The reactivity of solid residue (char) derived from diatom (Fistulifera sp.) after hydrothermal liquefaction (HTL) reaction at 673 K, 10 MPa, 30 min was investigated during oxidation in air at 553 − 1073 K. Results indicate the derivative thermo-gravimetric (DTG) curve of HTL char showed very small peak below 600 K, indicating HTL reaction effectively decomposed lipid, carbohydrates and protein. The activation energies of the HTL char derived from diatom during combustion up to 1073 K by FWO and KAS methods was 120.0 and 115.3 kJ/mol, respectively, when the char conversion α is 0.2 − 0.5 (i.e. pyrolysis). At higher char conversion (α ≥ 0.5), the activation energy monotonically increased as combustion reaction proceeds. However, this increment of activation energy of HTL char derived from diatom during oxidation stage was much smaller than those of de-oiled microalgae char reported in the literature. The HTL char derived from diatom has porous structure (specific surface area: 293.2 m²/g and total pore volume: 0.672 cm³/g). It was found this porosity is derived both the silicon structure of diatom and remaining carbon after HTL reaction. The total amount of oxygen functional groups (OFG) substantially increased by oxidation at 553 and 573 K. By holding the reaction temperature at 553 K up to 60 min, the total OFG monotonically increased to 1.04 mmol/g. At 573 K, the amount of total OFG peaked 1.08 mmol/g at 30 min and decreased. The decomposition of carboxyl groups is dominant reaction for reduction in total OFG after 30 min at 573 K during oxidation. The tendencies of BET surface area and total pore volume of char agreed with these results of char during oxidation.

在553 − 1073 K的空气中氧化过程中，研究了在673 K，10 MPa，30分钟的水热液化（HTL）反应后，硅藻（Fistulifera sp。）衍生的固体残留物（char）的反应活性。 HTL炭的重量（DTG）曲线在600K以下显示非常小的峰，表明HTL反应有效地分解了脂质，碳水化合物和蛋白质。当炭转化率α为0.2-0.5（即，当炭转化率α为0.2-0.5时，通过FWO和KAS方法，在高达1073 K的燃烧过程中，硅藻衍生的HTL炭的活化能分别为120.0和115.3 kJ / mol。热解）。在较高的焦炭转化率（α≥0.5）下，活化能随燃烧反应的进行而单调增加。然而，在氧化阶段衍生自硅藻的HTL炭的活化能增量要比文献中报道的脱油微藻炭小得多。源自硅藻的HTL炭具有多孔结构（比表面积：293.2 m ² / g，总孔体积：0.672 cm ³/G）。发现该孔隙率既来自硅藻的硅结构，又来自于HTL反应后剩余的碳。氧官能团（OFG）的总量通过在553和573 K处的氧化而显着增加。通过将反应温度保持在553 K达60分钟，总OFG单调增加至1.04 mmol / g。在573 K时，总的OFG量在30分钟达到峰值1.08 mmol / g，然后下降。在氧化过程中，在573 K下30分钟后，羧基的分解是减少总OFG的主要反应。BET表面积和炭的总孔体积的趋势与氧化期间炭的这些结果一致。