三维网状介孔整体材料的研制及其净化高温烟气中微细颗粒物的研究

The principal issue of air pollution in China recently is fine particulates(with aerodynamic diameters<2.5μm, PM2.5) pollution, which mainly come from coal-fired flue gas. Consequently, it is desiderated to develop filtration materials with high-efficiency and high-temperature resistance for hot gas cleaning. The reported filtration materials usually capture the particles by inertial impaction and Brownian diffusion deposition theories; unfortunately, the fine particles with size around 1μm are in the mixing zone of inertial impaction and Brownian diffusion. Thus, it is difficult to remove PM2.5 by use of the current filters. Aiming to solve the above-mentioned problems, this project proposes a strategy of shape-selective adsorption, and synthesis a new kind of filtration materials, i.e. 3D reticulate mesoporous materials monolith. These materials exhibit 3D reticulate structure with micro order and adjustable window size, which can trap and capture the fine particulate pollutants by geometric factor of "molecular sieve effect". Moreover, the framework of 3D reticulate structure possesses ordered mesopores, which are helpful for decreasing the pressure differential. We develop a facile shear flow synergetic primary particles assembling method, by which the 3D reticulate mesoporous materials monolith was successfully synthesized. The synthesis and functionalization and self-molding with special morphology of the mesoporous material were realized simultaneously through this one-pot method, promoting the application of mesoporous materials in devices. This project will reveal the mechanism of the controllable synthesis of the mesoporous materials with different structure and morphology from mesoscopic to microscopic and macroscopic scale. It also will find out the structure-activity relationship of the size and distribution of 3D reticulate structure with its capture efficiency for fine particles. The achievements in this project will provide technical support for the synthesis of new filtration materials with high-efficiency and high-temperature resistance for industrial application.

微细颗粒物（粒径<2.5μm, PM2.5）污染成为我国大气污染的首要问题，燃煤产生的高温飞灰是微细颗粒污染物的主要来源，因此，亟需开发高精度高温烟气净化过滤材料。由于1μm左右的颗粒处于惯性和扩散控制混合区，现有的凭借惯性碰撞拦截和扩散去除颗粒物的过滤材料，对PM2.5的去除效率较低。针对上述难题，本项目基于择形吸附原理，设计一种网格尺寸可控的微米级三维网状结构介孔过滤新材料，即利用微米级三维网格有效卡嵌、捕获微细颗粒物，同时介孔骨架有利于减小压降；提出一种剪切流协助的、初级粒子自组装法，合成三维网状结构介孔分子筛整体材料，实现了介孔材料合成、功能化与成型过程的一体化，有助于推动材料的器件化应用。项目的实施将揭示材料从介观-微观-宏观结构与形貌可控合成的机制，并探明三维网格大小、分布与材料捕获微细颗粒效率之间的构效关系。项目的研究成果有望为高精度高温过滤材料的制备和工业应用提供技术支持。

微细颗粒物（粒径<2.5μm, PM2.5）污染成为我国大气污染的首要问题，燃煤产生的高温飞灰是微细颗粒污染物的主要来源，但现有过滤材料对小于1μm微粒的去除效率较低，另外，高温燃煤烟气温度高、气体腐蚀性强、微细颗粒含量高等特点，因此亟需开发耐高温、耐腐蚀、高精度的过滤材料。针对上述问题，本项目提出研制一种三维网络结构介孔分子筛过滤材料，主要研究内容和成果包括：（1） 系统地考察了剪切流协助的溶胶凝胶体系中，不同参数的调变与氧化硅介观结构以及微观形貌之间的关联，通过调变合成工艺条件，实现了材料的织构性质例如比表面积、孔体积、最可几孔径等可以在较宽范围内调节，以及整体材料三维网格结构大小及分布的可控制备。最终探明剪切流协助的溶胶-凝胶合成体系中，氧化硅材料从介观——微观——宏观的结构与形貌可控合成的机制。（2）搭建吸附除尘装置并优化工艺参数，考察了三维网格结构介孔SBA-15单块整体材料的对2μm聚苯乙烯标准小球的除尘性能。结果表明，材料网格尺寸0.2~1μm（分布较均一）及0.5~5μm（分布较宽）的总体过滤效率能达到99%以上。随着温度的升高，过滤效率稍有下降。随着空速的增加，过滤效率基本不变，但压降显著增大，因此，压降问题也是此类整体材料需要解决的一个问题。（3）目前碳烟的去除主要采用催化燃烧法，但现有催化剂存在的问题是：催化剂与载体粘附力较差、易脱落，另外，受载体孔道尺寸的限制，较大尺寸的碳烟与催化活性组分接触性差，导致碳烟在较低的温度下燃烧不充分。鉴于此，我们原位合成了三维网状MnOx-CeO2/SBA-15整体催化剂，活性组分与载体作用力很强，另外，材料具有微米级三维网格结构，能够增强碳烟与活性位的可接触性，从而显著降低碳烟燃烧温度，其活性与负载型贵金属接近，为制备高活性碳烟燃烧催化剂提供了新思路。