From what I've read, the production of soot in a flame is still an open research topic. But some hydrocarbon fuels produce much more soot than others. Are there (simple) rules that tell which fuels produce more or less soot? Especially for aliphatics?
Some things that influence soot production that I am aware of:
- The amount of oxygen available and if this is pre-mixed with the fuel. I want to limit this question to diffusion flames (non-pre-mixed) with plenty of air available.
- According to Wikipedia, naphthalenes produce more soot than benzenes which produce more soot than aliphatics.
- Longer carbon chains generally produce more soot than shorter carbon chains.
But now I read that ethanol and diethylene glycol produce less soot than methane, even though both contains two-carbon chains and methane only a single carbon atom. Does it apply in general that hydrocarbons with oxygen atoms produce less soot, or are these an exception? And are there more general rules to predict which fuels produce more or less soot, short of setting up a full chemical simulation?