Experimental and theoretical insight into the soot tendencies of the methylcyclohexene isomers

Journal Article · 02 July 2018 · Proceedings of the Combustion Institute

DOI: https://doi.org/10.1016/j.proci.2018.06.095 · OSTI ID:1460764

Kim, Seonah  ^[1]; Fioroni, Gina M. ^[1]; Park, Ji-Woong  ^[2]; Robichaud, David J. ^[1]; Das, Dhrubajyoti D.  ^[3]; John, Peter C.  St. ^[1]; Lu, Tianfeng ^[2]; McEnally, Charles S.  ^[3]; Pfefferle, Lisa D. ^[3]; Paton, Robert S. ^[4]; Foust, Thomas D. ^[1]; McCormick, Robert L.  ^[1]

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1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. Univ. of Connecticut, Storrs, CT (United States)
3. Yale Univ., New Haven, CT (United States)
4. Univ. of Oxford (United Kingdom); Colorado State Univ., Fort Collins, CO (United States)

The formation of soot precursors during combustion of three positional isomers of methylcyclohexene was investigated in flow reactor experiments and through density functional theory simulations. As evidenced by a recently published structure-property model, the sooting tendencies of these compounds differ from those of structurally similar molecules - suggesting new or unusual reaction chemistry. It was demonstrated that 1-methyl-1-cyclohexene and 4-methyl-1-cyclohexene preferentially react via a retro-Diels-Alder pathway leading to ring opening and molecular weight reduction. 3-methyl-1-cyclohexene, which exhibits much higher yield sooting index, preferentially reacts via dehydrogenation to cyclohexadienes and toluene - consistent with higher soot formation. It was demonstrated that the relative stability of the first radical intermediate plays a considerable role in determining the branching ratio between formation of soot precursors and ring opened retro-Diels-Alder reaction products. This study underscores the importance that small structural features can have in determining the ultimate fate of carbon during combustion processes.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office (BETO)
• Grant/Contract Number: AC36-08GO28308; CBET 1604983; MCB-090159
• OSTI ID: 1460764
• Alternate ID(s): OSTI ID: 1694193
• Report Number(s): NREL/JA-5100-71629
• Journal Information: Proceedings of the Combustion Institute, Vol. 37, Issue 1; ISSN 1540-7489
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English