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1.
The effect of NO and SO2 on the oxidation of a CO? H2 mixture was studied in a jet‐stirred reactor at atmospheric pressure and for various equivalence ratios (0.1, 1, and 2) and initial concentrations of NO and SO2 (0–5000 ppm). The experiments were performed at fixed residence time and variable temperature ranging from 800 to 1400 K. Additional experiments were conducted in a laminar flow reactor on the effect of SO2 on CO? H2 oxidation in the same temperature range for stoichiometric and reducing conditions. It was demonstrated that in fuel‐lean conditions, the addition of NO increases the oxidation of the CO? H2 mixture below 1000 K and has no significant effect at higher temperatures, whereas the addition of SO2 has a small inhibiting effect. Under stoichiometric and fuel‐rich conditions, both NO and SO2 inhibit the oxidation of the CO? H2 mixture. The results show that a CO? H2 mixture has a limited NO reduction potential in the investigated temperature range and rule out a significant conversion of HNO to NH through reactions like HNO + CO ?? NH + CO2 or HNO + H2 ?? NH + H2O. The chain terminating effect of SO2 under stoichiometric and reducing conditions was found to be much more pronounced than previously reported under flow reactor conditions and the present results support a high rate constant for the H + SO2 + M ?? HOSO + M reaction. The reactor experiments were used to validate a comprehensive kinetic reaction mechanism also used to simulate the reduction of NO by natural gas blends and pure C1 to C4 hydrocarbons. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 564–575, 2003 相似文献
2.
Jorge Gimenez‐Lopez Christian Tihic Rasmussen Hamid Hashemi Maria U. Alzueta Yide Gao Paul Marshall C. Franklin Goldsmith Peter Glarborg 《国际化学动力学杂志》2016,48(11):724-738
A detailed chemical kinetic model for oxidation of acetylene at intermediate temperatures and high pressure has been developed and evaluated experimentally. The rate coefficients for the reactions of C2H2 with HO2 and O2 were investigated, based on the recent analysis of the potential energy diagram for C2H3 + O2 by Goldsmith et al. and on new ab initio calculations, respectively. The C2H2 + HO2 reaction involves nine pressure‐ and temperature‐dependent product channels, with formation of triplet CHCHO being dominant under most conditions. The barrier to reaction for C2H2 + O2 was found to be more than 50 kcal mol?1 and predictions of the initiation temperature were not sensitive to this reaction. Experiments were conducted with C2H2/O2 mixtures highly diluted in N2 in a high‐pressure flow reactor at 600–900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel‐rich conditions. Model predictions were generally in satisfactory agreement with the experimental data. Under the investigated conditions, the oxidation pathways for C2H2 are more complex than those prevailing at higher temperatures and lower pressures. Acetylene is mostly consumed by recombination with H to form vinyl (reducing conditions) or with OH to form a CHCHOH adduct (stoichiometric to lean conditions). Both C2H3 and CHCHOH then react primarily with O2. The CHCHOH + O2 reaction leads to formation of significant amounts of glyoxal (OCHCHO) and formic acid (HOCHO), and the oxidation chemistry of these intermediates is important for the overall reaction. 相似文献
3.
E. I. Sal’nikova P. O. Andreev S. M. Antonov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(8):1280-1283
Kinetic diagrams of Ln2O2SO4 (Ln = La, Pr, Nd, Sm) systems reduction in a H2 flow are plotted for the first time in temperature-duration of treatment coordinates in which there are five areas of phase states. The temperatures of formation are established for products of the Ln2O2SO4 + 4H2 = Ln2O2S + 4H2O reaction in the temperature range of 880–900 K and products of the Ln2O2SO4 + H2 = Ln2O3 + SO2+ H2O reaction in the temperature range of 1090–1220 K. The ranges of the temperature of formation of the homo-geneous Ln2O2S phase were found to decrease: 880–1220, 900–1200, 900–1180, and 900–1090 K in the sequence La-Pr-Nd-Sm. 相似文献
4.
