Zhang Shuai, Jia Xiangdong, Wang Xia, Chen Jianyu, Cheng Can, Jia Xichuan, Hu Haibo
College of Forestry, Nanjing Forestry University, Nanjing 210037, China.
Co-Innovation Center of Sustainable Forestry in Southern China, Nanjing 210037, China.
Plants (Basel). 2024 Feb 5;13(3):460. doi: 10.3390/plants13030460.
Temperature determines biochar structure during pyrolysis. However, differences in holding time and feedstock types may affect this relationship. The conditional process analysis model was used in this paper to investigate the potential to affect this mechanism. The branch and leaf parts of were separately pyrolyzed at 350, 450, 650, and 750 °C, and kept for 0.5, 1, and 2 h at each target temperature. We measured the fixed carbon and ash contents and the elemental composition (C, H, O and N) of the raw materials and their char samples. After plotting a Van Krevelen (VK) diagram to determine the aromatization of chars, the changes in the functional groups were analyzed using Fourier transform infrared (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS). The results revealed that pyrolysis at temperatures between 450 and 750 °C accounted for the aromatization of biochar because the atomic H/C ratio of branch-based chars (BC) decreased from 0.53-0.59 to 0.15-0.18, and the ratio of leaf-based chars (LC) decreased from 0.56-0.68 to 0.20-0.22; the atomic O/C ratio of BC decreased from 0.22-0.27 to 0.08-0.11, while that of LC decreased from 0.26-0.28 to 0.18-0.21. Moreover, the average contents of N (1.89%) and ash (13%) in LC were evidently greater than that in BC (N:0.62%; Ash: 4%). Therefore, BC was superior to LC in terms of the stability of biochar. In addition, the increasing I/I and I/I ratios in BC and LC indicated an increasing amount of the amorphous aromatic carbon structure with medium-sized (2~6 rings) fused benzene rings. According to the CPA analysis, an extension of the holding time significantly enhanced the increase in aromatic structures of LC with temperature. But this extension slightly reduced the growth in aromatic structures of BC. All indicate that holding time and feedstock types (branch or leaf feedstock) could significantly affect the variation in biochar aromatic structure with respect to temperature.
温度决定热解过程中生物炭的结构。然而，保持时间和原料类型的差异可能会影响这种关系。本文使用条件过程分析模型来研究影响这一机制的可能性。将[具体植物名称]的枝叶部分分别在350、450、650和750℃下进行热解，并在每个目标温度下保持0.5、1和2小时。我们测量了原材料及其炭样品的固定碳、灰分含量以及元素组成（C、H、O和N）。绘制范克雷维伦（VK）图以确定炭的芳构化程度后，使用傅里叶变换红外光谱（FTIR）、拉曼光谱和X射线光电子能谱（XPS）分析官能团的变化。结果表明，在450至750℃之间的温度下进行热解导致了生物炭的芳构化，因为基于树枝的炭（BC）的原子H/C比从0.53 - 0.59降至0.15 - 0.18，基于树叶的炭（LC）的该比例从0.56 - 0.68降至0.20 - 0.22；BC的原子O/C比从0.22 - 0.27降至0.08 - 0.11，而LC的原子O/C比从0.26 - 0.28降至0.18 - 0.21。此外，LC中N的平均含量（1.89%）和灰分（13%）明显高于BC（N：0.62%；灰分：4%）。因此，就生物炭的稳定性而言，BC优于LC。此外，BC和LC中I/I和I/I比值的增加表明具有中等大小（2至6个环）稠合苯环的无定形芳香碳结构的量在增加。根据CPA分析，保持时间的延长显著增强了LC的芳香结构随温度的增加。但这种延长略微降低了BC芳香结构的增长。所有这些都表明保持时间和原料类型（树枝或树叶原料）会显著影响生物炭芳香结构随温度的变化。
