INTERACTION OF ACETYLACETONE WITH HZSM-5 - VISUALIZATION OF NMR INVISIBLE ALUMINUM

Al-27 MAS n.m.r. spectroscopy, C-13 MAS n.m.r. spectroscopy, in situ infrared spectroscopy, and thermogravimetric analysis were employed to study acetylacetone adsorbed on HZSM-5 samples of varying acid-site concentration and extralattice aluminum content. Three types of adsorbed acetylacetone were observed: (1) physisorbed acetylacetone, (2) acetylacetone interacting strongly via the carbonyl groups with acid sites within the zeolite structure, and (3) acetylacetone weakly adsorbed on extralattice aluminum and giving rise to a sharp octahedral aluminum signal observed in the Al-27 MAS n.m.r. spectra. The extralattice aluminum acetylacetone species decomposes slowly under ambient laboratory conditions. The implications of these observations to the use of acetylacetone as a means of visualizing ''n.m.r. invisible'' aluminum are discussed.