CXN天然沸石的研究VII. 骨架高硅超稳化改性

以高硅超稳化辉沸石(STI)为基底沸石, 分别经盐酸脱铝或氟硅酸铵脱铝补硅处理后制备的改性H-STI沸石, 其非骨架铝含量明显减少, 而后者骨架硅铝比进一步提高. X射线荧光散射光谱(XRF), ²⁷Al高分辨率魔角旋转固体核磁共振(MAS NMR), 红外(FT-IR)光谱等表征证明改性后的沸石骨架硅铝原子比分别为6.8和11.4. 低温氮吸附表明, 经盐酸处理的高硅STI沸石孔道开放完美, 但经氟硅酸铵处理的样品孔道被部分堵塞. 分段程序升温焙烧表明前者骨架热稳定性略差, 1000 ℃焙烧后结构基本被破坏, 而后者热稳定性较好, 经相同温度段焙烧后仍保持较高的结晶度和热稳定性, 其结构基本实现超稳化.

Studies on CXN Natural ZeoliteVII. High-silica and Ultra-stable Modification of Framework

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.