分子离子NO+激发态的势能函数

100公里以上的大气分子离子主要为NO~+。它的辐射特点及它与电子、原子或分子的相互作用,对于理解大气的化学过程具有特别重要的意义。为了研究这些过程,确定NO~+分子离子基态及其各个激发态的分子势能函数是非常重要的。精确的X~1Σ~+,A~1Ⅱ和a~3∑~+势能曲线已发表;基于光电子谱的研究发现了NO~+的其它激发态,但对于这些激发态的研究尤其是势能函数的研究不多。本文研究并导出NO~+的基态和10个激发态的势能函数。     

OBrO+NO反应机理的量子化学研究

用密度泛函B3LYP/6-311+G^**和高级电子相关偶合簇CCSD(T)/6-311+G^**方法研究了OBrO与NO反应的微观机理.优化得到反应路径上的反应物、过渡态、中间体和产物的几何构型,通过频率振动分析对过渡态和中间体进行了确认.结果表明;该反应是多通道多步骤的放热反应,分别可以在单重态和三重态势能面上进行,OBrO与NO通过加成及加成-消除机理分别形成产物BrONO₂和BrO+NO₂,从能量上看,形成离解产物的通道更容易进行.     

17O excess transfer during the NO2 + O3 → NO3 + O2 reaction

The ozone molecule possesses a unique and distinctive (17)O excess (Δ(17)O), which can be transferred to some of the atmospheric molecules via oxidation. This isotopic signal can be used to trace oxidation reactions in the atmosphere. However, such an approach depends on a robust and quantitative understanding of the oxygen transfer mechanism, which is currently lacking for the gas-phase NO(2) + O(3) reaction, an important step in the nocturnal production of atmospheric nitrate. In the present study, the transfer of Δ(17)O from ozone to nitrate radical (NO(3)) during the gas-phase NO(2) + O(3) → NO(3) + O(2) reaction was investigated in a series of laboratory experiments. The isotopic composition (δ(17)O, δ(18)O) of the bulk ozone and the oxygen gas produced in the reaction was determined via isotope ratio mass spectrometry. The Δ(17)O transfer function for the NO(2) + O(3) reaction was determined to be: Δ(17)O(O(3)?) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99). The intramolecular oxygen isotope distribution of ozone was evaluated and results suggest that the excess enrichment resides predominantly on the terminal oxygen atoms of ozone. The results obtained in this study will be useful in the interpretation of high Δ(17)O values measured for atmospheric nitrate, thus leading to a better understanding of the natural cycling of atmospheric reactive nitrogen.     

NO+HCCCO反应势能面的理论研究

在CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPVE水平下, 对反应NO＋HCCCO进行了研究. 建立了反应势能面, 揭示了该反应的反应机理, 通过O迁移、C—C键或N—O键断裂等多步反应, 得到4种产物, 其中, 最主要产物为P1(HCCO+NCO).     

HOSO+NO反应的机理及动力学

在B3LYP/6-311++G(d,p)水平上研究了HOSO+NO的反应机理. 优化得到了反应势能面上各驻点的几何构型, 通过内禀反应坐标(IRC)确认了反应物、中间体、过渡态和产物的相关性. 在CCSD(T)/6-311++G(d,p)水平上对计算得到的构型进行了能量校正. 应用经典过渡态理论(TST)与变分过渡态理论(CVT), 并结合小曲率隧道(SCT)效应模型校正的方法计算了标题反应在200-3000 K温度范围内的速率常数k^TST、k^CVT和k^CVT/SCT. 计算结果表明: HOSO+NO反应在单重态和三重态条件下均可发生, 其中单重态反应为主反应通道, HNO+SO₂为主产物. 并利用电子密度拓扑分析方法研究主反应通道反应过程中的化学键变化.     

用TR-FTIR研究CH+NO2的反应

CH自由基是烃类燃烧过程中反应活性很高的重要的中间产物[1,2].CH自由基与氮氧化物的反应被认为是通过二次燃烧过程减少氮氧化物的主要反应之一,也是对火焰中氮化物的化学行为建立模型的关键步骤[3].但是,对于CH与NO2反应的研究还不是很深入,到目前为止,只有两篇论文报道了该反应在298 K时的总包反应速率常数[4,5],Taeg和Hershberger用红外二极管激光吸收法研究了该反应[6].他们在实验中只观测到了产物CO和NO,但一些较低能量的产物,如NH+CO2、OH+NCO等却没有被观察到.为了更深一步了解CH与NO2的反应产物及反应通道,我们用时间分辨傅立叶变换红外发射光谱(TR-FTIR)法研究了该反应.     

