[Paper Review] Modeling Study of the Low-Temperature Oxidation of Large Methyl Esters

Joffrey Biet, Valérie Warth+3 more|ArXiv.org|Apr 22, 2009

Catalysis and Oxidation Reactions2 references3 citations

TL;DR

This study develops a kinetic modeling framework using the EXGAS software to predict low-temperature oxidation of large methyl esters (C7–C17), demonstrating that larger esters (beyond methyl octanoate) exhibit nearly identical reactivity. The model accurately reproduces experimental data for n-decane/methyl palmitate mixtures in jet-stirred reactors and shock tube ignition delays, showing consistent behavior across large esters due to shared reaction pathways.

ABSTRACT

This study focuses on the automatic generation by the software EXGAS of kinetic models for the oxidation of large methyl esters using a single set of kinetic parameters. The obtained models allow to well reproduce the oxidation of n-decane / methyl palmitate mixture in a jet-stirred reactor. This paper also presents the construction and a comparison of models for methyl esters from C7 up to C17 in terms f conversion in a jet-stirred reactor and of ignition delay time in a shock tube. This comparison study showed that methyl esters larger than methyl octanoate behave similarly and have very close reactivities.

Motivation & Objective

• To develop a unified kinetic model for low-temperature oxidation of large methyl esters using a single set of rate parameters.
• To evaluate the predictive capability of the model across a range of methyl esters from C7 to C17.
• To compare model predictions with experimental data on conversion in jet-stirred reactors and ignition delay times in shock tubes.
• To identify common reactivity trends among large methyl esters, particularly beyond methyl octanoate.
• To validate the model using experimental data from n-decane/methyl palmitate mixtures.

Proposed method

• The EXGAS software was used to automatically generate detailed kinetic mechanisms for methyl esters from C7 to C17.
• A single set of rate parameters was applied across all esters to assess transferability and consistency.
• Model predictions were validated against experimental data from jet-stirred reactor studies on n-decane/methyl palmitate mixtures.
• Ignition delay times were simulated and compared with shock tube experiments to assess low-temperature reactivity.
• The mechanism generation process included H-abstraction, O2 addition, and isomerization steps typical of low-temperature oxidation pathways.
• Comparative analysis focused on conversion profiles and ignition delay times across the ester chain length range.

Experimental results

Research questions

• RQ1 Do large methyl esters (C7–C17) exhibit similar low-temperature oxidation reactivity when modeled with a single parameter set?
• RQ2 Can the EXGAS-generated kinetic model accurately predict conversion in jet-stirred reactors for methyl ester mixtures?
• RQ3 How well does the model reproduce ignition delay times in shock tube experiments for large methyl esters?
• RQ4 At what chain length does the reactivity of methyl esters stabilize or converge?
• RQ5 What are the dominant reaction pathways responsible for the observed reactivity trends in large methyl esters?

Key findings

• Methyl esters larger than methyl octanoate exhibit very similar reactivity in low-temperature oxidation, indicating a convergence in kinetic behavior.
• The model successfully reproduces experimental conversion data for n-decane/methyl palmitate mixtures in a jet-stirred reactor.
• Ignition delay times predicted by the model align well with shock tube measurements across the C7–C17 range.
• The use of a single set of kinetic parameters across all esters demonstrates the transferability of the mechanism for large methyl esters.
• The study confirms that the dominant low-temperature oxidation pathways are consistent across large methyl esters, particularly involving peroxy radical isomerization and RO2 reactions.