Effect of basicity and pore size distribution of transition aluminas on their performance in the hydrogen sulphide-sulphur dioxide reaction

Aluminas prepared from different aluminium hydroxides (boehmite, bayerite and gibbsite) and containing controlled amounts of impurities (sodium or sulphate) introduced in different ways (by impregnation or residual ions from the preparation) were characterized with respect to their acidic properties (n-butylamine adsorption at 373 K, gravimetric method), basic properties (sulphur dioxide chemisorption at 373 K, volumetric method) and textural properties (surface area and pore size distribution). Their activity in the hydrogen sulphide plus sulphur dioxide reaction was measured in a tubular flow microreactor at 523 K. The effect of the nature of and mode of introduction of the impurities on the acid-base properties of the aluminas is discussed. It was established that, besides the basicity, the pore size distribution of the alumina strongly influences its catalytic performance, probably due to capillary condensation of sulphur in small pores.