Ali Saffar-Teluri 《Research on Chemical Intermediates》2013,39(7):3337-3343
A combination of acetic anhydride, H2SO4-nano silica, wet-SiO2 (60 %), and K2Cr2O7 as a new oxidizing system for the selective oxidation of different types of alcohols to the corresponding aldehydes and ketones at room temperature under solvent-free conditions is introduced. Mild reaction conditions, high yields of the products, short reaction time, no further oxidation to the corresponding carboxylic acid, and easy work-up make this new system a useful method for oxidizing alcohols. 相似文献
5.
Y. Li 《Journal of solid state chemistry》2008,181(11):3151-3162
Phase transitions and reactions of non-oxidized and surface-oxidized mackinawite (FeS) in helium and H2S gas were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). DFT was used to obtain optimized structures of the iron-sulfur phases mackinawite, hexagonal pyrrhotite, greigite, marcasite and pyrite and to determine the thermochemical properties of reactions of mackinawite with H2S to these phases. The phase transitions of mackinawite to hexagonal pyrrhotite are endothermic, while reactions to greigite, marcasite and pyrite are exothermic. The experiments show that non-oxidized mackinawite converts into hexagonal pyrrhotite (Fe9S10 first and then Fe7S8) in He and also in H2S but at a lower temperature. No further reactions can be observed under these conditions. In the case of surface-oxidized mackinawite, the extent of surface oxidation determines the course and the final product of the reaction with H2S. If the extent of surface oxidation is low, only Fe2+ is oxidized to Fe3+. Under these conditions mackinawite converts into the mixed-valence thiospinel compound greigite. In case of pronounced surface oxidation all surface Fe centers are oxidized to the Fe3+ state and S2− is oxidized to SO42−. Oxidation of sulfur is a prerequisite for the formation of pyrite. 相似文献
6.
Ethylene oxidation and pyrolysis was modeled using a comprehensive kinetic reaction mechanism. This mechanism is an updated version of one developed earlier. It includes the most recent findings concerning the kinetics of the reactions involved in the oxidation of ethylene. The proposed mechanism was tested against ethylene oxidation experimental data (molecular species concentration profiles) obtained in jet stirred reactors (1–10 atm, 880–1253 K), ignition delay times measured in shock tubes (0.2–12 atm, 1058–2200 K) and ethylene pyrolysis data in shock tube (2–6 atm, 1700–2200 K). The general prediction of concentration profiles of minor species formed during ethylene oxidation is improved in the present model by using more accurate kinetic data for several reactions (principally: HO2 + HO2 → H2O2 + O2, C2H4 + OH → C2H3 + H2O, C2H2 + OH → Products, C2H3 → C2H2 + H). 相似文献
7.
Young-Gu Cho Dae-Kwang Park Dae-Won Park Hee-Chul Woo Jong-Shik Chung 《Research on Chemical Intermediates》2002,28(5):419-431
The selective oxidation of hydrogen sulfide containing excess water and ammonia was studied over vanadium-bismuth mixed oxide catalysts. The investigation was focused on understanding the complex reaction steps and the roles of each metal oxide. Therefore, supported V2O5/TiO2, V-Bi-O/TiO2 catalysts and a mechanical mixture of V2O5 + Bi2O3 were tested in the reaction. Ammonia reacted either with H2S or SO2, produced from the oxidation of H2S. Water vapor promoted the reaction of ammonia and SO2. Strong synergistic phenomena in catalytic activity were observed for the mechanically mixed catalyst of V2O5 and Bi2O3. V-Bi-O/TiO2 catalyst showed very high H2S conversion without any considerable emission of SO2. Temperature-programmed studies (TPR and TPO), XRD and Raman analyses revealed that the high catalytic performance of V-BiO/TiO2 catalyst originated from the high redox capacity of the bismuth vanadate phase. 相似文献
8.
