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失活加氢精制催化剂中硫铁相的高分辨透射电镜研究 总被引:1,自引:1,他引:0
利用高分辨透射电镜(HRTEM)结合X射线能谱仪(EDS)和选区电子衍射(SAED)分析,对运转后的加氢精制催化剂中含有的微量未知相的化学组成、晶体结构进行了研究.通过X射线能谱仪确定该未知相主要成分为硫和铁.根据选区电子衍射结果,该硫铁相为单晶结构.采用样品倾转的方法,获得3幅不同取向的选区电子衍射图,根据衍射谱中衍射斑点对应的晶体学信息及3幅电子衍射图取向间的夹角关系,确定该硫铁化合物属于正交晶系的硫化亚铁,分子式为Fe0.91S.该催化剂应用于高温高压下的加氢环境中,其中原料油中的酸性物质,尤其是环烷酸对加氢设备材质的腐蚀是导致硫铁化合物相形成的主要原因,并由此探讨了硫铁化合物相的形成机制. 相似文献
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基于前文错流移动床反应器模型方程,模拟计算并分析了该类反应器中气、固相流动对热煤气脱硫等非催化气固反应过程的影响。研究表明,床层在床深方向按反应速率的快慢可分为粗脱区和精脱区,在颗粒流动方向上气相浓度差异较大,并主要体现在粗脱区内,床层出口处颗粒转化率呈现较大分布,反应器内气固交错流动、气相浓度和颗粒转化率共同作用( 于气固反应速率) 等因素是造成过程特征的主要因素。因此反应器优化应满足对两相流动的优化,将粗脱区设置成错流移动床而精脱区设置成固定床,并使粗脱区内颗粒流速沿气流方向逐渐减小,以减小出口颗粒转化率的分布并提高颗粒利用率,同时沿颗粒流动方向应逐渐减小过床气流体积分率以利于床内气固反应速率的均一分布。由此指出对该类床型其底部渐缩下料段和过床气流对床内颗粒流动的影响以及床层结构及颗粒流动对过床气流分布的影响研究的必要性。 相似文献
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两段式气流床煤气化炉内气固流动数值模拟研究 总被引:3,自引:3,他引:0
建立了两段式气流床煤气化炉内气固两相流动的三维计算流体力学(CFD)模型,将气体视为连续介质,在Euler坐标系下考察气相的运动;将颗粒视为离散体系,在Lagrange坐标系下研究颗粒的运动。利用所建CFD模型对基本设计尺寸和操作条件下的两段式气流床煤气化炉内气固两相流动进行了模拟,给出了两段式气流床煤气化炉内的气固两相流动的规律和颗粒的分布规律。在此基础上,针对不同的结构(喉口直径变化)和不同的操作条件(两段气固进料量变化)进行了一系列的模拟比较。结果表明,喉口直径的变化对于炉内气固两相流动及颗粒分布有重要影响。随着喉口直径减小,喉口附近区域的气相回流增强,颗粒运动轨线变得更加曲折,颗粒分布发生明显变化。两段气固流量的改变可以明显改变炉内气固流动,随着一段反应区的气固流量增加和二段反应区气固流量减小,一段反应区内的气相回流更加显著, 二段反应区气相回流减弱,颗粒螺旋上升运动增强,反应器边壁处颗粒浓度增大,颗粒沉积现象减弱。 相似文献
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《中国稀土学报》2020,(5)
以时效态Mg-12Gd-3Y-1Sm-0.5Zr (%,质量分数)合金为研究对象,利用蠕变持久试验机在250℃/50 MPa下对合金的蠕变性能进行了测试,并采用TEM研究了合金在250℃/50 MPa下蠕变10, 30 min, 100 h过程中的显微组织和相的演变。结果表明:时效态Mg-12Gd-3Y-1Sm-0.5Zr合金相由α-Mg基体和β′相组成,β′相为纳米析出相,在高温蠕变过程中,晶内析出相明显长大,形貌由黑色椭圆形颗粒向菱形和长条状转变,经对应的选区电子衍射谱标定,相结构未发生变化;晶界上析出相粗化,转化为平衡相β相。本研究为开发高温高强抗蠕变耐热镁合金提供理论基础。 相似文献
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The HeH2 van der Waals complex has been identified in a molecular beam produced by a cryogenic (T0=24.7 K) free jet expansion of a 1% H2 mixture in 99% 4He gas. The weakly bound HeH2 complexes in the beam are identified via their first order diffraction angles after passing through a 100 nm period transmission grating. An electron impact mass spectrometer analysis of the diffraction patterns is used to discriminate against ion fragments of the constituent gas clusters. 相似文献
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The application of modern gas-phase electron diffraction for directly determining the populations of vibrational levels is demonstrated for the molecule I2. It is concluded that, under the conditions of the conventional electron diffraction experiment, a thermal equilibrium can reliably be assumed for a gas jet but at a temperature which can be markedly lower than that of the nozzle. The diffraction results favour a Boltzmann distribution of molecules over the vibrational states. 相似文献
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Yano YF Douguchi J Kumagai A Iijima T Tomida Y Miyamoto T Matsuura K 《The Journal of chemical physics》2006,125(17):174705
In situ x-ray diffraction measurements were carried out for investigating the liquid structure in the ultrasonic fountain jet to consider the mechanism of the "ultrasonic ethanol separation" reported by Sato et al. [J. Chem. Phys. 114, 2382 (2001)]. For pure liquids (water and ethanol), it was found that the high frequency ultrasound does not affect the liquid structure microscopically. For the 20 mol % ethanol-water mixture, the estimated ethanol mole fraction in the ultrasonic fountain jet by using the position of the main maximum in the x-ray diffraction profile coincided with that in the reservoir. This result suggests that the ethanol separation is not caused by any distorted liquid structure under the ultrasound irradiation and occurs when or after the generation of the liquid droplet mist. 相似文献
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V. V. Raznikov V. V. Zelenov E. V. Aparina A. R. Pikhtelev I. V. Sulimenkov 《Journal of Analytical Chemistry》2017,72(13):1345-1349
Generation of an ion beam and its transmission into a mass analyzer is one of central problems in mass spectrometry. The use of a narrowly directed supersonic gas jet has a number of advantages in comparison with other sampling methods. The aim of this work was to confirm the declared earlier properties of the jet formed at the outlet of a cylindrical channel when the free path length of gaseous atoms at the beginning of the channel is comparable with the channel diameter. The paper describes the ability of such a supersonic jet to conserve an additional energy of jet gas atoms. A significant influence of the temperature of the gas flow on the yield of cyclohexane fragment ions was found, cyclohexane being an admixture in the noble gas jet passing through an electron ionization ion source. A possibility of obtaining a flow of metastable electronically excited atoms inside the jet is also shown. The results of the work confirm the availability of the supersonic gas jet for the design of a high efficiency ion source inside the radio-frequency quadrupole at the input of the mass analyzer. 相似文献
