Kinetics of the gas-phase reaction of OH with HCl

The reaction of hydroxyl radicals with hydrogen chloride (reaction 1) has been studied experimentally using a pulsed-laser photolysis/pulsed-laser-induced fluorescence technique over a wide range of temperatures, 298-1015 K, and at pressures between 5.33 and 26.48 kPa. The bimolecular rate coefficient data set obtained for reaction 1 demonstrates no dependence on pressure and exhibits positive temperature dependence that can be represented with modified three-parameter Arrhenius expression within the experimental temperature range: k1 = 3.20 x 10(-15)T0.99 exp(-62 K/T) cm3 molecule(-1) s(-1). The potential-energy surface has been studied using quantum chemical methods, and a transition-state theory model has been developed for the reaction 1 on the basis of calculations and experimental data. The model results in modified three-parameter Arrhenius expressions: k1 = 8.81 x 10(-16)T1.16 exp(58 K/T) cm3 molecule(-1) s(-1) for the temperature range 200-1015 K and k1 = 6.84 x 10(-19)T2.12 exp(646 K/T) cm3 molecule(-1) s(-1) for the temperature dependence of the reaction 1 rate coefficient extrapolation to high temperatures (500-3000 K). A temperature dependence of the rate coefficient of the Cl + H2O --> HCl + OH reaction has been derived on the basis of the experimental data, modeling, and thermochemical information.     

Epoxidation of cyclohexene with molecular oxygen by electrolysis combined with chemical catalysis

This paper describes an electrochemical coupling epoxidation of cyclohexene by molecular oxygen (O₂) under mild reaction conditions. Herein, the electroreduction of O₂ to hydrogen peroxide (H₂O₂) efficiently proceeds in a relatively environmentally friendly acetone/water medium containing electrolytes at 25–30 °C on a self-assembled H type of electrolysis cell with tree electrodes system, providing ca. 44.3 mM concentration of H₂O₂ under the optimal electrolysis conditions. The epoxidation of cyclohexene with in situ generated H₂O₂ simultaneously occurs upon catalysis by metal complexes, giving ca. 19.8 % of cyclohexene conversion with 78 % of epoxidative selectivity over the best catalyst 5-Cl-7-I-8-quinolinolato manganese(III) complex (Q₃Mn^III (e)). The present electrochemical coupling epoxidation result is nearly equivalent to the epoxidation of cyclohexene with adscititious H₂O₂ catalyzed by the Q₃Mn^III (e).     

Can chlorine anion catalyze the reaction of HOCl with HCl?

The reaction of HOCl + HCl → Cl₂ + H₂O in the presence of chlorine anion Cl⁻ has been studied using ab initio methods. The overall exothermicity is 15.5 kcal mol⁻¹ and this reaction has been shown to have a high activation barrier of 46.5 kcal mol⁻¹. Cl⁻ is found to catalyze the reaction via the formation of HOCl·Cl⁻, ClH·HOCl·Cl⁻ and Cl⁻·H₂) intermediate ion-molecule complexes or by interacting with a concerted four-center transition state of the reaction of HOCl + HCl.     

Sorption capture of chlorine with carbon adsorbents from waste gases yielded by electrolysis of chloride solutions

The performance of various carbon materials in sorption capture of chlorine from waste gases yielded by electrolysis of nickel-manganese solutions was studied. A simple method was proposed for regeneration of carbons after sorption of chlorine, which makes them suitable for repeated use in sorption installations for chlorine capture.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1462–1466.Original Russian Text Copyright © 2004 by Stavitskaya, Tomashevskaya, Goba, Kartel, Strelko.     

Pseudo-potentiostatic electrolysis by potential buffering induced by the oxygen evolution reaction

A new approach is proposed in order to perform electrochemical oxidation of organics by working under galvanostatic conditions with the potential ‘buffered’ by the competing side reaction of oxygen evolution (OER). According to this process the working potential is fixed by the nature of electrode material and is buffered during organics oxidation by the side reaction of OER. This principle has been used for the selective oxidation of some model organic compounds on Ti/IrO₂ anode.     