Yu. S. Zimin G. G. Kutlugil’dina A. G. Mustafin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(3):419-423
The oxidative transformations of a polyvinyl alcohol in aqueous solutions are studied under the simultaneous action of the two oxidizing agents, an ozone–oxygen mixture and a hydrogen peroxide. Effective parameters a and b, which characterize the first and second channels of carboxyl group accumulation, respectively, grow linearly upon an increase in the initial concentration of H2O2. After the temperature dependence of a and b parameters (331–363 K) in a PVA + O3 + O2 + H2O2 + H2O reaction system is studied, the parameters of the activation of COOH group accumulation are found (where PVA is a polyvinyl alcohol). New data on the effect process conditions (length of oxidation, temperature, and hydrogen peroxide concentration) have on the degree of destructive transformations of polyvinyl alcohol in the investigated reaction system are obtained. 相似文献
9.
A kinetic study of the reactions of H atoms with CH3SH and C2H5SH has been carried out at 298 K by the discharge flow technique with EPR and mass spectrometric analysis of the species. The pressure was 1 torr. It was found: k1 = (2.20 ± 0.20) × 10?12 for the reaction H + CH3SH (1) and k2 = (2.40 ± 0.16) × 10?12 for the reaction H + C2H5SH (2). Units are cm3 molecule?1 s?1. A mass spectrometric analysis of the reaction products and a computer simulation of the reacting systems have shown that reaction (1) proceeds through two mechanisms leading to the formation of CH3S + H2 (1a) and CH3 + H2S (1b). 相似文献
10.
J.C. Eriksson C.-G. Go
lander A. Baszkin L. Ter-minassian-saraga 《Journal of colloid and interface science》1984,100(2)
The chemical constitution of KMnO4/H2SO4-oxidized (sulfated) polyethylene (PE) surfaces has been explored by means of ESCA utilizing chemical shifts, peak intensity data, and chemical tagging reactions. In addition, the adsorption of Ca2+ ions on sulfated PE was quantified by radiotracer measurements. Comparisons have been made with KClO3/H2SO4 and K2Cr2O7/H2SO4 as oxidizing agents and through replacing polyethylene by polystyrene. According to the present study the main chemical groups on a
. In the oxidation grooves, dissociable −COOH groups are also present in appreciable amounts. By annealing, a smoother and more homogeneous sulfated surface is produced, the composition of which strongly depends upon the state of the ionic groups at the heat treatment. 相似文献
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11.
H2 S selective catalytic oxidation technology is a prospective way for the treatment of low concentration acid gas with simple process operation and low investment.However,undesirable results such as large formation of SO2 and catalyst deactivation inevitably occur,due to the temperature rise of fixed reaction bed caused by the exothermic reaction.Catalyst with high activity in wide operating temperature window,especially in high temperature range,is urgently needed.In this... 相似文献
12.
By conducting an excimer laser photolysis (193 and 248 nm) behind shock waves, three elementary reactions important in the oxidation of H2S have been examined, where, H, O, and S atoms have been monitored by the atomic resonance absorption spectrometry. For HS + O2 → products (1), the rate constants evaluated by numerical simulations are summarized as: k1 = 3.1 × 10−11exp|-75 kJ mol−1/RT| cm3molecule−1s−1 (T = 1400-1850 K) with an uncertainty factor of about 2. Direct measurements of the rate constants for S + O2 → SO + O (2), and SO + O2 → SO2 + O (3) yield k2 = (2.5 ± 0.6) × 10−11 exp|-(15.3 ± 2.5) kJ mol−1/RT| cm3molecule−1s−1 (T = 980-1610 K) and, k3 = (1.7 ± 0.9) × 10−12 exp|-(34 ± 11) kJ mol−1/RT| cm3molecule−1s−1 (T = 1130-1640 K), respectively. By summarizing these data together with the recent experimental results on the H(SINGLE BOND)S(SINGLE BOND)O reaction systems, a new kinetic model for the H2S oxidation process is constructed. It is found that this simple reaction scheme is consistent with the experimental result on the induction time of SO2 formation obtained by Bradley and Dobson. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 57–66, 1997. 相似文献
13.
