Quasi-Classical Trajectory Studies of H + HX → H2 + X (X = Cl,Br, I) Reaction at High Collision Energy

Quasi-classical trajectory calculations have been performed to investigate the dynamics of the H + HX → H₂ + X reactions, where X = Cl, Br, and I. Calculations were performed for two collision energies, 16 and 36 kcal mol⁻¹. The results show that the dynamics of the abstraction reactions at these high collision energies are rather unusual. The product energy and angular distributions can be accounted for by a mechanism that involves an isolated interaction between the two H atoms in the system to form H₂ followed by hard-sphere scattering of this newly formed H₂ off the X atom.     

Light Scattering Probes of the H + H2 Reaction

We present calculated Raman and CARS (coherent anti-Stokes Raman scattering) spectra of the collinear H + H₂ reaction. These spectra, obtained by detuning the laser frequencies from all H₂ absorptions, show strong enhancements as the collision energy on the ground state potential energy surface is scanned through a reactive scattering resonance. We also demonstrate that the Rayleigh scattering and degenerate four-wave mixing spectra show enhancements greater by orders of magnitude than the corresponding Raman and CARS peaks. The experiments suggested in this paper offer a unique, direct method for obtaining information about the vibrational dynamics of the transition state of chemical reactions.     

Single and Merged Beam Studies of the Reaction H2+ (v = 0,1; j = 0,4) + H2 → H3+ + H

Different approaches for studying low-energy (meV) reactive ion-molecule collisions in molecular beams are presented. In particular, differences in the photoionization (REsonant Multi-Photon Ionization / REMPI, Pulsed Field Ionization / PFI) experiments using single molecular beams vs. merged and crossed beams are discussed. We address the question of the proper determination of cross sections and rate constants in single beam experiments and the factors that influence the width of the collision energy distributions. We identify space charge effects as the dominant contribution under our experimental conditions. Problems pertinent to state-selected primary ion preparation with narrow energy distributions are highlighted. In light of the detailed data analysis, the derived relations are applied to the four-center reaction H₂⁺ + H₂ → H₃⁺ + H, which was studied in single and merged molecular beam experiments. We present merged beam data for the absolute reaction cross section for primary ions created in a storage ion source in the energy range from 5 meV up to 5 eV and relative state-selected cross sections for different vibrational and rotational ion states (v = 0,1; j = 0–4) generated by (3+1) REMPI for a mean collision energy of about 10 meV.     

Interfacial Energies in the Si/SiC System and the Si+C Reaction

The high ratio of the SiC grain-boundary energy to the Si(l)/SiC interfacial energy is used to explain two microstructural observations: (1) the penetration of dense SiC by Si(l), and (2) the morphology of the SiC formed when glassy carbon is reacted with Si(l). Comments are made concerning the mechanism of the Si+C reaction and the effect of sintering aids on the SiC grain-boundary energy.     

Reaction Propagation Rates in HMX at High Pressure

We have measured the reaction propagation rate (RPR), or deflagration rate, in octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) powder in a diamond anvil cell over the pressure range 0.7–35 GPa. Numerical simulations of the RPR of pressurized HMX were also performed for comparison to the experimental results obtained. The simulated RPR values closely approximate the observed rates at pressures up to 3 GPa, and serve as a bridge to lower‐pressure deflagration rates for HMX in the literature. However, at higher pressures the simulated RPR values deviate significantly from our experimental results. This suggests that further refinement to the computational model is required for the calculated RPR values to approach those observed at higher pressures.     

CO2与水蒸汽对焦炭溶损反应的影响

采用自制气-固相反应测定仪,于950~1200℃温度范围内研究了焦炭与CO2、水蒸汽的溶损反应. 结果表明,焦炭与水蒸汽反应的气化率约为与CO2反应的2~7倍,随温度升高,二者气化率差距缩小;焦炭与CO2或水蒸汽的反应过程受界面反应控制较明显,可用未反应收缩核模型描述,反应的活化能分别为165.48和82.25 kJ/mol;随温度升高,焦炭颗粒由外到内溶损量呈减少趋势,焦炭与水蒸汽反应比与CO2反应更多发生在颗粒表面;不同部位气孔生成方式不同,焦炭与CO2、水蒸汽反应后,边缘部位大于10 mm的气孔所占比例分别增加66.98%和94.01%,中心部位大于10 mm的气孔所占比例分别降低21.22%和3.30%.     

