Biodiesel-diesel blend is a promising approach for petroleum diesel substitution but concurrently requires modifications to improve its properties. In this study, ethyl levulinate (EL) was synthesized via levulinic acid (LA) esterification over a sulfonated lignin-based carbon catalyst and employed as an additive to improve biodiesel-diesel blends. The catalyst was prepared from lignin as a carbon precursor, modified via hydrothermal sulfonation at 180 °C for 6 h, and finally characterized. The effects of reaction parameters for LA esterification, such as ethanol-to-LA molar ratio (3–15), catalyst loading (3–20 wt%), and reaction time (2–6 h) were studied. Ethyl levulinate with 80 mol% and 100 mol% concentrations were examined as a fuel additive for palm oil biodiesel-diesel blends of B10, B15, and B20. The effect of the additive on the density and viscosity of biodiesel-diesel blends, as well as carbon monoxide (CO) and nitrogen oxide (NO) emissions from engine combustion, was investigated. The results show that the catalyst has good acidity (1.30 mmol/g) and suggested thermal stability up to 200 °C, as well as unique surface morphology with a large surface area of 193 m/g contributed by mesopores and micropores. A high initial yield of EL of 84.3 mol% was obtained over LHS-400-1 at optimum conditions of 6 ethanol-to-LA molar ratio, 15 wt% of catalyst, and 5 h at 80 °C. The reusability study up to five cycles showed a gradual reduction in the LA conversion which indicated catalyst instability. As for the biodiesel-diesel blends, the presence of EL at 3 to 7 vol% reduced the viscosity and slightly increased the density. Furthermore, CO and NO emissions trends decreased with the addition of EL. The presence of LA in 80 mol% EL for biodiesel-diesel blends resulted in slightly high CO and NO emissions as compared to the blends with 100 mol% EL.

中文翻译：

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在磺化木质素基碳催化剂上合成乙酰丙酸乙酯，作为生物柴油-柴油混合物的燃料添加剂，以减少发动机排放

生物柴油-柴油混合物是一种很有前景的石油柴油替代方法，但同时需要进行改造以改善其性能。在这项研究中，乙酰丙酸乙酯（EL）是通过乙酰丙酸（LA）在磺化木质素基碳催化剂上酯化合成的，并用作改善生物柴油-柴油混合物的添加剂。该催化剂以木质素为碳前驱体，通过180℃水热磺化6h进行改性，并最终表征。研究了 LA 酯化反应参数的影响，例如乙醇与 LA 摩尔比 (3-15)、催化剂负载量 (3-20 wt%) 和反应时间 (2-6 小时)。研究了浓度为 80 mol% 和 100 mol% 的乙酰丙酸乙酯作为 B10、B15 和 B20 棕榈油生物柴油-柴油混合物的燃料添加剂。研究了添加剂对生物柴油-柴油混合物的密度和粘度以及发动机燃烧中一氧化碳 (CO) 和氮氧化物 (NO) 排放的影响。结果表明，该催化剂具有良好的酸性（1.30 mmol/g）和高达200℃的热稳定性，以及介孔和微孔带来的独特的表面形貌，表面积高达193 m/g。在乙醇与 LA 摩尔比 6、催化剂 15 wt%、80 °C 5 小时的最佳条件下，LHS-400-1 获得了 84.3 mol% 的高初始产率。最多五个循环的可重复使用性研究表明，LA 转化率逐渐降低，这表明催化剂不稳定。对于生物柴油-柴油混合物，3％至7％体积的EL的存在降低了粘度并略微增加了密度。此外，随着 EL 的添加，CO 和 NO 排放趋势有所下降。与 100 mol% EL 的混合物相比，80 mol% EL 中的 LA 存在导致生物柴油-柴油混合物的 CO 和 NO 排放量略高。