31-P NMR-STUDY OF ACIDIC SITES ON AL2O3 AND AL2O3-SNO2 AFTER REACTIONWITH CCL2F2 H-2/

The surface acidic properties of two series of samples, gamma-Al2O3 an d gamma-Al2O3-SnO2 after reaction with CCl2F2/H-2 (CFC12/H-2), have be en investigated by solid state high resolution CP/MAS 31-PNMR, using t rimethylphosphine (TMP) as a probe molecule. It was found after reacti on, that Bronsted acid sites were formed on the gamma-Al2O3 surface. T he longer the reaction time, the more rigidly TMP bonded to the acid s ites. For the gamma-Al2O3-SnO2 system, Bronsted acid sites were also f ound on both the Al2O3 and SnO2 surfaces after reaction of the gamma-A l2O3-SnO2 system with CFC12/H-2. The signal intensity relevant to thes e sites, indicates that the SnO2 component is attached to, and therefo re covers Bronsted sites of gamma-Al2O3. Two types of Lewis acid site initially present on SnO2 were not observed after reaction with CFC12/ H-2.