bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling and simulation of stationary catalytic processes
Authors: Salmi Tapio 
Published: January 2005

AbstractGeneralized models for steady state catalytic processes are presented in matrix form. Multistep reaction rate control is assumed. Numerical algorithms for solving of the created linear and nonlinear equation systems are developed and tested. Four examples are considered: an Eley–Rideal‐mechanism, a Langmuir–Hinshelwood mechanism, a dual route, dual site mechanism, and a monomolecular decomposition with steady state multiplicity. The overall reaction rates are simulated as a function of the reactant concentrations.A maximum reaction rate is obtained in the case of a Langmuir–Hinshelwood mechanism (example 2), the location of the rate maximum in the concentration domain is shifted towards the concentration of the reactant with the lowest adsorption constants. An Eley–Rideal mechanism (example 1) has always monotonously increasing rate curves. In the case of steady state multiplicity (example 4) all steady states could be simulated with the proposed algorithm. The computation of reaction rate surfaces is important in investigating the behavior of complicated catalytic systems (e.g., systems with multistep rate control and/or steady state multiplicity), in planning of experiments and in chemical reactor simulation.
Fourier transform infrared study of the self reaction of C2H5O2 radicals in air at 295 K
Authors: Wallington T. J. , Gierczak C. A. , Ball J. C. , Japar S. M. 
Published: January 2005

AbstractFourier transform infrared spectroscopy was used to identify and quantify products of the self reaction of ethylperoxy radicals, C2H5O2, formed in the photolysis of Cl2/C2H6 mixtures in 700 torr total pressure of synthetic air at 295 K. From these measurements, branching ratios for the reaction channels
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of k1a/(k1a + k1b) = 0.68 and k1c/(k1a + k1b + k1c) ⩽ 0.06 were established. Additionally, using the relative rate technique, the rate constant for the reaction of Cl atoms with C2H5OOH was determined to be (1.07 ± 0.07) × 10−10 × cm3 molecule−1 s−1. Results are discussed with respect to the previous kinetic and mechanistic studies of C2H5O2 radicals.
An absolute and relative rate study of the reaction of oh radicals with dimethyl sulfide
Authors: Nielsen Ole J. , Sidebottom Howard W. , Nelson Linda , Treacy Jack J. , O'farrell Denis J. 
Published: January 2005

AbstractThe gas phase reaction of OH radicals with dimethyl sulfide (CH3SCH3, DMS) has been studied using both an absolute and a relative technique at 295 ± 2 K and a total pressure of 1 atm. The absolute rate technique of pulse radiolysis combined with kinetic spectroscopy was applied. Using this technique a rate constant of (3.5 ± 0.2) × 10−12cm3molecule−1s−1was obtained. For the relative rate method, rate constants for the reaction of OH with DMS were found to increase with increasing concentrations of added NO. These results are compared with the large body of kinetic and mechanistic data previously reported in the literature.
The gas phase reactivity of aliphatic polyethers towards OH radicals: Measurements and predictions
Authors: Dagaut Philippe , Liu Renzhang , Wallington Timothy J. , Kurylo Michael J. 
Published: January 2005

AbstractUsing the flash photolysis resonance fluorescence technique, absolute rate constants were determined for the gas phase reactions of hydroxyl radicals with a series of aliphatic polyethers. At 298 K, the measured rate constants (in units of 10−12 cm3 molecule−1 s−1) were: 2,2‐dimethoxypropane, (3.9 ± 0.2); 2,2‐diethoxypropane, (11.7 ± 1.3); 1,2‐dimethoxypropane, (14.3± 1.5); 2‐methoxyethylether, (17.5 ± 1.1); 2‐ethoxyethlyether, (26.8 ± 2.4); 1,1‐dimethoxyethane, (8.9 ± 1.0); and 1,1,3‐trimethoxypropane, (16.7 ± 1.0).The temperature dependencies of the rate constants for 2,2‐dimethoxypropane and 2,2‐diethoxypropane, reactions (1) and (2), were studied over the temperature range 240–440 K and are expressed by the Arrhenius equations:

