Kinetics of radical reactions in sodium diffusion flames

1978 ◽  
Vol 56 (7) ◽  
pp. 941-949 ◽  
Author(s):  
Kenneth J. Mintz ◽  
Donald J. Le Roy
Keyword(s):  
Diffusion Flames ◽  
Hydrogen Abstraction ◽  
Spherical Model ◽  
Kinetic Studies ◽  
Alkyl Halides ◽  
Two Factors ◽  
Linear Differential ◽  
Sodium Diffusion ◽  
Kinetics Of ◽  
Good Agreement

The primary reaction in sodium diffusion flames, Na + RX = NaX + R, has been investigated as a possible source of free radicals for kinetic studies. A number of different alkyl halides were investigated as possible radical sources. Optimum conditions were found to minimize wall reactions and hydrogen abstraction from the halide, the two factors which invalidated previous work using this method. Rate constants were derived from product analyses by the numerical solution of simultaneous non-linear differential equations based on a spherical model involving diffusion. Values were obtained for the two modes of decomposition of n-C3H7, the abstraction of primary and secondary H atoms from C3H8 by CH3, and the addition of CH3 to C2H4. These are in reasonably good agreement with values determined by more conventional methods.

scholarly journals Estudo cinético da abstração do hidrogênio do acetato de metila

2020 ◽  
Author(s):  
Leandro da Silva Pereira ◽  
Leonardo Baptista
Keyword(s):  
Transition State Theory ◽  
Methyl Esters ◽  
Hydrogen Abstraction ◽  
State Theory ◽  
Basis Set ◽  
Rate Coefficients ◽  
Dft Methods ◽  
Carbon Chains ◽  
Kinetics Of ◽  
Good Agreement

Biodiesel is a fuel formed by methyl esters with large carbon chains. The investigation of the hydrogen abstraction reactions of small methyl esters can be helpful to the improvement and development of kinetics models of biodiesel combustion. For this reason, the present study aims to study the thermochemistry and kinetics of hydrogen abstraction of methyl ethanoate using DFT methods and transition state theory. The abstraction reactions by O2, O, HO2, and H were studied with the B3LYP-D3 and M06-2X functionals with cc-pVDZ, ccpVTZ, aug-cc-pVDZ, and aug-cc-pVTZ basis set. At 298 K, the rate coefficients evaluated are in good agreement with the literature’s coefficients and the faster reaction occurs in the presence of O atoms. The hydrogen abstraction by O2 molecule it is not important at 298 K, but should be included in the present study since it should be important at higher temperatures.

Polar Radicals. VIII. Kinetic Studies on the Mechanism of the Vapor Phase Bromination of 1-Chlorobutane. The Role of Reversible Hydrogen Abstraction

1975 ◽  
Vol 53 (14) ◽  
pp. 2202-2209 ◽  
Author(s):  
Dennis D. Tanner ◽  
Tony Pace ◽  
Tameichi Ochiai
Keyword(s):  
Vapor Phase ◽  
Hydrogen Bromide ◽  
Hydrogen Abstraction ◽  
Kinetic Studies ◽  
Abstraction Reaction ◽  
Substituted Alkanes ◽  
Kinetics Of ◽  
Hydrogen Abstraction Reaction ◽  
General Method

A general method for the evaluation of the kinetics of the vapor phase brominations of alkanes and substituted alkanes is presented. The method is applied to the bromination of 1-chlrobutane.The hydrogen abstraction reaction and its reversal are both found to be deactivated by the polar influence of the substituent; the effect, as predicted, falls off as the distance of the substituent from the C—H bond involved increases. In the vapor phase bromination of 1-chlorobutane, because of this deactivated reversal, transfer with hydrogen bromide cannot compete (< 10%) with transfer with molecular bromine.There was no evidence for anchimeric assistance by the neighboring chlorine atom during hydrogen abstraction.

scholarly journals Effects of the Size, the Number, and the Spatial Arrangement of Reactive Patches on a Sphere on Diffusion-Limited Reaction Kinetics: A Comprehensive Study

