Synthesis and characterization of new CoAPSO-40 and ZnAPSO-40 molecular sieves. Influence of the composition on the thermal and hydrothermal stability of AlPO4-40-based materials

Highly crystalline CoAPSO-40 and ZnAPSO-40 have been synthesized and charac terized by powder XRD, TG/DSC, SEM, EDX, Al-27, P-31 and Si-29 solid-state NMR, diffuse reflectance. UV-VIS spectroscopy, FT IR and catalytic tests us ing the m-xylene isomerization and n-heptane cracking as model reactions. T he simultaneous incorporation of silicon and a divalent metal in the framew ork of the AFR structure results in the generation of Bronsted acid sites s imilar to those found in SAPO-40 and MeAPO-40. The catalytic activity of th e samples for acid catalyzed reactions is higher than that of SAPO-40 with a homogeneous framework silicon distribution. The framework incorporation o f cobalt or zinc results in a decrease of the thermal and hydrothermal stab ility of the metal bearing AFR framework, when compared with AlPO4-40 and S APO-40. (C) 2000 Elsevier Science B.V. All rights reserved.