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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
15 Aug 2015-Fuel
TL;DR: In this paper, two structural models for pyrolysis and hydrothermal treatment of lignite were constructed to investigate the impact of water at high temperature on the structure and reaction processes.

51 citations

Journal ArticleDOI
TL;DR: In this paper, the Car−Parrinello projector augmented-wave (CP−PAW) density functional theory (DFT) methodology was used to perform ab initio molecular dynamics calculations on chemical reactions.
Abstract: A study designed to refine the procedure for performing ab initio molecular dynamics calculations (AIMD) on chemical reactions is presented. Of key interest is the calculation of changes in free energy along the entire reaction path. Several simple elementary reactions are studied with the Car−Parrinello projector augmented-wave (CP−PAW) density-functional theory (DFT) methodology. The illustrative gas-phase bimolecular addition reactions are (i) a σ complexation of BH3 + H2O → H2O·BH3, (ii) the Diels−Alder reactions of butadiene with ethene, C4H6 + C2H4 → cyclohexene, 1,3-cyclopentadiene (CP) and ethene, CP + C2H4→ norbornene, and the stereoselective reaction of 5-amino-CP with ethene, amino-CP + C2H4 → amino-norbornene, (iii) the carbene cyclopropanation Cl2C + C2H4→ Cl2C3H4, and (iv) the dimerization of ketene. These reactions were used to test both the slow-growth and point-wise thermodynamic integration (STI and PTI) methods of phase-space sampling as well as the Nose−Hoover and Andersen thermostats....

51 citations

Journal ArticleDOI
TL;DR: In this article, the intrinsic kinetics of CH4 steam reforming developed over Rh/Ce0.6Zr0.4O2 catalyst in an integral fixed bed reactor with no mass and heat transport limitations and far from equilibrium conditions are guaranteed.
Abstract: This paper presents the intrinsic kinetics of CH4 steam reforming developed over Rh/Ce0.6Zr0.4O2 catalyst in a relatively low temperature range of 475–575 °C and 1.5 bar pressure. The kinetic experiments are conducted in an integral fixed bed reactor with no mass and heat transport limitations and far from equilibrium conditions. Therefore, intrinsic reaction rate measurements are guaranteed. The model is based upon two-site adsorption surface hypothesis, and 14 elementary reaction steps are postulated. CH4 is dissociatively adsorbed onto the Rh active sites, and steam is dissociatively adsorbed on the ceria support active sites as an influential adsorption surface shown in the model. Therefore, no competition between CH4 and steam in adsorbing on the same site surface is observed. The kinetic rate expressions are derived according to the Langmuir–Hinshelwood formalism. The redox surface reactions between the carbon containing species and the lattice oxygen leading to CO and CO2 formation are considered as rate determining steps. The inhibitory effect of gaseous product species is also reflected in the kinetics. The model is found to be statistically accurate and thermodynamically consistent. The estimated activation energies and adsorption enthalpies are in agreement with literature for CH4 steam reforming reaction over Rh. The reaction kinetics is validated by steam reforming experiments at 550 °C and 1.5 bar using 150 mg catalyst in a diluted bed of 5 cm length. The kinetic model is implemented in a one-dimensional pseudo-homogenous plug flow reactor model and thus simulated at identical experimental conditions. The simulation results are in excellent agreement with the experimental values.

51 citations

Journal ArticleDOI
TL;DR: In this article, a model is developed which allows to calculate the amount of carbon erosion at a hydrogenated carbon surface under the impact of hydrogen ions and neutrals, and the results show that both, target temperature and impinging particle flux energy distribution, determine the hydrogen flux density dependent erosion yield and the location of the erosion below the surface.

50 citations

Journal ArticleDOI
TL;DR: The overall Gibbs free energy change (ΔG) of a chemical reaction is often termed the driving force of the reaction as discussed by the authors, which is strictly true for elementary reactions-reactions that pass through only one local maximum (the transition state) along the reaction coordinate connecting reactant and product states.
Abstract: The overall Gibbs free energy change (ΔG) of a chemical reaction is often termed the driving force of the reaction. The sign of ΔG defines the direction of spontaneous reaction, and the condition ΔG=0 defines the point of chemical equilibrium. This is strictly true for elementary reactions-reactions that pass through only one local maximum (the transition state) along the reaction coordinate connecting reactant and product states. However, under many circumstances it is also true for reactions that involve one or more intermediates, particularly if the steady state intermediate concentrations are very small

50 citations


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