Inhibition effect of methanol addition on carbon deposition in propane pyrolysis

Abstract

Methanol-mixed fuels consisting of methanol, propane, and a small amount of auxiliary solvent are widely used as inexpensive industrial fuels, but the carbon deposition in the pyrolysis of this fuel seriously restrains its popularization. This paper studied the characteristics of gaseous products and carbon deposition in the pure propane and methanol-propane mixture pyrolysis experimentally, analyzed the effect of methanol addition on the reaction path of propane pyrolysis and production rate of key species by using detailed reaction mechanism. Results show that methanol addition can restrain C2H4 converting to C2H2 in the later stage of pyrolysis. The carbon deposition rate and particle diameter increase exponentially with the increase of reaction temperature in both pure propane and methanol-propane blend pyrolysis. Methanol addition can significantly reduce the carbon deposition rate and particle diameter. The reaction path analysis indicates that the main reaction paths forming benzene are C3H3 → A1 and C4H4 → I-C6H6 → A1, and C3H3 is a key specie to form benzene. The pyrolysis of methanol-propane mixture generates more H2 and H than that of pure propane pyrolysis, which makes most C3H6 convert to C2H4, reduces the amount of C3H3 and suppresses the conversion of C2H4 to C2H2. And then the amount of benzene is reduced significantly and the generation of subsequent PAHs and carbon deposition is inhibited. Lots of H2 also restrains the hydrogen abstraction from benzene resulting in the delay of the formation of PAHs and carbon deposition. This study is of great significance to research the soot formation in hydrocarbon combustion with alcohol fuel.