摘要:

AbstractA model scheme incorporating reactant inhibition in the rate process has been analyzed with a view to study the instability of homogeneous solution due to diffusion. Conditions for the occurrence of Turing as well as phase instability are derived and show the existence of multiplicity in the parameter space. The Ginzburg‐Landau equation for the system is developed and solved numerically in various regions of the parameter space. The simple model system shows the existence of very rich behavior including normal and inverted bifurcations in the super and subcritical regimes. The various results are analyzed and discussed. © 1993 John Wiley&Sons, I

ISSN:0538-8066    

DOI:10.1002/kin.550250702

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractA laser flash photolysis‐long path absorption technique has been employed to study the kinetics of the reaction products as a function of temperature (248–346 K), pressure (16–800 torr), and buffer gas identity (N2, CF4). The reaction is found to be in the falloff regime between third and second‐order over the entire range of conditions investigated. This is the first study where temperature‐dependent measurements ofk1(P,T) have been reported at pressures greater than 12 torr; hence, our results help constrain choices ofk1(P,T) for use in models of lower stratospheric BrOxchemistry. Approximate falloff parameters in a convenient form for atmospheric modeling are derived. © 1993 John Wiley

ISSN:0538-8066    

DOI:10.1002/kin.550250703

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe relative hydroxyl radical reaction rate constants from the simulated atmospheric oxidation of selected acetates and other esters have been measured. Reactions were carried out at 297 ± 2Kin 100‐liter FEP Teflon®‐film bags. The OH radicals were generated from the photolysis of methyl nitrite in pure air. Using a rate constant of 2.63 × 10−11cm3molecule−1s−1for the reaction of OH radicals with propene, the principal reference organic compound, the rate constants (×1012cm3molecule−1s−1) obtained for the acetates and esters used in this study are:Textn–propyl acetate3.42 ± 0.87n–butyl acetate5.71 ± 0.94n–pentyl acetate7.53 ± 0.482–ethoxyethyl acetate10.56 ± 1.312–ethoxyethyl isobutyrate13.56 ± 2.322–ethoxyethyl methacrylate27.22 ± 2.064–pentene‐1‐yl acetate43.40 ± 3.853–Ethoxyacrylic acid ethyl ester33.30 ± 1.22Error limits represent 2σ from linear least‐squares analysis of data.A linear correlation was observed for a plot of the measured relative rate constants vs. the number of CH2groups per molecule of the following acetates: methyl acetate, ethyl acetate,n‐propyl acetate, butyl acetat

ISSN:0538-8066    

DOI:10.1002/kin.550250704

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThis qualitative study examines the response of the novel energetic material ammonium dinitramide (ADN), NH4N(NO2)2, to thermal stress under low heating rate conditions in a new experimental apparatus. It involved a combination of residual gas mass spectrometry and FTIR absorption spectroscopy of a thin cryogenic condensate film resulting from deposition of ADN pyrolysis products on a KCl window. The results of ADN pyrolysis were compared under similar conditions with the behavior of NH4NO3and NH2NO2(nitramide), which served as reference materials. NH4NO3decomposes into HNO3and NH3at 182°C and is regenerated on the cold cryostat surface. HNO3undergoes presumably heterogeneous loss to a minor extent such that the condensed film of NH4NO3contains occluded NH3. Nitramide undergoes efficient heterogeneous decomposition to N2O and H2O even at ambient temperature so that pyrolysis experiments at higher temperatures were not possible. However, the presence of nitramide can be monitored by mass spectrometry at its molecular ion (m/ℯ 62). ADN pyrolysis is dominated by decomposition into NH3and HN(NO2)2(HDN) in analogy to NH4NO3, with a maximum rate of decomposition under our conditions at approximately 155°C. The two vapor phase components regenerate ADN on the cold cryostat surface in addition to deposition of the pure acid HDN and H2O. Condensed phase HDN is found to be stable for indefinite periods of time at ambient temperature and vacuum conditions, whereas fast heterogeneous decomposition of HDN at higher temperature leads to N2O and HNO3. The HNO3then undergoes fast (heterogeneous) decomposition in some experiments. Gas phase HDN also undergoes fast heterogeneous decomposition to NO and other products, probably on the internal surface (ca. 60°C) of the vacuum chamber before mass spectrometric detection. © 1993 John Wiley&Sons

ISSN:0538-8066    

DOI:10.1002/kin.550250705

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractA fast‐flow technique suitable for measuring elementary rate constants over a wide range of pressures has been developed. The method operates under turbulent flow conditions, in contrast to laminar flow which characterizes the conventional low pressure technique. Flow visualization, velocity profile measurements, and tracer pulse studies have been carried out in a flow tube reactor to investigate the dynamics of both laminar and turbulent flow for chemical kinetics purposes. Furthermore, the wall collision frequency for the reactants has been determined: at the higher pressures it is greatly reduced in comparison with the frequency characteristic of the conventional low pressure laminar flow technique. Also, to test and validate the technique the bimolecular rate constants for the reactions H+Cl2and H+O3have been measured at total pressures in the 3–300 torr range; at pressures below 5 torr, as well as above 50 torr in the turbulent flow regime the agreement with the recommended literature values is excellent. © 1993 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550250706

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550250701

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY