While today’s biomass-based diesel fuels are used at relatively low blend levels in petroleum diesel, decarbonization of the heavy-duty trucking and off-road sectors is driving increasing use of higher level blends and the combination of hydroprocessing-derived renewable diesel (RD) with biodiesel (fatty acid methyl esters) to create a 100% renewable fuel. However, little data are available on the properties of biodiesel blends over 20 vol % into RD or conventional diesel, despite the potential for properties to fall well outside the normal range for diesel fuels. Here, we evaluate the properties of 20–80% blends of a soy-derived biodiesel into RD and petroleum diesel. Properties measured were flash point, cloud point, cetane number, surface tension, density, kinematic viscosity, distillation curve, lower heating value, water content, water solubility in the fuel, lubricity, and oxidation stability. Density and viscosity were measured over a wide temperature range. A key objective was to reveal properties that might limit blending of biodiesel and any differences between biodiesel blends into RD versus petroleum diesel and to understand research needed to advance the use of high-level blends and 100% renewable fuel. Properties that may limit blending include the cloud point, viscosity, distillation curve, and oxidation stability. Meeting cloud point requirements can be an issue for all distillate fuels. For biodiesel, reducing the blend level and use of lower cloud point hydrocarbon blendstocks, such as No. 1 diesel or kerosene, can be used in winter months. Alternatively, a heated fuel system that allows for starting the vehicle on conventional diesel before switching to pure biodiesel (B100) or a high-level blend has been successfully demonstrated in the literature. Some biodiesels can have kinematic viscosity above the upper limit for diesel fuels (4.1 mm²/s), which will limit the amount that can be blended. Biodiesel boils in a narrow range at the very high end of the No. 2 diesel range. Additional research is needed to understand how the high T90 of B100 and high-level blends and the very low distillation range of B100, some RD samples, and high-level biodiesel blends impact lube oil dilution, engine deposits, and diesel oxidation catalyst light-off. Blending with No. 1 diesel or kerosene or biodiesel-specific engine calibrations may mitigate these issues. Oxidation stability of higher level blends is poorly understood but may be addressed through the increased use of antioxidant additives. Finally, high-level biodiesel blends and B100 will have significantly higher density, viscosity, and surface tension compared to conventional diesel. In combination with the high boiling point, these properties may impact fuel spray atomization and evaporation, and additional research is needed in this area.

中文翻译：

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可能限制生物质柴油高含量混合物的特性

虽然当今的生物质柴油在石化柴油中的混合含量相对较低，但重型卡车和越野行业的脱碳正在推动更多地使用更高含量的混合燃料以及加氢处理衍生的可再生柴油 (RD) 的组合与生物柴油（脂肪酸甲酯）一起制造 100% 可再生燃料。然而，关于 RD 或传统柴油中超过 20 vol% 的生物柴油混合物的性能数据很少，尽管其性能可能远远超出柴油燃料的正常范围。在这里，我们评估了 20-80% 的大豆生物柴油与 RD 和石化柴油的混合物的特性。测量的性能包括闪点、浊点、十六烷值、表面张力、密度、运动粘度、蒸馏曲线、低热值、水含量、燃料中的水溶性、润滑性和氧化稳定性。密度和粘度是在很宽的温度范围内测量的。一个关键目标是揭示可能限制生物柴油混合的特性以及 RD 生物柴油混合物与石油柴油之间的任何差异，并了解推进高级混合物和 100% 可再生燃料的使用所需的研究。可能限制混合的特性包括浊点、粘度、蒸馏曲线和氧化稳定性。对于所有馏分燃料来说，满足浊点要求可能是一个问题。对于生物柴油，可以在冬季使用降低混合水平并使用较低浊点碳氢化合物混合原料，例如 1 号柴油或煤油。另外，文献中已成功演示了一种加热燃油系统，该系统允许在改用纯生物柴油 (B100) 或高级混合柴油之前使用传统柴油启动车辆。一些生物柴油的运动粘度可能高于柴油燃料的上限（4.1 mm ² /s），这将限制可混合的量。生物柴油的沸腾范围很窄，处于 2 号柴油范围的非常高端。需要进行额外的研究来了解 B100 和高级混合物的高 T90 以及 B100、一些 RD 样品和高级生物柴油混合物的极低馏程如何影响润滑油稀释、发动机沉积物和柴油氧化催化剂轻质离开。与 1 号柴油或煤油或生物柴油特定发动机校准混合可以缓解这些问题。人们对高级共混物的氧化稳定性知之甚少，但可以通过增加抗氧化添加剂的使用来解决。最后，与传统柴油相比，高级生物柴油混合物和 B100 的密度、粘度和表面张力显着更高。与高沸点相结合，这些特性可能会影响燃料喷雾雾化和蒸发，并且需要在该领域进行更多研究。