2020 ◽  
Vol 21 (3) ◽  
pp. 997 ◽  
Author(s):  
Changsun Eun
Keyword(s):  
Reaction Kinetics ◽  
Rate Constant ◽  
Brownian Dynamics ◽  
Kinetic Studies ◽  
Spatial Arrangement ◽  
The Finite Element Method ◽  
Diffusion Limited ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
Good Agreement

We investigate how the size, the number, and the spatial arrangement of identical nonoverlapping reactive patches on a sphere influence the overall reaction kinetics of bimolecular diffusion-limited (or diffusion-controlled) reactions that occur between the patches and the reactants diffusing around the sphere. First, in the arrangement of two patches, it is known that the overall rate constant increases as the two patches become more separated from each other but decreases when they become closer to each other. In this work, we further study the dependence of the patch arrangement on the kinetics with three and four patches using the finite element method (FEM). In addition to the patch arrangement, the kinetics is also dependent on the number and size of the patches. Therefore, we study such dependences by calculating the overall rate constants using the FEM for various cases, especially for large-sized patches, and this study is complementary to the kinetic studies that were performed by Brownian dynamics (BD) simulation methods for small-sized patches. The numerical FEM and BD simulation results are compared with the results from various kinetic theories to evaluate the accuracies of the theories. Remarkably, this comparison indicates that our theory, which was recently developed based on the curvature-dependent kinetic theory, shows good agreement with the FEM and BD numerical results. From this validation, we use our theory to further study the variation of the overall rate constant when the patches are arbitrarily arranged on a sphere. Our theory also confirms that to maximize the overall rate constant, we need to break large-sized patches into smaller-sized patches and arrange them to be maximally separated to reduce their competition.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

Thermochemical and kinetic studies of hydrogen abstraction reaction from C16H10 isomers by H atoms

2021 ◽  
Vol 1201 ◽  
pp. 113257
Author(s):  
Dorra Khiri ◽  
Sonia Taamalli ◽  
Duy Quang Dao ◽  
Thanh-Binh Nguyen ◽  
Laurent Gasnot ◽  
...  
Keyword(s):  
Hydrogen Abstraction ◽  
Kinetic Studies ◽  
Abstraction Reaction ◽  
Hydrogen Abstraction Reaction

scholarly journals Kinetic Studies of Cs+ and Sr2+ Ion Exchange Using Clinoptilolite in Static Columns and an Agitated Tubular Reactor (ATR)

2021 ◽  
Vol 5 (1) ◽  
pp. 9
Author(s):  
Muhammad Yusuf Prajitno ◽  
Mohamad Taufiqurrakhman ◽  
David Harbottle ◽  
Timothy N. Hunter
Keyword(s):  
Adsorption Capacity ◽  
Tubular Reactor ◽  
Process Intensification ◽  
Kinetic Studies ◽  
Breakthrough Curves ◽  
Maximum Adsorption Capacity ◽  
Batch Studies ◽  
Shear Mixing ◽  
Natural Clinoptilolite ◽  
Kinetics Of

Natural clinoptilolite was studied to assess its performance in removing caesium and strontium ions, using both static columns and an agitated tube reactor (ATR) for process intensification. Kinetic breakthrough curves were fitted using the Thomas and Modified Dose Response (MDR) models. In the static columns, the clinoptilolite adsorption capacity (qe) for 200 ppm ion concentrations was found to be ~171 and 16 mg/g for caesium and strontium, respectively, highlighting the poor material ability to exchange strontium. Reducing the concentration of strontium to 100 ppm, however, led to a higher strontium qe of ~48 mg/g (close to the maximum adsorption capacity). Conversely, halving the column residence time to 15 min decreased the qe for 100 ppm strontium solutions to 13–14 mg/g. All the kinetic breakthrough data correlated well with the maximum adsorption capacities found in previous batch studies, where, in particular, the influence of concentration on the slow uptake kinetics of strontium was evidenced. For the ATR studies, two column lengths were investigated (of 25 and 34 cm) with the clinoptilolite embedded directly into the agitator bar. The 34 cm-length system significantly outperformed the static vertical columns, where the adsorption capacity and breakthrough time were enhanced by ~30%, which was assumed to be due to the heightened kinetics from shear mixing. Critically, the increase in performance was achieved with a relative process flow rate over twice that of the static columns.

