Synergistic mechanism of CO2 and active functional groups during low temperature oxidation of lignite
Synergistic mechanism of CO2 and active functional groups during low temperature oxidation of lignite
复制标题
褐煤低温氧化过程中CO2与活性官能团的协同机制
DOI：
10.1016/j.fuel.2020.118407
复制
发表时间：
2020-10-15
期刊：
影响因子：
7.4
通讯作者：
Lou, Wen-tao
中科院分区：
文献类型：
--
作者：
Gao, Jing;Chu, Rui-zhi;Lou, Wen-tao
利用低温氧化模拟系统研究了氧化过程中的耗氧率和CO2释放率。实验中使用了六种不同官能团和孔结构的模型化合物。结果表明，6种模型化合物的耗氧速率主要受孔扩散控制，碳纳米管(CNT)模型化合物CNTS-Mac和CNTS-MES的CO2释放受含氧官能团的化学吸附控制，而CNTS-Mic化合物受通道扩散阻力的控制。吸附CO2的羧基是主要的吸附部位，其耗氧率高于羟基。采用两种不同的方法进一步研究了CO2与含氧官能团之间的关系：对褐煤的基本结构单元进行了量子化学模拟，并测定了经不同CO2浓度处理的两种褐煤的活化能。实验结果表明，羧基的O-H键长于羟基，且羧基的表面负势强于羟基。CO2的存在会削弱反应基团与煤大分子之间的非共价键。30%CO2与活性官能团之间存在协同作用，促进褐煤低温氧化。
The rate of oxygen consumption and the release of CO2 were studied using a low-temperature oxidation simulation system. Six model compounds with different functional groups and pore structures were used in the experiment. The results showed that the oxygen consumption rate of six model compounds was mainly controlled by pore diffusion; the release of CO2 for the carbon nanotube (CNT) model compounds CNTs-Mac and CNTs-Mes was controlled by chemical adsorption of oxygen-containing functional groups, while the CNTs-Mic compounds was by diffusion resistance in channels. The carboxyl group, where CO2 adsorbed, was the main adsorption site; this had a higher oxygen consumption rate than the hydroxyl group. Two different methods were employed in further studies to explore the relationship between CO2 and oxygen-containing functional groups: a quantum chemical simulation for basic structural units of lignite, and measuring the activation energy of two types of lignite pre-treated by different CO2 concentrations. Experimental results revealed that the O-H bond of the carboxyl was longer than that of the hydroxyl, and the negative surface potential of the carboxyl was stronger than that of the hydroxyl. The non-covalent bond between the reactive group and coal macromolecule could be weakened due to the presence of CO2. Finally, there was a synergistic effect between 30% CO2 and active functional groups to promote low-temperature oxidation of lignite.