Noble-metal efficient Pt-Ir-Co/SiO2 catalyst for selective hydrogenolytic ring opening of methylcyclopentane

Pt-Co/SiO2 and Pt-Ir-Co/SiO2 catalysts were prepared via galvanic replacement (GR) and employed for the hydrogenolytic ring-opening of methylcyclopentane (MCP). Selective deposition of the noble metals at the less expensive Co nanoparticle (NP) surface by GR greatly enhanced the utilization efficiency of the more active Pt or Pt and Ir atoms for the selective catalysis to the ring-opening reaction of MCP, as justified by comparison with catalysts from conventional impregnation preparation. The chemistry of GR was quantitatively studied by comprehension of the composition changes both in the preparation solution and in the solid samples. The structural features of GR catalysts were characterized as highly dispersed Pt or Pt and Ir clusters selectively deposited on Co NP surface. Compared to their counterparts from impregnation preparation, the GR catalysts showed much higher mass-specific activity normalized by overall noble metal loading (MSANM), due to the significantly enhanced utilization efficiency of Pt or Pt and Ir. In addition, the trimetallic Pt-Ir-Co/SiO2 catalyst showed a distinctly higher MSANM than the bimetallic Pt-Co/SiO2 and Ir-Co/SiO2 ones. This observation features a synergy between the highly dispersed Pt and Ir clusters in the catalysis, besides the enhanced noble metal utilization efficiency. Our catalytic data seem to suggest that a dicarbene mechanism was prevailing over the GR catalysts for the ring-opening reaction of MCP.