Texture of Coke Depositing on γ-Al2O3 Biporous Granules under Kinetic and Diffusion Regimes

Morphology and local distribution of coke is studied in gamma-Al(2)O(3) biporous granules coked with mixture of propane and butane under kinetic and diffusion regimes. Under kinetic regime at T < 923 K, coke is shown to distribute as a viscous-plastic phase that wets the catalyst surface. At low coke content, coke is localized at the sites of contact between the catalyst initial particles. At high coke content the coke deposits over the free areas with the surface negative curvature. The degree of surface coverage with coke increases as the coke content grows from a "mosaic" ( consisting of the patches covered and noncovered with coke) to full coverage. Under diffusion regime at T > 923 K, coke precipitates mainly on the surface of aggregates of the catalyst initial particles. The models and analytical relations are suggested for the analysis of coke distribution.