Transfer Effects in Poisoned Catalysts

In the previous section the effects of poisons on reaction rates were related to the active component surface, while the influence of mass transfer was disregarded. It has long been recognized, of course, that the overall rate and selectivity of chemical reactions in porous systems involves the coupling of chemical reactions with convective and diffusive mass transfer processes. Beginning with the pioneering work of Thiele (67), an entire discipline has evolved in which model systems are used to 

Acres et al. (22) have speculated on the modes of phosphorus and lead poisoning in monolithic catalysts, based on data obtained in simulated aging. Conversion vs. time-of-exposure curves for catalysts poisoned by either lead or phosphorus show quite different shapes, which the authors attribute to pore-mouth poisoning for phosphorus, and uniform poisoning 

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