Impregnation of alumina with copper chloride: evidence for differently immobilized copper species

Abstract

Radial copper concentration profiles from alumina pellets impregnated with aqueous solutions of copper(II) chloride are presented. Temperature programmed reduction and electron spin resonance measurements indicate the presence of at least two differently immobilized species. Copper ions which are reduced at temperatures between 350 and 400°C are assigned to immobilization by strong adsorption. The species which are reduced at lower temperatures (210 – 240°C) are predominantly formed during drying by precipitation from the liquid enclosed in the pore volume. The influence of impregnation time and concentration of the impregnant solution on the distribution of these two species is discussed. A precipitation step subsequent to impregnation leads to changes in the radial profiles and to prevalence of the copper ions reducible at low temperatures.