Implications of the results are discussed in terms of reaction mechanisms and the prediction of gas phase OH radical reaction rates for aliphatic polyethers.
Kinetic probe to study the structural behavior of the mixed aqueous‐organic solvents. Salt effects on the kinetics and mechanism of intramolecular general‐base‐catalyzed ethanolysis of ionized phenyl salicylate
Authors: Khan M. Niyaz , Audu A. A. 
Published: January 2005

AbstractThe reaction rates of ethanolysis of ionized phenyl salicylate, PS−, have been studied in the presence of different concentrations of various inorganic and organic salts in ethanol‐water solvent of different compositions. The observed pseudo first‐order rate constants,𝓀1, reveal a nonlinear increase with increase of thecontent of ethanol until it becomes ca. 85%, v/v. The rate constants, 𝓀1, begin to decrease with increase of ethanol content beyond ca. 85%, v/v. The observed data obtained at ethanol contents of <ca. 55%, v/v, follow the relationships 𝓀1 = 𝓀[EtOH]T/(1 + K[EtOH]T ) where 𝓀 and K represent the second‐order rate constant for thereaction of PS− with monomeric ethanol, EtOH, and association constant for dimerization of monomers of ethanol, respectively, and [EtOH]T is the total concentration of ethanol. The calculated values of 𝓀 and K obtained in the presence of 0.01 M tetraalkylammonium ions, R4N+, show ca. 15% and 40%, respectively, decrease with increase of the chain lengths of alkyl groups, R. The following conclusions have been derived from the observed data. (i) Lithium chloride causes ethanol structure‐making effect while NaCl, KCl, and CsCl show ethanol structure‐breaking effect. (ii) Tetraalkylammonium halide salts such as Me4NCl, Et4NI, andn‐Bu4NI reveal ethanol structure‐breaking effect due to the transfer of some water molecules from solvation shells of ethanol and R4N+ when favorable hydrophobic interaction between hydrophobic sites of ethanol and R4N+ results in. This effect is, however, partially off set by the direct interaction between monomeric ethanol and R4N+. Both inorganic and organic cations are preferentially solvated by only water molecules in EtOH‐H2O solvents with EtOH contents of <ca. 55%, v/v. The effects of 0.01 M LiOH on 𝓀1 values obtained within the ethanol content range of 35% to 97%, v/v, seemed to be unaffected due to the presence of 0.01 M NaCl.
Kinetics and mechanism of oxidation of excited state Tris‐(2,2′‐bipyridyl)‐ruthenium (II) complex by peroxomonosulfate, peroxodisulfate, and peroxodiphosphate
Authors: Venkatasubramanian Lakshmanan , Dharmalingam Periasamy , Maruthamuthu Pichai 
Published: January 2005

AbstractExcitation of Ru(bipy)32+ ion by visible radiation of wavelength λ = 436 nm in aqueous medium in presence of inorganic peroxides, peroxomonosulfate (PMS), peroxodisulfate (PDS), and peroxodiphosphate (PDP) was found to generate Ru(bipy)33+. The kinetics of this photochemical oxidation of Ru(bipy)32+ by each peroxide was followed spectrophotometrically and found to obey a total second‐order, first‐order each in [Ru(bipy)32+] and [peroxide]. In the absence of light, thermal reaction of PMS and PDS with Ru(bipy)32+ occurred but only when at 1.0 M [H+] and > 10−2M [peroxide]. The reaction of PMS with the complex is found to be cyclic, ie., Ru(bipy)33+ formed oxidizes PMS itself and such a reaction was not observed in the case of PDS and PDP. The effects of pH, [peroxide], and [Ru(bipy)32+] on the visible light induced oxidation of Ru(bipy)32+ by these peroxides are investigated. The results are discussed with suitable reaction mechanisms.
Toward a comprehensive mechanism for methanol pyrolysis
Authors: Norton T. S. , Dryer F. L. 
Published: January 2005

