Abstract
The samples of ultra-stable high-silica H-STI-I and H-STI-IⅡ 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 SiAl ratios of H-STI-I and H-STI-Ⅱ 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 illuminated 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.V.Ultra-stabilization of Structure
Keywords STI zeolite;ultra-stability;ion-exchange;temperature-programmed calcinations;solid NMR; N₂adsorption;FT-IR
