Characteristics of acidic sites on the surface of nontreated and dealuminated mordenites were investigated by measurements of heats of adsorption of ammonia. Dealumination was carried out by treatments with hydrochloric acid and silicon tetrachloride (SiCl
4). In case of hydrochloric acid treatment, adsorption energy of acidic site was widely distributed probably due to the difference of the environment in the vicinity of acidic sites. The amount of acidic sites of dealuminated mordenite with SiCl
4 decreased, which might result from the pore blockade of the by-product during the treatment. However, the intensity of acidic sites was the same as that of nontreated mordenite.
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