Reactions of NO in a Positive Streamer Corona Plasma

The reaction of NO in a streamer corona plasma is studied systematically as a function of the composition of the gas mixture, the initial concentration of NO, and the discharge repetition rate. The experimental results show that the reactions of NO depend strongly on the composition of the gas mixture. Reduction is observed in the absence of oxidants such as oxygen and water, but at very high energy cost (>200 eV/NO). In the presence of both these oxidants, more than 90% of the NO conversion is oxidation. The lowest energy costs, 24 eV/NO for He mixtures and 45 eV/NO for N ₂ mixtures, are obtained at water and oxygen concentration above 3% and at low discharge repetition rates (<10 Hz). Chemical kinetics calculations of the production of radicals in the plasma show a good agreement with the value derived from the experiments.     

Size-dependent reactivity of cobalt cluster ions with nitrogen monoxide: Competition between chemisorption and decomposition of NO

Reactions of NO molecules on cobalt cluster ions were studied in a beam-gas geometry by using a tandem mass spectrometer. Single-particle collision reactions of Co_mNO⁺ (m = 3–10) with NO were found to proceed in such a manner that NO decomposition dominates at m = 4–6 with the maximum reaction cross section at m = 5 and chemisorption dominates in m ≥ 7. On the other hand, in two-particle collision reactions of Co_n⁺ (n = 2–10) with NO, NO decomposition at n ≥ 5 and chemisorption of two NO molecules with Co atoms loss at n ≥ 8 were found to proceed. These results indicate that the size-dependency of the multiple collision reactions originates from secondary attacking of an NO molecule to primary products of the initial single collision reactions. The DFT calculation supports the scheme that both the decomposition and chemisorption of two-particle collision reactions proceed via a common intermediate, Co_mN₂O₂⁺, in which the two NO molecules are dissociatively chemisorbed on the cobalt cluster ion, and the size-dependency of the two-particle collision reactions is explained in terms of the structure of this reaction intermediate.     

金属氧化物表面化学吸附和反应的量子化学簇模型方法研究

综述了本研究小组利用量子化学簇模型方法研究金属氧化物表面化学吸附和反应的工作.提出了选簇的三个原则,即电中性原则、化学配比原则和配位原则.发现在符合前两个原则的基础上,一个具有最饱和配位、或最少悬空键的簇往往是一个用于化学吸附研究的好的簇模型.与此同时,探讨了如何恰当地考虑大块固体本底的长程影响,提出了用球电荷模拟簇模型的环境、环境与簇体进行电荷自洽的SPC簇模型方法.利用该模型研究了一系列具有催化背景的重要体系,包括H2/ZnO、O/MgO、NO/MgO、N2O/MgO、N2O/Li/MgO、CO/MgO、CO/NiO等.     

过渡金属团簇M+2(M=Fe、Co、Ni)与CO的化学反应

利用离子讲质谱计和激光溅射技术相结合,研究了Fe2＋、CO2＋、Ni2＋与CO气体的吸附反应,比较了它们的反应活性,给出了化学反应的速率常数及随反应气体压强的变化关系,并从理论上模拟了化学反应过程,测量结果与已有的实验值符合较好．     

氧化铈表面NO的热脱附性能

氧化铈表面ＮＯ的热脱附性能＊钟依均（浙江师范大学化学系，浙江金华３２１００４）罗孟飞黄宇增朱波袁贤鑫（杭州大学催化研究所，杭州３１００２８）关键词一氧化氮，热脱附，二氧化铈，表面反应ＣｅＯ２作为汽车尾气净化三效催化剂的助剂，由于其特殊的性能越来越引起...     

Gas-sensing properties of Fe2−xTixO3+γ (x = 0–1.4)

As part of a systematic study of mechanisms of response of semiconducting oxides as trace gas sensors, we have explored the behaviour of iron–titanium oxide solid solutions Fe_2−xTi_xO₃ (x = 0.1–1.4). The materials were single-phase for x = 0.1 with increasing proportions of a pseudobrookite second phase at higher degree of substitution. Unmodified, pure iron oxide does not show sensitivity to CO. A significant signal was developed for x = 0.1, that then diminished with increasing x and was lost for x = 1.4. Three effects have been deduced important for the gas response: significant surface segregation of Ti at low Ti content; grain growth inhibition and agglomeration into more massive, non-porous lumps as Ti content increased; and the appearance of a band-gap state associated with Fe(II) at higher Ti content. The effects of microstructure change have been analyzed by fitting the data to a simple 2-resistor model of gas-insensitive ‘grains’ in series with gas-sensitive ‘grain boundaries’. A Mars–van Krevelen type model for the response is presented, based on reactions at surface-segregated defect clusters, to develop and remove electrically-active surface trap states.     

