Zeolite tetramethylammonium-exchanged

Wu et al. (5) recently interpreted the thermal decomposition mechanism of tetramethylammonium-exchanged Y zeolite. The order of occurrence of the gaseous decay products is (mole %) (CH N (50), CH4 (11), (CH3)20 (10), CO (9), CH3OH (6), H2 (4), C4H8 (4), C2H4 (trace), for the decomposition carried out at 275°C under vacuum. At this temperature, a displacement reaction of water nucleophile on the tetramethyl cation, forming methanol and trimethylamine, is proposed ... 

Ion Exchange and Pyrolysis. A typical specimen of zeolite 0 contains approximately eight cations per unit cell, of which about six are sodium ions, and the remaining two are tetramethylammonium ions. The positions of these ions within the zeolitic framework can be determined by x-ray structural studies or by ion-exchange experiments if the structure of the framework is known. 

Materials. The methylammonium Y-zeolites (Table I) were prepared by ion-exchanging NaY (5 grams) with 4 100-ml portions of 1 N alkylammonium salt solution at 80 °C. Monomethylammonium (MMA) chloride, dimethylammonium (DMA) chloride, and tetramethylammonium (TTMA) bromide (Matheson, Coleman, and Bell) and the trimethyl-ammonium (TMA) chloride (Eastman Organic Chemicals) were used as received. 

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