廉价矿物原料水热法制备沸石分子筛的形成机理与晶体生长模型研究

【作者】 申少华；

【导师】 王大伟； 张术根；

【作者基本信息】 中南大学 ， 矿产普查与勘探， 2001， 博士

【摘要】 论文在综合分析国内外有关沸石分子筛的合成与应用、形成机理、以及晶体生长理论等大量文献资料的基础上，运用现代材料测试分析技术对红辉沸石和玻屑凝灰岩等廉价矿物原料水热法制备沸石分子筛的形成机理和晶体生长模型进行了全面系统的研究，主要内容如下： 通过广西资源红辉沸石和湖南临澧玻屑凝灰岩的矿物组成、化学成分和部分工艺性能的分析，对其资源特性进行了评价。并根据其资源特性，对这两种廉价矿物原料进行了预处理，使之成为沸石分子筛水热制备的合格原料。 以红辉沸石或玻屑凝灰岩(经预处理)为原料，采用水热法制备了沸石分子筛系列产品。并在大量实验研究的基础上，深入探讨了反应混合物组成和水热条件对沸石分子筛制备的影响，确定了A型、X型和P型沸石水热制备的最佳工艺技术参数。 结合水热反应过程中固相组分的化学成分及红外光谱变化特征，对沸石分子筛的形成条件、晶核的形成及其影响因素、晶体生长及其影响因素作了综合分析，指出水热反应体系沸石分子筛的形成机理为液相转化机理。 运用FKM法对水热反应初期的反应混合物进行TEM制样，并在透射电镜下对所制样品进行TEM观察和电子衍射分析，发现水热反应初期，伴随着前驱物的溶解，沸石分子筛以成核作用为主，并形成粒度为几个纳米的小粒子，这些纳米小粒子迅速聚合生长成约50nm的纳米晶粒，从而为纳米晶粒的聚合生长提供了有力的证据。 通过沸石分子筛的水热制备实验及其测试分析表征，结合沸石晶体生长动力学曲线，对水热条件下沸石的晶体生长过程作了深入的研究，提出了水热体系中存在着聚合生长和聚集生长两种生长方式，建立了晶体聚合生长模型。水热条件下聚合生长是小粒子之间相互作用形成粒度更大的粒子的过程；聚集生长则是物料从小尺寸粒子向大尺寸粒子输运的重结晶过程。两者的热力学驱动力都是粒子平均粒度的增大降低了体系总的表面自由能。水热条件下沸石晶粒的形成经历了前驱物溶解→成核并形成纳米小粒子→纳米晶粒和微米晶粒的聚合生长→微米晶粒的聚集生长这样四个阶段，最后得到的晶粒是以聚合生长为主，同时伴随着聚集生长的综合结果。 廉价矿物原料水热法制备沸石分子筛的形成机理和晶体生长模型研究，从本质上揭示了水热条件下沸石晶体生长的基本规律，提高和发展了沸石的晶体生长理论。不仅对廉价矿物原料高层次开发利用和降低沸石制备成本有着很高的实用价值，而且对实现新型沸石分子筛和纳米沸石制备技术研究的指导和预言具有重要的理论意义，同时对水热条件下陶瓷粉体制备技术研究也有着重要的指导意义。更多还原

【Abstract】 On basis of integrated analysis of a great deal of literatures and data about the synthesis and application and formation mechanism of zeolite molecular sieves as well as the theories of crystal growth model, This paper entirely and systematically studies the formation mechanism and crystal growth model of zeolite molecular sieves that are prepared in hydrothermal system of taking such cheap mineral materials as the stellerite and vitric tuff as the feedstock by using of modem material testing and analysing techniques. The main contents of the paper is as follows.The resource characteristics of the stellerite in Ziyuan county of Guangxi and the vitric tuff in Linli county of Hunan are evaluated after their mineral constitutes and chemical compositions and some technics performances are analyzed. According to their resource characteristics these two cheap mineral materials are pretreated adequately, then turned into eligible stocks that is used to prepare zeolite molecular sieves in hydrothermal method.Taking the stellerite or vitric tuff (pretreated) as the feedstock, a series of zeolite products are prepared by using the hydrothermal method. It is discussed in depth how the constitutes of the reaction mixture and hydrothermal conditions influence the hydrothermal preparation of zeolites, the best technical parameters of hydrothermal preparation of zeolite A and X and P are confirmed.Combining with the transformative characteristics of the chemical compositions and IR spectrum of the solid phases in the process of hydrothermal reaction, the author integratedly analyses the forming conditions of zeolite molecular sieves, formation of crystal nucleus and its influencing factors, crystal growth and its influencing factors. It is pointed out that the formation mechanism of zeolite molecular sieves hi hydrothermal system is the solution-mediated transformation crystallization mechanism.By using FKM method, the reaction mixture hi the earliest of hydrothermal reaction are made to the samples that can be used in TEM analysis. The TEM observation and electron diffraction analysis of these samples indicate that along with the dissolution of the feedstocks, zeolite nucleus are formed, simultaneously the small particles of several nanometer are formed, these small particles aggregate and form the crystal particles of about 50nm. These analytical results are the mighty evidences that are provided to prove that the nano-particles is formed by the aggregation of nano-small-particles.On basis of the hydrothermal preparation experiments of zeolite and its testing and analysing token as well as kinetics curve of crystal growth, the process of zeolite crystal growth hi hydrothermal conditon is investigated. It is put forward that there are such two kinds of growth mode as aggregation and coalescence. The crystal aggregation growth model is established. The aggregation growth is the process that the aggregation of small particles form big particles because the mutual action of the small particles. Thecoalescence growth is the recrystallizing process of particles because the small particles transport to big particles. The thennaldynamics drive force of the two growth is that the total surface free energy is reduced because the accretion of the average granularity of the particles. In hydrothermal condition, the formation of the zeolite crystal come through such four phases as from the dissolution of the feedstocks to the growth of nucleus and the formation of nano-small-particles to the aggregation growth of nano-crystal and micro-crystal to the coalescence growth of micro-crystal. The crystal that is prepared finally is the integrated results of aggregation and coalescence growth that aggregation growth give priority to coalescence.The study about the preparation and formation mechanism and crystal growth model of zeolite molecular sieves in hydrothermal system by taking the cheap mineral materials as the feedstock opens out the basic law of zeolite crystal growth in hydrothermal condition, improves and dev更多还原