Abstract: In order to study the thermal stability of X zeolite, X zeolite was synthesized by using hydrothermal crystallization method, and then was calcined at 500, 600, 700, 800 and 900 ℃ in nitrogen atmosphere. X zeolite and its calcination products were thoroughly characterized by X-ray diffraction, N₂ adsorption-desorption, scanning electron microscope, thermogravimetry, differential scanning calorimetry, magic angle spinning solid nuclear magnetic resonance and Fourier transform infrared spectroscopy. The results showed that when the calcination temperature was lower than 800 °C, the crystalline structure and micropores of X zeolite were not destroyed, the calcination products still maintained the same octahedral morphology as the original X zeolite, the Si-O-Al connection in the crystalline structure was stable, and no non-framework aluminum species were formed. When the calcination temperature reached 900 °C, the crystalline structure of X zeolite was completely destroyed after melting, leading to the formation of the amorphous species with smooth edge and the micropore volume of 0. There were still a lot of Si-O-Al and Si-O-Si connections, and no obvious independent amorphous aluminum species was observed in the calcination products.

Key words: zeolite, FAU topological structure, thermal stability