Rate coefficients for CS reactions with O2, O3 and NO2 AT 298 K

CS radicals have been produced by photodissociation of CS₂ at 193 nm and their disappearance monitored by LIF. The vibrationally excited CS radicals rapidly relax to CS(ν = 0). At 298 K, the rate coefficients for CS(ν = 0) reactions with O₂, O₃ and NO₂ are (2.9 ± 0.4) × 10_?19, (3.0 ± 0.4) × 10^?16 and (7.6 ± 1.1) × 10^?17 cm³ molecule^?1 s^?1 respectively. The quenching of CS(A ¹II)_ν=0 by He has a rate coefficient of (1.3 ± 0.2) × 10^?12 cm³ molecule^?1 s^?1.     

Kinetics of the reactions of isopropoxy radicals with NO,NO2, and O2

A fluorescence excitation spectrum of (CH₃)₂CHO (isopropoxy radical) is reported following photolysis of isopropyl nitrite at 355 nm. Rate constants for the reaction of isopropoxy with NO, NO₂, and O₂ have been measured as a function of pressure (1–50 Torr) and temperature (25–110°C) by monitoring isopropoxy radical concentrations using laser-induced fluorescence. We have obtained the following Arrhenius expressions for the reaction of isopropoxy with NO and O₂ respectively: (1.22±0.28)×10^?11 exp[(+0.62±0.14 kcal)/RT]cm²/s and (1.51±0.70)×10^?14 exp[(?0.39±0.28)kcal/RT]cm³/s where the uncertainties represent 2σ. The results with NO₂ are more complex, but indicate that reaction with NO₂ proceeds more rapidly than with NO contrary to previous reports. The pressure dependence of the thermal decomposition of the isopropoxy radical was studied at 104 and 133°C over a 300 Torr range using nitrogen as a buffer gas. The reaction is in the fall-off region over the entire range. Upper limits for the reaction of isopropoxy with acetaldehyde, isobutane, ethylene, and trimethyl ethylene are reported.We have performed the first LIF study of the isopropoxy radical. Arrhenius parameters were measured for the reaction of i-PrO with O₂, NO, NO₂, using direct radical measurement techniques. All reactions are in their high-pressure limits at a few Torr of pressure. The rate constant for the reactions of i-PrO with NO and NO₂ reactions exhibit a small negative activation energy. Studies of the i-PrO + NO₂ reaction produce data which indicate that O(³P) reacts rapidly with i-PrO. Unimolecular decomposition studies of i-PrO indicate that the reaction is in the fall-off region between 1 and 300 Torr of N₂ and the high-pressure limit is above 1 atmosphere of N₂.     

Rate coefficients for so reactions with O2 and O3 over the temperature range 230 to 420 K

SO was produced from SO₂ by pholodissociation with an ArFlaser (193 nm). SO₂ chemiluminescence from the SO + O₃ reaction was used to monitor the decay of SO and determine rate coefficients for SO reactions with O₂ and O₃ over the temperature range 230–420 K. The rate expressions are k_O2=(2.4^+2.6_?0.9) x 10^?13 exp[(?2370⁺²⁰⁰_?250)/T] and k_o3=(4.8^+1.6_?0.8) × 10^?12 exp[(?1170⁺⁸⁰_?120)/T] cm³ molecule^?1 s^?1.     

