Chemical Kinetics Underlying the Sooting Tendency and Auto-Ignition Characteristics of Linear, Branched, and Cyclic Ether Compounds

Conference · Fri Sep 16 04:00:00 EDT 2022

OSTI ID:1888768

Cho, Jaeyoung; Kim, Yeonjoon; Etz, Brian D.; Fioroni, Gina M.; Luecke, Jon; Zhu, Junqing; St. John, Peter C.; Zigler, B. T.; McEnally, Charles S.; Pfefferle, Lisa D.; McCormick, Robert L.; Kim, Seonah

Biofuels present opportunities for improving the performance and reducing emissions from internal combustion engines by incorporating oxygenated functional groups to the fuels. Among various oxygenates, ethers have been recognized as promising candidates for an alternative to conventional diesel fuel owing to their higher reactivity and lower sooting tendency. The detailed guidelines for designing ethers, however, have not been fully discussed, even though their combustion characteristics are sensitive to the molecular structure. This study was devoted to exploring the structure-property relationships, particularly focusing on the cetane number and yield sooting index, using five linear, branched, and cyclic ethers: di-amyl-ether, 4-butoxy-heptane, 3,3-dimethyl-oxetane, 2-ethyl-4-methyl-1,3-dioxolane, and 2-isopropyl-4-methyl-1,3-dioxolane. First, we examined the chemical kinetics underlying the sooting tendency of the test fuels. The combustion product distribution was measured from flow reactor experiments at 750-1100 K, F=3, at atmospheric pressure. As a result, it was revealed that the sooting tendency is closely related to the size of hydrocarbon intermediates in the high-temperature regime (>1000 K); that is, larger hydrocarbons lead to more soot precursor formation. The underlying chemistry determining the size of the hydrocarbons from the tested fuels was analyzed using reaction pathway analysis and quantum mechanics calculations, which showed that the branched and cyclic ether structures form abundant C3-C4 compounds. Moreover, the auto-ignition characteristics of the test fuels were studied using the flow reactor at low-temperature (400-700 K) and F=1. We found a clear difference in the combustion-product distribution from high and low reactivity fuels, which was then correlated to the systematic analysis of the key reaction energy barriers with the varying molecular structure.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1888768
• Report Number(s): NREL/PR-2700-79858; MainId:39076; UUID:96fd5d03-7481-4ca4-a6c9-1fedfee8f9bf; MainAdminID:65431
• Country of Publication: United States
• Language: English

Related Subjects

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
cetane
combustion
engines
ether
internal