The hydrothermal liquefaction reaction was carried out with Chlorella vulgaris as the feedstock, which has a high solid content (20–100 wt %). The effects of the reaction temperature (250–350 °C) and solid content on the characteristics of bio-oil (including yield, higher heating value (HHV), and elemental composition) were studied via central composite design (CCD) and response surface methodology (RSM) to model the relationships among these variables. This study reliably established a reaction model via response surface analysis, and the optimum reaction conditions calculated from the model were 350 °C and 59.04 wt % feedstock, resulting in a 37.94 wt % bio-oil yield, 37.36 MJ/kg HHV, 8.07 wt % N content, 0.375 wt % S content, and 6.69 wt % O content, respectively. Increasing the solid content under high-temperature conditions can effectively reduce the content of heteroatoms in bio-oil. GC–MS analysis of the bio-oil revealed a substantial increase in the concentrations of saturated hydrocarbons, unsaturated hydrocarbons, aliphatic alcohols, and aromatic compounds with increasing solid content. The most notable increase was observed for aromatic compounds, with a corresponding increase in content of up to 27.63%. The main condensation reaction occurs during the gradual increase in solid content, resulting in a hexadecanamide content of up to 10.84% at a solid content of 60 wt %. As the solid content increases beyond this point, the components in the bio-oil undergo a noticeable dehydration reaction, leading to a gradual increase in the hexadecanenitrile content to 4.33%, while the fatty acid content decreases. This change facilitates the subsequent hydrodesorption of heteroatoms.

中文翻译：

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提高高固体含量微藻水热液化生产的生物油的产量和性能：优化和建模


以小球藻为原料进行水热液化反应，其固体含量高 （20–100 wt %）。通过中心复合设计 （CCD） 和响应面法 （RSM） 研究了反应温度 （250–350 °C） 和固体含量对生物油特性（包括产率、更高热值 （HHV） 和元素组成）的影响，以模拟这些变量之间的关系。本研究通过响应面分析可靠地建立了反应模型，根据模型计算出的最佳反应条件为 350 °C 和 59.04 wt % 原料，生物油收率分别为 37.94 wt %、37.36 MJ/kg HHV、8.07 wt % N 含量、0.375 wt % S 含量和 6.69 wt % O 含量。在高温条件下增加固含量可有效降低生物油中杂原子的含量。生物油的 GC-MS 分析显示，随着固体含量的增加，饱和烃、不饱和烃、脂肪醇和芳香族化合物的浓度显著增加。芳香族化合物的增加最为显着，相应的含量增加了高达 27.63%。主要的缩合反应发生在固体含量逐渐增加的过程中，在固体含量为 60 wt % 时，十六烷酰胺含量高达 10.84%。随着固体含量的增加超过此点，生物油中的成分发生明显的脱水反应，导致十六烷腈含量逐渐增加到 4.33%，而脂肪酸含量则降低。这种变化促进了杂原子的后续加氢脱附。