锰替代菱铁矿热分解产物结构及脱硝活性

Siderite has a large storage, but not utilized effectively. And it is universal for the substitution of Mn for Fe in the crystal structure of siderite. The previous studies displayed that nano-structured iron-manganese oxide can be prepared by thermal treatment of siderite under controlled conditions. The Mn-substituted siderite displayed prodigious potential in selective catalytic reduction of NOx by NH3. Therefore, the study on the siderite of different places and series of synthetic Mn-substituted siderites with different Mn substitution amount will be carried out in virtue of Mössbauer, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Thermogravimetric Analysis, Specific Surface Area and Pore Analysis, Raman Spectroscopy, Transmission Electron Microscopy, Scanning Electron Microscopy and so on. The objectives are (1) to clarify the mineral composition of siderite ore of different places and the characteristic of the isomorphism of Mn in siderite, (2) to reveal the effect rule of Mn substitution amount on the mineralogical characteristics of siderite and the occurrence states of Mn; (3) to elucidate the effect rule of Mn substitution amount on the structures, physicochemical properties, and Mn occurrence states of thermally treated siderite, and (4) to investigate the effect rule of Mn substitution amount on the de-NOx activity and mechanism of nano-structured iron-manganese oxide derived from the thermal decomposition of Mn-substituted siderite and reveal the relationship between structure and activity. The results will promote the study of crystal chemistry and mineral physics of siderite, establish theoretical principle for the application of thermally treated Mn-siderite on flue gas de-NOx, and play an important significance of theory and guidance in the interdisciplinary research on nano-mineral material, air pollution control, and environmental mineralogy and so on.

菱铁矿储量丰富但尚未得到有效利用，通常富含晶格替代锰。前期研究发现在控制条件下热分解可制备多级孔纳米结构化铁锰复合氧化物，在催化氨还原脱硝方面显示出很大潜力。为此，本项目借助穆斯堡尔谱、红外光谱、拉曼光谱、X射线衍射、热重、比表面积和孔结构、透射电镜、扫描电镜等表征手段，对不同产地菱铁矿和合成不同锰替代量菱铁矿系列样品进行研究，查明不同产地菱铁矿矿石矿物组成及菱铁矿中锰替代特征；揭示锰替代量对菱铁矿矿物学特征的影响规律；阐明锰替代量对菱铁矿热分解产物结构、理化特性和锰赋存状态的影响规律。结合选择性催化还原脱硝活性评价，探讨锰替代量对菱铁矿热分解纳米结构化铁锰复合氧化物脱硝活性和作用机制的影响规律，揭示构效关系。成果可推动菱铁矿晶体化学和矿物物理研究；为锰替代菱铁矿热分解产物在烟气脱硝中的应用奠定理论基础；对纳米矿物材料、大气污染治理及环境矿物学等学科交叉研究具有重要的理论价值和指导意义。

菱铁矿储量丰富，分布较广泛，通常富含晶格替代锰。本项目借助红外光谱、拉曼光谱、X射线衍射、热重、比表面积和孔结构分析仪、透射电镜、扫描电镜等现代表征技术，结合表面活性评价实验，查明了陕西大西沟和铜陵菱铁矿矿物组成、化学组成及表面铁活性；揭示了菱铁矿热处理结构演化规律及理化性质的变化规律，查明了两地菱铁矿热分解产物催化脱硝的活性及可能的影响因素；阐明了不同H2O、不同浓度SO2及其不同浓度碱金属K存在下，菱铁矿热分解产物对NO转化的影响；揭示了锰替代对菱铁矿晶体结构、热稳定性及表面活性等矿物学特征的影响；查明了锰替代菱铁矿热分解产物锰的赋存状态；揭示了锰替代对菱铁矿热分解产物脱硝活性的影响规律；结合in-situ DRIFTS和Kinetic study探究锰替代菱铁矿热相变产物对NO作用过程和机制，明确锰替代菱铁矿热分解产物与脱硝活性内在联系；揭示了烟气中菱铁矿热分解产物对氮氧化物转化的影响；对比了菱铁矿与钒酸铁体系的脱硝活性。研究结果表明大西沟菱铁矿矿石主要由菱铁矿和石英组成，铜陵菱铁矿矿石主要由菱铁矿、针铁矿和石英组成；菱铁矿氧化气氛中形成的纳米尺寸赤铁矿有利于催化氨还原氮氧化物；相对大西沟菱铁矿，铜陵菱铁矿热分解产物具有具有更高的比表面积以及较高锰含量，提高了脱硝活性；碱金属、SO2、H2O对菱铁矿热分解产物脱硝活性具有较大影响；锰替代增加了菱铁矿分解活化能，提高了菱铁矿热稳定性；锰替代菱铁矿热分解产物中锰主要以类质同象形式进入赤铁矿晶格；锰替代量的增加提高了锰替代菱铁矿热分解产物的比表面积和表面酸位；锰的加入显著提高了锰替代菱铁矿热分解产物低温活性；E-R和L-H机理均存在于整个脱硝反应当中，锰替代显著提高了氨在B酸位的吸附，促进了单齿配位硝酸盐的生成。研究结果有助于进一步认识菱铁矿矿物学特征及燃煤过程氮氧化物的转化过程，对环境矿物学、矿物材料及大气污染治理等学科交叉研究具有重要的理论价值和指导意义。