Experimental and Modeling Study on the Oxidation Chemistry of Dibutyl and Dipentyl Carbonates in a Jet-Stirred Reactor

Dialkyl carbonates (DACs) have emerged as renewable alternative fuels, attracting considerable interest from researchers in their combustion characteristics. Compared with short-chain DACs, longer-chain DACs have a higher lower-heating value and are more reactive at low temperatures, making them more promising alternatives to diesel. Although extensive studies have been conducted on short-chain DACs, research on longer-chain DACs remains limited. This study conducted the first experimental and modeling investigation into the oxidation chemistry of the longer-chain dibutyl (DBC) and dipentyl (DPeC) carbonates using a jet-stirred reactor (JSR). The mole fractions of the reactants and oxidation products were measured at three equivalence ratios of 0.5, 1.0, and 2.0 within a temperature range of 500–1100 K. Notably, the results revealed that both DBC and DPeC exhibited a pronounced negative temperature coefficient (NTC) behavior, which was absent in short-chain DACs. A detailed kinetic mechanism was developed and validated against the experimental data. Furthermore, a comprehensive analysis of reaction pathways and sensitivity was performed based on the newly developed mechanism. The difference in the oxidation reactivity of DACs with a changed carbon chain length is also illustrated in detail. Analysis of the reaction path reveals that at low temperatures, the fuel molecules are primarily consumed through H-abstraction reactions, generating fuel radicals. A considerable amount of ketohydroperoxides (KHPs) undergo decomposition reactions to form alkyl radicals. The subsequent chain-branching pathways of both the primary fuel radicals and the alkyl radicals contribute to the pronounced low-temperature oxidation reactivity observed for DBC and DPeC. The sensitivity analysis indicates that H-abstraction reactions by OH radicals exert the most significant promoting effect at low temperatures, while the chain-terminating reactions of the key ROO species in both fuel and alkane oxidation chemistry exhibit notable inhibiting effects.