Preparation and catalytic properties of fine particles of Pt-Ge intermetallic compound formed inside the mesopores of MCM-41

Fine particles of Pt-Ge intermetallic compound were prepared by using mesoporous silica MCM-41 as a support and examined as a catalyst for H2–D2 equilibration and the hydrogenation of acetylene to clarify the catalytic properties of single-phase intermetallic compound with nano-order particle size. The mesopore structure of MCM-41 was not affected extensively by the introduction of Pt and Ge. Pt-Ge particles on MCM-41 gave very narrow particle-size distribution around 1.5 nm, suggesting the presence of Pt-Ge particles inside the mesopores of MCM-41, whereas those prepared on silica gel had the wide distribution of 1–6 nm. Though the Pt-Ge particles on MCM-41 were too small to identify their crystal phase by XRD, IR spectra of adsorbed CO indicated the presence of intermetallic phase, probably PtGe. Pt-Ge/MCM-41 showed lower catalytic activity than PtGe/SiO2 for H2–D2 equilibration at 77 K and an induction period was observed for the former catalyst. The physically adsorbed hydrogen molecules may hinder the diffusion of HD through the mesopores. Pt-Ge/MCM-41 showed higher selectivity to ethylene than Pt/MCM-41 in the hydrogenation of acetylene, which again indicates the formation of PtGe intermetallic compound.

Fine particles of an intermetallic compound, PtGe, were created inside the mesopores of MCM-41. Their particle size had very narrow distribution around 1.5 nm. The comparable catalytic activity of PtGe/MCM-41 to that of Pt/MCM-41 indicates the nano-size effect in H2–D2 equilibration. PtGe/MCM-41 exhibited the higher selectivity than Pt/MCM-41 for the formation of ethylene in the hydrogenation of acetylene.Figure optionsDownload high-quality image (130 K)Download as PowerPoint slide