State-Resolved Stereodynamics of an Insertion Reaction O(1D2) + H2(v = 0, j) → OH(X2Πi; v′, N′, f′) + H

The product state-resolved stereodynamics of the reaction of O(¹D₂) with H₂ have been studied at 300 K at a mean collision energy of ca. 12 kJ mol⁻¹, using polarized, Doppler-resolved laser-induced fluorescence to probe the scattered products, OH(X²Π_i; v′ = 0, N′, f′), and polarized photodissociation of N₂O to provide the reagent O(¹D₂) atoms. Product state-resolved differential cross sections, rotational polarizations, and excitation functions are in very good qualitative agreement with the results of quasi-classical trajectory (QCT) calculations, conducted on the Schinke-Lester, SL1 ab initio potential energy surface (PES) for the ground electronic state of the collision complex. The experimental and computational results are compared with those obtained in a complementary study of the reaction of O(¹D₂) with CH₄ and remarkable parallels have been exposed. The linear and angular momentum vector correlations are all consistent with an “insertion” mechanism, proceeding over an attractive PES, which presents no entrance barrier.     

Crossed-Beam and Quantum Dynamics Studies of the Reaction Cl + CHD3

The ground-state reaction of Cl + CHD₃ was studied with joint experimental and theoretical efforts. Experiments were performed under crossed-beam conditions using a time-sliced velocity imaging detection method. By taking the images over the energy range of chemical significance—from threshold to about 9 kcal/mol—the reactive excitation functions as well as the dependence of product angular distributions and of the energy disposal on initial collision energies were obtained for both isotopic product channels. Theoretically, reduced dimensionality quantum dynamics calculations were performed for the HCl + CD₃ channel, and the results are in excellent agreement with experimental findings. Comparisons with previously reported results on Cl + CH₄/CD₄, both experimental and theoretical, were also made to gain deeper insights into the dynamics of this benchmark atom + polyatomic reaction.     

四元体系NaCl+NaBO2+Na2CO3+H2O 298.15 K 相平衡研究

柴达木盐湖中具有丰富的盐湖离子,对其中的一个四元体系水盐相图开展研究,采用等温溶解平衡法开展了298.15 K时四元体系NaCl+NaBO₂+Na₂CO₃+H₂O相平衡研究,测定了体系平衡液相组成及密度和折光率,绘制了四元体系NaCl+NaBO₂+Na₂CO₃+H₂O 298.15 K的相图及相应的物化性质图。研究发现NaCl+NaBO₂+Na₂CO₃+H₂O四元体系298.15 K 时包含2个共饱点（E₁、E₂）、5条溶解度曲线（AE₁、BE₁、CE₂、DE₂、E₁E₂）、4个结晶区（NaCl、NaBO₂·4H₂O、Na₂CO₃·7H₂O、NaCl·NaBO₂·2H₂O）。其中三元体系NaCl+NaBO₂+H₂O在298.15 K下产生了复盐NaCl·NaBO₂·2H₂O,通过研究发现该四元体系NaCl+NaBO₂+Na₂CO₃+H₂O在298.15 K下也具有NaCl·NaBO₂·2H₂O复盐区。     

Solubility measurement and prediction of phase equilibria in the quaternary system LiCl + NaCl + KCl + H2O and ternary subsystem LiCl + NaCl + H2O at 288.15 K

Using isothermal dissolution method, the phase equilibrium relationship in quaternary system LiCl + NaCl + KCl + H₂O and the ternary subsystem LiCl + NaCl + H₂O at 288.15 K were investigated. Each phase diagram of two systems was drawn. The phase diagram of LiCl + NaCl + H₂O system contains two solid phase regions of crystallization LiCl·2H₂O and NaCl. In the phase diagram of LiCl + NaCl + KCl + H₂O system, there are three crystallization regions: LiCl·2H₂O, NaCl and KCl respectively. In this paper, the solubilities of phase equilibria in two systems were calculated by Pitzer's model at 288.15 K. The predicted phase diagrams generally agree with the experimental phase diagrams.     

