【摘要】 采用尿素和三聚氰胺改性酶解木质素,研究了改性前后木质素炭化制备的木质素基炭的化学结构演变过程。采用傅里叶变换红外光谱和X射线光电子能谱分析了不同炭化温度(300～900℃)对3种木质素基炭化学结构的影响,全面分析了炭的含氧和含氮化学官能团变化规律,研究结果显示:不管是未改性还是改性的酶解木质素,600～700℃是炭表面含氧和含氮基团发生显著变化的炭化温度区域。在600℃之前,3种木质素基炭主要含有羧基、羰基和羟基等含氧基团;高于600℃时得到的炭则主要含有羟基和羰基等含氧基团,且羟基官能团最多。经尿素和三聚氰胺改性后,600℃下木质素基炭含有的绝大部分含氮基团是吡啶氮和吡咯氮;达到700℃以后,升高炭化温度导致吡咯氮转化为季氮,季氮含量明显提高,木质素基炭含有的含氮基团则以吡啶氮、吡咯氮和季氮为主。更多还原

【Abstract】 This paper investigated the evolution of chemical structure of the chars prepared by carbonization of enzymatic hydrolysis lignin and the urea-modified and melamine-modified lignin. Fourier transform infrared spectra and X-ray photoelectron spectra were collected for these carbonized lignin in the temperature range of 300-900 ℃. Based on these spectra, a comprehensive analysis was conducted in order to elucidate the evolution in chemical functional groups and the oxygen and nitrogen-containing groups involved in these lignin-derived chars. The results showed that, 600-700 ℃ is an important carbonization temperature range where the remarkable evolution of the oxygen-containing and nitrogen-containing groups happens, independent of the lignin modification by urea or melamine. Below 600 ℃, carboxyl, carbonyl and hydroxyl predominate in the oxygen-containing groups of the carbonized lignin; above 600 ℃, the hydroxyls and carbonyls are dominant, of which hydroxyls are the most. For the urea-modified and melamine-modified lignin, the pyridine-like and pyrrole-like groups are the predominant nitrogen-containing groups in the carbonized lignin before 600 ℃. Above 700 ℃, with the increase in the carbonization temperature, pyrrole-like groups were gradually transformed into quaternary species and, as a result, the species of the pyridine-like, pyrrole-like, quaternary nitrogen become a predominant nitrogen groups in the carbonized lignin chars.更多还原