PROBING ACID SITES IN MAPO-36 BY SOLID-STATE NMR

An ordering of magnesium is observed in the as-synthesized MAPO-36 mol ecular sieve. Upon calcination, part of the magnesium is removed from the sample and part occupies extraframework positions thus rendering a random distribution of magnesium in the lattice. The shoulder observe d in the P-31 spectrum Of the calcined sample is assigned to P(3A1, 1M g) sites in conflict with the earlier assignment to P-OH groups. The b ridging hydroxyl groups located at these sites are detected in the H-1 MAS spectrum at 3.6 ppm. Further, MAPO-36 catalyzed acetone conversio n to mesityloxide that cracked at elevated temperature to yield acetic acid and aliphatics.