亚临界水煤气变换介导的活性氢转移对煤结构及粘结性的调控机理

Hydrogen transfer is one of the core chemical processes for converting low-rank coal to caking coal, which is very important to control coal structure and products properties. On the basis of the research findings, the active hydrogen H• mediated by subcritical WGSR was generated during coal modification in the Fe/Na catalytic subcritical H2O-CO system. However, there are still some scientific problems remain unclear: How to transfer the active hydrogen during coal modification and how to adjust the coal structure and caking property by hydrogen transfer? Aiming at these problems, the subject would carry out by using Fe/Na catalytic subcritical H2O-CO system. Combined with isotopic tracing and model compounds methods, the research is expanded as follows: ①the hydrogen transfer routing of active hydrogen H• mediated by subcritical WGSR, mainly including: a) the evolution of active hydrogen H• generation, b) the hydrogen migration routing from H• cutting chemical bond to generate stable hydrogen-containing groups; ② regulation mechanism on coal structure and caking property of the active hydrogen transfer, revealing the essence of caking property improvement though modulating coal structure by hydrogen transfer. The implementation of the project has important theory and application value to enrich the basic theory of hydrogenation transfer and promote the efficient utilization of low-order coal.

氢转移是低阶煤加氢改性制粘结性煤的核心化学过程之一，对调控煤结构及产物特性起着至关重要的作用。基于研究发现：在Fe/Na催化亚临界H2O-CO系统改性褐煤增粘过程中，具有水煤气变换反应（WGSR）介导的活性氢H•生成。但是，该活性氢在煤改性反应中如何转移、以及通过氢转移如何调变煤结构和粘结性等基础科学问题仍不明确。针对这一问题，本申请项目将利用Fe/Na催化亚临界H2O-CO系统，通过重氢D示踪（重水D2O替代水H2O），结合模型化合物等方法开展如下研究：①煤改性过程中，亚临界WGSR介导的活性氢转移路径研究，包括：探索活性氢生成量的变迁规律，明确活性氢切断、联结化学键直至稳定形成含氢化学新基团的迁移路径；②活性氢转移对煤结构及其粘结性的调控机理研究，揭示通过氢转移调变煤结构继而提高煤粘结性的作用机制。项目成果对丰富煤加氢转化氢转移基础理论以及促进低阶煤高效利用具有重要理论和应用价值。

针对亚临界H2O-CO体系低阶煤加氢改性过程中活性氢如何转移、以及通过氢转移如何调变煤结构和黏结性等基础科学问题，利用IRMS、NMR、py-GCMS和GPC等分析方法，系统开展了亚临界水煤气变换介导的活性氢转移对煤结构及粘结性的调控机理研究。主要结论如下：（1）活性氢生成量与反应温度呈现较好的线性关系，被消耗的活性氢引入至煤中的比例随反应温度升高而先增大后减小，在340 ℃时达到最大值97%，相应地获得的改性褐煤粘结指数达最大值97。（2）氢转移过程中会选择性切断氧醚键，并能较完整保留苯环；对单环芳香结构，活性氢按照脂肪侧链→苯环的顺序进行加氢，对多环芳香结构，活性氢则优先进入其脂肪侧链而后迅速加入该侧链所链接的芳香环。（3）随着改性温度的升高，引入至改性煤油相中的活性氢含量先降低而后增加，沥青烯和前沥青烯中活性氢量逐渐增加并在340 ℃时达到最大；活性氢通过与芳环Cα-Cβ 断裂形成的碳α自由基结合进入油相和沥青烯的Hα位，通过与前沥青烯中芳环取代烷烃侧链断裂形成自由基结合，进入TS的Hβ位。（4）适度供氢及H•优先进入Har、Hα和Hβ位有助于形成以多环脂肪烃/芳烃（重均分子量在1170-2900范围内）为核心骨架、取代基数量较多而链长较短的沥青质类致粘物质，从而使低阶煤的GRI值由0提高至90以上。该研究成果对丰富煤加氢转化氢转移理论和实现低阶煤加氢改性制炼焦煤具有重要理论和应用价值。