Hydrothermal Alumination of Zeolites

摘要: Magic-angle-spinning (MAS) NMR, quadrupole nutation infrared spectroscopy and X-ray diffraction measurements all indicate that aluminium atoms eliminated from the framework of zeolite Y by hydrothermal treatment (ultrastabilization) can be subsequently reinserted into with aqueous solutions strong bases (preferably KOH) at elevated temperatures. The extent efficiency reaction depend on temperature, duration especially kind concentration solution. degree crystallinity thermal stability products are primarily controlled composition parent material, while realumination is determined number available tetrahedral Si(0Al) sites. have a very different Si,Al distribution as-prepared same Al content. realumination-dealumination process performed in cyclic fashion yielding wide variety second-generation catalysts. 27 NMR reveals presence four kinds dealuminated Y: (F), non-framework (NFT), distorted (DFT) octahedral (NFO). DFT bonded to hydroxyl groups formed during dealumination. In realuminated samples both NFO NFT intensity signal correspondingly reduced. 1 H MAS confirms has taken place. sample contains twice as many Bronsted acid sites than ultrastable precursor and, an accuracy 20%, zeolite. However, not associated product accessible pyridine sample.