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以相变理论为基础,通过估算溶液表面能、X射线衍射物相分析、扫描电子显微镜形貌观察和能谱分析,研究了合成ZSM-5/丝光沸石(mordenite,MOR)共生分子筛溶液的变化特点、晶体的生长过程。结果证明:ZSM-5分子筛和MOR物相间的相变过程中存在自由能驱动力、相界面、位相关系、惯习面和应变能等明显的固相转变特征。结合液-固、液-液和固-液3种相变机理,建立了ZSM-5/MOR共生分子筛的合成机理为:合成溶液先出现固-液分相,形成富硅相和富铝相,在富硅相中生成ZSM-5,在富铝相中生成MOR;由于ZSM-5分子筛的表面能比MOR大,体系处于亚稳相,在成核生长后期,ZSM-5分子筛通过固态相变过程,逐渐转变为MOR,达到相态平衡。通过实验验证了ZSM-5/MOR共生分子筛合成中3种相变过程的存在及ZSM-5/MOR共生分子筛的生长机理。
Based on the theory of phase transition, the changes of the synthesized ZSM-5 / mordenite (MOR) intergrowth molecular sieve were studied by means of the surface energy of the solution, phase analysis of X-ray diffraction, morphology observation of scanning electron microscopy and energy spectrum analysis Features, crystal growth process. The results show that there are obvious solid-state transitions such as free energy driving force, phase interface, phase relation, habit plane and strain energy during phase transformation between ZSM-5 zeolite and MOR. The synthesis mechanism of the ZSM-5 / MOR intergrowth molecular sieve was established by combining the three liquid-solid, liquid-liquid and solid-liquid phase transition mechanisms: the solid-liquid phase appeared first in the synthesis solution, , ZSM-5 is generated in the rich silicon phase and MOR is formed in the aluminum-rich phase. Because the surface energy of the ZSM-5 zeolite is larger than that of MOR, the system is in a metastable phase. In the late nucleation stage, the ZSM-5 molecular sieve passes through the solid phase Change process, gradually transformed into MOR, to achieve phase equilibrium. The existence of three phase transitions in ZSM-5 / MOR symbiotic molecular sieve synthesis and the growth mechanism of ZSM-5 / MOR symbiotic molecular sieve were verified by experiments.