Low temperature hydrogenation of benzene and cyclohexene: A comparative study between γ-Al2O3 supported PtCo and PtNi bimetallic catalysts

Supported PtCo and PtNi bimetallic and Co, Ni, Pt monometallic catalysts were prepared by impregnation method on gamma-Al2O3 and evaluated for the hydrogenation of benzene and cyclohexene at low temperatures (273-343 K) and atmospheric pressure. Results from batch reactor studies with Fourier transform infrared spectroscopy (FTIR) and flow reactor studies both showed that PtCo bimetallic catalysts exhibited significantly higher activity than PtNi and monometallic Co, Ni, and Pt catalysts for benzene hydrogenation, while PtNi catalysts showed higher activity for cyclohexene hydrogenation. Results from H-2 chemisorption and H-2-temperature-programmed reduction (H-2-TPR) studies showed that a small amount of Pt addition could increase the chemisorption capacity and make the reduction of Co or Ni much easier, especially for Co-based catalysts. Extended X-ray absorption fine structure (EXAFS) results confirmed the formation of Pt-Co and Pt-Ni bimetallic bonds in the PtCo and PtNi bimetallic catalysts, supporting the argument from previous surface science and theoretical predictions that these two bimetallic catalysts would have higher hydrogenation activity than the corresponding monometallic catalysts. (C) 2008 Elsevier Inc. All rights reserved.