Experimental and Kinetic Modeling Study of 2-Methyl-2-Butene: Allylic Hydrocarbon Kinetics

Area of Science:

• Combustion chemistry and kinetics
• Chemical engineering and reaction dynamics
• Thermodynamics and fuel science

Background:

• Understanding the oxidation of branched olefins is crucial for developing advanced combustion strategies.
• 2-methyl-2-butene (2M2B) is an unsaturated hydrocarbon fuel relevant to gasoline formulations.
• Limited detailed kinetic data exists for larger unsaturated branched hydrocarbons compared to smaller or saturated analogues.

Purpose of the Study:

• To investigate the oxidation kinetics and reaction pathways of 2-methyl-2-butene.
• To compare the combustion behavior of 2M2B with related alkane and smaller olefin fuels.
• To elucidate the role of allylic species in the low-temperature reactivity of 2M2B.

Main Methods:

• Experimental measurements of ignition delay times using reflected shock waves.
• Detailed species mole fraction analysis in a jet-stirred reactor (JSR).
• Development and validation of a detailed chemical kinetic reaction mechanism.

Main Results:

• High-temperature oxidation of 2M2B is rapid, comparable to alkanes.
• The thermal stability of allylic pentenyl radicals suppresses low-temperature reactivity, preventing cool flames and negative temperature coefficient behavior.
• The kinetic model accurately captures experimental data across a range of temperatures and pressures.

Conclusions:

• The unique reactivity of 2M2B stems from the interplay between its olefinic structure and the stability of its allylic intermediates.
• The lack of low-temperature reactivity in 2M2B influences its octane sensitivity in gasoline engines.
• This research provides critical data for accurate combustion modeling of branched olefin fuels.