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Elementary reaction

About: Elementary reaction is a research topic. Over the lifetime, 2972 publications have been published within this topic receiving 76110 citations.


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Journal ArticleDOI
TL;DR: In this article, Baulch et al. proposed a new rate constant for N2O + OH HO2 + N2 with an upper limit of 5.5 s. This is considerably smaller than presently reported in the literature.
Abstract: Reaction experiments on mixtures of N2O/H2O/N2 were performed in a variable pressure flow reactor over temperature, pressure, and residence time ranges of 1103–1173 K, 1.5–10.5 atm, and 0.2–0.8 s, respectively. Mixtures of approximately 1% N2O in N2 were studied with the addition of varying amounts of water vapor, from background to 3580 ppm. Experimentally measured profiles of N2O, O2, NO, NO2, H2O, and temperature were compared with predictions from detailed kinetic modeling calculations to assess the validity of a reaction mechanism developed from currently available literature thermochemical and rate constant parameters. Sensitivity and reaction flux analyses were performed to determine key elementary reaction path processes and rates. Reaction rate constants for the uni-molecular reaction, N2O N2 + O, were determined at various pressures in order to match overall experimental and numerical decomposition rates of N2O. The numerical model included a newly determined rate constant for N2O + OH HO2 + N2 with an upper limit of 5.66 × 108 cm3 mol−1 sec−1 at 1123 K. This is considerably smaller than presently reported in the literature. The experimentally observed rate of N2O decomposition was found to be slightly dependent on added water concentration. The rate constant determined for the elementary decomposition is strongly dependent on the choice of rate constants for the N2O + O N2 + O2 and N2O + O NO + NO reactions. In the absence of accurate data at the temperatures of this work, and based on these and other experiments in this laboratory, we presently recommend rate constants from the review of Baulch et al. The basis for this recommendation is discussed, including the impact on the rate constants derived for elementary nitrous oxide decomposition. The uncertainties in the rate constants as reported here are ±30%. The present mechanism was applied to previously reported high-pressure shock tube data and yields a high-pressure limit rate constant a factor of three larger than previously reported at these temperatures. The following expressions for the elementary decomposition reaction are recommended: k = 9.13 × 1014 exp (−57, 690/RT) cm3 mol−1 s−1 and k∞ = 7.91 × 1010 exp(−56020/RT) s−1. Simple Lindemann fits utilizing these parameters reproduce the pressure dependent rate constants measured here within ±25%. © 1995 John Wiley & Sons, Inc.

52 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe semi-empirical models, based on thermochemistry and transition state theory, which are employed to estimate gas phase reaction rates over a wide range of temperatures and pressures.
Abstract: This paper reviews two physical chemistry topics related to atmospheric chemistry. First, we describe semiempirical models, based on thermochemistry and transition state theory, which are employed to estimate gas phase reaction rates over a wide range of temperatures and pressures. We also review briefly the experimental techniques utilized for measurements of elementary reaction rate constants, which provide the primary input to these models. We then address chemical reactions which take place in the atmosphere on the surface of solid, ice-like aerosol particles, discussing some current views on the mechanisms of these reactions and describing some laboratory techniques for the study of these heterogeneous processes.

52 citations

Journal ArticleDOI
TL;DR: In this article, the active phase, kinetics, and reaction mechanism of the water-gas-shift (WGS) reaction over the Rh-ZrO2 interface was explored.
Abstract: The industrially important water–gas-shift (WGS) reaction is a complex network of competing elementary reactions in which the catalyst is a multicomponent system consisting of distinct domains. Herein, we have combined density functional theory calculations with microkinetic modeling to explore the active phase, kinetics, and reaction mechanism of the WGS over the Rh–ZrO2 interface. We have explicitly considered the support and metal and their interface and find that the Rh–ZrO2 interface is far more active toward WGS than Rh(111) facets, which are susceptible to CO poisoning. CO2 forming on the zirconia support rapidly transforms into formate. These findings demonstrate the central role of the interface in the water–gas-shift reaction and the importance of modeling both the support and the metal in bifunctional systems.

52 citations

Book ChapterDOI
01 Jan 2005

52 citations

Journal ArticleDOI
TL;DR: In this paper, an activity relation for the heterogeneous catalytic oxidation of HCl (the Deacon Process) over rutile transition-metal oxide catalysts was established by combining density functional theory calculations (DFT) with microkinetic modeling.
Abstract: We establish an activity relation for the heterogeneous catalytic oxidation of HCl (the Deacon Process) over rutile transition-metal oxide catalysts by combining density functional theory calculations (DFT) with microkinetic modeling. Linear energy relations for the elementary reaction steps are obtained from the DFT calculations and used to establish a one-dimensional descriptor for the catalytic activity. The descriptor employed here is the dissociative chemisorption energy of oxygen. It is found that the commonly employed RuO 2 catalyst is close to optimal, but that there could still be room for improvements. The analysis suggests that oxide surfaces which offer slightly weaker bonding of oxygen should exhibit a superior activity to that of Ru0 2 .

52 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202229
202185
202088
201971
201871