氨合成铁催化剂上氮吸附态的研究——Ⅰ.氨合成铁催化剂表面上吸附氮的激光Raman光谱和红外光谱

关于在铁催化剂上氨合成反应的机理及其活性中心本质的认识,迄今未取得一致。主要分歧在于氮究竟是解离化学吸附或非解离化学吸附?吸附分子氮是先解离后加氢,抑或先部分加氢而后解离?氮分子的解离有否通过氢的作用?随着研究进展,在氨合成     

H2O在Pt电极上解离反应的理论研究

水解离生成氧气的反应（〇ER:H2〇—1/2〇2+2H+ +2e-)是阳极最重要的反应之一,且广泛应用于能量存储/转化的各种设备中。但是由于该反应需要很高的过电势,其在电解工业（如氯碱工业）中造成大量的能量损失,所以人们一直在努力寻找对于氧气析出反应有更高效率的阳极材料。人们熟知在一定的电势条件下,水会解离成氧化物种（如〇H和〇）吸附于电极表面,并且随着电势的增加,吸附的氧化物种会进一步耦合成氧气。研究了 H2〇在Pt电极上的解离反应。通过计算,获得了氧气析出过程中密堆积的Pt( 111)表面和台阶Pt(211)表 面的相图。结果显示台阶面能够更好的吸附氧化物种(〇和〇H),且在相同电势条件下比平台 (111)表面的氧覆盖度高。在金属表面发生氧覆盖的同时,我们发现在电势低于1. 4 V时表面氧化形成次表层的氧的过程在热力学上已经能够发生。如计算结果所示,Pt电极上的H2〇解离反应是表面敏感反应,并且在高电势条件下易于氧化腐蚀。     

担载型镍基催化剂上甲烷二氧化碳重整反应机理的研究

采用TPSR、TPD和脉冲反应等方法对担载型镍基催化剂上甲烷二氧化碳重整反应过程中二者的吸附和解离行为进行了详尽的研究．结果表明：CH4在镍基催化剂表面被吸附时至少可解离为三种表面碳物种——Cα、Cβ和Cγ．其中完全脱氢的Cα物种是活泼的反应中间体，而石墨态的Cγ物种则可能是造成催化剂积碳的前身物．高温下部分脱氢的Cβ物种可与H2或CO2反应生成CH或CO．另一方面，CO2仅在该催化剂表面发生弱吸附且只形成一种吸附态．在此基础上推测出甲烷二氧化碳重整反应的协同作用机理．     

氢在Ni(410)台阶面的吸附研究

应用嵌入原子模型(EAM)研究了氢在Ni(410)面的吸附和解离.首先计算单个氢原子在Ni(410)面上的吸附能Ead,吸附键长RH-Ni及吸附高度H0,发现氢在Ni(410)面上有3种相对稳定的吸附位:台面上的赝式四重洞位H1和H2位、台阶底部棱上的LB位和台阶一边棱位B.与低指数面Ni(001)相比,明显增加了台阶棱上的B位以及台阶底部棱上的LB位,相应洞位的吸附性也有增强.说明氢在Ni(410)表面的吸附性受到台阶的影响,从而台阶附近的吸附位增多且吸附性增强;然后计算了H2在Ni(410)表面解离吸附时的活化势垒Ea、吸附能Qad,氢-镍之间键长RH-Ni,构建了解离吸附等势面,计算结果表明台阶处是氢吸附和解离的活跃部位.     

NiMn双金属与MgO载体间的相互作用对氢气解离的影响

采用密度泛函理论,在电子水平上研究了NiMn双金属与MgO载体间的相互作用以及这种相互作用对H原子吸附和H_2解离的影响,并把所得结果与Ni/MgO上相应的结果作比较。研究过程中分别采用完美的和有缺陷的MgO载体负载Ni_2Mn_2簇,构建了两种催化剂模型。结果表明,表面有缺陷的MgO与活性组分Ni_2Mn_2间的相互作用大于完美面MgO与活性组分间的相互作用,H原子在有缺陷的MgO负载的Ni_2Mn_2催化剂上的吸附能大于完美面MgO负载的Ni_2Mn_2催化剂上的吸附能,并且有缺陷的MgO负载的Ni_2Mn_2催化剂更有利于H_2解离;与Ni4负载的MgO上金属与载体间相互作用相比较,添加第二种金属Mn会使活性组分与MgO载体间的相互作用减弱,吸附H原子的能力增强,但是不利于H_2解离。此结果为通过加入第二种金属或改变载体来调变金属-载体间相互作用进而改变催化剂性能的实验研究提供了理论线索。     

储氢材料富镧混合稀土镍锰α相吸氢动力学研究

本文讨论了储氢材料α相吸氢过程,在处理表面吸附解离反应时,以描述实际吸附解离反应的吸附等温式及对应的速率方程代替文献中普遍采用的、只适于理想吸附情况的Langmuir方程;所获得模型的计算值与实验数据比较符合。通过对富镧混合稀土镍锰MmNi4.5Mn0.5α相吸氢反应的实际处理,提出该反应的速率控制步骤随反应进程改变的反应机理。     

甲烷水蒸汽转化反应的动力学与机理

使用CD—1型无梯度反应器(反应条件:645—794℃,30公斤/厘米~2,水气比3:1—5:1).测定了CN—7转化催化剂(负载于Al_2O_3的镍催化剂上).甲烷蒸汽转化动力学,提出了在高温中压下镍催化剂上的反应机理,主要包括甲烷的解离吸附(速度控制步骤),水的解离吸附,以及新生产物的中间反应.由此导出的动力学方程与实验数据符合.     

变换-甲烷化催化剂上氢和水的吸附及其与CO的反应性能

本文应用脉冲色谱法,对镍基催化剂上H_2和H_2O的不可逆吸附,以及CO和它们的反应情况进行了研究。观察到水的解离吸附特点及其对变换-甲烷化反应,尤其是对CO活化吸附的影响。证明了实际镍基催化剂上甲烷化反应的表面碳机理。并对变换-甲烷化反应机理进行了探讨。     

微波场中甲烷部分氧化制合成气的反应机理

用ＸＰＳ技术对催化剂进行了测试，结果表明，催化剂表面上均存在着两类不同的表面氧种：晶格氧和吸附氧，且这两类表面氧种的相对含量与催化剂的活化方式有关。微波活化方式下的表面晶格氧含量普遍比常规活化方式下的高，这可归之于微波场加速了可动晶格氧的迁移所致。微波辐照下的ＰＯＭ反应可能是按甲烷解离机理来进行的，甲烷的解离是反应的决速步骤。     

NO在Ir(110)表面吸附和解离反应的泛函密度理论

采用密度泛函理论(DFT)和周期性平板模型,考察NO在Ir(110)表面上的吸附、解离及N2生成机理.计算结果表明:NO以N端向下在顶位吸附为最稳定的吸附方式,其次是短桥位,空位吸附最不稳定;顶位吸附的NO在表面存在2条解离通道:1)直接解离通道;2)由初始态扩散到短桥位,继而发生N—O键断裂生成N原子和O原子,是NO在表面解离的主要通道;解离后的N原子经联短桥位共吸附态发生N—N聚合反应生成N2,在表面共存的O原子促进了N2的生成,与实验结果相符.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with