NMR研究褐煤基吸附剂处理费托合成水的吸附性能及分子间作用机制

Fischer-Tropsch synthesis is an important approach for modern coal chemical industry to prepare the clean liquid fuels. It is well known that there is even more water (Fischer-Tropsch wastewater) produced when the desired liquid fuel is obtained. Fischer-Tropsch wastewater is rich in acidic compositions; therefore, it is very difficult to handle or treatment. The development of cheap adsorbents will be an effective and practical way to solve the water pollution of Fischer-Tropsch synthesis. Brown coal occupy a well-developed pore structure, rich in functional groups with adsorption ability, thus, it is expected to be employed in Fischer-Tropsch synthetic water treatment. This project will follow the "deal wastewater of coal industry by brown coal" standard, and the brown coal and its active model component, humic acid, will be employed to treat treatment Fischer-Tropsch wastewater. The NMR spectroscopy will be fully utilized to identify and classify the pollutant molecules in Fischer-Tropsch wastewater. The identification of adsorption active functional groups in the brown coal will also be carried out. The model compound, humic acid, will be chosen to elucidate the intermolecular interactions in the adsorption process at the molecular level. The competition and synergy between the various pollutants will be examined, and the capturing the "complex" formed between the pollutant molecules and the humic acid will be carried out. Then the stability, diffusion coefficient and migration properties of the "complex" will be measured by NMR techniques. Finally, we will use the “in situ” solid state NMR device, to study the adsorption of real system, which is composed by solid-liquid two-phase, and the the adsorption mechanism will be proposed. This project will help the modern coal chemical industry to overcome the hindrance of wastewater treatment burden, and it will also promote the rapid and sustainable development of coal chemical industry.

费托合成是现代煤化工制清洁液体燃料的重要途径，在获得液体燃料的同时，会排放更大量的反应生成水。费托合成水呈酸性、成分复杂、处理难度大。研制廉价吸附剂是解决费托合成水污染的有效途径。褐煤具有发达的孔道结构、丰富的吸附活性官能团，有望用于费托合成水处理。本项目将遵循“以煤治煤”原则，利用褐煤及其活性组分腐殖酸吸附处理费托合成水。项目研究将首先通过NMR谱学表征，完成费托合成水中污染物分子的识别与分类；开展褐煤结构中吸附活性官能团的辨认和空间网络模型搭建；进而利用模型化合物腐殖酸，在分子层面上阐明吸附过程中的分子间相互作用、多种污染物分子间的竞争性和协同性、捕获污染物分子和腐殖酸间形成的“复合物”，测定其稳定性及扩散、迁移性能；最后，将利用准原位固体NMR装置，开展固液两相真实体系中的吸附研究，阐明吸附机理。本项目的实施将缓解现代煤化工面临的反应生成水排放压力，促进煤化工快速、可持续发展。

费托合成(Fischer-Tropsch synthesis, F-T)合成是20世纪20年代由Franz Fischer和Hans Tropsch提出的经典催化反应，该反应可将一氧化碳(CO)和氢气(H2)转化为液体燃料或含氧化合物，但同时也会产生大量的费托反应生成水。费托反应生成水中含有多种挥发性有机物(VOCs)，如醇类、醛类、羧酸类、酮类等，这些污染物小分子会造成严重的环境问题。水处理已成为困扰费托合成工艺快速发展和工业化的瓶颈之一。褐煤具有发达的孔道结构、丰富的吸附活性官能团，可大规模用于费托反应生成水处理。NMR技术作为一种可以提供原位信息的非侵入性、非破坏性表征方法，可从分子层面探究吸附过程、有效避免样品固有信息的丢失。.本项目执行过程中，我们完成了褐煤基吸附剂和费托反应生成水收集、分类；发展了扩散排序谱、选择性激发全相关谱、定量氢谱、三维核磁共振谱、纯化学位移谱等多种高级液体NMR方法，用于表征以费托反应生成水为代表的复杂混合物体系；以丁醇异构体为模型化合物，研究了污染物小分子和腐殖酸的相互作用，阐明了污染物小分子结构对其与腐殖酸相互作用的影响；以丙酸和丁醇构建的二元模型体系为研究对象，考察了褐煤基吸附剂对费托反应生成水中的醇类物质和酸类物质的竞争性吸附，阐明了正丁醇与腐殖酸作用时包裹在腐殖酸的疏水区域，且不受溶液pH的影响。酸性条件下丙酸质子化，烷基链与腐殖酸的疏水作用为吸附驱动力，碱性条件下，丙酸羧基去质子化，羧酸根的亲水作用占主导地位；考察了褐煤，干酪根和两种铬改性干酪根（物理吸附铬离子和化学负载铬离子）对费托反应生成水的吸附性能、优化了吸附工艺；通过FTIR，XPS，TEM-EDS和SEM-EDS表征了Cr（VI）对干酪根中官能团的影响以及这些影响对吸附性能的调变规律，阐明了固液两相吸附机理。.通过上述研究工作，我们识别了褐煤基吸附剂结构中的吸附活性官能团，拓展了高级NMR方法的应用，揭示了不同化学性质的污染物分子与腐殖酸的作用模式，拓展了褐煤利用途径、丰富褐煤利用的化学基础理论。