ISSN:0538-8066    

DOI:10.1002/kin.550171002

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractPart I: Kinetic data for the static system silane pyrolysis (from 640–703 K, 60–400 torr) are presented. For conversion from 3–30%, first‐order kinetics are obtained, with silane loss rates equal to half the hydrogen formation rates. At conversions greater than 40%, rate inhibition attributable to the back reaction of hydrogen with silylene occurs. Overall reaction rates are not surface sensitive, but disilane and trisilane yield maxima under some conditions are. A nonchain mechanism capable of describing quantitatively all stages of the silane pyrolysis is proposed. Post 1.0% initiation is both homogeneous (gas phase) and heterogeneous (on the walls), and reaction intermediates are silylenes and disilenes. Free radicals are not involved at any stage of the reaction. Rate data at high conversions and with added hydrogen provide kinetics for the addition of silylene to hydrogen [reaction (−1)1] relative to its addition to silane [reaction (2)]:k−1,/k2= 10−0.65×e−3200 cal/RT. WithE2= 1300 cal, this gives a high pressure activation energy for silylene insertion into hydrogen ofE−1= 8200 cal.Part II: An analysis is made of each rate constant of the silane mechanism and the modeling results are compared with experimental results. Agreement is excellent. It is concluded that the dominant sink reaction for silylene intermediates is 1,2—H2elimination from disilane (followed by Si2H4polymerization and wall deposition). The model is in accord with slow isomerization between disilene and silylsilylene and near exclusive 1,2—H2elimination from Si2H6. It is also concluded that disilene is about 10 kcal/mol more stable than silylsilylene and that the activation energy for isomerization of silylsilylene to disilene is gr

ISSN:0538-8066    

DOI:10.1002/kin.550171003

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractKinetic data and product studies are reported for the silane pyrolysis in the presence of olefins and acetylene. The kinetics of silane loss in the presence of acetylene was found to be identical to the initial gas phase silane decomposition step (SiH4+ M → SiH2+ H2+ M) when corrected for pressure fall‐off effects. This result and the absence of methane or ethane from the pyrolysis of SiH4in the presence of 1‐butene or 1‐pentene demonstrate that silyl radicals and H atoms are not involved in silane‐olefin or silane‐acetylene reactions. Qualitative aspects and kinetic data from the SiH4pyrolysis in the presence of propylene are in accord with propylsilane formation via propylsilylene formed by silylene addition t

ISSN:0538-8066    

DOI:10.1002/kin.550171004

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe condensed‐phase thermal decomposition of aliphatic nitrate ester explosives is generally autocatalytic. The object of this article is to show that the agent of the autocatalysis is not the product NO2, as is generally believed, but to suggest that it may be the product formaldehyd

ISSN:0538-8066    

DOI:10.1002/kin.550171005

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractRate constants for the reaction OH + CO have been measured as functions of temperature (340–1220 K) and water concentration in the presence of 1 atm of argon. Results at zero water concentration yield the expression, logkƒ(cm3molecule−1S−1) = −12.96 + 4.7 × 10−4T, for the reaction rate constant as a function of temperature. These results are in very good agreement with previous direct measurements and in reasonable agreement with flame and shock tube measurements. Explanations are offered for the involvement of the water molecule in the present experiments and earlier measurements from this laboratory throughout the entire temperature range. Results are consistent with previous results showing little, if any, pressure effect of Ar on the reaction up to

ISSN:0538-8066    

DOI:10.1002/kin.550171006

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractAn ArF excimer laser was used to perturb radical concentrations and a tunable dye laser was used to follow the rise and subsequent decay of OH and CH in rich (ϕ = 1.6–1.8) atmospheric pressure methane flames. The excimer beam is only slightly focussed to minimize temperature excursions and the influence of diffusion and convection on the decay rates. The observed OH decay is consistent with that predicted using a detailed kinetic mechanism. The observed CH decay is much faster than predicted. The effects of equivalence ratio and height above burner suggests that a major CH decay channel involving an intermediate with higher concentration in rich flames is not properly treated in the mechani

ISSN:0538-8066    

DOI:10.1002/kin.550171007

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn the case of catalytic dehydrogenation of cyclohexane, the linear relation between reaction rate and affinity holds at an appreciable distance away from equilibrium on both sides. In fact, in order to explain this observation, it is necessary to invoke a high value of three for the stoichiometric number of the rate determining step. This in turn can be explained by a reasonable mechanism for the reaction.

ISSN:0538-8066    

DOI:10.1002/kin.550171008

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractFlash photolysis of dimethyl oxalate produced the radicals CH3, CH3O, and COOCH3. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40‐torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO2, CH4, C2H4, C2H6, CH2O, CH3OH, CH3OCH3, HCOOCH3, CH3COOCH3, CH3OCOOCH3, CH3C6H11, and CH3OC6H11. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals,k1= 2.7 × 1010dm3mol−1s−1, measured with the same equipment.The rate coefficients for reactions (5)–(8) are:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} k_5 = (3.1 + 0.5) \times 10^{10} \,{\rm dm}^{\rm 3} \,{\rm mol}^{{\rm - 1}} \,{\rm s}^{{\rm - 1}} \\ k_6 = (2.1 + 0.2) \times 10^{10} \,{\rm dm}^{\rm 3} \,{\rm mol}^{{\rm - 1}} \,{\rm s}^{{\rm - 1}} \\ k_7 = (2.3 + 0.1) \times 10^{10} \,{\rm dm}^{\rm 3} \,{\rm mol}^{{\rm - 1}} \,{\rm s}^{{\rm - 1}} \\ \end{array} $$\

ISSN:0538-8066    

DOI:10.1002/kin.550171009

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThese tables of evaluated rate constants for use in stratospheric modeling have been taken from the most recent report of the NASA Panel that has been periodically producing such reviews. They are reproduced here to make a broader community aware of their existence.This article should NOT be cited, nor should these rate constants be used without consulting the full report. All citations should be to that original report (JPL Publ. 85‐37), which contains extensive documentation and discussion of the rationale of the evaluation. Copies may be obtained by requesting JPL Publ. 85‐37 from Documentation Services, 111‐116B, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA

ISSN:0538-8066    

DOI:10.1002/kin.550171010

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550171011

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY