Infrared, Microcalorimetric, and Electron Spin Resonance Investigations of the Acidic Properties of the H-ZSM-5 Zeolite

摘要: The infrared spectra of the H-ZSM-5 zeolite calcined at temperatures up to 1173 K, and corresponding electron spin resonance microcalorimetric data are discussed. Two types hydroxyl groups characterized by absorption bands 3720 3605 cm −1 , a small shoulder being present 3665 . Infrared were also recorded after pyridine adsorption, showing presence Bronsted acid sites Lewis sites. After calcination increasing temperatures, dehydroxylation is observed: above 675 number decreases, while that strong increases; however, dealumination occurs as shown chemical analysis measurements XPS data. Moreover, enhances constraint character this zeolite, observed inability titrate total Electron studies trapped hydrogen atoms, adsorbed NO, benzene radical cations formed on various discussed in terms strength It suggested which very similar those H-mordenite although slightly stronger. A study ammonia adsorption confirms acidic shows their dependence heterogeneity upon temperature.