Low-temperature oxidation chemistry of 2,4,4-trimethyl-1-pentene (diisobutylene) triggered by dimethyl ether (DME): A jet-stirred reactor oxidation and kinetic modeling investigation

Abstract
This paper explores the low-temperature (low-T) oxidation chemistry of 2,4,4-trimethyl-1-pentene (IC8D4, diisobutylene) by using jet-stirred reactor (JSR) experiments of both IC8D4/dimethyl ether (DME) mixture and pure IC8D4 at near atmospheric pressure and low temperatures. Oxidation species are measured using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), gas chromatography (GC) and GC combined with mass spectrometry (GC/MS). It is found that the oxidation of pure IC8D4 at atmospheric pressure presents negligible low-T reactivity and negative temperature coefficient (NTC) behavior, and that the oxidation reactivity of IC8D4/DME mixture is lower than that of butene/DME mixtures previously studied. A kinetic model for low-T IC8D4/DME oxidation is developed from recent oxidation models of IC8D4 and DME. Thermodynamic data of IC8D4 and key species in its sub-mechanism are obtained from theoretical calculations in this work, while rate constants of critical reactions are updated from recent theoretical calculation studies in literature. Based on the modeling analysis, four main pathways are found to be responsible for the consumption of IC8D4 at low temperatures. Among them, the first three pathways initiated by H addition, OH addition and H abstraction on allylic carbon sites are similar to those in 1-butene/DME and isobutene/DME oxidation. These three pathways are mainly responsible for promoting or retaining OH formation. The fourth pathway initiated by H abstraction on the alkyl carbon site differs from the other three in that it is only important in IC8D4/DME oxidation while not important in butenes/DME oxidation. This fourth pathway incorporates stepwise O2 addition and cycloaddition reaction sequences, which can promote and inhibit OH formation, respectively. The increasing contribution of this fourth pathway in IC8D4/DME oxidation reduces its reactivity compared to that of butenes/DME oxidation.

Citation
Zhang, X., Cao, C., Zou, J., Li, Y., Zhang, Y., Guo, J., … Li, Y. (2021). Low-temperature oxidation chemistry of 2,4,4-trimethyl-1-pentene (diisobutylene) triggered by dimethyl ether (DME): A jet-stirred reactor oxidation and kinetic modeling investigation. Combustion and Flame, 234, 111629. doi:10.1016/j.combustflame.2021.111629

Acknowledgements
The authors appreciate the funding support from National Key R&D Program of China (2017YFE0123100) and National Natural Science Foundation of China (91841301, U1832171). The authors acknowledge fundings from KAUST Clean Fuels Consortium (KCFC) and its member companies. The authors would like to thank KAUST Supercomputing Laboratory for supporting the quantum chemistry calculations, and Mr. Nitin Lokachari and Ms. Geyuan Yin for sharing the IC8D4 models in their papers. The authors are also grateful to Mr. Jonathan Peterson for checking the English.

Publisher
Elsevier BV

Journal
Combustion and Flame

DOI
10.1016/j.combustflame.2021.111629

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S0010218021003722

Permanent link to this record