不同形貌高炉渣基沸石的合成及反应机理的探讨

Synthesis and reaction mechanism of zeolite based on blast furnace slag with different morphology

高炉渣是高炉炼铁过程中的副产品,是一种复杂的硅酸盐,高炉渣酸浸后的滤渣是硅凝胶,可以作为硅源,从而合成沸石。以高炉渣为前驱体,采用碱熔融-水热法合成不同形貌沸石,通过X射线衍射分析、扫描电子显微镜等表征手段探讨了最佳合成条件及反应机理。结果表明,体系中硅铝比为影响沸石结构种类的关键因素,n(Si)/n(Al)=0.4~1.2范围内,能够合成A型沸石;n(Si)/n(Al)=1.6~2.0范围内,能够合成八面沸石;n(Si)/n(Al)=1.4处为A型与八面沸石共存体系;八面沸石的形成需经过溶解-成核-结晶等几个过程,属于双相转化反应机理;合理控制晶化温度可将八面沸石转变为P型沸石。

Blast furnace slag is a by-product of blast furnace ironmaking and a kind of complex silicate. After soaked in acid, blast furnace slag becomes silica gel, which can be used as silicon source to synthesize zeolite. In this paper, zeolite with different morphology was synthesized by alkali melting hydrothermal method with blast furnace slag as precursor. The optimum synthetic conditions and reaction mechanism of zeolites were investigated by means of X-ray diffraction and scanning electron microscopy. The results show that the ratio of Si to Al in the system was the key factor affecting the structure of zeolites. Zeolite A could be synthesized in the range of n(Si)/n(Al) of 0.4-1.2. Faujasite could be synthesized in the range of n(Si)/n(Al)=1.6-2.0. The coexisting system of zeolite A and faujasite could be synthesized in the range of n(Si)/n(Al)=1.4. The formation of faujasite need several processes, such as solid phase dissolution, nucleation in gel, nucleation growth, secondary crystallization and crystallization completion. The transition from faujasite to zeolite P could be realized by reasonably controlling the crystallization temperature of the reaction system.