Chemical Vapor Deposition of Trimethylaluminum on Dealuminated Faujasite Zeolite

Chemical vapor deposition of trimethylaluminum (TMA) was explored as an approach for the preparation of model faujasite-type catalysts containing extraframework aluminum. The decomposition of the grafted organoaluminum species was investigated in hydrogen and oxygen atmosphere. The process of grafting Al-containing species and the associated changes of the zeolite hydroxyl groups were followed by in situ FTIR spectroscopy. The state of intrazeolite Al atoms, the changes in zeolite structure and acidity caused by the CVD procedure as well as by subsequent treatment were analyzed in detail by 1H, 29Si, and 27Al MAS NMR, COads IR, H/D exchange of acidic hydroxyl groups with perdeuterobenzene, and propane cracking. Reaction of an extraframework aluminum-free high-silica faujasite zeolite with TMA leads to nearly complete substitution of the bridging hydroxyl groups with Al species. The reaction, however, does not produce uniform homogeneously distributed species. Because of the high reactivity of TMA, the zeo...