The hydrothermal liquefaction of biomass produces many hydrophilic substances in the aqueous phase (AP). The sustainability of the liquefaction process largely depends on the effective usage of the AP. In this work, C-Phycocyanin (C-PC), a model compound, represents the typical protein in microalgae. The interactions between liquefaction temperature and residence time of the model compound were investigated, and operation parameters were optimized based on the experimental design. Moreover, liquefaction with AP recycling was performed at different temperatures (265–345 °C) and residence times (15–55 min). All experiments were conducted in a 50 mL reactor with 3 g feedstock and 30 mL water-based solvent (10 wt% loadings). The highest bio-oil yield of 32 wt% was obtained at around 305 °C and 35 min, and the yield was further increased to 37.4 wt% by replacing part of the water solvent with AP. The promotion effect of AP recycling on bio-oil was enhanced mainly within the temperature range of 285–325 °C. Results showed that the organic acids in the AP were reduced after recycling, indicating a transformation of organic acids from the AP to the oil phase. Based on the investigation of C-PC liquefaction with AP recycling, a reaction pathway was finally proposed.

生物质的水热液化在水相（AP）中产生许多亲水性物质。液化过程的可持续性很大程度上取决于 AP 的有效使用。在这项工作中，模型化合物 C-藻蓝蛋白 (C-PC) 代表了微藻中的典型蛋白质。研究了模型化合物的液化温度和停留时间之间的相互作用，并根据实验设计优化了操作参数。此外，在不同的温度（265-345°C）和停留时间（15-55 分钟）下进行 AP 循环液化。所有实验均在具有 3 g 原料和 30 mL 水基溶剂（10 wt% 负载）的 50 mL 反应器中进行。在 305 °C 和 35 min 左右获得最高的 32 wt% 的生物油产率，产率进一步提高到 37。4 wt% 通过用 AP 代替部分水溶剂。AP回收对生物油的促进作用主要在285~325℃温度范围内增强。结果表明，AP中的有机酸在循环后被还原，表明有机酸从AP向油相转化。基于AP回收利用C-PC液化的研究，最终提出了反应途径。