纳米催化过氧氧化技术用于选择性制取腐植酸及其模板效应研究

Coal-based humic acid, which is the main commercial humic source and derived from low-rank coals such as lignite and weathered coal, is a class of natural organic macromolecules with chemical and biological activity, and has broad applications in the fields of agriculture, water treatment, and medicine. However, the current preparation of humic acid by HNO3 oxidation suffers from drawbacks such as corrosion and environmental pollution. Here, one of our goals is to develop a green technique of oxidation catalyzed by metal oxide nanomaterials for preparation of humic acid. The effects and mechanism of particle size- and shape/morphology-catalytic activity would be investigated and discussed. The second goal is for the usage of humic acid as a unique template for the fabrication of singly/multiply shelled hollow metal oxide nanostructures. Such hollow structures would be fabricated by adsorption of metal cat-ions on humic acid attached to hydroxyl and carboxylic groups, followed by high-temperature annealing for removal of the template and for conversion into metal oxide. The third goal is to explore the applications of the hollow nanostructures in gas sensors and catalysis, in order to reveal the effects and mechanism of the number and surface of shells on adsorption and reaction of gas molecules on metal oxide. Expected results from this fund would be helpful for green and clean production of humic acid and its templating application, and also favor of searching for a new template for hollow nanostructures with good gas sensing and catalytic properties. Such a research provides a new idea and route for effective development and creative application of massive weathered coal produced from Xinjiang, China.

煤基腐植酸是一类从褐煤、风化煤等低阶煤中制取的具化学与生物活性的天然有机大分子混合物，也是目前商用腐植酸的主要来源，在农业、水处理和医学等领域有着广泛应用。然而，现有通过硝酸氧化制取腐植酸技术存在设备腐蚀、环境污染等缺点。这里，我们拟开发纳米催化绿色氧化技术选择性制取腐植酸，探讨纳米颗粒的尺寸和形貌对催化活性的影响机制。其次，以腐植酸作为模板，利用其分子结构中的羟基和羧基吸附目标金属离子，然后通过高温焙烧单/多壳层中空金属氧化物纳米结构。最后，利用中空纳米结构制备气体传感器，探究中空壳层表面和数目对气体分子吸附和反应的影响机制。所获研究结果将有助于腐植酸的清洁生产和应用拓展，也有利于寻找合成中空纳米气敏和催化剂材料的新模板。该研究还将为中国新疆巨大的风化煤等劣质煤资源的有效开发与创新应用提供新思路。

煤系腐植酸是腐植酸的重要来源之一，探索利用催化氧化风化煤提高提取率的方法有助于减少残渣量。同时，腐植酸分子的结构复杂性和表面荷电性质增加了对其利用的难度。因此，需通过多个层面研究腐植酸同其它物质，特别是无机化合物间的相互作用。.本课题围绕风化煤系腐植酸的制备和借助腐植酸的特性探索其在功能材料合成中的应用。利用腐植酸的弱酸性、配位作用、表面强荷电性、弱还原性和可碳化性等特点，采用不同方法制备复合物催化剂和电极材料。通过XRD、SEM、TEM、BET等表征技术，结合FTIR、XPS、Raman、UV-vis-NIR、ESR等分析手段，考察风化煤制取的腐植酸盐产物的官能团特征；考察腐植酸辅助制备的复合物材料的结构、组成、表面性质、光学吸收等物性参数，通过对比试验考察腐植酸在合成中的作用；评价腐植酸辅助制备的复合材料的催化和电化学性能。主要研究结果表明：1) 不同形貌的纳米氧化铜有助于提升过氧化氢氧化风华煤制取腐植酸盐产率；2) 采用腐植酸辅助共沉淀-焙烧法制备出具有高松比的膨润土负载铜镁铝氧化物催化剂，腐植酸有助于改善催化剂活性组分的分布和增加比表面积，进而影响催化剂在对硝基苯酚还原和一氧化碳氧化反应中的催化活性，这一调节作用可能源自于腐植酸胶体的表面配位基团和荷电性质；3) 借助腐植酸的配位作用和胶体性质，采用腐植酸辅助沉淀-焙烧法制备的钼酸铁催化剂在紫外光降解邻硝基苯胺中表现良好的催化活性；4)采用腐植酸辅助沉淀-焙烧法制备的g/Ag2MoO4和Ag/Ag2WO4复合物催化剂在还原硝基和偶氮芳烃化合物时表现出良好的催化活性；5) 借助腐植酸的弱还原性，利用腐植酸在水热体系中还原高锰酸钾以及高温后处理的手段制备具有良好电化学性能的MnO2/C簇状纳米颗粒聚集体；6) 发挥腐植酸的配位、可碳化和还原性作用，采用共沉淀-惰性气氛焙烧制备具有良好催化活性的C/Cu/Fe3O4三元复合物催化剂。