To obtain insight into the catalytic reaction mecha-nism of biodiesels over ZSM-5 zeolites,the pyrol-ysis and catalytic pyroly-sis of methyl butanoate,a biodiesel surrogate,with H-type ZSM-5(HZSM-5)were performed in a flow re-actor under atmospheric pressure.The pyrolysis products were identified and quantified using gas chromatography-mass spectrometry(GC-MS).Kinetic modelling and experimen-tal results revealed that H-atom abstraction in the gas phase was the primary pathway for methyl butanoate decomposition during pyrolysis,but dissociating to ketene and methanol over HZSM-5 was the primary pathway for methyl butanoate consumption during catalytic pyrolysis.The initial decomposition temperature of methyl butanoate was reduced by ap-proximately 300 K over HZSM-5 compared to that for the uncatalyzed reaction.In addition,the apparent activation energies of methyl butanoate under catalytic pyrolysis and homoge-neous pyrolysis conditions were obtained using the Arrhenius equation.The significantly re-duced apparent activation energy confirmed the catalytic performance of HZSM-5 for methyl butanoate pyrolysis.The activation temperature may also affect some catalytic properties of HZSM-5.Overall,this study can be used to guide subsequent catalytic combustion for practical biodiesel fuels.