褐煤分子结构和高温转化反应机理研究

Theoretical and experimental studies on the coal structure and its pyrolytic conversion reaction mechanism have attracted more and more attention in the field of the coal science. Components of coal and its supermolecular structure are very complex. There are also various noncovalent interactions between structural fragments of coal. So, it is quite difficult to study relationships between the coal structure and its reaction mechanism in the molecular level. In the project, the molecular dynamics simulation and the quantum-chemical calculation are applied to investigate structures of some lignite samples in the molecular level. The relationship between structure/dynamics and thermal reactivity of lignite are studied. Thus, we can understand important roles and effects of the molecular structures of lignite in the thermal reactions such as pyrolysis, liquefaction, gasification and desulphurization. The results can provide theoretical basis for designs of the above reaction processes. Meanwhile, systematic methods of creating molecular models of lignite samples are built by element analysis, spectral characterizations, quantum-chemical calculations and so on. Furthermore, experiments about structural characterizations of lignite and its thermal reactions are purposefully carried out under the guidance of theoretical calculations. Thus, theoretical and experimental studies are tightly combined and cross-checked with each other.

煤的结构与反应机理的理论与实验研究是当前煤化学研究的热点。由于煤的组成及其超分子结构十分复杂，结构片段之间存在多种非共价相互作用，从分子水平上研究煤的结构以及煤结构与反应机理关系是当前煤化学研究的难点。本项目首先通过元素分析和光谱方法等实验表征，结合量子化学计算，建立描述褐煤分子结构模型的系统方法。在此基础上，采用动力学模拟和量子化学计算的理论方法，从分子水平上深入研究若干种类的褐煤的结构，以及在高温转化过程中体现出的超分子结构和反应机理的关系，从分子层面深刻理解褐煤的微观结构在热解，液化，气化和脱硫等高温转化过程中所起的重要作用，为这些反应工艺的设计提供理论依据。同时，本项目还将在理论计算的指导下有目的性的开展的褐煤结构的表征和高温转化反应实验研究，与理论计算紧密配合，相互验证。

褐煤结构和反应的复杂性是其高效洁净利用研究的瓶颈问题。本项目采用理论与实验相结合的方法，从微观角度解释褐煤样品的分子结构及其高温转化反应机理。我们首先建立了构建褐煤样品三维分子结构模型的系统方法。根据褐煤结构模型，采用分子动力学方法模拟了褐煤的热解，水热，氢化，氧化和气化等高温转化过程。并结合相应的实验，解释了以上过程的微观机理。重点解释了小分子气体对褐煤热解的催化作用；褐煤在不同反应环境中小分子气体的形成规律和反应性；硫、氮元素在半焦、焦油和气体产物中的分布、存在形式和迁移机理。此外，我们还将此研究方法拓展到更高变质程度的煤样品之中，解释褐煤和其他种类煤的分子结构及其高温转化反应机理的差异。本项目研究是对低阶褐煤结构的一次重要探索，可对褐煤在化工生产中反应条件的确定提供理论支持。这有助于褐煤资源应用于化工生产领域，提高其利用率并减少环境污染。