Why does methane burn cleaner than kerosene ($ ext{RP-1}$)?

Answer

Methane has a higher hydrogen-to-carbon ratio than kerosene.

The simpler chemical structure and higher proportion of hydrogen relative to carbon in methane result in a combustion process that produces significantly less performance-degrading soot.

Why does methane burn cleaner than kerosene ($	ext{RP-1}$)?
fuelrocketpropellantcombustionMethane