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Development of Reaction Mechanism by Quantum Chemistry methods

 

Main Objectives

Application of computational quantum chemistry (ab inito and DFT calculations) is used to estimation of thermochemical properties and kinetic parameters of small and large species, including biochemicals, large aromatic intermediates in soot formation, carbon nanotubes and many other systems.

 

 

Introduction

Aromatic and poly-aromatic compounds are important components of fuels. They are also formed in pyrolysis reactions and in fuel rich regions of flames and other thermal systems, where they are considered important precursors and intermediates in soot and PAH formation. The decomposition products of these species in combustion and oxidation reactions involve the incorporation of oxygen through reactions with oxygenated radicals and with molecular oxygen forming species like hydroperoxides or unsaturated oxy-hydrocarbon.

This work involves the development of an extensive thermochemical property data base on unsaturated (olefinic, acetylenic and aromatic) oxygenated hydrocarbon chemical species: enthalpy of formation, bond energies, standard entropy and heat capacity data as a function of temperature are calculated. These data serves the modelling communities in the area of atmospheric chemistry, combustion, industrial processes relating to synthesis and use in synthesis of hydroperoxides, peroxides and peroxy radical species. These parameters are available over a wide range of temperature (200 to over 5000 K) which can be applied to all of the above areas.

Peroxides and peroxy species are perhaps the most important intermediates in all low and moderate (1200 – 1300 K) combustion and in atmospheric photochemical oxidation processes of hydrocarbons and derivatives. Examples of the importance of these peroxides and peroxy intermediates include: control of self ignition in internal combustion engines (knock in spark ignited engines plus fuel ignition in diesels and in the new and upcoming HCCI engines. The peroxy radical reaction chemistry also controls the negative temperature behavior of hydrocarbons where there is a competition between the complex chain branching paths and termination reactions. Alkyl hydroperoxide species are also important in limiting soot formation and in soot burn-out in hydrocarbon pyrolysis and combustion.

A very significant quantity of thermochemical parameters are generated for stable molecules, intermediate radicals and transition state structures of oxygenated hydrocarbon molecules, particularly unsaturated and aromatic carbon – oxygen systems.

 

 

Example of Work

One example of oxidative destructive in aromatics involves conversion of dibenzofurans and / or dioxins in combustion systems. The destruction of the aromatic moiety often starts with loss of a phenyl hydrogen, through abstraction by radical pool species, such as H, O, OH, or Cl, forming a phenyl or benzofuranyl radical. This occurs even at moderate temperatures in downstream zones of an incinerator. The phenyl radicals will rapidly react with molecular oxygen in the combustion environment to form an energized (phenyl peroxy) adduct,  which can undergo further reaction through several pathways. Figure 1 illustrates some of the intermediate products from decomposition reactions (beta scission (unzipping) and oxidation) of a benzofuran di-aldehyde formal radical, which is estimated is the major product from reaction of molecular oxygen with a dibenzofuran – phenyl radical. The decomposition reaction results in a number of intermediates and radical products, which do not have thermochemistry or groups for use in group additivity estimations. Knowledge of the thermochemical properties of these species is important to understanding the decomposition and oxidation pathways of these intermediates, which result from initial oxidative ring opening of the aromatics.

 

 

For such larger molecules, high level, calculation techniques are computationally expensive or not possible. Density Functional Theory may be one of the few applicable calculation methods for these large molecules systems.

 

 

 

 

 

Computational Method

All of the calculations are performed using the Gaussian 03 program suite, which calculates the total energies, the frequencies and moment of inertia. The determination of the entropies and heat capacities are calculated with the help of two codes: SMCPS and ROTATOR.

 

 

 

 

Publications

 

“Experimental and Numerical Investigation of the Degradation of Chlorinated Hydrocarbons in Incineration Systems”

Kraft, M.; Fey, H.; Procaccini, C.; Smith, K. A.; Longwell, J. P.; Sarofim, A. F.; Bonni, P.; Rutz, L.; Sebbar, N.; Bockhorn, H. VDI-Bericht 18. Deutsch-Niederländischen Flammentag, 1997.

 

“Structures, Thermochemical Properties (Enthalpy, Entropy and Heat Capacity), Rotation Barriers, Bond Energies of Vinyl, Allyl, Ethynyl and Phenyl hydroperoxides”

Sebbar, N.; Bockhorn, H.; Bozzelli, J. W. Phys. Chem. Chem. Phys. 2002, 4, 3691-3703.

 

“Thermodynamic Properties (S(298), Cp(T)), Internal Rotations and Group Additivity Parameters in  Vinyl     and Phenyl Hydroperoxides”

Sebbar, N.; Bockhorn, H.; Bozzelli, J. W., Phys. Chem. Chem. Phys. 2003, 5, 300-307.

