Factors controlling the retention of chlorine in platinum reforming catalysts

Abstract

The influence of various preparative and operational parameters on the uptake and retention of chlorine in Pt-alumina and Pt-Sn-alumina is reported. Catalysts based on eta-alumina adsorb and retain more Cl⁻ than those based on the gamma form. It is shown that Cl⁻ ion-exchanges for OH on the alumina surface. During the simultaneous adsorption of HCL and H₂PtCl₆, while Cl⁻ions do not affect the uptake of Pt significantly on eta-alumina, there is a decrease in the case of gamma-alumina as the concentration of Cl⁻ increases. Apart from the type of alumina used (eta- or gamma-) the temperature of calcination/reduction and the water content of the air/H₂ used are found to be the two major factors which control the retention of chlorine during the activation of these catalysts. The nature of chlorine held on alumina is discussed.