AbstractA single kinetic mechanism for methanol pyrolysis is tested against multiple sets of experimental data for the first time. Data are considered from static, flow, and shock tube reactors, covering temperatures of 973 to 2000 K and pressures of 0.3 to 1 atmosphere. The model results are highly sensitive to the rates of unimolecular fuel decomposition and of various chain termination reactions that remove CH2OH and H radicals, as well as to experimental temperature uncertainties. The secondary fuel decomposition reaction CH3OH = CH2OH + H, which has previously been included only in mechanisms for high temperature conditions, is found to have a significant effect at low temperatures as well, through radical recombination. The reaction CH3O + C = CH3 + CO2, rather than CH3OH + H = CH3 + H2O, is found to be the dominant source of CH3 at low temperatures. The reverse of CH3 + OH = CH2OH + H is important to CH3 production at high temperatures.
A kinetic study of the autocatalytic permanganate oxidation of formic acid
Authors: Perez‐Benito Joaquin F. , Arias Conchita , Brillas Enrique 
Published: January 2005

AbstractThe kinetics of the permanganate oxidation of formic acid in aqueous perchloric acid has been studied. The results indicate that this reaction is autocatalyzed by both manganese(II) ion (formed as a reaction product) and colloidal manganese dioxide (formed as an intermediate). The apparent rate constants corresponding to the noncatalytic and autocatalytic reaction pathways are given, respectively, by the following equations

The activation energies associated with the true rate constants, 𝓀, 𝓀, 𝓀, 𝓀, 𝓀, and 𝓀 are 37.2, 62.5, 70.9, 52.5, 40.8, and 59.9 kJ mol−1, respectively. The percentage of the total reaction corresponding to each pathway is given for typical experimental conditions. Mechanisms in agreement with the kinetic data are proposed for the six different reaction pathways observed.
Kinetics of the reactions of O(3P) and Cl(2P) with HBr and Br2
Authors: Nicovich J. M. , Wine P. H. 
Published: January 2005

AbstractA laser flash photolysis‐resonance fluorescence technique has been employed to study the kinetics of reactions (1)–(4) as a function of temperature.
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In all cases, the concentration of the excess reagent, i.e., HBr or Br2, was measured in situ in the slow flow system by UV‐visible photometry. Heterogeneous dark reactions between XBr (X = H or Br) and the photolytic precursors for Cl(2P) and O(3P) (Cl2 and O3, respectively) were avoided by injecting minimal amounts of precursor into the reaction mixture immediately upstream from the reaction zone. The following Arrhenius expressions summarize our results (errors are 2σ and represent precision only, units are cm3 molecule−1 s−1): 𝓀1 = (1.76 ± 0.80) × 10−11 exp[(40 ± 100)/T]; 𝓀2 = (2.40 ± 1.25) × 10−10 exp[−(144 ± 176)/T]; 𝓀3 = (5.11 ± 2.82) × 10−12 exp[−(1450 ± 160)/T]; 𝓀4 = (2.25 ± 0.56) × 10−11 exp[−(400 ± 80)/T]. The consistency (or lack thereof) of our results with those reported in previous kinetics and dynamics studies of reactions (1)–(4) is discussed.
A pyrolysis mechanism for ammonia
Authors: Davidson D. F. , Kohse‐Höinghaus K. , Chang A. Y. , Hanson R. K. 
Published: January 2005