 

“Structures, Thermochemical Properties (Enthalpy, Entropy and Heat Capacity), Rotation Barriers,

Bond Energies of Vinyl, Allyl, Ethynyl and Phenyl peroxides”

Sebbar, N.; Bockhorn, H.; Bozzelli, J. W. J. Phys. Chem. A  2004, 108(40), 8353-8366.

 

“Thermochemical Properties, Rotation Barriers, and Group Additivity for Unsaturated Oxygenated Hydrocarbons and Radicals Resulting from Reaction of Vinyl and Phenyl Radical Systems with O2” Sebbar, N.; Bockhorn, H.; Bozzelli, J. W. J. Phys. Chem. A; 2005, 109, 2233-2253.

 

“Enthalpy of Formation and Bond Energies on Unsaturated Oxygenated Hydrocarbons using G3MP2B3 Calculation Methods”

Sebbar, N.; Bockhorn, H.; Bozzelli, J. W. Int. J.  Chem. Kinet.  2005, 37, 633–648.

 

“Thermodynamic and Ab Initio Analysis of the Controversial Enthalpy of Formation of Formaldehyde”

daSilva, G.; Bozzelli, J. W.; Sebbar, N.; Bockhorn, H. ChemPhysChem, 2006, 7, 1119 – 1126.

 

“Thermodynamic Properties of the Species Resulting from the Phenyl Radical with O2 Reaction System”

Sebbar, N.; Bockhorn, H.; Bozzelli, J. W., Int. J. Chem Kinet 40: 583–604, 2008

 

“Thermochemical similarities among three reaction systems:

Vinyl O2 – Phenyl O2 – Dibenzofuranyl O2

Sebbar, N.; Bozzelli, J. W.; Bockhorn, H. Combust. Sci. and Tech., 180: 959–974, 2008.

 

 

Proceedings

 

“Reaction of Phenyl Radical with O2: Thermodynamic Properties, Important Reaction Paths and Kinetics”

Bozzelli, J. W.; Sebbar, N.; Pitz, W.; Bockhorn, H., The 2nd Joint Meeting of the US Sections of the

Combustions Institute, Oakland, California, March 25-28, 2001.

 

“Reaction of Dibenzofuran radical with O2

Nadia Sebbar and Henning Bockhorn and Joseph W. Bozzelli Proceeding of the European Combustion Meeting 2003, Orléans, France, October 25-28, 2003.

 

“The Phenyl O2 Reaction: Thermodynamics and kinetics”

Sebbar, N.; Bockhorn, H., Bozzelli, J. W. Third European Combustion Meeting 2005, Chania, Crete, 11-13 April 2007.

 

“Thermochemical similarities among three reaction systems: Vinyl O2 – Phenyl O2 – Dibenzofuranyl O2

Sebbar, N.; Bozzelli, J. W.; Bockhorn, H.

Fifth Mediterranean Combustion Symposium – MCS5, Monastir, Tunisia, September 9-13, 2007.

 

“The oxidation reaction of C6H5C·(=O) radical”

Sebbar, N.; Bozzelli, J. W.; Bockhorn, H.

Sixth Mediterranean Combustion Symposium – MCS6, Ajaccio ,Corsica, France, June 7-11, 2009

 

Presentations

 

“Reaction of Phenyl Radical with O2: Thermodynamic Properties, Important Reaction Paths and Kinetics”

Joseph Bozzelli, Nadia Sebbar, William Pitz and Henning Bockhorn

The 2nd Joint Meeting of the US Sections of the Combustions Institute, Oakland, California, March 25-28, 2001

 

“Reaction of Phenyl Radical and Dibenzofuran with O2:  Thermodynamic Properties, Reaction Pathways, Kinetics and Initial Steps for Dibenzofuran Oxidation”

Nadia Sebbar, Henning Bockhorn and Joseph W. Bozzelli

Seventh International Congress on Toxic Combustion By-Products. June 4 – 6, 2001, Research Triangle Park, North Carolina USA.

 

“Reaction of Phenyl Radical and Dibenzofuran with O2

Nadia Sebbar, Henning Bockhorn and Joseph W. Bozzelli

Joint Meeting of the Belgian and Dutch Sections of the Combustion Institute, Brussels Belgium. April 2002.

 

“Thermochemical and Kinetic Analysis: Oxidation of Aromatics - Benzene, Toluene, Xylene”

Bozzelli, J. W.; da Silva, G.; Chen, C-C.; Sun, H.; Sebbar, N.; Bockhorn, H.

Informal kinetics and dynamics conference Albany, NY, Jan-267 2007.

 

“Numerical Investigation of the Dibenzofuranyl O2 Reaction System: Thermodynamics, Kinetics, and Reaction Paths”

Sebbar, N.; Bockhorn, H.; Bozzelli, J. W.

