Effect of the carbon pre-treatment on the properties and performance for nitrobenzene hydrogenation of Pt/C catalysts

G.C. TORRES; E.L. JABLONSKI; G.T. BARONETTI; A.A. CASTRO; S.R. DE MIGUEL; O.A. SCELZA; M.D. BLANCO; M.A. PEÑA JIMENEZ; J.L.G. FIERRO

APPLIED CATALYSIS A-GENERAL

Elsevier

Lugar: Amsterdam; Año: 1997 vol. 161 p. 213 - 226

0926-860X

This paper reports a study of the effect of the purification and functionalization treatments of a peach pit derived carbon on the properties and performance for nitrobenzene hydrogenation reaction of Pt/C catalysts. Results show that the elimination of inorganic impurities, mainly sulphur, enhances the nitrobenzene hydrogenation rate. Moreover, the functionalization treatments of purified carbon with ozone and hydrogen peroxide have a positive effect both on the Pt dispersion and on the hydrogenation capacity of the catalyst, while the HNO3-treatment has 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 H202- and O3-treated carbons show an important concentration of weak acid sites but a low concentration of strong acid sites, according to the TPD results. Moreover, the H2PtCI6 isotherms in liquid phase at 298 K show a stronger interaction of the metallic precursor with the carbons of low acidity (like those treated with H202 or 03) than with the most acidic carbon (treated with HNO3). Carbons functionalized with weak oxidants, which develop acidic sites with moderate strength and show strong interaction with H2PtC16 during impregnation, would favour the PI dispersion on the carbon surface and consequently the catalytic behaviour.