IR and 1H NMR studies on the adsorption of gaseous hydrogen chloride on γ-alumina

Abstract

The reaction of HCl at 100–600 °C with γ-alumina preheated at 200–600 °C has been studied at various reaction times by a combination of FTIR and ¹H MAS NMR. The two primary reactions considered were the exchange reaction with hydroxy groups and the dissociation reaction of HCl. The evolution of water in the exchange reaction and subsequent rehydration were taken into account. The results showed that the exchange reaction occurred under all conditions, with the basic OH groups being more reactive. The dissociation reaction increased in importance at lower reaction temperatures, as did the secondary reaction of evolved water. It is suggested that the exchange reaction occurred with isolated OH groups rather than with associated ones. The new OH groups formed from the dissociation of water appeared to be acidic in nature.