粉煤灰基P型分子筛晶粒生长过程界面传质与结构协同控制

The preparation of molecular sieve is an important way for the utilization of coal fly ash. Due to the incompletely removal of impurity from the raw material and the lower efficiency of mass transfer, the crystal growth is not easy to control, which is the disadvantage for the preparation of molecular sieve from coal fly ash. The idea for regulating the process of grain growth and interfacial transfer mass intensified by external force was suggested to solve these above problems. The mechanism of regulating of grain growth and inhibiting the growth of impurity crystal was revealed by the regulation of nucleation and grain growth. For the enhancement of mass transfer by ultrasonic, single grain growth and the control of crystal size and structure was obtained.. The regulation of grain size, shape and structure was revealed via the control of nucleation and grain growth by steric effect with different molecular space structure of organic compounds. Under the coupling of ultrasonic mechanical, cavitation and chemical effect, the interfacial mass transfer between gel and crystal was enhanced, the grain accumulation was reduced and the equilibrium of crystallization and dissolution was under control. The synthetic regulation mechanism of interfacial mass transfer and sturcture of zeolite was investigated by steric effect and intensification of interfacial mass transfer in the process of zeolite grain growth. It provided theoretical foundation for the preparation of P molecular sieve with controlled structure from coal fly ash.

制备分子筛是粉煤灰资源化利用的重要途径，由于原料中杂质完全脱除困难和合成过程界面传质效率差，致使分子筛晶粒生长不易控制成为粉煤灰制备分子筛的共性问题,为了解决上述问题，提出了晶粒生长过程调控和外场强化界面传质的思路。通过空间位阻调控晶核形成、晶粒生长过程，揭示晶粒生长调控和杂晶生长抑制机理。通过超声波强化界面传质，实现晶粒单一生长和晶体尺寸和结构控制。. 通过有机分子空间结构的位阻效应大小调控晶核形成与晶粒生长速度，揭示晶粒尺寸、形状和结构调控规律。通过超声波机械、空化和化学耦合效应增强凝胶和晶体界面传质，减少晶粒聚积，实现结晶-溶解平衡的控制。通过P型分子筛晶粒生长过程空间位阻作用与强化界面传质，揭示分子筛界面传质与结构协同调控机制，为粉煤灰制备结构可控的P型分子筛技术提供理论依据。

本项目基于“以废治污”核心科学理念，以固体废弃物粉煤灰为原料，通过高温活化和分级处理提取高纯度硅铝组分，解决了原料中杂质难以脱除的问题；通过超声波等外场强化传质作用，克服了分子筛合成过程界面传质效率差的缺点；通过在粉煤灰制备分子筛过程中引入空间位阻作用实现了晶粒生长的可调控。重点研究了过渡金属掺杂、前驱体赋存形式、空间位阻效应和外场强化传质、传热等多种方式单独和耦合作用对NaP分子筛晶相、粒径、形貌、孔结构和晶粒分散性的调控规律。研究结果表明，粉煤灰经高温活化、酸浸碱熔与分级处理等步骤，通过合成工艺参数优化，制备出纯度为90.6%的NaP分子筛，合成体系引入溴离子，产率由87.8%提高至94.2%。在水热合成过程通过改变有机分子空间结构的位阻效应大小实现了对晶核形成与晶粒生长速度的调控；通过超声波机械、空化和化学耦合效应可有效缩短晶粒成核时间、提高晶粒生长速率和减少晶粒聚积，有利于达到结晶-溶解平衡；通过掺杂过渡金属和改变硅源和铝源前驱体的赋存形态，可调控NaP分子筛的孔结构、形貌和晶粒尺寸。由此，可将NaP的应用领域由重金属离子污水处理延伸到有机污染物废水净化，为NaP分子筛的工业化利用提供良好的理论基础和技术支持。