低阶煤OH可控氧化与电制H2O2原位协同机制

Rich in water and volatile components, low-rank coal shows huge potential as oil and gas resources. Compared with solvent extraction, hydrothermal extraction has the advantage of low cost, environmentally friendly. The key of effective extraction in mild conditions is improving the oxidative ability of the extraction system. The advantages of hydrothermal fade away when using acids, alkaline and salts system. (1) This program found: a synergetic effect exists between ionic reaction and radical reaction in hydrothermal process. Naturally, H+ and OH- can transport a long distance, while ·OH just transport a distance at micro-nano scale, since it has an extremely short lifetime. Therefore, making the character of ionic transport compatible with radical reaction, becomes the key of effective and controllable oxidation. (2) Synergetic enhancement of short-distance oxidation of ·OH and long-distance transport of H+ and OH- could be achieved by the introduction of electrokinetic-Fenton. The novel part of this idea is that H2O2 was electrogenerated by O2 reduction at cathode vicinity, and then catalyzed to produce ·OH and oxidize trarget in-situ. Moreover, H+ and OH- was govern by electric field to match the oxidation process of low-rank coal. In-situ utilization of water from coal, effective and controllable oxidation in mild conditions, green and environmentally friendly overall the process, could all be achieved in this program. It has great potential for application in engineering.

低阶煤富含水分和挥发分，油气资源潜力巨大。相比有机溶剂萃取，水热萃取具有成本低、环境友好的巨大优势。高效温和萃取的关键在于提高氧化降解能力，现有酸碱盐氧化技术抵消了水热萃取的绿色优势。（1）项目发现：水热反应中存在离子反应和自由基反应的协同效应。H+和OH-可在反应器内进行长程迁移，而氧化物种·OH寿命短，只能进行微纳尺度的短程迁移。因此，调动离子迁移匹配自由基反应，是实现高效可控氧化的关键。（2）项目将电动-Fenton引入低阶煤水热体系，可协同强化·OH的短程氧化行为和H+和OH-长程迁移匹配行为，从而实现对低阶煤的高效温和可控氧化。其创新构想是在阴极区域内O2电还原产生H2O2，进而分解产生·OH，原位氧化目标物质；通过电场驱动H+和OH-定向匹配低阶煤氧化降解反应。本项目方案可望同时实现低阶煤原水分利用、高效温和可控氧化、且全程绿色环保，具有巨大的工程应用潜力。

低阶煤高效温和萃取的关键在于提高体系的氧化降解能力。项目提出在阴极区域内由O2电还原产生H2O2，进而分解产生强氧化性·OH，通过调动H+/OH-离子反应匹配自由基反应，从而实现对低阶煤的高效温和可控氧化。取得以下进展：（1）研究了碳基阴极电合成H2O2的规律并提出强化合成方法。项目构筑了低成本的活性炭/不锈钢网复合阴极，可同时实现H2O2合成及分解。提出了基于电极极性互换的碳阴极掺氧改性方法，改性电极的O2还原活性明显提高，H2O2产量可提高近2倍。（2）提出了H2O2合成体系中物种扩散的调控方法及流动反应器。为强化反应物O2向多孔阴极的扩散，项目提出“漂浮阴极”新结构，H2O2产量提高4.3倍。提出了脉冲电流抑制H2O2电还原路径、强化H2O2向体相扩散新构想，H2O2产量可提高61.3%。（3）首次提出了脉冲电催化合成H2O2体系的调控机制及方法。项目研究了脉冲宽度、占空比及脉冲电位对H2O2产量的影响，当脉冲宽度为1s、占空比为30%、脉冲电位为-1.0V时，H2O2产量可提高138.1%。DFT计算证明双电层的放电过程显著增强*O2吸附, 并削弱*OOH及H*的吸附，有利于2eORR。（4）研究了煤水体系绿色氧化辅助电催化制氢的基本规律。项目研究了煤阶、煤中含氧基团和矿物质对煤水体系电催化制氢的影响。提出两步法煤水体系电催化制氢新路线，可实现高电流低电耗制氢，当电压为1.2V，所产生的电流密度达100mA/cm2，电耗为2.63kWh/Nm3。（5）提出了H2O2体系氧化煤的机制及强化方法。项目对煤的氧化转化规律进行了研究，提出强化煤与H2O2的反应性的方法，以此对煤的氧化机制和液相产物的组成形成认识。提出了Fe2+与冰乙酸协同催化H2O2与煤的反应，既可提高H2O2与煤的反应性，又可高产率获得有价值的液相产物。基于本项目研究，发表学术论文23篇，其中SCI检索14篇，EI检索1篇，会议论文3篇，学位论文5篇；培养博士研究生6名，2名已毕业，硕士研究生4名，3名已毕业；与美国东北大学针对项目关键问题已开展合作及学生联合培养。