Catalytical conversion of silicon tetrachloride to trichlorosilane. Characterization of the nickel silicalite catalyst by ferromagnetic resonance spectroscopy
The formation of nickel silicide in the reaction between nickel supported on silicalite and a gas mixture (molar ratio, H2 : SiCl4= 6 : 1) is studied. By ferromagnetic resonance (FMR) based Curie temperature measurements, it was determined that the formation of metal silicides starts at 723 K. From the signal intensity, it follows that the Si content of the silicides increases with increasing temperature from ca. 1 atom% at 723 K up to 6 atom% at 865 K. The geff values suggest the presence of two kinds of alloy containing ca. 1 atom% Si: one kind, produced at temperatures up to 723 K, forms a shell layer at the surface of the Ni metal particle, and the other, generated by decomposition of silicon-rich silicides formed at 865 K, is homogeneously alloyed over the whole particle.