Kinetic modeling of ethane pyrolysis at high conversion
Chen Xu1, Ahmed Sultan Al Shoaibi, Chenguang Wang
1Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado 80401, USA.
The Journal of Physical Chemistry. A
|August 19, 2011
Summary
This study refines ethane pyrolysis models by improving molecular weight growth kinetics. New calculations enhance predictions of minor species, crucial for understanding hydrocarbon reactions.
Area of Science:
- Chemical kinetics
- Combustion science
- Pyrolysis modeling
Background:
- Accurate ethane pyrolysis kinetics are vital for hydrocarbon combustion and oxidation analysis.
- Existing models show discrepancies in minor species concentrations related to molecular weight growth.
Purpose of the Study:
- Develop an improved first-principle-based mechanism for ethane pyrolysis molecular weight growth kinetics.
- Enhance the characterization of radical addition reactions contributing to molecular weight growth.
Main Methods:
- Flow reactor experiments with ethane/nitrogen mixtures (550-850 °C, ~0.8 atm).
- Computational analysis using CBS-QB3 for C(3)H(7), C(4)H(7), and C(4)H(9) potential energy surfaces.
- Extended C(6)H(9) potential energy surface to include vinyl addition to butadiene.
- Calculation of pressure-dependent rate constants for radical addition reactions.
Main Results:
- The improved mechanism significantly enhances the description of species involved in molecular weight growth.
- Identified vinyl addition to butadiene as a particularly important reaction.
- Observed that several radical addition reactions are partially equilibrated, necessitating accurate thermodynamic parameters.
- Found H addition to olefins inhibits molecular weight growth.
Conclusions:
- The refined mechanism provides a more accurate representation of ethane pyrolysis, especially concerning molecular weight growth.
- Understanding radical addition reaction equilibria and thermodynamics is critical for accurate pyrolysis modeling.
- The study highlights the importance of specific reactions like vinyl addition to butadiene and H addition to olefins in controlling pyrolysis pathways.
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