Beam-gas chemiluminescent reactions of Eu and Sm with O3, N2O,NO2 and F2

Studies are made of the visible chemiluminescence resulting from the reaction of an atomic beam of samarium or europium with O₃, N₂O, NO₂ and F₂ under single-collision conditions (～10^?4 torr). The spectra obtained for SmO, EuO, SmF, and EuF are considerably more extensive than previously observed. The variation of the chemiluminescent intensity with metal flux and with oxidant flux is investigated, and it's concluded that the reactions are bimolecular. From the short wavelength curoff of the chemiluminescent spectra, the following lower bounds to the ground state dissociation energies are obtained: D⁰₀(SmO) > 135.5 +- 0.7 kcal/mole, D⁰₀(EuO) > 131.4 ± 0.7 kcal/mole, D⁰₀(SmF) > 123.6 ± 2.1 kcal/mole, and D⁰₀(EuF) > 129.6 ± 2.1 kcal/mole. Using the Clausius-Clapeyron equation, the latent heats of sublimation are found to be ΔH₁₀₅₂ (Eu) = 42.3 ± 0.7 kcal/mole for europium and ΔH₁₀₈₄(Sm) = 47.9 ± 0.7 kcal/mole for samarium. Total phenomena- logical cross sections are determined for metal atom removal. Relative photon yields per product molecule are calculated from the integrated chemiluminescent spectra and it is found that Sm + F₂ → SmF^* + F is the brightest reaction. The comparison of the photon yields under single-collision conditions with those at several torr shows that energy transfer collisons play an important role in the mechanism for chemiluminescence at the higher pressures. A simple model is presented which explains the larger photon yields of the Sm reactions compared to the Eu reactions in terms of the greater number of electronic states correlating with the reactants in the case of samarium.     

低阶煤半焦利用热重在O2/CO2、O2/N2和O2/Ar气氛下燃烧特性研究

利用热重研究了两种中国西北典型低阶煤半焦的燃烧特性。探究了不同气氛（O₂/CO₂、O₂/N₂和O₂/Ar）和不同氧气浓度对其燃烧特性的影响。实验结果表明,无论是反应气氛还是氧气浓度都会对低阶煤半焦的燃烧产生影响。相比于N₂和Ar,CO₂明显有利于燃烧反应进行：当反应气氛由O₂/CO₂变为O₂/Ar时,两种不同低阶煤半焦的燃尽温度分别升高了63.7和68.8℃;而当反应气氛由O₂/CO₂变为O₂/N₂时,两种不同低阶煤半焦的燃尽温度分别升高了135.9和129.6℃。在研究范围内,氧气浓度的提高也能明显提高半焦的燃烧性能。与此同时,半焦燃烧特性的动力学分析表明,随着氧气浓度提高,两种半焦燃烧反应的表观活化能E和指前因子A均呈增大趋势。通过对E和A两者关系的分析结果表明,半焦富氧燃烧的活化能和指前因子存在动力学补偿效应。     

Asymmetric hydroformylation with Pt-phosphine-SnCl2 and Pt-bisphosphine-CuCl2 (or CuCl) catalytic systems

A study has been made of asymmetric hydroformylation of styrene with PtCl₂(PPh₃)₂ + bisphosphine + SnCl₂ (bisphosphine: BDPP = (−)-(2S,4S)-2,4-bis(diphenylphosphino)pentane or DIOP = (−)-(4R,5R)-2,2-dimethyl-4,5-bis(diphenylphosphinomethyl)-1,3-dioxolane) and PtCl₂(bisphosphine) + PPh₃ + SnCl₂ catalysts prepared “in situ”. The presence of an excess of the phosphine ligand slightly lowered the reaction rate, but the enantioselectivity of these systems is significantly higher than those involving PtCl(SnCl₃)(bisphosphine) catalysts. Under mild reaction conditions 88.8% enantiomeric excess was achieved. Replacing SnCl₂ in these catalysts by CuCl₂ or CuCl gave a new homogeneous catalytic system which is active at higher reaction temperature (> 100°C), but has a rather moderate enantioselectivity.     

Kinetics of the reaction OH (v = 0) + O3 → HO2 + O2

The rate constant of the reaction OH (v = 0) + O₃

HO₂ + O₂ was measured over the temperature range from 220 to 450°K at total pressures between 2 and 5 torr using ultraviolet fluorescent scattering for the detection of OH radicals. An Arrhenius expression, k₁ = 1.3 × 10^?12 exp(?1900/RT) cm³/sec was obtained and the rate constant for the reaction HO₂ + O₃

OH + 2O₂ was inferred to be less than 0.1 k₁ over the entire temperature interval.     