Radiation-Thermal Decomposition of NO2–NO Mixtures in a 60Co γ-Radiation Field

The effect of nitrogen monoxide (up to 60 wt %) on the radiation-thermal decomposition of a dissociating mixture based on N₂O₄ in a ⁶⁰Co -radiation field was studied over the temperature range 200–300° at a pressure of 2 MPa. A comparison of the experimental results with data calculated using an additive mathematical model of radiolysis and data obtained in previous studies on processes in an n,-radiation field led to the conclusion that the role of intermolecular energy-transfer processes is insignificant. The currently available mathematical model adequately describes the radiolysis of nitrogen oxides over wide temperature and pressure ranges.     

HCO+NO2反应势能面的理论研究

在B3LYP/6-311G(d,p)和CCSD(T)/6-311G(d,p)水平上给出了HCO+NO₂反应详细的势能面信息.计算结果表明,该反应采用两种无垒进攻方式,分别得到两种加合物H(O)CNO₂和H(O)CONO.找到7种能量低于反应物且合理的产物及相应的反应路径.通过对热力学和动力学的分析,产物HONO+CO(P2,P3),HNO+CO₂(P1)和H+CO₂+NO(P6)的形成更为有利.计算结果同实验相符,且有助于深入了解HCO自由基的化学行为.     

H+CH3NO2H2+CH2NO2反应途径和变分速率常数计算研究

采用MP2(FULL)/6-311G**从头算方法, 优化了H+CH3NO2H2+ CH2NO2反应的过渡态结构, 得出该反应的正逆反应的活化位垒分别是82.73和57.14 kJ*mol-1. 沿IRC分析指出该反应是一个H-H键生成和C-H键断裂的协同反应, 而且在反应途径上存在一个引导反应进行的振动模式, 这一反应模式引导反应进行的区间在-0.7～0.2( amu)1/2*a0之间; 在1 000～1 400 K温度范围内, 运用变分过渡态理论(CVT), 计算了该反应的速率常数, 计算结果与实验相一致.     

Synthesis of Mg–Al–Fe–NO3 layered double hydroxides via a mechano-hydrothermal route

Mg–Al–Fe–NO₃ layered double hydroxides (LDHs) with a constant Mg²⁺/(Al³⁺ + Fe³⁺) molar ratio but varying Al³⁺/Fe³⁺ molar ratios were successfully synthesized by a mechano-hydrothermal (MHT) method from Mg(OH)₂, Al(OH)₃ and Fe(NO₃)₃·9H₂O or Mg(NO₃)₂·6H₂O as starting materials. The resulting LDHs (MHT-LDHs) were characterized by XRD, TEM, SEM, FT-IR, and zeta potential, size distribution and specific surface area analyses. It was found that pre-milling played a key role in the LDH formation during subsequent hydrothermal treatment. The MHT route is advantageous in terms of low reaction temperature compared with the conventional hydrothermal method, and the target products are of high crystallinity and good dispersion compared with the conventional mechanochemical (MC) method. The MHT-LDHs had higher specific surface area and zeta potential, and lower hydrodynamic diameter than LDHs obtained by MC method (MC-LDHs). Furthermore, the removal of Cr(VI) from aqueous solutions using the LDHs was examined, showing that the MHT-LDHs are of higher removal efficiency than MC-LDHs for the heavy metal pollutant.     

四元轻稀土硝酸盐水溶液体系{H2O+La(NO3)3+Pr(NO3)3+Nd(NO3)3}的热力学研究

在298.15 K条件下, 利用等压法研究了四元轻稀土硝酸盐水溶液{H2O La(NO3)3 Pr(NO3)3 Nd(NO3)3}及其3个二元亚系{H2O La(NO3)3}, {H2O Pr(NO3)3}和{H2O Nd(NO3)3}的热力学性质. 以NaCl或CaCl2水溶液为参考溶液, 测定了不同水活度条件下该四元溶液的渗透系数及各溶质组元的活度系数. 实验结果表明, 上述四元系与其3个二元亚系之间存在简单共性, 在实验误差允许范围之内(|Δ|≤0.0010), 该四元系符合偏理想溶液模型.     

