PECULIARITIES OBSERVED IN H-D EXCHANGE BETWEEN PERDEUTERIOISOBUTANE AND H-ZEOLITES

H-D exchange between perdeuterioisobutane and NaH-Y-zeolites and H-mor denite (H-M) was studied using the pulse technique. Nine of the ten D atoms in the isobutane molecule were exchanged for H on the most acidi c Y-zeolites at the lowest temperature (200 degrees C) where H-D excha nge was observed, while other transformations of isobutane were not. T he reaction is thought to be initiated by protonation of the tertiary C-D bond on the Bronsted acid sites of the catalyst and the exchange t o proceed via the t-butyl carbenium ion intermediate. Release of the i on from the surface occurs via hydride transfer conserving the identit y of the tertiary position. At higher temperatures and over the more a cidic H-mordenite at even lower temperature (125 degrees C) an extensi ve intermolecular H-D exchange occurs between perdeuterioisobutane and its exchanged products. A more detailed understanding of this reactio n chemistry is developed herein. (C) 1995 Academic Press, Inc.