Catalytically active phosphorus-containing zeolites/molecular sieves, particularly ultrastable zeolite Y, are prepared by reacting an exchanged zeolite/molecular sieve with a phosphorus compound such as H.sub.3 PO.sub.4, steaming, and reacting the steamed product with additional phosphorus compound....http://www.google.es/patents/US5378670?utm_source=gb-gplus-sharePatente US5378670 - Phosphorus zeolites/molecular sieves
