Abstract

The gas-phase hydrogenolysis of methylcyclopentane (MCP) was investigated over the bimetallic Ir-Au/gamma-Al2O3 catalysts. The bimetallic systems containing the atomic Au/Ir ratios in the range of 0.125-8 and a fixed total metal content of 8 wt.%, were prepared by the sequential impregnation (SI) and co-impregnation (CI) methods. The corresponding monometallic Ir/gamma-Al2O3 and Au/gamma-Al2O3 catalysts were also prepared. The materials were characterized by ICP, XRD, N-2 adsorption, TEM, and H-2 chemisorption. Highly dispersed Ir nanoparticles were obtained in all cases, while the size of Art nanoparticles increased (up to 50 nm) upon the increasing Au content in the catalyst. The monometallic gold catalyst did not adsorb H-2. The incorporation of Au increased the amount of irreversible adsorbed H-2 in the Ir-Au/gamma-Al2O3 catalysts with respect to the monometallic ones. The products obtained in the MCP hydrogenolysis were 2-methylpentane (2-MP), 3-methylpentane (3-MP) and n-hexane (n-H). The initial rate (molecules of MCP reacted s(-1) g(lr)(-1)) increased with the An content. The deactivation was lower for bimetallic catalysts, particularly for the CI ones. The addition of Au played a significant effect on chemisorption and catalytic properties of Ir. (c) 2007 Elsevier B.V. All rights reserved.