三效催化剂作用下的NO+CO催化反应机理

NO与CO在Pt/Rh/Pd及载体组成的三效催化剂上的氧化还原应用是控制汽车尾气对空气污染的一个关键反应，这一反应随着近年来对环境保护的日益重视而成为国内外研究的热点，本文主要综述了NO及CO在Pt,Rh,Pd上的吸附及反应机理的实验及理论研究现状，总结得出：在三效催化剂对NO CO的催化反应中，Pt,Pd对CO的催化氧化起主要作用，而Rh对NO的解离有很好的活化作用。     

Catalytic oxidation of NO over Mn–Co–Ce–Ox catalysts: effect of reaction conditions

Manganese–cobalt–cerium oxide (Mn–Co–Ce–Ox) catalysts were synthesized by the co-precipitation method and tested for activity in low-temperature catalytic oxidation of NO in the presence of excess O₂. With the best Mn–Co–Ce mixed-oxide catalyst, approximately 80 % NO conversion was achieved at 150 °C and a space velocity of 35,000 h^?1. The effect of reaction conditions (reaction temperature, volume fractions of NO and O₂, gas hourly space velocity (GHSV), and catalyst stability) was investigated. The optimum reaction temperature was 150 °C. Increasing the O₂ content above 3 % results in almost no improvement of NO oxidation. This catalyst enables highly effective removal of NO within a wide range of GHSV. Furthermore, the stability of the Me–Co–Ce–Ox catalyst was excellent; no noticeable decrease of NO conversion was observed in 40 h.     

High-pressure densities and P–T–x–y diagrams for carbon dioxide+linalool and carbon dioxide+limonene

Liquid and vapor densities for carbon dioxide+linalool, and carbon dioxide+limonene were measured by using a system consisting of two vibrating tube densimeters. The P–T–x–y diagrams and saturated liquid and vapor densities for these two binary mixtures were determined at 313, 323 and 333 K, respectively, as well as at pressures up to 11 MPa. The density of the saturated CO₂ phase increased with increasing pressure. At higher pressure, the density of the liquid phase decreased with increasing pressure, corresponding to an increasing amount of carbon dioxide.     

Radioluminescence of Europium(III) in POCl3–SnCl4–235UO2+ 2–Eu3+, and D2O–235UO2+ 2–Eu3+ Solutions

Results of studying the spectral and luminescent properties of Eu³⁺ ions upon homogeneous excitation of POCl₃–SnCl₄–^-UO²⁺ ₂–Eu³⁺ and D₂O–²³⁵UO²⁺ ₂–Eu³⁺ solutions by -particles are presented. It was found that the radioluminescence intensity of Eu³⁺ ions in both solvents increases proportionally to the energy input by -particles. The yield of radioluminescence photons from europium ions in the POCl₃–SnCl₄–UO²⁺ ₂–Eu³⁺ solutions is more than nine times as high as that in D₂O–UO²⁺ ₂–Eu³⁺. The radiation-chemical yields of excited ⁵ D ₀ states of Eu³⁺ ions are 0.74 ± 0.07 and 0.18 ± 0.02 ions/100 eV in POCl₃–SnCl₄–UO²⁺ ₂–Eu³⁺ and D₂O–UO²⁺ ₂–Eu³⁺ solutions, respectively.     

芳烃硝化中的NO_2~++NO→NO_2+NO~+电子转移

用电子转移半经典理论,在谐振势近似下,导出交叉反应电子转移的动力学模型,在UHF/6-31G基组水平上,优化电子转移NO_2~++NO→NO_2+NO~+的碰撞络合物结构,用线性反应坐标研究了电子转移反应的透热势能面,反应活化能,电子转移矩阵元等动力学参量,对此交叉反应及相应的自交换反应体系NO_2~+/NO_2和NO~+/NO作动力学计算,得这3个基元步骤的活化能分别为81.4,128.8,和39.3KJ·mol~1.用过渡态结构参数估算溶剂重组对活化能的贡献,计算了300K时的速率常数.高的活化能垒可能影响NO_2~+在芳烃硝化中作为氧化剂的反应活性.     