AbstractThe mechanism of NH3pyrolysis was investigated over a wide range of conditions behind reflected shock waves. Quantitative time‐history measurements of the species NH and NH2were 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 NH2in this experimental database have also been summarized graphically.Rate coefficients for several reactions which influence the NH and NH2profiles were fitted in the temperature range 2200 K to 2800 K. The reaction and the corresponding best fit rate coefficients are as follows:with a rate coefficient of 4.0 × 1013exp(−3650/RT) cm3mol−1s−1,with a rate coefficient of 1.5 × 1015T−0.5cm3mol−1s−1andwith a rate coefficient of 5.0 × 1013exp(−10000/RT) cm3mol−1s−1. The uncertainty in rate coefficient magnitude in each case is estimated to be ±50%. The temperature dependences of these rate coefficients are based on previous estimates.The experimental data from four earlier measurements of the dissociation reactionwere reanalyzed in light of recent data for the rate of NH3+ H → NH21 + H2, and an improved rate coefficient of 2.2 × 1016exp(−93470/RT) cm3mol−1s−1in the temperature range 1740 to 3300 K was obtained. The uncertainty in the rate coefficient magnitude is estimated to be ± 15%.
Comment: A re‐evaluation of the rate constant for abstraction of hydrogen from isobutane by methyl radicals
Authors: Zhang H.‐X. , Back M. H. 
Published: January 2005

AbstractThe rate constant for abstraction of hydrogen from isobutane by methyl radicals has been re‐examined making use of new measurements at temperatures above 660 K. Most of the data over the temperature range 300–855 K can be accommodated by the following values for the rate constants for abstraction from primary and tertiary hydrogen atoms:

This activation energy for abstraction of the tertiary hydrogen atom in isobutane is essentially the same as expressed in a previous evaluation, which considered data only below 500 K, but the magnitude of the rate constant is about 0.25 log units greater.
High temperature pyrolysis of methane in shock waves. Rates for dissociative recombination reactions of methyl radicals and for propyne formation reaction
Authors: Hidaka Yoshiaki , Nakamura Takuji , Tanaka Hiroya , Inami Koji , Kawano Hiroyuki 
Published: January 2005

AbstractThe pyrolysis of 2% CH4 and 5% CH4 diluted with Ar was studied using both a single–pulse and time–resolved spectroscopic methods over the temperature range 1400–2200 K and pressure range 2.3–3.7 atm. The rate constant expressions for dissociative recombination reactions of methyl radicals, CH3 + CH3 → C2H5 + H and CH3 + CH3 → C2H4 + H2, and for C3H4 formation reaction were investigated. The simulation results required considerably lower value than that reported for CH3 + CH3 → C2H4 + H2. Propyne formation was interpreted well by reaction C2H2 + CH3 → P‐C3H4 + H with 𝓀 = 6.2 × 1012 exp(−17 kcal/RT) cm3 mol−1 s−1.
The mechanism of the homogeneous pyrolysis of acetylene
Authors: Kiefer John H. , Von Drasek William A. , Von Drasek William A. 
Published: January 2005

AbstractThe experimental literature on the pyrolysis of C2H2 is reviewed and summarized. These observations divide naturally into three temperature regimes: (i) T < 1100 K, where the homogeneous reaction is a molecular polymerization; (ii) 1100 < T < 1800 K, where the process is still dominated by a molecular polymerization, but a fragment radical chain is clearly involved; and (iii) T > 1800 K, where a fragment chain carried by C2H and H drives a polymerization to polyacetylenes. A combined molecular/fragment chain mechanism is developed and applied to the modeling of three shock‐tube studies which span the two higher‐temperature regimes. The core of the mechanism is a set of 5 mainly molecular reactions whose rates are derived from an application of unimolecular rate theory and detailed balance to recent measurements on the decomposition of vinylacetylene. The combination of this core with consequent fragment radical reactions provides a satisfactory description of most features of the chosen experiments including several‐isotope exchange, hydrogenation to C2H4, and C6H2 formation‐which are almost entirely the result of fragment radical chain reaction. Possible detailed paths for the molecular dimerization are suggested and some possible molecular paths for the “Berthelot synthesis” of benzene are also proposed.
UV‐Absorption spectrum of the methylperoxy radical and the kinetics of its disproportionation reaction at 300 K
Authors: Simon Franz‐Georg , Schneider Wolfgang , Moortgat Geert K. 
Published: January 2005

