CAJ | 학술논문

为了解纤维素在水热降解过程中产物的理化特性及其形成机制，该文对生物质主要组分-纤维素的水热降解特性进行了系统地研究，全面分析了反应温度和停留时间对纤维素水热产物分布的影响，并从产物的化学结构入手，对纤维素水热解机理进行了探索。随着温度的升高，重质油产率在250℃时达到最大，重质油组分变得复杂，焦炭产率逐渐降低。随着停留时间的延长重质油产率呈现先增加后降低的趋势，焦炭产率变化趋势较小，然而通过对焦炭的热重、红外、元素、电子扫描显微镜和X射线光电子能谱仪分析表明停留时间的延长可以提高焦炭的化学官能性，这为生物质水热机理的研究提供了依据。
위료해섬유소재수열강해과정중산물적이화특성급기형성궤제，해문대생물질주요조분-섬유소적수열강해특성진행료계통지연구，전면분석료반응온도화정류시간대섬유소수열산물분포적영향，병종산물적화학결구입수，대섬유소수열해궤리진행료탐색。수착온도적승고，중질유산솔재250℃시체도최대，중질유조분변득복잡，초탄산솔축점강저。수착정류시간적연장중질유산솔정현선증가후강저적추세，초탄산솔변화추세교소，연이통과대초탄적열중、홍외、원소、전자소묘현미경화X사선광전자능보의분석표명정류시간적연장가이제고초탄적화학관능성，저위생물질수열궤리적연구제공료의거。
The characteristics of cellulose’s products under hydrothermal treatments in an autoclave were investigated at various temperature (200~400℃) and residence time (5~120 min). With the temperature increasing from 200℃ to 250℃, heavy oil yield increased sharply from 5% to 14.75%. The temperature of 250℃ was suitable for the liquefaction to obtain higher yield of liquid products, with a maximum of 14.75%. With the increase in residence time, heavy oil yield increased in the first 10 minutes, and thereafter decreased with further increase in residence time because of the cracking reaction occurring in the primary hydrothermal product of heavy oil. The hydrochar yield decreased in the first 5 minutes, and then increased. At the same temperature with residence time of 5 min, the hydrochar yield reached a maximum of 50%and heavy oil yield was 16.25%. The yields of light oil and gas increased with the time increasing. The chemical compounds of heavy oil identified at 200, 250, 300, 350, and 400℃ in residence time of 30 min were mainly furans, phenols, carboxylic acids, aldehydes and ketones, and high molecular compounds were determined by gas chromatography-mass spectrometry (GC-MS). Aldehydes, phenols, ketones, acid groups and sugars in the light oil were determined by GC-MS as well as Fourier transform infrared (FTIR). The hydrochar was analyzed by elemental analyzers, scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis, x-ray photoelectron spectroscopy (XPS) and FTIR. The elemental composition of the hydrochar from hydrothermal degradation of cellulose at 200~400℃ for 30 min showed the relationship between the hydrogen/carbon (H/C) and oxygen/carbon (O/C) ratios of the hydrochar. The ratios of H/C and O/C decreased continuously with increasing temperature, however, after the temperature increased to 250℃, the ratios became constant at higher temperatures. These results were consistent with the yield of the gases and hydrochars at the same temperature. Through the SEM and TEM, it was found that the hydrochar had a core-shell structure. From the FTIR spectra, the hydrochar from cellulose hydrothermally treated at 250℃ with residence time of 30 min and 2 h exhibit was completely different from the cellulose FTIR traces. There was no O=C=O adsorption peak under the conditions of 250℃ and residue time of 2 h. The adsorption peak of the C=O vibration was wider, which indicated the existence of ketones and aldehydes. The results showed that the hydrochar was composed of aromatics and polymeric products, which revealed that aromatization processes took place during hydrothermal treatment. The XPS spectra of cellulose and hydrochar produced from hydrothermal treatment at 250℃ for 2 h showed that there was a large amount of hydroxyl groups attached to carbon atom in the cellulose, and the hydrochar contained additional aliphatic/aromatic carbon groups (C-C/C=C) and carboxylic groups, esters, or lactones (-COOR). Compared with the results from the FTIR spectra, the basic behavior of the hydrochar’s functional groups could be investigated by XPS. The CH, C-O, and C=O groups decreased with the increase in residence time, similar to the results obtained with FTIR. From the chemical point of view, oxygen groups of the hydrochar differed in the core and shell, inferred from the XPS and FTIR measurements. Indeed, the core contained ketone and ether groups and the shell contained carboxylic and carbonyl groups. In conclusion, the formation of the hydrochar is through hydrolysis and dehydration of cellulose, and the hydrochar has a core-shell structure and better physicochemical characterization at lower temperature and longer residence time.