Internal Structure of Incipient Soot from Acetylene Pyrolysis Obtained via Molecular Dynamics Simulations

Area of Science:

• Chemical Engineering
• Materials Science
• Computational Chemistry

Background:

• Soot formation is a critical process in combustion, impacting air quality and energy efficiency.
• Understanding the internal structure of incipient soot particles is key to controlling soot formation.

Purpose of the Study:

• To investigate the internal structure of incipient soot particles from acetylene pyrolysis.
• To classify these particles based on their structural characteristics.
• To analyze the influence of temperature on soot particle formation.

Main Methods:

• Reactive molecular dynamics simulations using the ReaxFF potential.
• Analysis of 3324 incipient soot particles across four temperatures.
• Characterization of particle mass, volume, density, C/H ratio, and cyclic structures.

Main Results:

• Incipient soot particles were classified into two types: type 1 (smaller, no dense core) and type 2 (larger, dense core).
• Distinct radial distributions of density, cyclic structures, and C/H ratio were observed between type 1 and type 2 particles.
• A dense core in type 2 particles was identified, with its boundary approximately 50-60% of the radius of gyration.

Conclusions:

• Acetylene pyrolysis yields two distinct classes of incipient soot particles with differing internal structures.
• Particle size is a key differentiator between type 1 and type 2 soot particles.
• The presence or absence of a dense core significantly impacts soot particle morphology and formation pathways.