Recent Advances on Confining Noble Metal Nanoparticles Inside Metal-Organic Frameworks for Hydrogenation Reactions

Hydrogenation reaction is one of the pillars of the chemical industry for the synthesis of drugs and fine chemicals. To achieve high catalytic performance, it is still highly desirable for constructing novel supported metal catalysts. Different from conventional supports like metal oxides, zeolites and carbon materials, metal-organic frameworks(MOFs) as the emerging porous materials have Hexhibited great potential to host metal nanoparticles (NPs) for achieving hydrogenation reactions with high catalytic efficiency, due to their unique porous structures. Recently, many progresses have been made, and thus, it is necessary to summarize the recent progresses on confining metal NPs inside MOFs for hydrogenation reactions. In this review, we first introduced the general synthesis methods for confining noble metal NPs inside MOFs. Then, the applications of noble metal NPs/MOFs catalysts in hydrogenation reactions were summarized, and the synergistic catalytic performances among noble metal NPs, metal nodes, functional groups, and pore channels in MOFs were illustrated. Subsequently, the hydrogen spillover effect involved in the hydrogenation reactions was discussed. Finally, we provide an outlook on the future research directions and challenges of confining noble metal NPs inside MOFs for hydrogenation reactions.     

非催化气固反应动力学热分析方法与仪器

准确测量近本征反应速率和计算反应动力学参数是热化学工程和应用化学工程领域的重要研究问题.以热重为代表的传统热分析方法与仪器在非催化气固反应的测试与分析中得到了广泛应用,形成了许多典型的非等温反应分析方法与模型方程.本研究概述了现有热分析的方法原理及在气固反应分析中存在的缺陷,剖析了自主研发的利用微型流化床反应器强化反应...     

分子筛笼内铂羰基簇合物在CO＋NO反应中的催化研究

研究了ＮａＹ分子筛超笼内包容的Ｐｔ羰基簇合物催化剂在ＣＯ＋ＮＯ反应中的催化性能。「Ｐｔ１２（ＣＯ）２４」＾２－／ＮａＹ和「Ｐｔ９（ＣＯ）１３」＾２－／ＮａＹ在此反应中表现出比较高的活性。Ｎ２Ｏ被认为是ＣＯ＋ＮＯ反应的中间产物，同时笼内羰基簇合物还表现了比ＳｉＯ２负载的簇合物好的热稳定性，动力学研究表明，在「Ｐｔ１２（ＣＯ）２４」＾２－／ＮａＹ上，ＮＯ被还原和Ｎ２Ｏ生成的反应级数，相对于ＣＯ分压为小     

ZK-4、NaA和NaHS3种沸石的铝化

用高温气-固相置换法对ZK-4、NaA和NaHS3种沸石进行铝化。组成分析、尾气分析、X射线衍射、晶体形貌分析、红外光谱和²⁹Si高分辨魔角固体核磁结果表明,3种低硅铝比沸石铝化后骨架可能存在Al-O-Al键。     

Functionalizing Single Crystals: Incorporation of Nanoparticles Inside Gel‐Grown Calcite Crystals

Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe₃O₄ nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution‐grown crystals do not. As such, our work extends the long‐history gel method for crystallization into a platform to functionalize single‐crystalline materials.     

Comparative Study of NO and CO Oxidation Reactions on Single-Atom Catalysts Anchored Graphene-like Monolayer

Noble metal single-atom catalysts (NM-SACs) anchored at novel graphene-like supports has attracted enormous interests. Gas sensitivity, catalytic activity, and d-band centers of single NM (Pt and Pd) atoms at graphenylene (graphenylene-NM) are investigated using first-principle calculations. The adsorption geometries of gas reactants on graphenylene-NM sheets are analyzed. It is found that the adsorption energies of reactant species on graphenylene-Pt are larger than those on graphenylene-Pd, because the d-band center of the Pt atom is closeser to the Fermi level. The NO and CO oxidation reactions on graphenylene-NM are investigated via four catalytic mechanisms, including Langmuir-Hinshelwood (LH), Eley-Rideal (ER), New ER (NER), and termolecular ER (TER). The results show that the NO and CO oxidations via LH and TER mechanisms can occur owing to the relatively small energy barriers. Moreover, the interaction of 2NO+2CO via ER mechanism is the energetically more favorable reaction. Although the NO oxidation via the NER mechanism has rather low energy barriers, the reaction is unlikely to occur due to the low adsorption energy of O₂ compared with CO and NO. This research may provide guidance for exploring the catalytic performance of SACs on graphene-like materials to remove toxic gas molecules.     

Nonenzymatic Simulation of Nitrogenase Reactions and the Mechanism of Biological Nitrogen Fixation

The development of biologically relevant model systems of nitrogenase permitted the simulation of virtually all known reactions of the nitrogen reducing enzymes under nonenzymatic conditions. On the basis of these experiments, a mechanism of biological nitrogen fixation is formulated which is in accord with the available enzymological evidence. The key reactions of the substrates of nitrogenase occur at a molybdenum active site. The non-heme iron, which is bound to sulfur and protein-S^? groups, mediates the transport of electrons to the molybdenum active site but does not participate directly in the reduction of the substrates. ATP is required for the acceleration of the reduction and activation of the molybdenum site and is hydrolyzed to ADP and inorganic phosphate. Diimine and hydrazine were detected as intermediates in the reduction of molecular nitrogen under nonenzymatic conditions.     

