Hydrolysis of crystalline aluminosilicate catalysts. 27AI NMR of hydrated zeolite 13-x

Abstract

NMR relaxation times, linewidths, and intensities for 27Al in Na X zeolite materials are compared for a hydrolyzed specimen and a specimen carefully protected against hydrolysis. The only parameter differing between the two materials is the relative intensity; only 75% of the aluminum nuclei in the hydrolyzed material are thus accounted for. In conjunction with older similar NMR data for protons and 23Na in these materials it is concluded that the “hydrolysis complex” is actually in the form Al(OH) a. The diffusion coefficient for this entity is estimated as D = 10 -8 exp( −3.08 RT ) cm 2sec -1 where R is in units kcal mol −1 deg −1. After completion of the paper D. H. Olson compared the hydrolyzed and normal zeolite specimens by electron probe microanalysis (specimens identical in Si/Al ratio), lattice parameter (hydrolyzed specimen 0.04 Å larger), atomic absorption spectroscopy (sodium concentrations not significantly different), and surface acidity (protons of the complex not acidic). As the amounts available for analysis were small (ca. 0.3 g), the replications necessary for good statistics in the sodium analysis could not be carried out. The result of the sodium analysis, while not confirming the model put forth in this paper (wherein sodium should be lost from the zeolite) is not taken as a completely trustworthy result because of this lack of replication. The NMR relative intensity measurements, nondestructive in character, were easily replicated in contrast.