无模板两步法合成亚微米A型沸石

Synthesis of Submicron Zeolite A Without Organic Template

不添加有机模板剂,采用较廉价的硅酸钠和铝酸钠分别作为硅源和铝源,经由两步法合成粒度分布均匀且晶型较好的亚微米A型沸石。研究了经不同陈化时间后硅铝凝胶结构发生的变化及经过晶化后产物的粒径变化。结果表明:陈化时间为0~85h时,主要表现为诱导成核,在这段时期硅铝凝胶中对A型沸石成核过程有重要影响的四元环、双四元环数量显著增加,而陈化时间为85~139h主要表现为晶核的生长;随着陈化时间的延长硅铝凝胶中SiO2/Al2O3逐渐减小,且尺寸也逐渐变小;在0~85h区间,合成最终产物的平均粒径随着陈化时间延长而减小,在85h时最小,可达500nm左右;继续延长陈化时间至139h将导致小颗粒A型沸石发生团聚,且形貌也变的不规整。

Submicron zeolite A was synthesized by a two-step method with organic template-free aluminosilicate gel system.The aluminosilicate gel was prepared with Na2SiO3·9H2O and NaAlO2 as silica and alumina source,respectively.The solid phase of aluminosilicate gel in the aging stage and the crystal size of the final products after crystallization at 100℃for 4h were investigated.The results indicate that in the nucleation period,the number of intermediate species of four-ring(4R)and double four-ring(D4R)increases when the aging time is 0--85 h.The nucleus grow when the aging time increases from85 hto 139h.The SiO2/Al2O3 ratio and the crystal size of the solid phase of aluminosilicate gel decrease with increasing the aging time.The crystal size of final products decreases with the increase of aging time,and it becomes the minimum size of ca.500 nm when the aging time is 85 h.The products become the aggregates of small particles with the irregular morphology when the aging time is 139 h.