Kinetics of the reactions OH (v = O) + NH3 →; H2O + NH2 and OH(v = O) + O3 → HO2 + O2 AT 298°K

The rate constants for the reactions OH(X₂Π, ν = O) + NH₃ → ^k1 H₂O + NH₂ and OH(X²Π, ν = O) + O₃^k2 → HO₂ + O₂ were measured at 298°K by the flash photolysis resonance fluorescence technique. The values of the rate constants thus obtained are K₁ = (4.1 ± 0.6) × 10^?14 and k₂ = (6.5 ± 1.0) × 10^?14 in units of cm³ molecule ^?1 sec¹. The results are discussed in terms of understanding the dynamics of the perturbed stratosphere.     

ZnCl2、KOH和HNO3改性MWCNT对苯酚的吸附行为研究

通过扫描电子显微镜、X射线衍射仪、N₂吸附分析仪及Boehm滴定法获得ZnCl₂、KOH和HNO₃化学处理对高纯多壁碳纳米管的结构和表面含氧官能团的影响,通过批处理实验考察吸附条件（吸附时间、初始浓度、温度）对处理前后的碳纳米管吸附苯酚行为的影响,并采用准一级、准二级、Evolich动力学模型和热力学方程拟合其吸附数据,分析其动力学行为、热力学行为和吸附机理。结果表明,虽然ZnCl₂、KOH和HNO₃化学处理法均未对碳纳米管BET比表面积产生显著影响,但会影响其表面化学性质（即,对于ZnCl₂和KOH化学处理降低表面羧基、内酯基含量和增大碱性官能团量,而对于HNO₃化学处理可以增大表面羧基、内酯基含量,而碱性官能团略有增加）;改性处理影响碳纳米管去除苯酚效率：由于ZnCl₂和KOH改性处理降低碳纳米管表面羧基量,故其提高了苯酚去除率,而HNO₃处理则略减小碳纳米管的苯酚去除率,可能是由于碳纳米管结构和表面化学性质共同影响所致;碳纳米管的苯酚去除率均随苯酚溶液初始浓度的增大而减小;高温不利于吸附;热力学研究发现碳纳米管吸附苯酚过程是自发的和放热的,属于物理吸附;动力学研究表明,吸附过程符合准二级动力学方程。通过ZnCl₂和KOH化学处理,可以显著提高碳纳米管对苯酚的吸附性能。     

Solvent-free mechanochemical chlorination of hydrocarbons with CuCl2

Solvent-free chlorination of biphenyl and naphthalene was performed under mechanochemical stressing by high-energy ball milling (HEM) of a mixture of CuCl₂ (95 wt %) and the hydrocarbon (5 wt %). The reactivity of the selected hydrocarbons towards CuCl₂ during HEM partially correlates with their ionisation potentials (IP): hexadecane (9.91 eV) > biphenyl (8.27 eV) > naphthalene (8.14 eV).     

Rate coefficients for the reactions of BF with O and O2

Bimolecular reaction rate coefficients of k = (1.4 ± 0.2) × 10^?10 and < 5 × 10^?17 cm³/molecule s have been measured at T = 294 K in a flowtube facility for BF + O → BO + F and BF + O₂ → products, respectively. These results are discussed in terins of the electronic structure of boron monofluoride.     

On the photosynthesis of dioxygen(1+) hexafluoroarsenate in the systems O2-F2-AsF5, OF2-AsF5 and O2-OF2-AsF5

The photochemical reactions in the systems O₂-F₂-AsF₅, OF₂-AsF₅ and O₂-OF₂-AsF₅, yielding O₂AsF₆ as the reaction product were investigated. The influence of the mole ratio of the reactants upon the rate of formation of O₂AsF₆ was studied and a reaction mechanism is suggested which is based on the formation of O₂F· radicals. Regarding the preparation of O₂AsF₆, the best results were obtained using the system O₂-F₂-AsF₅ with the mole ratio 1:1-1.5:1.     

Ordered perovskites in the A(Li1/4Nb3/4)O3-A(Li2/5W3/5)O3 (A=Sr, Ca) systems

Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A²⁺(Li_1/4Nb_3/4)O₃-(x)A²⁺(Li_2/5W_3/5)O₃ systems, A²⁺=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P2₁/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with b⁻b⁻c⁺ octahedral tilting. Rietveld refinements of the ordered A(B^I_1/3B^II_2/3)O₃ structures give a good fit to a model with B^I occupied by Li and Nb, B^II by W and Nb, and a general stoichiometry (Sr,Ca)(Li_3/4+y/2Nb_1/4−y/2)_1/3(Nb_1−yW_y)_2/3O₃, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites.     

