Abstract
The samples of ulra-stable high-silica H-STI-I and H-STI-Ⅱ zeolites were prepared using the method of ion-exchange combined with controlled calcinations.Characterizations with EDX,29si MAS NMR,27Al MAS NMR and FT-IR indicate that the framework Si/Al ratios of H-STI-I and H-STI-IⅡ are 4.43 and 10.62,respectively.Investigations of the samples obtained in the processs of stage-temperature-pro- grammed calcinations with XRD proved that the structure stability of both samples could be kept at tem-
perature up to 1000 ℃.Type I isotherms of N₂adsorption at 77 K illminated that the ultra-stable H-STI
samples possessed perfect channel systems with opening micro-pore structures.The more structural defects
in the framework of H-STI-II,which has been treated with acid in the process of preparation,led to worse thermal stability,lower surface area and pore volume than those of H-STI-I.
