Abstract
Configurational and the physical structures of supported nickel catalysts were observed with electron microscope and the texture of catalytic active center was examined by observing carbon films deposited in catalytic cracking of ethylene. Results obtained are as follows.
1. Supported nickel particles were either (a) chain-like or(b) granular. The chain-like particles (a) consisted of many crystallites, whereas most granular particles (b) consisted of a single crystallite.
2. The nickel particles supported on a clear fused-silica surface had two kinds of catalytic active centers. The one was high-active center formed only on (a), and the other was moderate-active center formed on the border between the nickel particles of (a) or (b) and the silica support.
The former sintered easily but the latter was resistant to heat treatment. It is thus concluded that the catalytic surface of supported nickel particles is heterogeneous, and the active centers correspond to the various kinds of lattice deformation produced in the catalyst crystals.
