Formation of polycyclic aromatic hydrocarbons and their growth to soot—a review of chemical reaction pathways

Lignocellulosic biomass pyrolysis mechanism: A state-of-the-art review

Chemical reactions and physical processes responsible for the formation of polycyclic aromatic hydrocarbons and soot in hydrocarbon flames are reviewed. The discussion is focused on major elements in the present understanding of the phenomena, clarification of concepts central to the present state of the art, and a summary of new results.

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Reaction mechanism of soot formation in flames

Hierarchical and comparative kinetic modeling of laminar flame speeds of hydrocarbon and oxygenated fuels

This paper analyzes the main kinetic features of biomass pyrolysis, devolatilization, and the gas phase reactions of the released species. Three complex steps are faced in sequence: the characterization of biomasses, the description of the release of the species, and finally, their chemical evolution in the gas phase. Biomass is characterized as a mixture of reference constituents: cellulose, hemicellulose, and lignin. This assumption is verified versus experimental data, mainly relating to thermal degradation of different biomasses. Devolatilization of biomasses is a complex process in which several chemical reactions take place in both the gas and the condensed phase alongside the mass and thermal resistances involved in the pyrolysis process. A novel characterization of the released species is applied in the proposed devolatilization models. The successive gas phase reactions of released species are included into an existing detailed kinetic scheme of pyrolysis and oxidation of hydrocarbon fuels. Compa...

Chemical Kinetics of Biomass Pyrolysis

Lumping procedures in detailed kinetic modeling of gasification, pyrolysis, partial oxidation and combustion of hydrocarbon mixtures

The kinetic modeling of soot precursors in a butadiene flame

Detailed kinetic schemes of hydrocarbon pyrolysis, partial oxidation, and combustion are now becoming more available in the technical literature, and despite their dimensions and complexity they are based on only a limited set of independent kinetic parameters and simplifying assumptions. These hypotheses and kinetic parameters as well as the automatic generation of these reaction mechanisms are discussed and analyzed in this paper. Some examples are reported to demonstrate the reliability of these mechanistic schemes, both in pyrolysis processes for ethylene production and in the oxidation of hydrocarbon mixtures in internal combustion engines.

Primary Pyrolysis and Oxidation Reactions of Linear and Branched Alkanes

In this work, the oxidation of MTBE, ETBE, DIPE, and TAME was investigated experimentally in a high-pressure jet-stirred reactor (JSR) in the high-temperature oxidation regime (800–1150 K, 10 atm,=0.5–2, 0.1% of ether, and 0.5 s). New experimental data on mole fractions of reactants, intermediates, and final products were measured using probe sampling followed by gas chromatograph (GC) analyses. These data were used to extend an already available oxidation reaction model for primary reference fuels. This extension to the ether components only required the insertion of a small subset of new primary reactions where kinetic parameters are evaluated on the basis of similarity and analogy rules inside reaction classes and generalized prediction methods for H-abstraction reactions. The fair agreement observed between experimental data and model predictions in different operating conditions confirms the validity of the proposed approach and allows the modeling of oxidation and combustion of commercial gasoline.

Oxidation of oxygenated octane improvers: MTBE, ETBE, DIPE, and TAME

New experimental data for propyne and allene oxidation were obtained in a jet-stirred reactor (JSR) in the temperature range 800–1200 K at 1–10 atm for different fuel/oxygen equivalent ratios (0.2–2.0). Experimental data clearly indicate the different oxidation behavior of the two isomers and provide valuable information for extending the simulation capabilities of an already existing comprehensive kinetic scheine. Critical reactions are presented and discussed together with extended comparisons of model predictions with experimental data obtained in the JSR conditions, in the Princeton turbulen flow reactor (PTFR). and in a shock tube at higher temperatures. Finally, the effects on reaction paths of allene addition to a fuel-rich acetylene premixed flame, are also discussed. Isomerization reactions proceeding via direct and H addition routes are significant in the oxidation. As a result of H-abstraction reactions, both propyne and allen form the resonantly stabilized propargyl radical. These species are important intermediates in all the combustion processes, and their successive reactions are relevant candidates in explaining the formation of aromatic and polyaromatic species, possible presursors of particulate and soot. The analysis of the mild combustion conditions of the JSR reactor also allows the reliability of the overall kinetic scheme to be extended to the so-called flameless conditions.

A. Goldaniga

Papers

Lumping procedures in detailed kinetic modeling of gasification, pyrolysis, partial oxidation and combustion of hydrocarbon mixtures

The kinetic modeling of soot precursors in a butadiene flame

Primary Pyrolysis and Oxidation Reactions of Linear and Branched Alkanes

Oxidation of oxygenated octane improvers: MTBE, ETBE, DIPE, and TAME

An experimental and kinetic modeling study of propyne and allene oxidation