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Jet flows provide an effective mode of energy transfer or mass transfer in industrial applications. When compared to traditional cooling through convection, jet flows have high heat and mass transfer coefficients. Further, the devices equipped with jet flow provides efficient use of fluid and also offers enhanced heat and mass transfer rates. Hence in this study, the jet flow of Casson nanofluid containing gyrotactic microorganisms that stabilises the nanoparticle suspension is discussed. To control the fluid from outside external magnetic field is imposed. The model with these characteristics are useful in the appliances like coolants in automobiles, nuclear reactors, micro-manufacturing, metallurgical process etc. Such a model is created by employing PDE, which are then transformed into a system of ODE. The DTM is employed to obtain the solution to system of equations, and the results are interpreted using graphs. It is perceived that the velocity of the nanofluid flow is decreased because of the increased yield stress created by the greater values of the Casson parameter. As a result, the temperature profile is found to be increasing. Meanwhile, it is observed that for increased value of chemical reaction parameter diminishes the nanoparticle concentration. The motile density is found to decrease for increase in the Peclet number and the bioconvection Schmidt number. Further, the thermophoresis improves the temperature and concentration profile of the nanofluid. 相似文献
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M. B. Shavelkina R. Kh. Amirov N. R. Alikhanov I. R. Vakhitov T. B. Shatalova 《Journal of Structural Chemistry》2018,59(4):773-779
A single-stage catalyst free synthesis of hydrogenated graphene was studied in the process of methane conversion in a helium plasma jet created by a plasma torch at the power up to 45 kW and the pressure of 710 Torr. The synthesis products were studied by the methods of scanning and transmission electron microscopy, thermal analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. 相似文献
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Christoph T Koch Somnath Bhattacharyya Manfred Rühle Rapha?lle L Satet Michael J Hoffmann 《Microscopy and microanalysis》2006,12(2):160-169
Amorphous 1-2-nm-wide intergranular films in ceramics dictate many of their properties. The detailed investigation of structure and chemistry of these films pushes the limits of today's transmission electron microscopy. We report on the reconstruction of the one-dimensional potential profile across the film from an experimentally acquired tilt series of energy-filtered electron diffraction patterns. Along with the potential profile, the specimen thickness, film orientation with respect to the grain lattice and specimen surface, and the absolute specimen orientation with respect to the laboratory frame of reference are retrieved. 相似文献
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A novel ordered mesoporous catalyst was prepared from rice husk (MRH catalyst) through condensation–evaporation method in alkaline media. The process used cetyltrimethylammonium bromide (CTAB) as a structure-directing agent (template) and sulfonated biochar obtained from partial rice husk carbonization (SBRH) as precursor. Various parameters such as temperature and CTAB/SBRH mass ratios were investigated to improve the mesoporous structure. The chosen catalyst was based on its degree of order of the mesoporous channels, and its activity was also tested in the methanolysis of linseed oil to methyl esters which was considered as a valuable blending composition for commercial jet fuels. The results showed that the temperature and CTAB/SBRH mass ratio should be of 70 °C and 0.3/1, respectively. The catalyst samples were characterized by many techniques including X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ammonia-temperature programmed desorption (NH3-TPD). The methyl ester composition of the as-synthesized biofuel was determined using gas chromatography supported by mass spectroscopy detector (GC–MS). The results of the characterizations showed that the catalyst possessed superacidic sites (NH3-TPD) caused by –SO3H groups (confirmed by FT-IR analysis) and ordered mesoporous structure (XRD). The mesoporous channel distribution was also observed by TEM images. The methanolysis yield reached 93.5% (calculated through GC–MS analysis) at mild conditions with high purity of methyl ester products strongly proving the catalyst activity and selectivity. 相似文献