Synthesis Of Ge-containing Zeolites

ITQ-16 is a new zeolite family formed by polymorphs A,B and C of the beta intergrowth in which the proportion of polymorph C can be controlled by changing the organic structure directing agent and/or by changing the Ge content of the synthesis gel.It can be used as an additive of FCC catalysts,or as a component of de-paraffining and iso-paraffining catalysts.In addition to the factors upon,the systematic study of the influence of other factors on the synthesis of ITQ-16 zeolite has not been reported.In this paper,a self-made high-active silica gel was used as the silicon source.By mixing with the other materials,ITQ-16 zeolite was synthesized through dynamic crystallization.The characteristics of our products were analyzed by means of various characterization methods,which helped to investigate the effects of the factors such as Si/Ge ratio,water content and temperature on the structure type,particle size,and crystallinity of our products.It turns out that the change of Si/Ge ratio,water content as well as the temperature would all affect the proportion of polymorph C in ITQ-16 zeolite,which means by changing those factors,the proportion of polymorph C in the synthetic progress could be further controlled.After that,we further studied the synthesizable range of nano-sized ITQ-16 and ITQ-17 zeolites,and the pore structure and particle size of nano-sized ITQ-16 were measured.Synthesis of high crystallinity nano zeolites is one of the difficulties in the synthesis of molecular sieves.High crystallinity ITQ-16 and ITQ-17 zeolites were synthesized by using fluorion as mineralizer,rich-hydroxyl silica gel as silicon source in the presence of low crystallization temperature and low water content,then the boundary of synthesis condition was further explored.The introduction of germanium can improve the proportion of polymorph C in the product,which is beneficial to the synthesis of nano zeolites.The average particle sizes of nano-sized ITQ-16 zeolites are between 50-60 nm,the specific surface areas are between 489?563 m~2/g,the micropore volumes are between 0·16?0.220 cm~3/g,the micropore specific surface areas are about 512 m~2/g.