ISOLATION AND CHARACTERIZATION OF A NOVEL LAMELLAR-TYPE ALUMINOPHOSPHATE, ALPO4-L, A COMMON PRECURSOR FOR ALPO4 MOLECULAR-SIEVES

Several aluminophosphate molecular sieves (AlPO4-5, AlPO4-22,;AlPO4-16 and SAPO-35) are formed via a common lamellar aluminophosphate materi al (AlPO4-L) during hydrothermal synthesis from a gel containing Al2O3 , P2O5, SiO2 and hexamethyleneimine (HEM) in aqueous (H2O), or non-aqu eous (ethyleneglycol, EG) media. Depending on the concentration of the template HEM, AlPO4-L transforms into AlPO4-5, AlPO4-16 and AlPO4-22, while SAPO-L transforms into SAPO-35. AlPO4-L was isolated in a pure form from H2O as well as EG media and characterized by PXRD, SEM, TG/D TA, TG/MS and FTIR spectroscopic techniques. It is a lamellar aluminop hosphate, intercalating HEM and H2O, and is thermally stable up to 250 degrees C. AlPO4-L is believed to form by the rearrangement of macroa nionic [3HEMH](3+) Al3P4O163- sheets formed in the reaction medium. (C ) 1998 Elsevier Science B.V. All rights reserved.