The Kinetics of Complexed and Free Ho2 Radical in the Reaction of Ce+4 and H2O2

The intermediates formed in the reaction of Ce⁺⁴ with H₂O₂ in 0.5 M perchloric acid were studied, spectrophotometrically and through the quenching method, using a stopped-flow system. The spectrum in the UV range and the kinetics of the generated radicals and their dependence on Ce⁺³ concentration were investigated. On adding Ce⁺³ to the mixture, a change in the spectrum as well as in the recombination rate constant was observed. This behaviour was attributed to the formation of a complex between the cerous ion and the HO₂ radical. The values of the recombination rate constant of the complexed radical is 4.0 ± 0.4·10⁶ F^?1 sec^?1 while that of the free HO₂ radical is 0.9 ± 0.1·10⁶ F^?1 sec^?1. The stabilization constant of the complex was found to be 60 ± 18 F^?1.     

氢气在松脂和松香中的高压平衡溶解度

采用FYX-2G型高压搅拌釜,在温度353~573K、压力2.0~10.0MPa、搅拌转速600rmin-1的实验条件下,根据气体等容吸收降压原理,测定了氢气在松脂和松香中的平衡溶解度。结果表明其溶解度随温度和压力的升高而增加,溶解度—压力曲线为通过原点的直线,符合Henry定律。在相同温度、压力下,氢气在松脂中的溶解度大于松香。 根据 Vuuren提出的溶解度系数计算式,回归出溶解度系数与温度之间的关联式及溶解热:0.04459exp(496.8/)ST=-松脂, 4.1304HD=松脂soln, mkJmol-1;0.1885exp(1360.8/)ST=-松香, 11.314HD=松香soln, mkJmol-1,为松脂、松香催化加氢反 应机理研究和化学动力学模型的建立提供了基础数据。     

三元体系MgCl_2+NH_4Cl+H_2O 298.15K稳定相平衡

采用等温溶解平衡法研究了三元体系MgCl2+NH4Cl+H2O 298.15 K的稳定相平衡,测定了平衡时各组分的溶解度及平衡液相的密度、折光率等物化性质。该三元体系在298.15 K时的稳定相图含有2个共饱点E1,E2,3条单变量曲线AE1,E1E2,E2B,3个结晶区。3个结晶区分别对应MgCl2.6H2O,NH4Cl及复盐铵光卤石(NH4Cl.MgCl2.6H2O)。2个共饱点中,E1为不相称共饱点,对应的平衡固相为NH4Cl.MgCl2.6H2O+NH4Cl,平衡液相组成为w(NH4Cl)=7.79%,w(MgCl2)=21.90%;E2为相称共饱点,对应的平衡固相为NH4Cl.MgCl2.6H2O+MgCl2.6H2O,平衡液相组成为w(NH4Cl)=0.21%,w(MgCl2)=32.27%。研究结果表明:该三元体系为复杂三元体系,有不相称复盐NH4Cl.MgCl2.6H2O生成。MgCl2对NH4Cl有强烈的盐析作用。平衡液相的密度和折光率随着溶液中MgCl2质量分数的增加而增大。采用经验公式对密度和折光率进行计算,计算值与实验值吻合度较好,相对偏差小于0.012。     

The Formation of CrO2+2 in the Reaction of Cr2+ + O2 in Aqueous Acid Solutions

The reduction rate of Cr³⁺ by e_aq was determined, k₈ = 1.7 × 10¹⁰ M^?1 s^?1. The reaction of Cr²⁺ with O₂ was studied, k₂ = 1.6 × 10⁸ M^?1 s^?1. The spectrum of CrO²⁺₂ was obtained both with the pulse radiolysis method and by mixing Cr²⁺ with excess of O₂. It was shown that CrO²⁺₂ decays slowly to yield HCrO^?₄. The results suggest that the reaction of Cr²⁺ with O₂ is a two electron transfer process.     

