Hydrothermal liquefaction (HTL) is considered as one of the most promising methods for converting algal biomass to bio-oil and other value-added chemicals. The conventional HTL process, however, is limited by its incapability of recovering high-value bioactive compounds that are desirable for enhancing overall process feasibility. The two-stage sequential hydrothermal liquefaction (SEQHTL) process was proposed as an alternative to overcome this limitation. SEQHTL operates at reduced temperature and pressure to facilitate production of co-products in addition to bio-oil. This article offers a comprehensive review of the SEQHTL process in comparison with conventional HTL. Main topics include: operation principles and targeting final products of HTL, reaction mechanisms of algal biomass in the HTL process, recent publications on algae-related HTL studies, features of the SEQHTL process, advantages of the SEQHTL process for production of high quality bio-oil as well as extraction of prospective high-value co-products that may be harvested from microalgae biomass, cost advantage of the SEQHTL process, challenges identified with techno-economic and life-cycle assessments, and suggested future HTL research and development in comparison with other conversion technologies. All these aspects collectively provide an overview of the SEQHTL technology.

水热液化（HTL）被认为是将藻类生物质转化为生物油和其他增值化学品的最有前途的方法之一。然而，常规的HTL方法受到其不能回收高价值生物活性化合物的能力的限制，这是增强整体方法可行性的理想方法。提出了两步顺序水热液化（SEQHTL）工艺来克服该限制。SEQHTL在降低的温度和压力下运行，以促进除生物油以外的副产物的生产。本文提供了与常规HTL相比对SEQHTL过程的全面回顾。主要主题包括：HTL的操作原理和目标最终产品，HTL过程中藻类生物质的反应机理，有关藻类相关HTL研究的最新出版物，SEQHTL工艺的特点，SEQHTL工艺在生产高质量生物油方面的优势以及可从微藻生物质中收获的潜在高价值副产品的提取，成本优势SEQHTL流程，技术经济和生命周期评估中确定的挑战，并提出与其他转换技术相比未来的HTL研究与开发。所有这些方面共同提供了SEQHTL技术的概述。技术经济和生命周期评估所确定的挑战，并建议与其他转换技术相比，未来的HTL研究与开发。所有这些方面共同提供了SEQHTL技术的概述。技术经济和生命周期评估所确定的挑战，并建议与其他转换技术相比，未来的HTL研究与开发。所有这些方面共同提供了SEQHTL技术的概述。