超（亚）临界水热合成制备粉煤灰沸石及其煤气脱汞研究

Coal fly ash (CFA) is one of the largest amount of industrial solid wastes in our country. It is an important target of the Twelfth Five-Year Plan to realize the large-scale and high-value utilization of CFAs. It is proposed to synthesize adsorption catalytic materials zeolites and Me-zeolites from CFA by the supercritical hydrothermal synthesis which has many advantages, such as the rapid chemical reaction rate, high nucleation rate, low surface tension, and strong permeability. It can be realized the coupling of in-situ activation, reaction and crystallization of Si and Al of CFA, the in-situ permeation of transition metal of CFA into the skeleton and channel of the Me-zeolites during preparation process. The essential condition of synthesis zeolites and Me-zeolites from CFAs in supercritical water (SCW) will be investigated using the batch and continuous supercritical water reaction equipment, respectively. The influence of operation conditions, alkaline activator, metal precursor solution and the physical and chemical properties of CFA on the zeolites' crystal type and structure will be discussed. The essence of the CFA zeolites formation and the in situ activation of transition metal of CFA or additional metal in SCW will be revealed. On this basis, the activity of Hg and H2S removal over the as-synthesized zeolites and Me-zeolites from coal derived fuel gas will be studied. The internal connection network among the preparation condition, zeolites and Me-zeolites and the performance of gas absorption will be structured. The basis data will be provided for the industrial applications of the preparation of the CFA zeolites by supercritical hydrothermal synthesis.

粉煤灰是我国产生量最大的工业固体废弃物之一。实现粉煤灰的规模化高值化利用是"十二五"规划的一项重要目标。课题提出利用超临界水超快的化学反应速率，高的成核率，低表面张力，强渗透性，实现粉煤灰中Si和Al的原位活化、反应和晶化和粉煤灰中过渡金属原位渗透到沸石骨架或孔道中的耦合，原位制备粉煤灰沸石和Me-沸石吸附催化材料。拟采用间歇式和连续式超临界水反应装置，考察超临界水热合成粉煤灰沸石的必备条件，探讨活化剂、金属前驱体溶液和粉煤灰物理化学性质等因素对制备的沸石和Me-沸石类型及结构的影响规律，揭示超临界水反应介质中沸石形成和粉煤灰固有或外加过渡金属原位活化的过程本质。在此基础上，考察粉煤灰沸石和Me-沸石脱除煤气中的重金属Hg和H2S的性能。构建制备条件-沸石和Me-沸石-气体吸附性能三者之间的内在关联网络，为超临界水热合成法制备粉煤灰沸石的工业应用奠定基础。

粉煤灰是我国产生量最大的工业固体废弃物之一，实现粉煤灰的规模化高值化利用是“十二五”规划的一项重要目标。我国2017年粉煤灰的产生量约为6亿吨，综合利用率为77.3%，且主要被应用于生产水泥、混凝土、墙体材料等建筑材料、筑路材料和土壤改良，产品附加值低。为了提高粉煤灰利用的附加值，本项目提出超（亚）临界水热合成粉煤灰沸石并将其用于环境净化脱除单质汞的研究思路。利用超临界水的超快化学反应速率，高成核率，低表面张力，强渗透性，实现粉煤灰中Si和Al的原位活化、反应和晶化及粉煤灰中过渡金属原位渗透到沸石骨架或孔道中的耦合，原位制备粉煤灰沸石吸附催化材料。考察了不同化学组成的粉煤灰在不同碱种类和浓度下的反应特性，探索了合成粉煤灰沸石的晶相和组分不同的原理，分析了粉煤灰经超临界水热反应前后，碱金属Ca、Na、K等的赋存形态，进而探讨了粉煤灰组成与沸石之间的适配关系。在此基础上，研究了天然矿石高岭石及煤矸石经超临界水热反应后的产物与粉煤灰沸石之间的异同之处。结果表明，粉煤灰、高岭石、煤矸石可通过调节碱种类及浓度超临界水热快速合成结晶度高的方钠石、钙霞石、钾霞石、方沸石、八面沸石等。合成沸石不同的原因为初始凝胶中Ca、K、Na浓度和Si/Al不同造成的。合成的粉煤灰沸石和经贵金属Pd改性、HCl改性后粉煤灰沸石可用于脱除废水中的Hg2+、煤气中的Hg和烟气中的Hg。此外，本项目研究了煤矸石经超临界水热活化后耦合酸浸制备了氧化铝和高比表面积的白炭黑，拓展了固废利用的新途径，提高了煤矸石利用的附加值。本项目的研究阐明了制备条件-沸石-脱汞性能三者之间的内在关联网络，为该技术的工业应用提供理论支持。