Copper-mediated intra-ligand oxygen transfer in gas-phase complexes with 3-nitrotyrosine

Gas-phase ternary complexes with Cu(II) and 2,2'-bipyridine (bpy) of tyrosine, 3-aminotyrosine, 3-nitrotyrosine and 3-nitrotyrosine methyl ether are formed readily upon electrospraying aqueous methanol solutions containing the components. In contrast to Cu(bpy) complexes of tyrosine, 3-aminotyrosine and other aromatic amino acids, the complexes of 3-nitrotyrosine and its methyl ether undergo unusual collisionally activated dissociations (CADs) that involve Cu-mediated transfer of an oxygen atom from the nitro group. With 3-nitrotyrosine this results in an expulsion of carbonic acid, H(2)CO(3), whereas with 3-nitrotyrosine methyl ether an OH migration forms Cu(OH)bpy(+) as the predominant product. To the best of our knowledge, this is the first case of an intra-ligand redox reaction in a gas-phase organometallic complex. The reaction mechanism of this unusual dissociation was elucidated by a combination of isotope labeling, accurate mass measurements, energy-resolved CAD mass spectra and density functional theory calculations of ion structures and relative energies.     

Kinetics, mechanism, and thermochemistry of the gas-phase reaction of atomic chlorine with pyridine

A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of atomic chlorine with pyridine (C(5)H(5)N) as a function of temperature (215-435 K) and pressure (25-250 Torr) in nitrogen bath gas. At T> or = 299 K, measured rate coefficients are pressure independent and a significant H/D kinetic isotope effect is observed, suggesting that hydrogen abstraction is the dominant reaction pathway. The following Arrhenius expression adequately describes all kinetic data at 299-435 K for C(5)H(5)N: k(1a) = (2.08 +/- 0.47) x 10(-11) exp[-(1410 +/- 80)/T] cm(3) molecule(-1) s(-1) (uncertainties are 2sigma, precision only). At 216 K < or =T< or = 270 K, measured rate coefficients are pressure dependent and are much faster than computed from the above Arrhenius expression for the H-abstraction pathway, suggesting that the dominant reaction pathway at low temperature is formation of a stable adduct. Over the ranges of temperature, pressure, and pyridine concentration investigated, the adduct undergoes dissociation on the time scale of our experiments (10(-5)-10(-2) s) and establishes an equilibrium with Cl and pyridine. Equilibrium constants for adduct formation and dissociation are determined from the forward and reverse rate coefficients. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the addition reaction: Delta(r)H = -47.2 +/- 2.8 kJ mol(-1), Delta(r)H = -46.7 +/- 3.2 kJ mol(-1), and Delta(r)S = -98.7 +/- 6.5 J mol(-1) K(-1). The enthalpy changes derived from our data are in good agreement with ab initio calculations reported in the literature (which suggest that the adduct structure is planar and involves formation of an N-Cl sigma-bond). In conjunction with the well-known heats of formation of atomic chlorine and pyridine, the above Delta(r)H values lead to the following heats of formation for C(5)H(5)N-Cl at 298 K and 0 K: Delta(f)H = 216.0 +/- 4.1 kJ mol(-1), Delta(f)H = 233.4 +/- 4.6 kJ mol(-1). Addition of Cl to pyridine could be an important atmospheric loss process for pyridine if the C(5)H(5)N-Cl product is chemically degraded by processes that do not regenerate pyridine with high yield.     

