Characterized with X-ray fluorescence scattering spectroscopy (XRF), ²⁷Al MAS NMR and FT-IR techniques, the non-framework aluminum in the raw material of the ultra-stable high-silica stilbite (STI) zeolite has been proved to become decreased, and the zeolite framework Si/Al ratio to reach 6.8 and 11.4 after treatment by HCl or by ammonium hexafluorosilicate solution, respectively. N₂ adsorptions indicate that the modified high-silica STI zeolites treated with HCl solution possessed open and perfect channels, and the pores of the zeolite samples treated with ammonium hexafluorosilicate soulution were partially blocked. Investigations on the samples obtained in the process of stage-temperature-programmed calcination with XRD proved that the structural stability of the former sample was weaker than that of the latter, which was collapsed under calcination at 1000 ℃. In comparison, the latter sample with better structural stability remained stable when calcined at the same temperatures, to possess high crystallinity, showing the ultra-stabilization of its framework.

Key words: high-silica stilbite zeolite, ultra-stabilization, stage-temperature-programmed calcination, solid NMR, N₂ adsorption, FT-IR spectrum, modification with dealumination