Abstract Microalgae is identified as a promising feedstock for producing renewable liquid transportation fuels; however, lipids extraction from microalgae for downstream processing to biofuels is one of the important challenges for algal based biorefineries. This work aims at evaluating the potential of applying flash hydrolysis (FH) as a chemical-free technique to increase the lipids extractability of algal biomass as well as its integration with the hydrothermal liquefaction (HTL) of microalgae to enhance the biocrude yields and characteristics for fuel production. To this aim, the FH process was performed on three different algal species (Scenedesmus sp., Nannochloropsis sp., and Chlorella vulgaris) at 280 °C and 10 s of residence time. Following FH, in addition to the nutrients rich hydrolysate, approximately, 40 wt% of solids containing almost all (>90 wt%) the lipids termed as biofuels intermediates (BI), were recovered. Kinetics study on lipids extractability from the BI and their lipid profile analyses were conducted for each algal species. The results showed that the FH process had significantly enhanced the lipids extractability. For all three algae species, lipid yields from BI were higher than that of the raw algae. Lipid yields of Chlorella vulgaris in the first 15 min were more than five times higher (52.3 ± 0.8 vs. 10.7 ± 0.9 wt%) than that of raw algae during n-hexane based solvent extraction. The kinetics of lipids extractability followed a zero-order reaction rate for all wet raw microalgae and the BI of Scenedesmus sp., while the BI recovered from the other two algal species were determined as a second-order reaction. Comparison of fatty acids profiles indicated the contribution of the FH process in saturating fatty acids. Subsequent to lipids extraction, a conventional hydrothermal liquefaction was performed at 350 °C and 1 h to compare the biocrude yields from raw versus BI of Chlorella vulgaris microalgae. The results showed that the biocrude yields from the BI and its quality was significantly enhanced post FH than that of raw algae. The FH process was proven to be a viable option for lipid extraction by increasing the extent of recovery and decreasing the extraction time. Its integration with HTL notably impact the biocrude yields and characteristics for fuel production.

中文翻译：

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藻类快速水解后脂质可提取性的评价

摘要 微藻被确定为生产可再生液体运输燃料的有前途的原料；然而，从微藻中提取脂质用于下游加工成生物燃料是基于藻类的生物精炼厂的重要挑战之一。这项工作旨在评估应用快速水解 (FH) 作为一种无化学物质的技术来提高藻类生物质的脂质可提取性以及将其与微藻的水热液化 (HTL) 结合以提高生物原油产量和特性的潜力。燃料生产。为此，在 280 °C 和 10 秒的停留时间下对三种不同的藻类（Scenedesmus sp.、Nannochloropsis sp. 和 Chlorella vulgaris）进行了 FH 过程。在 FH 之后，除了富含营养的水解产物外，大约，回收了 40 wt% 的固体，其中包含几乎所有 (>90 wt%) 称为生物燃料中间体 (BI) 的脂质。对每个藻类物种进行了关于从 BI 中提取脂质的动力学研究及其脂质谱分析。结果表明，FH 工艺显着提高了脂质的可提取性。对于所有三种藻类，来自 BI 的脂质产量高于原始藻类的脂质产量。在基于正己烷的溶剂提取过程中，小球藻在前 15 分钟的脂质产量比原料藻类高五倍多（52.3 ± 0.8 与 10.7 ± 0.9 wt%）。对于所有湿的原始微藻和栅藻属的 BI，脂质可提取性的动力学遵循零级反应速率，而从其他两种藻类物种中回收的 BI 被确定为二级反应。脂肪酸谱的比较表明 FH 过程对饱和脂肪酸的贡献。在脂质提取之后，在 350 °C 和 1 小时下进行常规水热液化，以比较普通小球藻微藻的生物质与 BI 的生物原油产量。结果表明，与生藻相比，BI 的生物原油产量和质量在 FH 后显着提高。通过提高回收率和减少提取时间，FH 工艺被证明是脂质提取的可行选择。它与 HTL 的集成显着影响了燃料生产的生物原油产量和特性。常规水热液化在 350 °C 和 1 小时下进行，以比较普通小球藻微藻的生物质与 BI 的生物原油产量。结果表明，与生藻相比，BI 的生物原油产量和质量在 FH 后显着提高。通过提高回收率和减少提取时间，FH 工艺被证明是脂质提取的可行选择。它与 HTL 的集成显着影响了燃料生产的生物原油产量和特性。常规水热液化在 350 °C 和 1 小时下进行，以比较普通小球藻微藻的生物质与 BI 的生物原油产量。结果表明，与生藻相比，BI 的生物原油产量和质量在 FH 后显着提高。通过提高回收率和减少提取时间，FH 工艺被证明是脂质提取的可行选择。它与 HTL 的集成显着影响了燃料生产的生物原油产量和特性。通过提高回收率和减少提取时间，FH 工艺被证明是脂质提取的可行选择。它与 HTL 的集成显着影响了燃料生产的生物原油产量和特性。通过提高回收率和减少提取时间，FH 工艺被证明是脂质提取的可行选择。它与 HTL 的集成显着影响了燃料生产的生物原油产量和特性。