Kinetic study of surface reactions of O2 and H2 on polycrystalline copper

Adsorption and transformation of O₂, H₂, water and methanol on polycrystalline copper in the 300–400 K range have been studied by surface potential variations. In particular, O₂ reacts with H(a) to form OH(a) with a first order kinetic law, whereas OH(a) reacts with H₂ to form water which desorbs and restores H(a) with an Elovich kinetic law.     

ZnCl2 and CuCl promoted aldol reactions of isocyanoacetate with α,β-unsaturated carbonyl compounds

Reaction of ethyl isocyanoacetate with α,β-unsaturated carbonyl compounds was promoted by a stoichiometric amount of ZnCl₂ or a catalytic amount of CuCl/Et₃N (1:1) to give 5-alkenyl-4-carboethoxyoxazolines (3) in moderate yields. The oxazolines (3) were converted by palladium catalyst to 2-formamino-2,4-alkadienoic acid ethyl esters (5).     

A further study of the near-thermoneutral reactions O2H+ + H2 ⇌ H3+ + O2

The forward and reverse rate coefficients for the reactions (1) O₂H⁺ + H2 ? H₃⁺ + O₂ and (2) O₂D⁺ + D₂ ? D₃⁺ + O₂ have been determined in a SIFT at 80 and 300 K, from which values of the enthalpy and entropy changes in the reactions have been obtained. The data indicate that the proton affinity of H₂ is greater than that of O₂ by 0.33 ± 0.04 kcal mole^?1; similary, the deuteron affinity of D₂ is 0.35 ± 0.04 kcal mole^?1 greater than that of O₂. The measurements of entropy changes confirm that O₂H⁺ has a triplet electronic ground state.     

Rate constants of the O(D) reactions with N2, O2, N2O, and H2O at 295 K

Using a technique of laser flash photolysis coupled with vacuum ultraviolet laser-induced fluorescence spectroscopy, the rate coefficients of O(¹D) reactions with N₂, O₂, N₂O, and H₂O at 295 ± 2 K have been determined to be , k_O2=(4.06±0.24)×10^-11, k_N2O=(1.35±0.08)×10^-10 and . The quoted uncertainties include estimated errors and are the 95% confidence level. The k_N2 and k_N2O values obtained are larger than the current NASA/JPL recommendations by 26% and 16%, respectively, although they are still within the error limits associated with the recommendations.     

CH2+O2反应的反应机理

The mechanisms of the CH2＋ O2→ H2O＋ CO and CH2＋ O2→ H2＋ CO2 reactions have been studied by performing ab initio CAS(8,8)/6-31G(d,p) calculations, and five intermediates(IMn) and eight transitions(TSn) have been located along the reaction paths. The predicted path for the CH2＋ O2→ H2O＋ CO is: CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS5→ H2O＋ CO. For the CH2＋ O2→ H2＋ CO2 reaction, there are two paths: (i) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS6→ H2＋ CO2 and (ii) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS7→ IM4b→ TS8→ H2＋ CO2, with the latter path more favorable energetically.     

Direct kinetic studies of the reactions of 2-butoxy radicals with NO and O2

This Letter reports the first kinetic study of 2-butoxy radicals to employ direct monitoring of the radical. The reactions of 2-butoxy with O₂ and NO are investigated using laser-induced fluorescence (LIF). The Arrhenius expressions for the reactions of 2-butoxy with NO (k₁) and O₂ (k₂) in the temperature range 223–311 K have been determined to be k₁=(7.50±1.69)×10⁻¹²×exp((2.98±0.47) kJmol⁻¹/RT) cm³ molecule⁻¹ s⁻¹ and k₂=(1.33±0.43)×10⁻¹⁵×exp((5.48±0.69) kJmol⁻¹/RT) cm³ molecule⁻¹ s⁻¹. No pressure dependence was found for the rate constants of the reaction of 2-butoxy with NO at 223 K between 50 and 175 Torr.