Source of Activity in Silica-Alumina

Tsumya, T. Sato, and Y. Yoneda, Bull. Chem. Soc. Japan, 1972, 45, 3409. 

Liang used n.m.r. to characterize amines adsorbed on hydrated silica-alumina they found evidence for protonated species on sites which were not sterically hindered. Further work on the thermal desorption of pyridine and n-butylamine from silica-aluminas (13 and 25 wt % AI2O3) showed that the stronger acid sites, where pyridine was adsorbed, were of varied acid strength, and both number and strength of the sites were affected by alkali poisoning. An i.r. study of pyridine adsorbed on sodium-poisoned silica-alumina also showed both Lewis and Bronsted sites to be affected. 

Schwarz, Russell, and Harnsberger have developed a technique combining transmission infrared spectroscopy and temperature-programmed desorption and used it to study the interaction of pyridine with three silica-aluminas. On the 10 wt % AI2O3, acid sites were calculated to be 0.27 [xmole m (84% Lewis acid sites under experimental conditions). The activation energies for 

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