Influence of chlorine on the activity and stability of Pt/Al2O3 catalysts in the complete oxidation of toluene

In this paper we discuss the effect of chlorine, added either as a part of the platinum precursor salt or after the noble metal impregnation, on the c atalytic activity of Pt/Al2O3 for complete oxidation of toluene. Three diff erent chlorinated and nonchlorinated platinum precursor salts have been use d for the preparation of the catalysts. Characterisation of the catalysts h as been carried out by N-2 adsorption, NH3 TPD, TPR, HREM, and CO adsorptio n under oxidising conditions followed by DRIFTS. The catalytic activity has been studied by toluene ignition curves and additional stability tests hav e been carried out under isothermal conditions. The inhibitory effect of ch lorine has been proved and assigned to the formation of oxychlorided platin um species. A model of chlorine mobility, responsible for the observed stab ility trends, is also proposed. (C) 2001 Academic Press.