Dealumination of proton form mordenite with high aluminum content in atmosphere

Abstract

A proton form mordenite with Si/Al 2 = 10 was prepared by heating of an ammonium type sample at 813 K in a nitrogen flow and transferred into an NMR (nuclear magnetic resonance) cell in a dry box filled with a controlled atmosphere, and the framework aluminum content was measured by means of 29Si NMR. It was estimated that almost all the aluminum atoms were located in the framework on the sample treated in helium which was purified by passing a liquid nitrogen trap. On the other hand, a considerable amount of extra-framework aluminum was estimated on the sample treated in commercially supplied nitrogen. After the cap of NMR cell was opened for several seconds in atmosphere, also the extra-framework aluminum was observed. These findings point out the readily dealumination of the proton form mordenite at room temperature. The dealumination resulted in the decrease of acidity and catalytic activity for cracking of octane and cumene [(1-methylethyl)benzene]. On the basis of the experiments using mordenite with Si/Al 2 = 15, the extent of dealumination was considered to decrease with decreasing the aluminum content and increasing the alkaline content.