乙炔基自由基(C2H·)与二氧化氮(NO2)气体反应势能面的理论研究

在 CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPE 水平上对反应C2H+NO2 进行了计算, 建立了反应势能面并得到了3种产物. 利用RRKM理论估算了反应的总速率和分支比. 总速率为1.427×10-12×T0.556×exp(190.547/T) cm3*molecule-1*s-1, 其中主要产物P1(HCCO+NO)比例大于96%, 次要产物P2(HCNO+CO)和P3(HCN+CO2)小于4%.     

氮、 硼掺杂石墨烯活性位点及其在氧化反应中作用的研究进展

随着绿色化学的逐渐推广,碳材料作为最有前途的绿色无金属催化剂而备受关注。通过对石墨烯引入杂原子进行化学掺杂是目前最常用于改良碳材料催化活性的有效方法。从结构上看,掺杂石墨烯内特定活性物种在催化过程中起到活性位点的作用,且催化剂的催化活性随活性位点含量增加而增强。且其内部活性位点含量可通过改变制备方法中制备条件实现调控,这有助于开发具有高催化活性的掺杂石墨烯催化剂。本文综述了氮掺杂石墨烯和硼掺杂石墨烯内可作为活性位点的官能团,提出制备方法对活性位点含量的影响,并讨论了内部活性位点在氧化反应中的作用。最后对未来研究方向提出了建议和展望,为开发更高效掺杂石墨烯催化剂提供了思路。     

Perovskite Oxide as A New Platform for Efficient Electrocatalytic Nitrogen Oxidation

Electrocatalytic nitrogen oxidation reaction (NOR) offers an efficient and sustainable approach for conversion of widespread nitrogen (N₂) into high-value-added nitrate (NO₃⁻) under mild conditions, representing a promising alternative to the traditional approach that involves harsh Haber–Bosch and Ostwald oxidation processes. Unfortunately, due to the weak absorption/activation of N₂ and the competitive oxygen evolution reaction, the kinetics of NOR process is extremely sluggish accompanied with low Faradaic efficiencies and NO₃⁻ yield rates. In this work, an oxygen-vacancy-enriched perovskite oxide with nonstoichiometric ratio of strontium and ruthenium (denoted as Sr_0.9RuO₃) was synthesized and explored as NOR electrocatalyst, which can exhibit a high Faradaic efficiency (38.6 %) with a high NO₃⁻ yield rate (17.9 μmol mg⁻¹ h⁻¹). The experimental results show that the amount of oxygen vacancies in Sr_0.9RuO₃ is greatly higher than that of SrRuO₃, following the same trend as their NOR performance. Theoretical simulations unravel that the presence of oxygen vacancies in the Sr_0.9RuO₃ can render a decreased thermodynamic barrier toward the oxidation of *N₂ to *N₂OH at the rate-determining step, leading to its enhanced NOR performance.     

亨利反应的不对称催化研究进展

在有机合成中,亨利反应是一个非常有效的构造碳碳键的反应[1],1895年,Henry首先发现了此反应[2],它主要是硝基烷烃（提供亲核试剂）与醛或者酮类（作为亲电试剂）反应生成β-硝基醇类化合物,此产物可以作为一种重要的中间原料,能用来制备多种多样有机物,特别是通过不对称亨利反应并进一步还原得到的手性β-氨基醇类化合物...     

铯盐促进的有机反应

铯盐如Cs₂CO₃, CsF等因在钯催化碳碳偶联, N, O, S的烃基化反应中表现出良好的性能而引起了人们的广泛关注. 介绍了铯盐在钯催化的Suzuki, Heck, Stille, Sonogashira反应, 烯醇盐的芳基化, 酚类的邻位芳基化以及羰基化反应中的促进作用. 同时还对铯盐参与的N, O, S等的烃基化反应进行了讨论, 并侧重于与其他碱金属盐的对比.     

痕量NO测定的三阶跃库仑仪

设计了一种新型三阶跃库仑仪 ,其阶跃电位和阶跃停留时间皆可调 ,输出信号为将电流经积分转换为库仑数 ,并以数字显示 ,直接读出被测物的浓度 ,用于痕量NO测定 ,具有体积少 ,重量轻 ,抗干扰能力强 ,使用方便 ,灵敏度高 ,适合于现场测定等特点。特别适合经氧化、还原、再氧化时灵敏度增加的体系 ,可使检测限降至 3.5× 1 0 - 1 0 mol/L ,线性范围为 1 .5× 1 0 - 9～ .5× 1 0 - 6mol/L。