EFFECT OF THE CARBON PRETREATMENT ON THE PROPERTIES AND PERFORMANCE FOR NITROBENZENE HYDROGENATION OF PT C CATALYSTS/

This paper reports a study of the effect of the purification and funct ionalization treatments of a peach pit derived carbon on the propertie s and performance for nitrobenzene hydrogenation reaction of Pt/C cata lysts. Results show that the elimination of inorganic impurities, main ly sulphur, enhances the nitrobenzene hydrogenation rate. Moreover, th e functionalization treatments of purified carbon with ozone and hydro gen peroxide have a positive effect both on the Pt dispersion and on t he hydrogenation capacity of the catalyst, while the HNO3-treatment ha s a lower effect. The effect of the different oxidants can be related to the nature of the functional groups developed on the carbon surface . Thus, HNO3-treated carbon displays a high density of both strong and weak acid sites, while H2O2- and O-3-treated carbons show an importan t concentration of weak acid sites but a low concentration of strong a cid sites, according to the TPD results. Moreover, the H2PtCl6 isother ms in liquid phase at 298 K show a stronger interaction of the metalli c precursor with the carbons of low acidity (like those treated with H 2O2 or O-3) than with the most acidic carbon (treated with HNO3). Carb ons functionalized with weak oxidants, which develop acidic sites with moderate strength and show strong interaction with H2PtCl6 during imp regnation, would favour the Pt dispersion on the carbon surface and co nsequently the catalytic behaviour. (C) 1997 Elsevier Science B.V.