, showing suppression in H2 oxidation. Au/ZnO–TiO2 prepared at pH 6 had a higher CO conversion and higher selectivity of CO oxidation than those prepared at other pH values. The addition of ZnO on TiO2 resulted in higher dispersion of gold particles and narrow particle size distribution. The stronger the Au–Zn(OH)2 interaction, the finer the supported Au nanoparticles, and the better the catalytic performance of the catalyst for PROX reaction. Part of Au was in Au+ state due to the interaction with Zn(OH)2 and nano Au size. The oxidation state of gold species played an important role in determining its CO conversion and selectivity of CO oxidation in hydrogen stream. The catalysts were stable at 80 °C for more than 80 h. 相似文献
11.
A dual bed catalyst system consisting of a metallic Ni monolith catalyst in the front followed by a supported nickel catalyst Ni/MgAl2O4 has been studied for the autothermal partial oxidation of methane to synthesis gas. The effects of bed configuration, reforming bed length, feed temperature and gas hourly space velocity on the reaction as well as the stability are investigated. The results show that the metallic Ni monolith in the front functions as the oxidation catalyst, which prevents the exposure of the reforming catalyst in the back to the very high temperature, while the supported Ni/MgAl2O4 in the back functions as the reforming catalyst which further increases the methane conversion by 5%. A typical 5 mmNi monolith–5mmNi/MgAl2O4 dual bed catalyst exhibits methane conversion and hydrogen and carbon monoxide selectivities of 85.3%, 91.5% and 93.0%, respectively, under autothermal conditions at a methane to oxygen molar ratio of 2.0 and gas hourly space velocity of 1.0 × 105 h−1. The dual bed catalyst system is also very stable. 相似文献
12.
This study shows the hydrogen desorption kinetics and reversible hydrogen storage properties of 0.55LiBH4–0.45Mg(BH4)2 melt-infiltrated in different nanoporous carbon aerogels with different BET surface areas of 689 or 2660 m2/g and pore volumes of 1.21 or 3.13 mL/g. These investigations clearly show a significantly improved hydrogen storage capacity after four cycles of hydrogen release and uptake for bulk 0.55LiBH4–0.45Mg(BH4)2 and infiltrated in carbon aerogel and the high surface area scaffold, where 22, 36 and 58% of the initial hydrogen content remain after four cycles of hydrogen release and uptake, respectively. Nanoconfinement in high surface area carbon aerogel appears to facilitate hydrogen release illustrated by release of 13.3 wt% H2 (93%) and only 8.4 wt% H2 (58%) from bulk hydride in the first cycle using the same physical condition. Notably, nanoconfinement also appear to have a beneficial effect on hydrogen uptake, since 8.3 wt% H2 (58%) is released from the high surface area scaffold and only 3.1 wt% H2 (22%) from the bulk sample during the fourth hydrogen release. 相似文献
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14.
Shu-Sheng Liu Li-Xian Sun Jian Zhang Yao Zhang Fen Xu Yong-Heng Xing Fen Li Jijun Zhao Yong Du Wang-Yu Hu Hui-Qiu Deng 《International Journal of Hydrogen Energy》2010
To improve the dehydrogenation properties of MgH2, a novel hydrogen storage system, MgH2–Li3AlH6, is prepared by mechanochemical milling. Three physical mixtures containing different mole ratios (1:4, 1:1 and 4:1) of MgH2 and Li3AlH6 are studied and there exists a mutual destabilization effect between the components. The last mixture shows a capacity of 6.5 wt% H2 with the lowest starting temperature of dehydrogenation (170 °C). First, Li3AlH6 decomposes into Al, LiH and H2, and then the as-formed Al can easily destabilize MgH2 to form the intermetallic compound Mg17Al12 at a temperature of 235 °C, which is about 180 °C lower than the decomposition temperature of pristine MgH2. Finally, the residual MgH2 undergoes a self-decomposition whose apparent activation energy has been reduced by about 22 kJ mol−1 compared with pristine MgH2. At a constant temperature of 250 °C, the mixture can dehydrogenate completely under an initial vacuum and rehydrogenate to form MgH2 under 2 MPa H2, showing good cycle stability after the first cycle with a capacity of 4.5 wt% H2. The comparison between 4 MgH2 + Li3AlH6 and 4 MgH2 + LiAlH4 mixtures is also investigated. 相似文献
15.
16.