氧弹分解-高效液相色谱法测定煤中氯

煤炭是我国的大宗出口商品 ,煤中氯对煤的工业利用影响很大。氯含量超过 0 .3%的煤 ,在燃烧过程中使各种管道和碳化室壁遭到强烈的腐蚀 ,且在煤气化和液化过程中会产生多种有机氯化物而污染环境和危害人体健康。因此煤中氯含量的测定已作为出口煤炭品质检验的主要项目之一。目前国内外测定煤中氯的标准方法大多是容量法 [1] 和氧弹法 [2 ] ,前者分析周期长且操作繁琐 ,后者虽缩短了煤样的预处理过程 ,但最终都是通过硝酸银溶液滴定后计算出煤中氯的含量。出口煤中氯含量范围在 0 .0 5 %以下 ,对于如此低含量的氯 ,滴定的相对误差较大 ,难以…     

Effect of nitrogen oxides NOx on gas-phase oxidation of methane by oxygen

We propose a kinetic model for gas-phase oxidation of methane by oxygen in the presence of nitrogen oxides NOx. The model calculations agree satisfactorily with experimental kinetic data provided in the literature. We consider the basic principles for the effect of nitrogen oxides on the rate of the process and the selectivity with respect to methanol and formaldehyde. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 113–118, March–April, 2006.     

Production of singlet oxygen by the reaction of non-basic hydrogen peroxide with chlorine gas

Non-basic hydrogen peroxide was found to be very easy to react with Cl(2) to produce singlet oxygen O(2)(a(1)Δ(g)) (i.e. the molecular oxygen in its first electronic excited state) when an H(+) absorbent such as C(5)H(5)N, CH(3)COONH(4), HCOONH(4) or NH(4)F was added into H(2)O(2) aqueous solution, and the long concealed fact that molecular H(2)O(2) can react with Cl(2) to produce O(2)(a(1)Δ(g)) was then uncovered. It is only when an H(+) absorbent has provided a stronger base than H(2)O to absorb the H(+) produced during the reaction that O(2)(a(1)Δ(g)) can be produced.     

Improvement of electrochemical properties of LiFePO4/C cathode materials by chlorine doping

The olivine-type cathode materials of LiFePO₄ were prepared via solid-state reaction under argon atmosphere and doped by chlorine to improve their electrochemical performances. The crystal structure, morphology, and electrochemical properties of the prepared samples were investigated using thermogravimetry–differential scanning calorimetry, X-ray diffraction, Fourier transform infrared, scanning electron microscopy, cyclic voltammetry, and charge–discharge cycle measurements. The result showed that the electrochemical performance of LiFePO₄ had been improved by chlorine doping, and the effect of chlorine in lattice was discussed. The heavily doped samples show better electrochemical performance in relative high rates.     

Alkenoxy radicals in gas-phase reactions of alkenes with oxygen atoms or ozone

Observations in the O₃ + trans-2-butene reaction system and in the O + trans-2-butene + O₂ reaction system suggest the intermediacy of alkenoxy radicals. A mechanism is proposed for the production of C_n and C_m (m <n) alkenoxy radicals by the reaction of C_nH_2n alkenes with oxygen atoms or with ozone.     

十氢萘气相氧化裂解制低碳烯烃的研究

十氢萘气相氧化裂解（GOC）与传统的热裂解工艺相比,O2的存在降低了十氢萘GOC反应的活化能,使反应在较低温度下具有高的反应性能;O2同时起到消除积炭的作用,提高体系的抗积炭能力。十氢萘GOC反应在较低温度下即可获得较高的液体收率;高温下由于十氢萘裂解深度较高,低碳烯烃收率可高于液体收率,在所得的液体中,芳烃,尤其是BTX（苯、甲苯和二甲苯）占主要部分。十氢萘GOC反应制备低碳烯烃的适宜反应条件为,700℃~800℃,停留<0.4s,烷氧摩尔比0.3~0.5,空气可代替纯氧进料。800℃,烷氧摩尔比0.5,停留0.4s,可获得37％左右的低碳烯烃收率和50%左右的液体收率（BTX收率为29％）。     

Energy-efficient hydrogen production coupled with methanol oxidation using NiFe LDH@NiMo alloy heterostructure

