Study of copper(2+)-doped zeolites Na-rho, K-rho, and Ca-rho by electron spin resonance and electron spin echo modulation spectroscopies

Abstract

The location and adsorbate interaction of Cu/sup 2 +/ in Na-, K-, and Ca-rho zeolites doped with Cu/sup 2 +/ has been studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies. It is found that the activation process varies very little with the type of countercation and the major hydrated species in zeolite rho is a square-coplanar or square-pyramidal Cu/sup 2 +/ bound to two water molecules. Adsorption of polar molecules, such as ammonia, methanol, and ethanol, results in complexing with the Cu/sub 2//sup +/ although in the case of methanol the number of ligands is less for Na-, K-, and Ca-rho than for H-rho studied previously. Nonpolar molecules, such as ethylene, are essentially excluded from the zeolite by the Na, K, and Ca cations which are located in the octagonal prisms blocking entrance to the zeolite interior.