Exploring fuel molecular structure effects on the pyrolysis chemistry of branched hexenes

3,3-Dimethyl-1-butene (NEC6D3) and 2,3-dimethyl-2-butene (XC6D2) are representative branched alkene components in gasoline. This work experimentally investigated the pyrolysis of NEC6D3 and XC6D2 in a flow reactor ( T = 950-1350 K, P = 0.04 atm) and a jet-stirred reactor ( T = 730-1000 K, P = 1 atm) using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and gas chromatography (GC). A pyrolysis model of branched hexenes was proposed and validated against the new experimental data. The combined experimental observations and modeling analyses provide insights into the predomi-nant fuel decomposition pathways and specific formation pathways of products under pyrolysis conditions. NEC6D3 exhibits a much higher reactivity than XC6D2 due to the existence of allylic C -C bonds. Uni-molecular decomposition reactions play the most crucial role in NEC6D3 decomposition, while in XC6D2 pyrolysis, fuel consumption is dominated by H-abstraction reactions and the H-assisted isomerization reac-tion. Fuel-specific pathways can remarkably influence the formation of pyrolysis products, especially the key C 1 -C 2 products, isomer pairs and dialkenes. Furthermore, the reactions involving propargyl radical domi-nate the formation of fulvene and aromatic products in the pyrolysis of both fuels, leading to more abundant production of C 6 and larger cyclic products in XC6D2 pyrolysis.& COPY; 2022 The Combustion Institute.