The traditional electrochemical water splitting is extremely restricted by the sluggish kinetics of the anodic oxygen evolution reaction (OER). In this context, replacing OER with a more thermodynamic favorable oxidation reaction, such as methanol oxidation reaction (MOR), is an effective strategy to improve the hydrogen evolution reaction (HER) efficiency while still obtaining some valuable by-products. In this work, nickel-iron layered double-hydroxide [NiFe LDH]@NiMo alloy heterostructure is synthesized by electrodeposition process and its bi-functional electrocatalytic activities for both hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR) are evaluated. For the HER, the catalyst exhibits low overpotential of 82.5 mV at 100 mA/cm², with a Tafel slope of 61 mV/dec as well as splendid long-term stability. For the MOR, the required potential decreases by 74 mV at 100 mA/cm² compared to oxygen evolution reaction (OER). Moreover, 97% process yields toward value-added formic acid (HCOOH) are obtained at the anode, with a faradaic efficiency of approximately 100% for HER at the cathode. The superior catalytic performance results from the synergic contribution of NiFe LDH and NiMo alloy. The formation of NiFe LDH@NiMo alloy heterostructure leads to the redistribution of electrons among nickel (Ni), iron (Fe) and molybdenum (Mo) elements. Therefore, the charge transfer process has been greatly promoted. This study provides a scalable energy saving strategy for hydrogen energy development.     

Facilitating oxygen reduction by silver nanoparticles on lanthanum strontium ferrite cathode

Journal of Solid State Electrochemistry - Single-phase silver (Ag)-doped La0.85-xSr0.15AgxFeO3-δ (x = 0–0.05) materials (LSAF) were synthesized by wet synthesis route and...     

Advance in highly efficient hydrogen production by high temperature steam electrolysis

High Temperature Steam Electrolysis (HTSE) through a solid oxide electrolytic cell (SOEC) has been receiving increasing research and development attention worldwide because of its high conversion efficiency (about 45%-59%) and its potential usage for large-scale production of hydrogen. The mechanism, composition, structure, and developing challenges of SOEC are summarized. Current situation, key materials, and core technologies of SOEC (solid oxide electrolytic cell) in HTSE are re- viewed, and the prospect of HTSE future application in advanced energy fields is proposed. In addition, the recent research achievements and study progress of HTSE in Tsinghua University are also intro- duced and presented.     

煤浆电解制氢的动力学研究

研究了煤浆电解过程中电压、温度、H₂SO₄浓度、Fe³⁺浓度等因素的影响,并进行了电解前后煤粉样品的热重测试和电解后溶液的成分分析。结果表明,电压、温度、添加的Fe³⁺浓度、H₂SO₄浓度等参数对电解过程的电流密度有较大影响。其中,温度对电流密度的影响符合阿伦尼乌斯方程,在电解电压1 V条件下煤浆电解活化能为31.87 kJ/mol。TGA和ICP分析表明,电解后煤中的部分金属离子溶入溶液,导致结构和灰分成分发生了较显著的变化。     

Advances,opportunities, and challenges of hydrogen and oxygen production from seawater electrolysis: An electrocatalysis perspective

With increasing energy consumption and greenhouse gas emissions, the importance of developing renewable energy sources to replace fossil fuels has become a vital global task. Hydrogen produced via water electrolysis powered by renewable energy systems at a large scale is an essential measure to reduce greenhouse gas and particulate emissions. Electrolysers use a substantial amount of water (mainly freshwater) to produce hydrogen and oxygen at the cathode, and anode, respectively. However, seawater is preferred because it is the most abundant water resource. Although many R&D efforts on seawater electrolysis have been carried out since the 1970s, the barriers are the undesired chlorine gas evolution reaction at the anode, and corrosion induced by chloride ions. Unlike the available data for electrocatalyst materials based upon platinum group metals in pure solutions, limited data is available for electrocatalysts in seawater. Therefore, there is an urgent need to develop new electrocatalysts for seawater electrolysis.     

A delafossite-based copper catalyst for sustainable Cl2 production by HCl oxidation

A copper catalyst based on a delafossite precursor (CuAlO(2)) displays high activity and extraordinary lifetime in the gas-phase oxidation of HCl to Cl(2), representing a cost-effective alternative to RuO(2)-based catalysts for chlorine recycling.