Nitrogen incorporation in AIPO 4-5 molecular sieves by thermal ammonolysis

Abstract

AIPO 4-5 samples were treated with NH 3 or NH 3/CO mixtures at temperatures up to 1173 K. The samples were characterized by powder X-ray diffraction (XRD), infrared (i.r.) spectroscopy, and high-resolution solid-state nuclear magnetic resonance (n.m.r.) spectroscopy ( 27Al, 31P, 1H, and natural abundance 15N). At all temperatures, ammonia was adsorbed by the molecular sieve through the coordination of one or two NH 3 molecules with aluminum to yield five- and six-fold coordinated Al. During ammonium treatment above 1073 K, oxygen bridges were broken, leading to -PNH 2 and -AlOH terminal groups. -AlNHP- bridging groups were not observed.