International Journal of Chemical Kinetics
Công bố khoa học tiêu biểu
* Dữ liệu chỉ mang tính chất tham khảo
The chain length (i.e., relative quantum yield) for the oxidation of 2‐propanol by peroxodisulfate ion at 25°C has been studied. A number of initial experiments were carried out in order to clarify the influence of dissolved oxygen, light intensity, cupric ion, and acetone absorption. After these problems were understood, conditions satisfactory for evaluation of chain length were chosen. The chain length was found to be 500 (to within ±100). The difference between this value and the thermal oxidation chain length of 1800 at 60° is, in both direction and magnitude, as expected for a common mechanism and a low activation energy for the propagation steps. A remarkable difference is seen for comparable reactions of peroxodisulfate and peroxodiphosphate anions.
Using a relative rate method, rate constants for the gas phase reactions of O3with 1‐ and 3‐methylcyclopentene, 1‐, 3‐, and 4‐methylcyclohexene, 1‐methylcycloheptene,
Rate constants for the gas‐phase reactions of O3 with a series of monoterpenes and related compounds have been determined at 296 ± 2 K and 740 torr total pressure of air or O2 using a combination of absolute and relative rate techniques. Good agreement between the absolute and relative rate data was observed, and the rate constants obtained (in units of 10−17 cm3 molecule−1 s−1) were: α‐pinene, 8.7; β‐pinene, 1.5; Δ3‐carene, 3.8; 2‐carene, 24; sabinene, 8.8;
Rate constants for the gas‐phase reactions of O3 with the sesquiterpenes α‐cedrene, α‐copaene, β‐caryophyllene, α‐humulene, and longifolene, and with the monoterpenes limonene, terpinolene, α‐phellandrene, and α‐terpinene, have been measured using a relative rate technique at 296 ± 2 K and atmospheric pressure of air. The rate constants obtained (in units of 10−17 cm3 molecule−1 s−1) are: limonene, 20.1 ± 5.1; terpinolene, 188 ± 67; α‐phellandrene, 298 ± 105; α‐terpinene, 2110 ± 770; α‐cedrene, 2.78 ± 0.71; α‐copaene, 15.8 ± 5.6; β‐caryophyllene, 1160 ± 430; α‐humulene, 1170 ± 450; and longifolene, <0.07, where the indicated errors include the estimated overall uncertainties in the rate constants for the reference organics. Hydroxyl radical formation yields were also determined for the O3 reactions with the sesquiterpenes, of 0.67 for α‐cedrene, 0.35 for α‐copaene, 0.06 for β‐caryophyllene, and 0.22 for α‐humulene, all with estimated overall uncertainties of a factor of ca. 1.5. The tropospheric lifetimes of the sesquiterpenes due to reaction with O3 are calculated. © 1994 John Wiley & Sons, Inc.
The kinetics of the esterification of acetic acid with the secondary alcohol, 2‐propanol, catalyzed by the cation exchange resins, Dowex 50Wx8‐400, Amberlite IR‐120, and Amberlyst 15 has been studied at temperatures of 303, 323, and 343 K; acid to alcohol molar ratios of 0.5, 1, and 2; and catalyst loadings of 20, 40, and 60 g/L. The equilibrium constant was experimentally determined, and the reaction was found to be mildly exothermic. External and internal diffusion limitations were absent under the implemented experimental conditions. Systems catalyzed by gel‐type resins (Dowex 50Wx8‐400 and Amberlite IR‐120) exhibit some similarities in their reaction kinetics. Increase in reaction temperature, acid to alcohol ratio, and catalyst loading is found to enhance reaction kinetics for the three catalysts. The pseudohomogeneous (PH), Eley Rideal (ER), Langmuir Hinshelwood (LH), modified Langmuir Hinshelwood (ML), and Pöpken (PP) models were found to predict reaction kinetics with mean relative errors of less than 5.4%. However, the ML model was found to be better for predicting reaction kinetics in the systems catalyzed by gel‐type resins, while the PP model was better for the system catalyzed by the macroreticular catalyst, Amberlyst 15. The
The reaction kinetics of esterification of acetic acid with
Oxidative kinetics of diethyl ketone in perchloric acid media in the presence of mercuric acetate have been studied by using
In this work, we report a detailed chemical kinetic mechanism to describe the flame inhibition chemistry of the fire‐suppressant 2‐bromo‐3,3,3‐trifluoropropene (2‐BTP), under consideration as a replacement for CF3Br. Under some conditions, the effectiveness of 2‐BTP is similar to that of CF3Br; however, like other potential halon replacements, it failed an U.S. Federal Aviation Authority (FAA) qualifying test for its use in cargo bays. Large overpressures are observed in that test and indicate an exothermic reaction of the agent under those conditions. The kinetic model reported herein lays the groundwork to understand the seemingly conflicting behavior on a fundamental basis. The present mechanism and parameters are based on an extensive literature review supplemented with new quantum chemical calculations. The first part of the present article documents the information considered and provides traceability with respect to the reaction set, species thermochemistry, and kinetic parameters. In additional work, presented more fully elsewhere, we have combined the 2‐BTP chemical kinetic mechanism developed here with several other submodels from the literature and then used the combined mechanism to simulate premixed flames over a range of fuel/air stoichiometries and agent loadings. Overall, the modeling results qualitatively predicted observations found in cup‐burner tests and FAA Aerosol Can Tests, including the extinguishing concentrations required and the lean‐to‐rich dependence of mixtures. With these data in hand, in a second phase of the present work, we perform a reaction path analysis of major species under several modeled conditions. This analysis leads to a qualitative understanding of the ability of 2‐BTP to act as both an inhibitor and a fuel, depending on the conditions and suggests areas of the kinetic model that should be further investigated and refined.
The Ni(II) ion catalyzed thermal decomposition of peroxomonosulfate (PMS) was studied in the pH range 3.42–5.89. The rate is first order in [PMS] and Ni(II) ion concentrations. At pH greater than or equal to 5.23, the reaction becomes zero order in [PMS] and this changeover in the order of the reaction occurs at a higher concentration of nickel ions. The first‐order kinetics in PMS can be explained as a rate‐limiting step and is the transformation of nickel peroxomonosulfate into nickel peroxide. This peroxide intermediate reacts rapidly with another PMS to give oxygen and Ni(II). The formation of nickel peroxide is associated with a small negative or nearly zero entropy of activation. The zero‐order kinetics in [PMS] can be explained by the fact that the hydrolysis of aquated nickel(II) ions into hydroxocompounds is the rate‐limiting step. The turnover number is 2 at pH 3.42 and increases with pH. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 320–237, 2007
The mechanism of NH3 pyrolysis was investigated over a wide range of conditions behind reflected shock waves. Quantitative time‐history measurements of the species NH and NH2 were made using narrow‐linewidth laser absorption. These records were used to establish an improved model mechanism for ammonia pyrolysis. The risetime and peak concentrations of NH and NH2 in this experimental database have also been summarized graphically.
Rate coefficients for several reactions which influence the NH and NH2 profiles were fitted in the temperature range 2200 K to 2800 K. The reaction and the corresponding best fit rate coefficients are as follows:
The experimental data from four earlier measurements of the dissociation reaction
- 1
- 2
- 3
- 4
- 5
- 6