Flow reactor experiments were performed to study moist CO oxidation in the presence of trace quantities of NO (0–400 ppm) and SO2 (0–1300 ppm) at pressures and temperatures ranging from 0.5–10.0 atm and 950–1040 K, respectively. Reaction profile measurements of CO, CO2, O2, NO, NO2, SO2, and temperature were used to further develop and validate a detailed chemical kinetic reaction mechanism in a manner consistent with previous studies of the CO/H2/O2/NOX and CO/H2O/N2O systems. In particular, the experimental data indicate that the spin‐forbidden dissociation‐recombination reaction between SO2 and O‐atoms is in the fall‐off regime at pressures above 1 atm. The inclusion of a pressure‐dependent rate constant for this reaction, using a high‐pressure limit determined from modeling the consumption of SO2 in a N2O/SO2/N2 mixture at 10.0 atm and 1000 K, brings model predictions into much better agreement with experimentally measured CO profiles over the entire pressure range. Kinetic coupling of NOX and SOX chemistry via the radical pool significantly reduces the ability of SO2 to inhibit oxidative processes. Measurements of SO2 indicate fractional conversions of SO2 to SO3 on the order of a few percent, in good agreement with previous measurements at atmospheric pressure. Modeling results suggest that, at low pressures, SO3 formation occurs primarily through SO2 + O(+M) = SO3(+M), but at higher pressures where the fractional conversion of NO to NO2 increases, SO3 formation via SO2 + NO2 = SO3 + NO becomes important. For the conditions explored in this study, the primary consumption pathways for SO3 appear to be SO3 + HO2 = HOSO2 + O2 and SO3 + H = SO2 + OH. Further study of these reactions would increase the confidence with which model predictions of SO3 can be viewed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 317–339, 2000 相似文献
14.
The variation of the electroactivity range with composition of water+ sulphuric acid mixtures has been studied. It is shown that ferrocene provides a reference potential independent of solvent at low H2SO4 contents while polynuclear hydrocarbons fulfill the same function at high H2SO4 contents. Water+H2SO4 mixtures become more oxidizing (reduction limit) and less reducing (oxidation limit) when the H2SO4 concentration increases. 相似文献
15.
Product studies were made using the Fourier transform infrared method in the uv (300–400-nm) photolysis of mixtures containing CH3SCH3, C2H5ONO, and NO in ppm concentrations in 700 torr of O2–N2 diluent. Methyl thionitrite, CH3SNO, arising from the reaction CH3S + NO, was detected as an intermediate product. In addition, the yields of the major sulfur-containing products SO2 and CH3SO3H coincided with those of the oxidation of the CH3S radicals generated directly by the photodissociation of CH3SNO. The formation of CH3S in the HO-initiated oxidation of CH3SCH3 in the presence of NO suggests a reaction scheme involving the H-abstraction reaction HO + CH3SCH3 → CH3SCH2 + H2O as the primary step. 相似文献
16.
He Bian Honghong Zhang Ling Pei Qian Wang Fang Wang Yun Zhang Jinshe Chen 《International journal of quantum chemistry》2020,120(8):e26146
Density functional theory was adopted in this work to reveal the reaction mechanism of CH2SH with HO2. Reaction rate constants were computed from 200 to 2000 K using the transition state theory combined with Wigner and Eckart tunneling correction. Moreover, localized orbital locator, atoms in molecules and Mayer bond order analyses were used to study the essence of chemical bonding evolution. Eleven singlet paths and three triplet ones are located on the potential surface (PES). The results show that the main products on the singlet PES are 1CH2S and H2O2, whereas on the triplet PES they are CH3SH + 3O2, which are coincident with the similar reaction of CH3S and HO2. This conclusion is also supported by rate constant calculation results. Interestingly, all the possible paths are involved in the hydrogen transfer. The results have provided underlying insights to the analogous reactions and further experimental studies. 相似文献
17.
