凹凸棒石黏土合成NaY及ZSM-5/NaY复合沸石的研究

Synthesis of NaY and ZSM-5/NaY Composite Zeolites from Palygorskite

以凹凸棒石黏土为原料,在水热条件下原位晶化制备了NaY沸石,随后利用二次晶化法制备ZSM-5/NaY复合沸石。结果表明,导向剂是合成NaY沸石的关键,在导向剂作用下,仅以凹凸棒石黏土为原料即可合成NaY沸石,铝源NaAlO2的加入可以有效提高沸石的结晶度。随后在ZSM-5沸石合成体系中,添加的NaY沸石溶解为第一阶段形成的ZSM-5沸石提供营养,最后形成ZSM-5/NaY复合沸石,该复合沸石的性质不同于机械混合物的性质,形成了新的酸中心,其酸中心主要为中等程度的酸中心。

NaY zeolites were synthesized from palygorskite via in situ hydrothermal method.ZSM-5/NaY composite zeolites were subsequently prepared from palygorskite using a secondary crystallization method.The results indicated that the guiding agent was the key factor controlling the synthesis of NaY zeolites.NaY zeolites could prepared from palygorskite without adding NaAlO2 at the presence of the guiding agent and the intensity of NaY zeolites increased with NaAlO2.The added NaY zeolites were dissolved and provided the nutriment needed in the growth process of ZSM-5 zeolite crystals obtained the first crystallization stage under the ZSM-5 zeolite synthesis system and then ZSM-5/NaY composite zeolites were synthesized.The properties of the composite zeolites were different with that of the mechanical mixture of ZSM-5 zeolites and NaY zeolites.New acid sites mainly attributed to medium acid sites were formed in the composite zeolites.