(535h) Synthesis, Characterization, and Performance of Alkyl Levulinate-Diesel Blends

Renewable diesel plays an important role in decarbonizing the transportation sector. It has an increasing demand particularly for sectors where electrification is not practical or economically feasible such as heavy duty-vehicles, rails, highway freight, and maritime transport. Alkyl levulinates (ALs), which are derivatives of levulinic acid, have garnered significant interest as promising bio-based fuel additives and diesel blend components. In contrast to biodiesel, the components of ALs, levulinic acid and alcohols, can be sustainably produced from various sources of cellulosic biomass, including non-food sources such as wood waste, grass, and organic waste, without competing with food production.

Most of the previous studies have focused on short-chain levulinates (e.g., methyl and ethyl levulinates), which exhibit less favorable fuel properties, for example, poor miscibility, low heating value, and high water solubility. However, long-chain ALs extend the alkyl chain of the levulinate ester, thereby improving the energy density, miscibility, and hydrophobicity of the fuel. Therefore, investigating the potential of both short- and long-chain ALs as diesel blend components is worthwhile.

In this study, synthesis and characterization of short- and long-chain ALs and the performance of alkyl levulinate-diesel blends as fuel blend component are investigated. The ALs were produced via the catalytic esterification of levulinic acid with alcohol using an acid catalyst. A heterogeneous catalyst such as the ion-exchange resin (e.g., Amberlyst-15) is used for the esterification reactions because of the high efficiency of catalyst recovery and product separation. The effect of reaction conditions (reaction temperature, reaction time, catalyst loading, and molar ratio of levulinic acid to alcohol, etc.) on conversion and yield are investigated. The effect of varying alkyl chain lengths in ALs on fuel properties is also studied. Both short-chain (methanol and ethanol) and long-chain (butanol, hexanol, octanol, etc.) alcohols are used to produce ALs with different carbon chain lengths. ALs are recovered from the reaction mixture via distillation and refined to a high-purity final product. Chemical composition and purity of the products are determined by gas chromatography (GC-MS and GC-FID), FTIR, and Karl Fischer titration methods.

Subsequently, ALs are blended with Ultra Low-Sulfur Diesel (ULSD) in different blend ratios (5-20 vol. % blends) and analyzed for physicochemical properties such as solubility, density, flash point, viscosity, heat of combustion, hydrogen content, cetane number, etc. according to standard ASTM methods. Combustion dynamics and emission testing are conducted using a Kohler KD440 single-cylinder diesel engine in genset configuration to investigate the effect of ALs on engine performance, durability, and emission characteristics.