scispace - formally typeset
Search or ask a question
Topic

Elementary reaction

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


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, the Single Event Microkinetic (SEMK) methodology has been applied towards "ethylbenzene dealkylation/xylene isomerization" under industrially relevant conditions.
Abstract: The Single-Event Microkinetic (SEMK) methodology has been applied towards “ethylbenzene dealkylation/xylene isomerization” under industrially relevant conditions. This includes the isomerization of xylenes towards thermodynamic equilibrium, the dealkylation of ethylbenzene as well as a limited amount of xylene transalkylation into toluene and trimethylbenzenes. By accounting for symmetry effects through the calculation of the number of single events and defining elementary reaction families rather than applying product lumping, a huge reduction in the number of adjustable parameters can be achieved without the loss of the molecular detail in the reaction network. In the kinetic model, 37 components, 78 intermediates and a total of 327 elementary reaction steps, classified in families such as (de-)protonation, alkyl shift, dealkylation, transalkylation and hydrogenation, are considered. Only reactant protonation enthalpies and the activation energies of the considered reaction families, are estimated by model regression to experimental data acquired on a bifunctional Pt/H-ZSM-5 catalyst, while the remaining parameters are determined from first principles or retrieved from literature information. The experimental data are adequately described with physically significant parameter values. Dealkylation is found to be energetically most demanding with an activation energy amounting to 198 kJ mol −1 , while alkyl shift and transalkylation reactions are having the lowest activation energies. Entropic effects result in the lowest rate coefficient for transalkylation, however, and rate coefficients of a similar order of magnitude for alkyl shift and dealkylation. The investigated catalyst is shown to have an adequate acid strength for establishing the thermodynamic equilibrium between the xylene isomers.

55 citations

Journal ArticleDOI
TL;DR: A reaction mechanism for the formation of four-ring aromatics, pyrene and fluoranthene, through the combination of benzyl and indenyl radicals is presented.
Abstract: Resonantly stabilized radicals, such as propargyl, cyclopentadienyl, benzyl, and indenyl, play a vital role in the formation and growth of polycyclic aromatic hydrocarbons (PAHs) that are soot precursors in engines and flames. Pyrene is considered to be an important PAH, as it is thought to nucleate soot particles, but its formation pathways are not well known. This paper presents a reaction mechanism for the formation of four-ring aromatics, pyrene and fluoranthene, through the combination of benzyl and indenyl radicals. The intermediate species and transition structures involved in the elementary reactions of the mechanism were studied using density functional theory, and the reaction kinetics were evaluated using transition state theory. The barrierless addition of benzyl and indenyl to form the adduct, 1-benzyl-1H-indene, was found to be exothermic with a reaction energy of 204.2 kJ mol−1. The decomposition of this adduct through H-abstraction and H2-loss was studied to determine the possible products. The rate-of-production analysis was conducted to determine the most favourable reactions for pyrene and fluoranthene formation. The premixed laminar flames of toluene, ethylbenzene, and benzene were simulated using a well-validated hydrocarbon fuel mechanism with detailed PAH chemistry after adding the proposed reactions to it. The computed and experimentally observed species profiles were compared to determine the effect of the new reactions for pyrene and fluoranthene formation on their concentration profiles. The role of benzyl and indenyl combination in PAH formation and growth is highlighted.

55 citations

Journal ArticleDOI
TL;DR: In this paper, three elementary reaction mechanisms Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW), and Hattori with assumptions, such as quasi-steady state conditions for the surface species and methanol adsorption, and surface reactions as the rate-determining steps were applied to predict the catalyst surface coverage and the bulk concentration using a multiscale simulation framework.
Abstract: The heterogeneously catalyzed transesterification reaction for the production of biodiesel from triglycerides was investigated for reaction mechanism and kinetic constants. Three elementary reaction mechanisms Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW), and Hattori with assumptions, such as quasi-steady-state conditions for the surface species and methanol adsorption, and surface reactions as the rate-determining steps were applied to predict the catalyst surface coverage and the bulk concentration using a multiscale simulation framework. The rate expression based on methanol adsorption as the rate limiting in LHHW elementary mechanism has been found to be statistically the most reliable representation of the experimental data using hydrotalcite catalyst with different formulations.

54 citations

Journal ArticleDOI
TL;DR: In this paper, a first-principles-based kinetic Monte Carlo simulation was used to track the elementary surface transformations involved in the catalytic decomposition of NO over Pt(100) and Rh(100), under lean-burn operating conditions.
Abstract: First-principles-based kinetic Monte Carlo simulation was used to track the elementary surface transformations involved in the catalytic decomposition of NO over Pt(100) and Rh(100) surfaces under lean-burn operating conditions. Density functional theory (DFT) calculations were carried out to establish the structure and energetics for all reactants, intermediates and products over Pt(100) and Rh(100). Lateral interactions which arise from neighbouring adsorbates were calculated by examining changes in the binding energies as a function of coverage and different coadsorbed configurations. These data were fitted to a bond order conservation (BOC) model which is subsequently used to establish the effects of coverage within the simulation. The intrinsic activation barriers for all the elementary reaction steps in the proposed mechanism of NO reduction over Pt(100) were calculated by using DFT. These values are corrected for coverage effects by using the parametrized BOC model internally within the simulation....

54 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the NO heterogeneous reduction mechanism in the presence of hydroxyl ( OH) and carbonyl (>C O) groups, and provided energy and kinetics for the proposed pathways by density functional theory and conventional transition state theory, respectively.

54 citations


Network Information
Related Topics (5)
Catalysis
400.9K papers, 8.7M citations
83% related
Hydrogen
132.2K papers, 2.5M citations
82% related
Adsorption
226.4K papers, 5.9M citations
80% related
Aqueous solution
189.5K papers, 3.4M citations
79% related
Combustion
172.3K papers, 1.9M citations
79% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202229
202185
202088
201971
201871