Dae-Woon Jeong Hari S. PotdarJae-Oh Shim Won-Jun JangHyun-Seog Roh 《International Journal of Hydrogen Energy》2013
To develop a single stage water–gas shift reaction (WGS) catalyst for compact reformers, Pt/CeO2, Pt/ZrO2, and Pt/Ce(1−x)Zr(x)O2 catalysts have been applied for the target reaction. The CeO2/ZrO2 ratio was systematically varied to optimize Pt/Ce(1−x)Zr(x)O2 catalysts. Pt/CeO2 showed the highest turnover frequency (TOF) and the lowest activation energy (Ea) among the catalysts tested in this study. It has been found that the reduction property of the catalyst is more important than the dispersion for a single stage WGS. Pt/CeO2 catalyst also showed stable catalytic performance. Thus, Pt/CeO2 can be a promising catalyst for a single stage WGS for compact reformers. 相似文献
17.
18.
Qifu Huang Wenzhi Li Qizhao Lin Xusheng Zheng Haibin Pan Dong Pi Chunyu Shao Chao Hu Haitao Zhang 《能源学会志》2018,91(5):733-742
In this paper, the catalyst of Pd–NiCo2O4/SiO2 was prepared and applied to the catalytic combustion of lean methane. Pd and NiCo2O4 nanoparticles were uniformly distributed on the SiO2 support, so that every Pd or NiCo2O4 nanoparticle was separated from each other by another component. Comparing with Co3O4/SiO2, NiCo2O4/SiO2, Pd–Co3O4/SiO2 and Pd#NiCo2O4/SiO2 (catalysts without uniform distribution of Pd and NiCo2O4 nanoparticles), Pd–NiCo2O4/SiO2 had the highest catalytic activity in the catalytic combustion of lean methane, with a methane total conversion temperature at 378 °C. In addition, the high activity did not decrease during the long time reaction, which showed good thermal stability. TEM and BET results showed that the nanoparticle sizes of Pd and NiCo2O4 were very small. The XRD patterns indicated that the Pd nanoparticles were highly dispersed on the surface of SiO2. The XPS spectra demonstrated the formation of NiCO2O4, the presence of enough active oxygen species on the catalyst surface and the high ratio of PdO/Pd0. The enhanced influence of Ni introduction was also proved by comparison tests. All these results indicated that the high catalytic activity of Pd–NiCo2O4/SiO2 mainly comes from the nanoparticle distribution and the Ni cation enhancement. 相似文献
19.
Xiaowei Chen Feng Yuan Qinfen Gu Yingbin Tan HuaKun Liu Shixue Dou Xuebin Yu 《International Journal of Hydrogen Energy》2013
A combined strategy via mixing Mg(BH4)2·6NH3 with ammonia borane (AB) is employed to improve the dehydrogenation properties of Mg(BH4)2·6NH3. The combined system shows a mutual dehydrogenation improvement in terms of dehydrogenation temperature and hydrogen purity compared to the individual components. A further improved hydrogen liberation from the Mg(BH4)2·6NH3–6AB is achieved with the assistance of ZnCl2, which plays a crucial role in stabilizing the NH3 groups and promoting the recombination of NHδ+?HBδ−. Specifically, the Mg(BH4)2·6NH3–6AB/ZnCl2 (with a mole ratio of 1:0.5) composite is shown to release over 7 wt.% high-pure hydrogen (>99 mol%) at 95 °C within 10 min, thereby making the combined system a promising candidate for solid hydrogen storage. 相似文献
20.
Yongfeng Liu Yu ZhangHai Zhou Yi ZhangMingxia Gao Hongge Pan 《International Journal of Hydrogen Energy》2014
The dehydrogenation/hydrogenation properties of LiBH4-xMg(OH)2 were systematically investigated. The results show that the LiBH4-0.3Mg(OH)2 composite possesses optimal dehydrogenation properties: approximately 9.6 wt% of hydrogen is released via a stepwise reaction with an onset temperature of 100 °C. In the range of 100–250 °C, a chemical reaction between LiBH4 and Mg(OH)2 first occurs to give rise to the generation of LiMgBO3, MgO and H2. From 250 to 390 °C, the newly developed LiMgBO3 reacts with LiBH4 to form MgO, Li3BO3, LiH, B2O3 and Li2B12H12 with hydrogen release. From 390 to 450 °C, the decomposition of LiBH4 and Li2B12H12 proceeds to release additional hydrogen and to form LiH and B. A further hydrogenation experiment indicates that the dehydrogenated LiBH4-0.3Mg(OH)2 sample can take up 4.7 wt% of hydrogen at 450 °C and 100 bar of hydrogen with good cycling stability, which is superior to the pristine LiBH4. 相似文献