P. Narayanchar P. Basaveswara Rao M. Aneesuddin 《Journal of Thermal Analysis and Calorimetry》1989,35(5):1553-1560
The preparation of MnSO4 by reacting pyrolusite at high temperatures with SO2 generated from pyrite was followed by DTA, and the process conditions were optimized to fix the minimum time and temperature of reaction required to obtain the maximum yield of pure MnSO4 from stoichiometric amounts of reactants in a natural draught of air. The presence of MnO and Fe3O4 in the reaction products, detected by DTA, indicates that the SO2 is initially oxidized to SO3 by reducing MnO2, Mn2O3 and Fe2O3 to MnO and Fe3O4. SO3 finally attacks MnO to form MnSO4. When an intimate stoichiometric blend of pyrite and pyrolusite is heated at temperatures ranging from 873 K to 973 K for 3 hrs, about 93% of the Mn is converted to ironfree MnSO4. 相似文献
18.
The kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine
(E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]
o
, fractional-order in [substrate]
o
, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The
variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect
on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was
studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for
CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic
relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed
and the derived rate law are consistent with the observed kinetics. 相似文献
19.
A detailed investigation of the photolysis of t-C4HgSH has been carried out in the absence and presence of the inert gas, C2H6. A mechanssm consisting of three primaRy photochemical steps: t-C4H9SH → t-C4H9S + H (1), t-C4H9SH → t-C4H9 + SH (2), t-C4H9SH → i-C4H8 + H2S (3), six hot and seven thermal reaction steps, adequately explains all the experimental observations. As in the case of hot H* atoms, both the H-atom abstraction H + t-C4H9SH → H2 + t-C4H9S (7), and the SH-displacement reactions, H + t-C4H9SH → H2S + i-C4H8 (8) occur with thermalized H-atoms. The Arrhenius expression of the rate constant ratio, k7/k8 for the latter reactions has been determined over the temperature range 25-14° C to be: ln(k7/k8) = (0.3 ± 0.1) + (420 ± 80)/RT. 相似文献
20.
New experimental results were obtained for the mutual sensitization of the oxidation of NO and methane in a fused silica jet‐stirred reactor operating at 105 Pa, over the temperature range 800–1150 K. The effect of the addition of sulfur dioxide was studied. Probe sampling followed by online FTIR analyses and off‐line GC‐TCD/FID analyses allowed the measurement of concentration profiles for the reactants, stable intermediates, and final products. A detailed chemical kinetic modeling of the present experiments was performed. An overall reasonable agreement between the present data and modeling was obtained. According to the present modeling, the mutual sensitization of the oxidation of methane and NO proceeds via the NO to NO2 conversion by HO2 and CH3O2. The conversion of NO to NO2 by CH3O2 is more important at low temperatures (800 K) than at higher temperatures (850–900 K) where the production of NO2 is mostly due to the reaction of NO with HO2. The NO to NO2 conversion is favored by the production of the HO2 and CH3O2 radicals yielded from the oxidation of the fuel. The production of OH resulting from the oxidation of NO accelerates the oxidation of the fuel: NO + HO2 → OH+ NO2 followed by OH + CH4→ CH3. In the lower temperature range of this study, the reaction further proceeds via CH3 + O2→ CH3O2; CH3O2+ NO → CH3O + NO2. At higher temperatures, the production of CH3O involves NO2: CH3+ NO2→ CH3O. This sequence of reactions is followed by CH3O → CH2O + H; CH2O +OH → HCO; HCO + O2 → HO2 and H + O2 → HO2 → CH2O + H; CH2O +OH → HCO; HCO + O2 → HO2 and H + O2 → HO2. The data and the modeling show that unexpectedly, SO2 has no measurable effect on the kinetics of the mutual sensitization of the oxidation of NO and methane in the present conditions, whereas it frequently acts as an inhibitor in combustion. This result was rationalized via a detailed kinetic analysis indicating that the inhibiting effect of SO2 via the sequence of reactions SO2+H → HOSO, HOSO+O2 → SO2+HO2, equivalent to H+O2?HO2, is balanced by the reaction promoting step NO+HO2 → NO2+OH. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 406–413, 2005 相似文献