scholarly journals Biochar Chemistry in a Weathered Tropical Soil: Kinetics of Phosphorus Sorption

Agriculture ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 295
Author(s):  
Marina Moura Morales ◽  
Nicholas Brian Comerford ◽  
Maurel Behling ◽  
Daniel Carneiro de Abreu ◽  
Iraê Amaral Guerrini
Keyword(s):  
Mineral Soil ◽  
Soil Surface ◽  
Kinetic Studies ◽  
Inorganic Phosphorus ◽  
Initial Reaction ◽  
Phosphorus Sorption ◽  
P Sorption ◽  
Published Research ◽  
Kinetics Of

The phosphorus (P) chemistry of biochar (BC)-amended soils is poorly understood. This statement is based on the lack of published research attempting a comprehensive characterization of biochar’s influence on P sorption. Therefore, this study addressed the kinetic limitations of these processes. This was accomplished using a fast pyrolysis biochar made from a mix of waste materials applied to a highly weathered Latossolo Vermelho distrofico (Oxisol) from São Paulo, Brazil. Standard method (batch method) was used. The sorption kinetic studies indicated that P sorption in both cases, soil (S) and soil-biochar (SBC), had a relatively fast initial reaction between 0 to 5 min. This may have happened because adding biochar to the soil decreased P sorption capacity compared to the mineral soil alone. Presumably, this is a result of: (i) Inorganic phosphorus desorbed from biochar was resorbed onto the mineral soil; (ii) charcoal particles physically covered P sorption locations on soil; or (iii) the pH increased when BC was added SBC and the soil surface became more negatively charged, thus increasing anion repulsion and decreasing P sorption.

INHOMOGENEOUS LARGE DEFORMATION KINETICS OF POLYMERIC GELS

2013 ◽  
Vol 05 (01) ◽  
pp. 1350001 ◽  
Author(s):  
WILLIAM TOH ◽  
ZISHUN LIU ◽  
TENG YONG NG ◽  
WEI HONG
Keyword(s):  
Large Deformation ◽  
Soft Matter ◽  
Inner Core ◽  
Kinetic Studies ◽  
Fe Model ◽  
One Dimensional ◽  
Simplified Approach ◽  
Deformation Kinetics ◽  
Polymeric Gels ◽  
Kinetics Of

This work examines the dynamics of nonlinear large deformation of polymeric gels, and the kinetics of gel deformation is carried out through the coupling of existing hyperelastic theory for gels with kinetic laws for diffusion of small molecules. As finite element (FE) models for the transient swelling process is not available in commercial FE software, we develop a customized FE model/methodology which can be used to simulate the transient swelling process of hydrogels. The method is based on the similarity between diffusion and heat transfer laws by determining the equivalent thermal properties for gel kinetics. Several numerical examples are investigated to explore the capabilities of the present FE model, namely: a cube to study free swelling; one-dimensional constrained swelling; a rectangular block fixed to a rigid substrate to study swelling under external constraints; and a thin annulus fixed at the inner core to study buckling phenomena. The simulation results for the constrained block and one-dimensional constrained swelling are compared with available experimental data, and these comparisons show a good degree of similarity. In addition to this work providing a valuable tool to researchers for the study of gel kinetic deformation in the various applications of soft matter, we also hope to inspire works to adopt this simplified approach, in particular to kinetic studies of diffusion-driven mechanisms.

Ab Initio Study on the Kinetics of Hydrogen Abstraction for the H + Alkene → H2+ Alkenyl Reaction Class

2007 ◽  
Vol 111 (11) ◽  
pp. 2156-2165 ◽  
Author(s):  
Lam K. Huynh ◽  
Sylwester Panasewicz ◽  
Artur Ratkiewicz ◽  
Thanh N. Truong
Keyword(s):  
Ab Initio ◽  
Hydrogen Abstraction ◽  
Ab Initio Study ◽  
Kinetics Of

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

Sign in / Sign up

Export Citation Format

Share Document