Multimetal-substituted aluminophosphate molecular sieves

Highly crystalline, microporous multimetal-substituted ATS aluminophosphate molecular sieves were hydrothermally synthesized. The types of incorporated multimetals are MgSi, MgCo, MgV, MgCoSi, MgCoMn, CoMnZn, MgCoMnZn, CoMnZnV, MgVCoMnZn. The materials were characterized by elemental analysis, XRD, SEM, XPS, BET, FTIR, DRS and solid state Al-27 and P-31 MAS NMR. The characterization of the materials revealed the crystalline nature and the phase purity. XPS analysis of the multimetal samples infers that the surface and bulk composition are different and all the examined samples show a significant Al segregation at the solid surface. In situ FTIR techniques were employed to identify the types of hydroxyl groups present on the materials. Acid strengths of these molecular sieves were investigated by temperature programmed desorption of pyridine from 323 to 673 K using a gas chromatographic technique. The acidity results showed that the acid strength varies for the molecular sieves and is mostly dependent on the type of metal(s) substituted in the aluminophosphate framework. The catalytic performance of these materials were studied in n-aliphatic and aromatic hydrocarbon conversion reactions. Most of the multimetal-incorporated AlPO molecular sieves exhibit high catalytic properties. The physio-chemical properties of the multimetal-incorporated materials were compared with the unimetal-incorporated AlPO molecular sieves. (C) 1998 Elsevier Science B.V. All rights reserved.