AbstractMolecular modulation spectroscopy combined with ultraviolet spectroscopic techniques have been used to observe the behavior of the CH3O2 radicals generated in the gas phase by near‐ultraviolet modulated photolysis of flowing Cl2CH4O2 mixtures. The kinetics of the disproportionation reaction (1)
equation image
and the absorption cross‐sections of CH3O2 were measured by computer fitting of the modulated absorption traces obtained in the wavelength range 220 to 270 nm at 300 K and 240 torr. The rate constant for the elementary self‐reaction 𝓀1 = 𝓀1(a) + 𝓀1(b) + 𝓀1(c) was determined to be (3.61 ± 0.55) × 10−13 cm3 molecule−1 s−1. The parameter 𝓀obs/σ (where 𝓀obs is the observed apparent second‐order rate constant) was measured from the decay curves in the dark phase of the modulated photolysis period in the wavelength range 230–260 nm, and had a value 1.16 × 105 cm2 s−1 at 250 nm. At 250 nm the absorption cross‐section was determined as σ(CH3O2) = 4.14 × 10−18 cm2 molecule−1, leading to a value of 𝓀obs, = (4.8 ± 0.5) × 10 13 cm3 molecule−1 s−1. In addition, the absorption spectrum of CH3O2 was measured in the range 210–295 nm using diode array spectroscopy. A detailed review of all previous studies concerning the kinetics and spectrum of the CH3O2 radical is presented, and a recommended spectrum, representing an average from selected recent studies, is proposed.
The rate constant for the intramolecular isomerization of pentyl radicals
Authors: Marshall Roger M. 
Published: January 2005

AbstractThe thermal decomposition of n‐pentane has been investigated in the temperature range 737 to 923 K. Making various assumptions, the detailed distribution of major products (methane, ethane, ethene, propene, and 1‐butene) is used to evaluate the rate constant for the unimolecular isomerization
equation image
which proceeds via a five‐membered, cyclic transition state. Two alternative sets of assumptions are used. Common to both of them are assumptions concerning the thermochemistry and rate constants for decomposition of the C5H11 radicals. Method 1 assumes that all secondary CH bonds are equally reactive towards hydrogen abstraction in which case, in addition to the value of 𝓀10, the ratio of the rate constants for abstraction from primary and secondary CH bonds is evaluated. Values about a factor of two higher than published values for similar molecules are obtained. The alternative, method 2, assumes that the ratio of abstraction from the 1‐ and 2‐ positions of n−pentane is the same as that published for n−butane, in which case, in addition to the value of 𝓀10, the ratio of the rates of abstraction from the 3‐ and 2‐ positions of n‐pentane is obtained. The value obtained is 0.401 which is to be compared with the statistically expected (and assumed in method 1) 0.5. Detailed discussions of the values of 𝓀10 obtained leads to the conclusion that method 1 leads to the best value

where θ = 2.303RT in kcal/mol and error limits are two standard deviations. Combination of this value with values recalculated from published lower temperature data gives

which, it is concluded, is the best value in the range 438 to 923 K.
Kinetics and products of the gas‐phase reactions of the OH radical and O3 with allyl chloride and benzyl chloride at room temperature
Authors: Tuazon Ernesto C. , Atkinson Roger , Aschmann Sara M. 
Published: January 2005

