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ITQ-2 zeolites were prepared by sequential alkali-swelling and ultrasonic-delamination of precursor MCM-22 and characterized by X-ray powder diffraction,scanning electron microscopy,nitrogen adsorption-desorption,ammonia temperature-programmed desorption and in-situ Fourier-transform infrared spectroscopy.The delamination induced a change in the morphology of ITQ-2 zeolites from aggregated thin platelets to scattered platelets,together with a significant increase in external specific surface area,which reached a plateau at the ultrasonic treatment time of 3 h.The catalytic cracking of n-dodecane over ITQ-2 zeolites was evaluated with ITQ-2 coated on the inside wall of a tubular reactor at 550 ℃ and 4 MPa.The sample obtained by ultrasonic treatment of 3 h(ITQ-2-3) gave the highest initial conversion of n-dodecane.whereas those of 5 h and 1 h gave the conversion even lower than MCM-22,which was in agreement with the trend of the ratio of strong Lewis acid to the total acid amount.Although the amount of cokes deposited on ITQ-2-3 was larger than that on MCM-22,the former deactivated slowly,suggesting that a large external specific surface area benefits the stability of zeolite coatings.
ITQ-2 zeolites were prepared by sequential alkali-swelling and ultrasonic-delamination of precursor MCM-22 and characterized by X-ray powder diffraction, scanning electron microscopy, nitrogen adsorption-desorption, ammonia temperature-programmed desorption and in-situ Fourier-transform infrared spectroscopy. The delamination induced a change in the morphology of ITQ-2 zeolites from aggregated thin platelets to scattered platelets, together with a significant increase in external specific surface area, which reached a plateau at the ultrasonic treatment time of 3 h. cracking of n-dodecane over ITQ-2 zeolites was evaluated with ITQ-2 coated on the inside wall of a tubular reactor at 550 ° C and 4 MPa.The sample was obtained by ultrasonic treatment of 3 h (ITQ-2-3) gave the highest initial conversion of n-dodecane. whereas of 5 h and 1 h gave the conversion even lower than MCM-22, which was in agreement with the trend of the ratio of strong Lewis acid to the total acid amount. Altho ugh the amount of cokes deposited on ITQ-2-3 was larger than that on MCM-22, the former deactivated slowly, suggesting that a large external specific surface area benefits the stability of zeolite coatings.