Gibbs Free Energies of Formations of the Magnesium and Calcium Germanates at High Temperatures

The relative chemical potentials and partial molar solution enthalpies of the quasi-binary systems MgO-GeO₂ and CaO-GeO₂, were determined by means of solid-state galvanic cells and high-temperature solution calorimetry, respectively. The standard free energies of formation of the corresponding germanates, MgGeO₃, CaGeO₃, CaGe₄O₉, are presented as a function of temperature.     

ESR Studies of Uncomplexed and Complexed HO2 Radical Formed in the Reaction of H2O2 with Ce4+, Fe2+ and Ti3+ Ions

Excess of H₂O₂ reacting in 0.5N HClO₄ with Ce⁴⁺, Ti³⁺ and Fe²⁺ yields the uncomplexed HO₂ radical. This radical gives a broad ESR signal with a line width of 27±1 gauss and a g-value of 2.0140±0.0015. The HO₂ radical forms a complex with excess of Ce³⁺ which gives an ESR spectrum with a linewidth of 1.3±0.1 gauss and a g-value of 2.0180±0.0005. The equilibrium between complexed [Ce³⁺‥HO₂] and uncomplexed HO₂ was studied. Two complexes are formed between HO₂ and [Ti⁴⁺…H₂O₂]. These complexes give two ESR signals with a linewidth of 0.7 ± 0.1 and 0.5± 0.1 gauss and g-value of 2.0140± ± 0.0005 and 2.0120± 0.0005 respectively.     

Methanol Synthesis on Potassium-Modified Cu(100) from CO + H2 and CO + CO2 + H2

Methanol cannot be produced from CO + H₂ on a clean copper surface, but a promotional effect of potassium on methanol synthesis from mixtures of CO + H₂ and CO + CO₂ + H₂ at a total pressure of 1.5 bar on a Cu(100) surface is shown in this work. The experiments are performed in a UHV chamber connected with a high-pressure cell (HPC). The methanol produced is measured with a gas chromatograph and the surface is characterized with surface science techniques. The results show that potassium is a promoter for the methanol synthesis from CO + H₂, and that the influence of CO₂ is negligible. Investigation of the post-reaction surface with TPD indicates that potassium carbonate is present and plays an important role. The activation energy is determined as 42 ± 3 kJ/mol for methanol synthesis on K/Cu(100) from CO + H₂.     

高浓度H2O-NH3-CO2体系汽液平衡计算

A vapor liquid equilibrium model and its related interactive energy parameters based on UNIQUAC model for the H2O-NH3-CO2 system without solid phase at the conditions of temperature from 30℃ to 90℃,pressure from 0.1 MPa to 0.4 MPa, and the maximum NH3 mass fraction up to 0.4 are provided. This model agrees with experimental data well (average relative error ＜ 1%) and is useful for analysis of industrial urea production.     

The Reaction of Bacterial Catalase with H2O2

The kinetics of the reaction of bacterial catalase with H₂O₂ has been examined. By applying a non-steady state analysis, the formation curve of the transient intermediate and the kinetics of its formation have been explained. The discussion has been based on the peroxidatic model of catalase action. The rate constants of the reaction are The (corrected) spectrum of the transient intermediate has been evaluated.     

Reaction of Silane with Atomic Oxygen at High Temperatures

The reaction of silane with atomic oxygen (³P) was investigated by the shock-tube–laser-photolysis method over the temperature range of 900–1170 K. Oxygen atoms were produced by the ArF laser photolysis of SO₂ behind reflected shock waves and monitored with atomic resonance absorption spectroscopy. The rate constant for the SiH₄ + O reaction was evaluated by taking the possible contribution of the consecutive reaction into consideration. The Arrhenius temperature coefficient was determined to be E_a= 26.6 kJ mol⁻¹, which is much higher than the experimental activation energies obtained at lower temperatures. Rate constants calculated by a transition state theory with the reaction barrier height of E₀= 10.2 kJ mol⁻¹ agreed well with both the present and the previous experimental results for a wide temperature range.