AbstractThe kinetics of the gas‐phase reactions of allyl chloride and benzyl chloride with the OH radical and O3 were investigated at 298 ± 2 K and atmospheric pressure. Direct measurements of the rate constants for reactions with ozone yielded values of 𝓀(O3 + allyl chloride) = (1.60 ± 0.18) × 10−18 cm3 molecule−1 s−1 and 𝓀(O3 + benzyl chloride) < 6 × 10−20 cm3 molecule−1 s−1. With the use of a relative rate technique and ethane as a scavenger of chlorine atoms produced in the OH radical reactions, rate constants of 𝓀(OH + allyl chloride) = (1.69 ± 0.07) × 10−11 cm3 molecule−1 s−1 and 𝓀(OH + benzyl chloride) = (2.80 ± 0.19) × 10−12 cm3 molecule−1 s−1 were measured. A study of the OH radical reaction with allyl chloride by long pathlength FT‐IR absorption spectroscopy indicated that the co‐products ClCH2CHO and HCHO account for ca. 44% of the reaction, and along with the other products HOCH2CHO, (ClCH2)2CO, and CH2  CHCHO account for 84 ± 16% of the allyl chloride reacting. The data indicate that in one atmosphere of air in the presence of NO the chloroalkoxy radical formed following OH radical addition to the terminal carbon atom of the double bond decomposes to yield HOCH2CHO and the CH2Cl radical, which becomes a significant source of the Cl atoms involved in secondary reactions. A product study of the OH radical reaction with benzyl chloride identified only benzaldehyde and peroxybenzoyl nitrate in low yields (ca. 8% and ⩽4%, respectively), with the remainder of the products being unidentified.
cis‐RuCl2(DMSO)4‐catalyzed oxidation of sulfides by N‐methylmorpholine N‐oxide (NMO)
Authors: Caroling G. , Rajaram J. , Kuriacose J. C. 
Published: January 2005

AbstractThe induction period observed in the cis‐RuCl2(DMSO)4 catalyzed oxidation of thioethers (S) to sulfoxides by N‐methylmorpholine N‐oxide (NMO) is attributed to the rate of formation of the active species viz. RuCl2(DMSO)3S. Cyclic voltammetric studies indicate formation of the RuIV = 0 species. Based on the variable orders in NMO and first order in each of the other reactants, a mechanism is proposed where the active species generated in situ reacts with NMO in a slow step to form RuIV oxo complex which then decomposes to give the product.
Kinetic modeling of the reactions of C3H3+ with acetylene, deuteroacetylene, and diacetylene
Authors: Wiseman Floyd L. , Ozturk Feza , Zerner Michael C. , Eyler John R. 
Published: January 2005

AbstractThe reactions of ℓ‐C3H3+ (propargylium cation) with acetylene and diacetylene have been modeled kinetically. Data were obtained from Fourier Transform Ion Cyclotron Resonance (FTICR) experiments on these systems, which are themselves models for soot particle initiation. Acetylene forms an encounter complex with ℓ‐C3H3+, but, in the absence of a third body collision, the complex decomposes to acetylene and c‐C3H3+ (cyclopropenylium cation) at about 1/3 the rate it decomposes to acetylene and ℓ‐C3H3+, in spite of the fact that c‐C3H3+ is ca. 115 kJ/mol more stable than ℓ‐C3H3+. The encounter complex is long enough lived, and energetic enough, to scramble deuterium in reactions between ℓ‐C3H3+ and C2D2. These reactions have been successfully modeled, yielding a nearly statistical distribution of deuterium, and a rather large kinetic isotope effect. The more complex reactions of ℓ‐C3H3+ with diacetylene have also been modeled.
A product study of the gas‐phase reaction of Isoprene with the OH radical in the presence of NOx
Authors: Tuazon Ernesto C. , Atkinson Roger 
Published: January 2005

AbstractThe gas‐phase reaction of isoprene with the OH radical, in the resence of NOx, was investigated at 298 ± 2 K and atmospheric pressure of air by long path length FT‐IR spectroscopy. The primary products identified and their formation yields were: methacrolein, 0.21 ± 0.05; methyl vinyl ketone, 0.29 ± 0.07; and HCHO, with the observed yield being consistent with the sum of the methacrolein and methyl vinyl ketone yields. Combined with the previously reported yield of 0.044 ± 0.006 for 3‐methylfuran, these products accounted for 55 ± 9% of the isoprene which reacted. Under conditions where the dark reaction of isoprene with NO2is not significant, the balance of the isoprene consumed could possibly be accounted for by the “organic nitrates” and “other carbonyl compounds” formed in estimated overall yields of ca. 12% and ca. 25%, respectively.