溶剂溶胀-离子交换金属离子对低变质煤热解焦油组成分布调控机理研究

Coal pyrolysis is an important way for coal processing and high efficiency utilization. How to improve the coal tar yield and the selectivity of important chemicals in coal tar are the key points in the research of low rank coal pyrolysis. Coal swelling, ion exchange with metal ions are important methods to analyze coal molecular structure / functional groups, however the researches of swelling-ion-exchange with metal ions on the mechanism of coal pyrolysis process and the composition distributions of pyrolysis products were reported rarely. Therefore, in this research, the effects of types of metal ions on the pyrolysis process of swelling coal were investigated, to build the pyrolysis kinetic model of swelling-ion-exchange coal and to reveal the distribution laws of pyrolysis products (gas, tar and semi-coke). The effects of swelling-ion-exchange with metal ions on coal molecular structure / functional groups were analyzed. The effect laws of the pyrolysis kinetics of swelling-ion-exchange coal, the composition distributions of pyrolysis products, and the treatments of swelling and ion exchange with metal ions on coal molecular structure / functional groups were illuminated. The regulated mechanism of swelling-ion-exchange with metal ions on the composition distributions of coal tar was investigated. By ways of the selection of metal ions used in ion exchange and the parameter optimization of coal pyrolysis, the new regulation method and the basic theory of the important chemicals in coal tar were formed. This research is of great theoretical significance to improve coal pyrolysis efficiency and to clarify coal pyrolysis mechanism.

煤炭热解是煤分质加工高效利用的重要途径。如何提高焦油收率及焦油中重要化学品的选择性是低变质煤热解研究所关注的重要问题。煤的溶胀、离子交换金属离子是研究煤分子/官能团结构的重要方法，但较少看到用溶胀-离子交换金属离子方法探测煤热解过程机理和热解产物组成分布的研究。本项目拟探讨离子交换金属离子种类对溶胀煤热解过程的影响，建立溶胀-离子交换金属离子煤的热解动力学模型并揭示其气、液、固产物分布规律。研究溶胀-离子交换金属离子对煤分子/官能团结构的影响规律；溶胀-离子交换金属离子煤的热解反应动力学与产品的组成分布规律以及溶胀、金属离子对热解过程中煤分子/官能团的作用规律。阐明溶胀-离子交换金属离子作用对煤热解焦油组成分布的调控机理；通过对离子交换金属离子筛选及热解过程工艺参数的优化，建立煤热解焦油中重要化学品选择性调控新方法和基础理论。该研究工作对于提高煤的热解效率，阐明煤热解机理有重要的理论意义。

煤炭热解是煤分质加工高效利用的重要途径。如何提高热解焦油收率及焦油中重要化学品的选择性是低变质煤热解研究所关注的重要问题。煤的溶胀、离子交换金属离子是研究煤大分子/官能团结构的重要方法，但较少看到用溶胀-离子交换金属离子方法探测低变质煤热解过程机理和热解产物组成分布规律的研究。本项目提出采用溶剂溶胀-离子交换金属离子原位改变煤分子/官能团结构来实现对煤热解过程的扰动，探索基于溶剂溶胀-离子交换金属离子预处理方法的低变质煤定向热解机制。研究了离子交换金属离子种类对溶剂溶胀低变质煤热解过程的影响以及热解反应动力学与产品的组成分布规律，建立溶胀-离子交换金属离子煤的热解动力学模型并揭示其气、液、固产物分布规律。研究表明：煤离子交换金属离子Na+、K+、Ca2+降低了焦油收率，交换Co2+、Ni2+则有利于热解焦油的生成；离子交换金属离子均提高了热解焦油中芳烃的相对含量，且碱金属离子对高环数芳烃裂解为低环数芳烃具有促进作用。溶剂对煤惰质组及镜质组溶胀率顺序为：THF>乙酸>苯酚>乙醇≈丙酮>苯>正庚烷。溶胀后镜质组的孔径孔容变大，孔隙结构更加发达，有利于热解挥发分的逸出。单独的溶胀预处理和离子交换预处理均具有较好的促进热解挥发分产率的作用，但是将二者结合，热解失重率并没有进一步提升，反而相较最佳溶胀条件下的样品失重率反而减少。混合溶剂溶胀的VD通过离子交换方式负载金属离子，热解焦油产率均有所增加。焦油可检测收率的大小顺序为：VDS-Co> VDS-Mg> VDS-Na > VDS-Ca > VDS-Ni > VDS-K，其中VDS-Co的焦油收率大于16%。不同溶胀-离子交换金属离子煤样热解焦油的组成存在一定差异，溶胀煤样通过离子金属交换使焦油中芳烃含量减少，含氧化合物的比重增加。该研究工作对于提高煤的热解效率，阐明低变质煤热解机理有重要的理论意义，有助于煤高效清洁热转化理论体系的建立。