CUPRIC ION LOCATION AND ADSORBATE INTERACTIONS IN CUPRIC ION-EXCHANGED H-SAPO-5 MOLECULAR-SIEVE AS DETERMINED BY ELECTRON-SPIN-RESONANCE AND ELECTRON-SPIN ECHO MODULATION SPECTROSCOPIES

Locations of Cu2+ ions exchanged into H-SAPO-5 and interactions of Cu2+ ions with water, ammonia, and methanol have been investigated by electron spin resonance and electron spin echo modulation techniques. It has been determined that Cu2+ ions locate at a position inside a 12-ring channel, close to the center of a 6-ring window in hydrated, ammonia-adsorbed, and methanol-adsorbed CuH-SAPO-5 samples. The Cu2+ ion directly coordinates to three framework oxygens in all systems studied; it also directly coordinates to three water molecules in the hydrated sample and to three ammonia molecules in the ammonia-adsorbed sample. In methanol-adsorbed samples, the Cu2+ ion directly coordinates to two methanol molecules and indirectly coordinates to one methanol molecule at a greater distance. The more bulky size of methanol molecules compared to water and ammonia is likely the cause of fewer methanol molecules directly coordinated to Cu2+.