INFRARED STUDY OF SURFACE ACIDITY OF GERMANIC NEAR-FAUJASITE ZEOLITE BY PYRIDINE ADSORPTION

The acidic properties of germanic near-faujasite zeolite have been investigated by pyridine adsorption measurements on the sodium, calcium, and partially protonated forms. As for the silicic X and Y analogs, no acidity could be detected on Na-GeX. In contrast to the silicic sieves, a 73% calcium-exchanged sample did not show the ir band at 1540 cm-1 characteristic of pyridine in interaction with Brønsted acid sites. The fact that residual water molecules are not dissociated to a measurable degree on the germanic sieve has been attributed to the Al content of this sieve, which is higher than in the X and Y homologs. Both Brønsted and Lewis acid centers were found on partially protonated germanic faujasite, but the weak interaction of pyridine with those sites indicates an acid strength lower than in the silicic homologs. The weak overall acidity of the germanic sieve is consistent with the lower activities and higher selectivities when this solid is used as a catalyst in the isomerization reaction of the n-butenes. © 1978.