Catalyst designs to enhance diffusivity and performance—I: Concepts and analysis

A catalytic material with high reactivity but low diffusivity can achieve higher performance from blending with an additive material with high diffusivity. The performance of such a composite catalyst depends both on the meso-structure of the continuous connectivity of the additive, and on the macro-structure of the gradient of additive in the catalyst pellet. Among the best meso-structures are the coated sphere and the penetration structures. The composite catalyst with a uniform distribution of additive can be designed to be many times more active than the starting catalytic material without additive. A gradient macro-structure, with more additives on the surface than in the interior of a pellet, can be designed to be much more reactive compared to the uniform structure with the same average loading of additives.