为研究煤粉不同气氛和温度活化后的热半焦在微观结构上的变化规律，采用拉曼光谱对煤焦碳架结构进行表征，采用X射线光电子能谱（XPS）检测C和O的表面官能团，固态核磁共振碳谱（13C-NMR）表征碳共价键。将3种测量方法互相验证，提高结果可靠性，从微观层面表征半焦的化学结构，分析煤粉中温活化反应中温度和气氛对煤焦化学结构和表面官能团演变的影响，并探讨中温活化机理。结果表明，60～900 ℃下CO2和水蒸气对半焦活性均有显著增强作用，这可能是气体分子与煤焦分子结合形成羰基或羧基，在羰基或羧基分子影响下相连的碳键削弱断裂，从而破坏芳香环，产生新的活性位点，增强煤炭反应活性。经800 ℃下CO2活化或900 ℃下水蒸气活化后的半焦，活性位点数量均增加2倍以上，同时羰基和羧基占比之和由18%分别增至32%和34%，而CO2中温活化引起接氧脂碳由0.02增至0.11，水蒸气活化后桥碳比为0.01，相比N2热解半焦桥碳比大幅降低。煤粉中温活化反应主要通过形成羰基或羧基破坏芳香结构形成更多活性位点，但二者作用范围及决速步骤不同导致形成的产物有一定差别，CO2主要通过将焦炭边缘的sp2结构转化为富含sp3杂化的碳结构起到活化效果，水蒸气可通过抑制层内石墨化进程达到活化效果。

In order to study the microstructure changes of hot semi-coke activated by pulverized coal under different atmospheres and temperatures, Raman spectroscopy was used to characterize the carbon frame structure of coal coke, X-ray photoelectron spectroscopy (XPS) was used to detect the surface functional groups of C and O, and solid state 13C nuclear magnetic resonance spectroscopy (13C-NMR) was used to characterize the carbon covalent bond. The three measurement methods were verified with each other to improve the reliability of the results, and the chemical structure of semi-coke was characterized from the microscopic level. The influence of temperature and atmosphere on the chemical structure and surface functional group evolution of coal coke in the mesothermal activation reaction was analyzed, and the mechanism of mesothermal activation was discussed on this basis. The results show that the activity of char at 600-900 ℃ can be significantly enhanced by both CO2 and water vapor, which may be caused by the combination of gas molecules and coal coke molecules to form carbonyl or carboxyl groups. Under the influence of carbonyl or carboxyl molecules, the carbon bonds connected are weakened and broken accordingly, thus destroying the aromatic ring and generating new active sites to enhance the reaction activity of coal. After CO2 activation at 800 ℃ or water vapor at 900 ℃, the number of active sites of semi-coke are increased by more than two times, respectively, and the proportions of carbonyl and carboxyl groups each increase from 18% to 32% and 34%. However, aliphatic carbons bonded to oxygen increase from 0.02 to 0.11 due to moderate CO2 activation, and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.01 after steam activation, which is significantly lower than that of semi-coke after N2 pyrolysis. The mesophilic activation reaction of pulverized coal mainly forms more active sites through the formation of carbonyl and carboxyl group to destroys the aromatic structure. However, the products formed by the two groups are different due to their different scopes and rate-determining steps. CO2 mainly plays the activation effect by transforming the sp2 structure of coke edge into  the carbon structure rich in sp3 hybridization, while water vapor can be activated by inhibiting the graphitization process in the layer.

0 引言

1 试验

   1.1 试验样品

   1.2 试验装置及方法

2 结果与讨论

   2.1 碳结构变化

   2.2 碳氧官能团变化

   2.3 C—H—O共价键变化

3 结论