Quantitative determination of Bronsted acid site concentrations in calcined H-mordenite and H-ZSM-5 by means of conductometric titration and infrared spectroscopy reveals that the concentration of Bronsted acid sites present is lower than would be expected on the basis of the aluminum content. This discrepancy is attributed to dealumination and dehydroxylation processes occurring during calcination. A model is proposed according to which the degree of these processes strongly depends on the concentration of vicinal aluminum T sites in the zeolite: Bronsted acid sites associated with these T sites are lost, and the remaining Bronsted acidity is related to the concentration of the (remaining) isolated aluminum T sites. This model quantitatively correlates the experimentally determined concentration of Bronsted acid sites with the concentration of isolated aluminum T sites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.