STUDY OF CU(II) LOCATION AND ADSORBATE INTERACTION IN CUH-SAPO-34 MOLECULAR-SIEVE BY ELECTRON-SPIN-RESONANCE AND ELECTRON-SPIN ECHO MODULATION SPECTROSCOPIES

H-SAPO-34 doped with Cu(II) ions is studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) techniques. In the hydrated sample Cu(II) was determined to be octahedrally coordinated to three framework oxygens and three water molecules. The most likely location for this copper ion complex to reside is at a site displaced from the hexagonal window into the ellipsoidal cavity. Upon dehydration at 400-degrees-C two distinct Cu(II) complexes are generated. The ESR parameters for one of the Cu(II) complexes formed on dehydration is suggestive of trigonal symmetry, where the complex is formed in the plane of the six-membered ring or displaced from the six-membered ring. One type of Cu(II) complex is observed with the adsorption of water, ammonia, ethylene, dimethyl sulfoxide, ethanol, and 1-propanol while two different Cu(II) complexes are observed with the adsorption of methanol. From ESEM it is determined that Cu(II) interacts with three equivalent ammonia molecules, one ethylene molecule, and one dimethyl sulfoxide molecule. Through ESEM spectroscopy the Cu(II) cation is determined to interact with three molecules of ethanol, two of which interact at a shorter distance than the third.