ACIDIC PROPERTY OF DEALUMINATED MORDENITE TREATED BY HYDROCHLORIC-ACID

Acidic properties of dealuminated Mordenite treated by hydrochoric aci d were characterized by TPD method and isomerization reactions of bute nes. The ratio of aluminum contents and the strong acid amounts in Mor denite is almost 1 : 1 in the ranges of SiO2/Al2O3; 35 similar to 70, and when the ratio of SiO2/Al2O3 deviates from these values, the stron g acid amounts do not correspond to aluminum contents. The ratio of th e weak acid amounts and the strong acid amounts is about 1 : 2. Since heats of adsorption of NH3 are 149+/-2 kJ/mol in all ranges of SiO2/ A l2O3, it is suggested that the strength of the acid is independent of aluminum contents. Desorption products of C3H6-TPD are dependent on Si O2/Al2O3 ratio of Mordenite. In small ratio of SiO2/Al2O3, propene mol ecules are adsorbed directly on the acid sites and desorbed with produ ction of normal hydrocarbons which are produced by interactions betwee n adsorbates. In medium ratio of SiO2/ Al2O3, oligomers are formed on the acid sites and they are desorbed producing branched isomers. In th e isomerization reactions of butenes, the Mordenite having the larger amount of the acid reveals the higher catalytic activity. The catalyti c activity is higher in the isomerization reaction of butenes, as amou nts of the acid of Mordenite are larger, but the acid strength of the catalyst is not influenced by the amounts of the acid.