Fachtagung AEM 2007 Gemeinsame Sitzung der ProcessNet-Arbeitsausschüsse „Adsorption“ und „Extraktion" und des Arbeitskreises „Molekulare Modellierung und Simulation für Prozess- und Produktdesign", 21-23 march, 2007.

 

“An Elementary Mechanism for the Oxidative Degradation of Dibenzofuran”

Nadia Sebbar and Henning Bockhorn,

Tenth International Congress on Toxic Combustion By-Products. June 17 – 20, 2007, Ischia, Italy.

 

“Thermochemical Similarities among Three Reaction Systems: Vinyl O2 – Phenyl O2

Dibenzofuranyl O2

Nadia Sebbar, Henning Bockhorn and Bozzelli, J. W.

Fifth Mediterranean Combustion Symposium – MCS5 September 9-13, 2007, Monastir, Tunisia.

 

“The Oxidation of Dibenzofuranyl: Thermodynamic Properties and Reaction Pathways”

Nadia Sebbar, Henning Bockhorn and Bozzelli, J. W.,

20th International Conference on Chemical Thermodynamics August 3-8, 2008, Warsaw, Poland.

 

Posters

 

“Numerical and Experimental Investigation of Pyrolysis and Oxidation of Dioxin Precursors and other Toxic By Products”

Petra Bonni, Leonhard Rutz, Nadia Sebbar and Henning Bockhorn

WIP. The combustion Institute, 27th International Symposium on Combustion, 1998 University of Colorado, Boulder, USA, August 2- 7.

 

“Atomized Validation of a Detailed Mechanism for the Description of Dioxins Formation and other by products” Nadia Sebbar, Jörg Appel and Henning Bockhorn

The Combustion Institute, Joint Meeting of the British, German and French Sections. 18 – 21 May, Nancy – France, 1999

 

“Atomized Validation of a Detailed Mechanism for the Description of Dioxins Formation and other by products” Nadia Sebbar, Jörg Appel and Henning Bockhorn

The Sixth International Congress on Toxic Combustion By products. June 27 – 30, 1999, University of Karlsruhe, Germany.

 

“Reaction of Phenyl and Dibenzofuran Radicals with O2: Thermodynamic Properties, Reaction Pathways and kinetics”

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli.

The combustion Institute, 28th International Symposium on Combustion, 30 July – 4 August, 2000, Edinburgh, Scotland

 

“Thermodynamic properties (Enthalpies, Entropies and Heat Capacities) and Reactions of Vinyl Hydroperoxides, peroxy radicals and phenyl hydroperoxides”

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli.

Seventh International Congress on Toxic Combustion By-Products. June 4 – 6, 2001, Research Triangle Park, North Carolina USA

 

“Thermodynamic properties (Enthalpies, Entropies and Heat Capacities) and Reactions of Vinyl hydroperoxides, peroxy radicals and phenyl hydroperoxides”

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli.

5th International Conference on Chemical Kinetics, 16 – 20 July 2001, National Institute of standards and Technologies, Gaithersburg , MD USA

 

“Thermodynamic properties and reactions of vinyl hydroperoxides and phenyl hydroperoxides”

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli.

Deutsche Bunsen-Gesellschaft für Physikalische Chemie. 77th International Discussion Meeting 

„Formation and Degradation of Hydrocarbons in High-Temperature Reactions, October 2001

 

“Reaction of Phenyl Radical and Dibenzofuran with O2: Thermodynamic Properties, Reactions Pathways, Kinetics and Initial Steps for Dibenzofuran”.

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli.

Deutsche Bunsen-Gesellschaft für Physikalische Chemie. 77th International Discussion Meeting

„Formation and Degradation of Hydrocarbons in High-Temperature Reactions, October 2001.

 

“Reaction of Phenyl Radical with O2: Thermodynamic Properties, Reaction Pathways and Kinetics”

Nadia Sebbar and Henning Bockhorn, Chiung-ju Chen and Joseph, W. Bozzelli.

17th International Symposium on Gas Kinetics, Essen, August 24-29, 2002.

 

“Reaction of Dibenzofuran radical with O2: Thermodynamic Properties, Reaction Pathways and Kinetics”

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli.

The 8th International Congress on Combustion by-Products: Origin, Fate and Health Impacts, Umeå, Sweden, June 17-19, 2003. 

“Development of an extensive Thermochemical Database on unsaturated oxygenated hydrocarbon species”

Nadia Sebbar, Henning Bockhorn and Joseph, W. Bozzelli,

The 10th International Congress on Combustion by-Products: Origin, Fate and Health Impacts, Ischia, Italy, June 17-20, 2007.

 


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