柳桉快速热裂解炭改性制取多级孔道活性炭的研究

Upgrading of Char from Lauan Pyrolysis for Production of Activated Char with Multilevel Pore Structure

摘要:

以柳桉快速热裂解制取生物油的固体副产物为原料，通过物理化学活化法，采用微波预处理和传统焙烧加热相结合的方式对其进行活化，改善其结构和表面性质。采用氮气物理吸附、扫描电镜、X射线衍射、热重分析和红外光谱等多种表征技术对活化后的生物炭进行表征。结果表明，活化后的生物炭具有丰富的微孔和介孔，形成了多级孔道结构，其中微孔比表面积占36%~48%。微波预处理结合N2气氛焙烧活化的生物炭具有更高的比表面积，其值为1224m2/g，这归因于微波均匀加热产生微孔和气氛焙烧进一步形成介孔的高效协同作用。此外，不同活化方式对生物炭的红外特性有着显著影响，经过活化后的生物炭表面含氧基团大量减少。活化后的生物炭热稳定性显著提高，有利于生物炭作为催化剂载体进行高值化利用。

Abstract:

Char from lauan pyrolysis was used as feedstock, and its structure and surface properties were improved through physical and chemical activation way with microwave-assisted method and the traditional calcination method. After being activated, the biochar was characterized by various characterization techniques, including nitrogen adsorption, scanning electron microscope, X-ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy. The results showed that the activated biochar had abundant micropores and mesopores which formed a multilevel pore structure, and the surface area of the micropores accounted for 36%~48%. In addition, the biochar activated through microwave pretreatment and N2 atmosphere calcination had a high surface area of 1224m2/g. The uniform microwave heating produced micropores and the mesopores were further formed through calcination. The efficient synergistic effect of both the two thermal treatments led to the high surface area and multilevel pore structure. The activated biochar yield of 42% was obtained under the condition of microwave pretreatment and N2 calcination. Besides, different activation methods had a significant effect on the infrared properties of biochar, and the oxygen-containing groups on the surface of activated biochar were greatly reduced. The thermal stability of biochar after activation was significantly improved and there were no apparent weight loss peaks, which was beneficial for the utilization of biochar as catalyst support.