褐煤中弱键合结构与其热解焦油品质之间关系的研究

Problems that include poor product quality, plugging of the downstream system and subsequent processing difficulties start to show in almost all of coal fast pyrolysis technologies now. The insight on the fundamental chemistry of coal pyrolysis in a view point of the dissociation of weak bonds in lignite and the reaction of free radicals in tars will provide solutions to these problems. The purpose of this project is to study the relationship between weak bonds in lignite and the quality and stability of pyrolysis tars. To accomplish this task, first, pretreated lignites having different macromolecule network are prepared by the dissolution of weak bonds in lignite with ionic liquids. Then, the yield and composition (especially heavy products, free radicals, and dust content) of tars and the reactions of free radicals in tars under various heating and product quenching conditions are especially investigated. Finally, in order to reveal the relationship between weak bonds in lignite and the quality and stability of pyrolysis tars and control methods for high-quality tars, the correlation of weak bonds in lignite with the stability and quality of tars and the reactions of radical fragments in tars is investigated. This study will not only help to reveal the pyrolysis behaviors of weak bonds in lignite and the relationship between weak bonds in lignite and the quality and stability of pyrolysis tars, but also lay some theory foundation for high-efficient pyrolysis of lignite pyrolysis process control.

目前煤快速热解制油技术均面临焦油质量很差、系统易堵塞和后续加工困难等问题。从煤中弱键合结构解离和焦油中自由基反应层面上认识煤热解过程，可为这些问题的解决和热解过程调控提供理论基础。本项目以褐煤中弱键合结构与热解焦油的品质和稳定性之间关系为研究目标，借助离子液体对褐煤中弱键合结构的存在形态进行调控来制备含有不同弱键合结构的预处理煤（处理煤），进而重点研究原煤及这些处理煤在不同热解条件下所得焦油的产率、组成（特别是重质产物、自由基和尘含量）变化规律及焦油中大自由基在不同条件下的反应行为；将焦油品质和焦油中大自由基反应行为与褐煤中弱键合结构相关联，揭示褐煤中弱键合结构与热解焦油品质和稳定性之间的关系及提高焦油品质的褐煤中弱键合结构和热解条件的调控机制。本研究不仅有助于揭示褐煤中弱键合结构的热解行为及其与焦油品质和稳定性之间的关系，而且可为褐煤高效热解和热解过程调控提供理论基础。

本项目以褐煤中弱键合结构与热解焦油的品质和稳定性之间关系为目标，重点研究了离子液体预处理对褐煤热解焦油收率和组成的影响，主要取得了如下进展：（1）研究了褐煤经4种离子液体预处理后的结构变化情况与预处理后褐煤热解焦油收率和组成之间的关系；分析研究了离子液体结构和预处理条件-褐煤的交联结构、氢键种类和分布及含氧官能团-焦油收率和组成关系，发现通过选择离子液体种类和预处理方式调控褐煤弱键合结构可显著提高褐煤热解焦油收率和品质（特别是高附加值组分含量）。（2）研究了不同类煤结构模型化合物在离子液体作用下的解离，揭示了离子液体对类煤模型化合物中桥键的解离规律，发现离子液体对特定的弱共价键具有解离作用、离子液体促进煤中弱共价键解离生成较多的自由基及离子液体作用下醚键和羰基可分别促进-CH2-和-O-的解离。（3）研究了褐煤和烟煤热解挥发分反应温度及停留时间对热解焦油组成和收率的影响规律，揭示了煤种、挥发分反应条件对焦油组成的影响规律，发现反应温度挥发分及焦油组成的影响最大，煤阶次之，停留时间的影响最小；挥发分反应导致焦油中脂肪类化合物种类减少、苯类化合物含量增加、酚类化合物含量急剧减少。项目执行期间在国际能源燃料领域主流SCI刊物发表论文19篇、EI论文2篇、在国内能源主流刊物发表论文3篇、会议论文6篇，申请发明专利 10件，培养硕士生7名。