Fuel Properties of Oxymethylene Ethers with Terminating Groups from Methyl to Butyl

Journal Article · 12 August 2022 · Energy & Fuels

DOI:https://doi.org/10.1021/acs.energyfuels.2c01414· OSTI ID:1887888

Lucas, Stephen P.; Liang Chan, Fan; Fioroni, Gina M.; Foust, Thomas D.; Gilbert, Alayna; Luecke, Jon; McEnally, Charles S.; Serdoncillo, Justine John A.; Zdanowicz, Andrew J.; Zhu, Junqing; Windom, Bret

Oxymethylene ethers (OMEs) have been studied as possible additives or replacements for diesel fuels. Typically, studies have considered only methyl-terminated OMEs. Recent structure-property relationship models suggest that extended-alkyl OMEs may provide improvements to many of the properties of methyl-terminated OMEs that make them less suitable as diesel fuel blendstocks. In this work, we describe the synthesis and characterization of 16 different OMEs with methyl-, ethyl-, propyl-, butyl-, isopropyl-, and isobutyl-terminating alkyl groups with varying oxymethylene chain lengths. Indicated cetane number, lower heating value, flash point, density, viscosity, vapor pressure, and oxidative stability are tested via ASTM standard methods. Additionally, water solubility, boiling point, seal material compatibility, and sooting propensity (via the yield sooting index) are measured for these fuels. For diesel compatibility, all tested OMEs except smaller methyl and ethyl OMEs and the branched isopropyl OME meet cetane number requirements. Extending the alkyl end group increases the heating value, but all OMEs, due to their oxygen content, have heating values less than diesel. Despite this, all OMEs show significant reductions in soot production per unit heating value. Only the heaviest OMEs meet diesel viscosity requirements, and most are higher density than diesel. OMEs with larger alkyl groups show the highest stability under accelerated auto-oxidation conditions. Increases in alkyl group length cause order of magnitude reduction in water solubility, from hundreds of g/L for methyl terminated OMEs to hundreds of mg/L for butyl terminated OMEs. Limited seal material testing indicates that PEEK polymers are unaffected by OMEs, and while extended alkyl groups may improve compatibility with FKM (Viton), other common elastomers (NBR, silicone) remain incompatible with all tested OMEs. Overall, it is found that methyl-terminated OMEs exhibit the most potential for soot reduction, but OMEs with larger propyl- and butyl-terminating alkyl groups show improved compatibility with existing diesel systems.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B), Co-Optimization of Fuels and Engines (Co-Optima) Initiative
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1887888
• Report Number(s): NREL/JA-5400-82778; MainId:83551; UUID:2f872eb4-cf25-43bf-a037-2749f110f119; MainAdminID:65476
• Journal Information: Energy & Fuels, Journal Name: Energy & Fuels Journal Issue: 17 Vol. 36
• Country of Publication: United States
• Language: English

Related Subjects

ADVANCED PROPULSION SYSTEMS
BIOMASS FUELS
OME
alkyl groups
diesel fuel blendstocks
methyl-terminated OME
oxymethylene ethers
soot reduction