Flame-made Pt/TiO2 catalysts for the liquid-phase selective hydrogenation of 3-nitrostyrene

The liquid-phase selective hydrogenation of 3-nitrostyrene (NS) was investigated over nanocrystalline Pt/TiO2 catalysts synthesized by the single-step flame spray pyrolysis (FSP) method. The obtained powder was characterized by N-2 physisorption, X-ray diffraction (XRD), CO pulse chemisorption, transmission electron spectroscopy (TEM), temperature-programmed reduction (TPR), and infrared spectroscopy of adsorbed CO (CO-IR). High dispersion of small Pt particles (d(p) 1.2 nm) on high anatase/rutile TiO2 was obtained by the FSP method. The catalyst performances of the FSP-made catalysts (F-Pt/Ti) in terms of both hydrogenation activity and selectivity to vinylaniline (VA) improved from 61 to 66% and from 40 to 73% by reduction at high temperature. Compared to F-Pt/Ti, Pt/TiO2 obtained by conventional impregnation (I-Pt/Ti) on a sal-gel TiO2 contained higher amount of rutile phase composition and exhibited much lower Pt dispersion and hydrogenation activity (5% after reduction at 200 degrees C and 50% at 500 degrees C). The TOFs for NS hydrogenation were calculated to be 22-113 s(-1). Complete transformation of anatase TiO2 to rutile occurred after reduction at 600 and 700 degrees C for the I-Pt/Ti and F-Pt/Ti, respectively, leading to excessive decoration of Pt by the reducible TiOx species and poor catalytic performances. (C) 2014 Elsevier B.V. All rights reserved.