Electron transfer NO_2~++NO→NO_2+NO~+ in aromatic nitration

A simple model for computing the electron transfer rate constant of a cross-reaction has been proposed in the framework of semiclassical theory and employed to investigate the electron transfer system NO2+/NO.The encounter complex of electron transfer NO2++NO→NO2+NO+has been optimized at the level of UHF/6-31G.In the construction of diabatic potential energy surfaces the linear coordinate was used and the kinetic quantities,such as the activation energies and the electron transfer matrix elements,have been obtained.For comparison,the related self-exchange reation systems NO2+/NO2 and NO+/NO were kinetically investigated.The calculated activation energies for the electron transfer reactions of systems NO2+/NO,NO2+/NO2,and NO+/NO are 81 4,128.8,and 39.8kJ mol-1,respectively With the solvent effect taken into account,the contribution of solvent reorganization to the activation energy has been estimated according to the geometric parameters of the transition states.The obtained rate constants show that the     

Selective catalytic reduction of NO with CO on Pt/W–Ce–Zr catalysts

Various Pt catalysts (Pt/ZrO₂, Pt/CeO₂, Pt/CeZrO, Pt/WO₃/ZrO₂ and Pt/WO₃/CeZrO) were prepared and characterized, and their catalytic reduction reactions of NO by CO, with or without the presence of excess oxygen, were investigated. The results of temperature-programmed experiments showed that CO could be easily oxidized over Pt/CeO₂ and Pt/CeZrO while the introduction of WO₃ into the catalyst (Pt/WO₃/CeZrO) inhibited the reduction of catalyst surface; NO could not dissociate over those catalysts in oxidized state but after CO reduction at a low temperature, NO dissociation took place only over Pt/CeO₂ and Pt/CeZrO catalysts. For NO + CO reaction, those easily reduced catalysts Pt/CeO₂ and Pt/CeZrO exhibited better catalytic performances, and NO could be rapidly converted below 350 °C. For the reaction with the presence of excess O₂, the NO conversions were significantly inhibited, but better NO conversions were obtained over the tungstate-contained catalysts when compared with Pt/CeO₂ and Pt/CeZrO. The higher activities of Pt/W–Ce–Zr catalysts were attributed to their high acidities.     

Reactivity of Cl–P+–Cl toward cyclic organic ethers

The dichlorophosphenium ion (Cl-P(+)-Cl) undergoes a variety of reactions with cyclic organic ethers in the gas phase in a Fourier-transform ion cyclotron resonance mass spectrometer. Most of the reactions are initiated by Cl-P(+)-Cl-induced heterolytic C-O bond cleavage. However, the observed final products depend on the exact structure of the ether. For saturated ethers, e.g., tetrahydropyran, tetrahydrofuran, and 2-methyltetrahydrofuran, the most abundant ionic product corresponds to hydroxide abstraction by Cl-P(+)-Cl. This unexpected reaction is rationalized by a multistep mechanism that involves an initial heterolytic C-O bond cleavage accompanied by a 1,2-hydride shift, and that ultimately yields a resonance-stabilized allyl cation and HOPCl2. The process is estimated to be highly exothermic (AM1 calculations yield delta H = -(33-38) kcal mol(-1) for the ethers mentioned above). However, the adducts formed from most of the unsaturated ethers are unable to undergo hydride shifts and hence cannot react via this pathway. In some of these cases, e.g., for 2,5-dihydrofuran and 2,5-dihydro-3,4-benzofuran, the C-O bond heterolysis is followed by oxygen/chlorine exchange to yield the O=PCl radical and a resonance-stabilized carbocation (AM1 calculations yield delta H = -14 kcal mol(-1) for the reaction of 2,5-dihydro-3,4-benzofuran). Hydride abstraction by Cl-P(+)-Cl also yields an abundant product for these two ethers. On the other hand, the ethers with low ionization energies, such as 2,3-dihydrofuran and 2,3-dihydrobenzofuran, react with Cl-P(+)-Cl by electron transfer. Finally, a unique pathway, addition followed by elimination of HCl, dominates the reaction with furan. The observed reactions are rationalized by thermochemical data obtained from semiempirical molecular orbital calculations.