Effect of the sequence of impregnation on the activity and sulfur resistance of Pt-Ni/g-Al2O3 bimetallic catalysts for the selective hydrogenation of styrene

CAROLINA P. BETTI; JUAN BADANO; M. JULIANA MACCARRONE; VANINA A. MAZZIERI; CARLOS R. VERA; MÓNICA E. QUIROGA

APPLIED CATALYSIS A-GENERAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 435 p. 181 - 186

0926-860X

The influence of the preparation on the activity and sulfur resistance of bimetallic Pt-Ni catalysts for  styrene semi-hydrogenation was studied. Preparation variables assessed were the sequence of impregnation and the kind of nickel precursor used. The catalysts were tested in reaction and further characterized by the techniques of ICP, TPR, XPS and pyridine TPD. All catalysts showed high selectivities to ethylbenzene (> 98%). Bimetallic catalysts were more active than the monometallic one and the following activity order was found: Pt < NiClPt < NiNPt < PtNiCl < PtNiN. After poisoning with 300 ppm of thiophene the following order of sulfur resistance was found: PtNiCl < Pt < PtNiN < NiClPt < NiNPt. Differences in activities and sulfur resistance between the catalysts were atributed to electronic effects related to the presence of different electron-rich and electron-deficient surface species of Pt and Ni on the surface that interact between themselves and with the support. The bimetallic catalyst with the highest Cl/Pt atomic ratio on the surface (as obtained by XPS) proved to be the most sulfur resistant; this higher poison resistance was rationalized in terms of both steric and electronic effects.