Preparation and catalytic properties of uniform particles of Ni3Ge intermetallic compound formed inside the mesopores of MCM-41

Uniform particles of Ni3Ge intermetallic compound (IMC) were prepared inside the pores of MCM-41 mesoporous silica with various mesopore diameters. XRD and TEM revealed that Ni–Ge/MCM-41 thus prepared contained mainly fine metallic particles smaller than the pore size. IR spectra of adsorbed CO suggest the formation of a Ni–Ge IMC, probably Ni3Ge, and the electron transfer from Ni to Ge. For H2–D2 equilibration, Ni3Ge/MCM-41 had higher intrinsic activity than Ni/MCM-41 because of the high activity of Ni atoms at the corner and edge sites. Among MCM-41 and SiO2 supports, those with smaller mesopores gave higher activity. The similar effect of pore size also was observed for the hydrogenation of cyclohexene. The difference in activity is discussed in terms of the confinement effect inside mesopores. For the hydrogenation of acetylene, Ni3Ge gave higher ethylene selectivity than Ni because of the geometric and electronic effects through the formation of IMC.