CHARACTERISTICS AND CATALYTIC PROPERTIES OF Pt CATALYSTS SUPPORTED ON Zn AND La-MODIFIED TiO2 IN SELECTIVE HYDROGENATION OF 3-NITROSTYRENE

Abstract

The effect of Zn and La modified TiO2 on the catalytic performances of Pt/TiO2 was studied in the liquid-phase selective hydrogenation of 3-nitrostyrene (NS). Titanium dioxide (TiO2) was prepared by the solvothermal method at 320 °C with and without Zn and La modification and used as a support for preparation of TiO2 supported Pt catalysts. The catalysts were reduced at low (200 °C) and high (500°C) reduction temperatures before the reaction tests. The hydrogenation of NS was carried out batchwise at H2 pressure 2 MPa and 40 °C. The catalysts were characterized by N2-physisorption, X-ray diffraction (XRD), H2-temperature program reduction (H2-TPR), CO chemisorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and FT-IR analysis of adsorbed CO (CO-IR). The use of Zn-modified TiO2 provided higher NS conversion (64%) compared to the unmodified one (44%) at high reduction temperature. According to the N2-physisorption and CO chemisorption results, the Pt/Zn-modified TiO2 had greater BET surface areas compared to the Pt/TiO2 and higher amount of Pt active sites (higher Pt dispersion). The Zn-modified TiO2 supported Pt catalysts also exhibited high VA selectivity. In contrast, the Pt/La-modified TiO2 provided the lower vinylaniline yield compared to the unmodified catalysts because of lower amount of active sites as determined by the CO-chemisorption results.