Methods for Catalyst Regeneration

For catalysts poisoned by sulfur, the metal-sulfur bond is usually broken in the presence of steam, as shown for nickel  

The equilibrium for the second reaction favors H2S until extremely high temperatures are reached ( 700°C). Thus, sintering of the catalyst could be a problem. Furthermore, S02 can act as a poison for some catalysts. If sintering or SO, poisoning precludes steam treatment, it is usually possible to remove deposited sulfur by passing a sulfur-free gas stream over the catalyst at moderate temperatures for an extended period of time. 

Regeneration of coked catalysts may be accomplished by gasification with oxygen, steam, hydrogen, or carbon dioxide  

The first reaction is strongly exothermic, and may lead to high local temperatures within the catalyst. Thus, temperature must be carefully controlled to avoid sintering. 

Data For the catalyst, De = 0.10 cm2 s-1, Le = 0.7 cm (exterior surface concentration) = 0.012 mol L-1. The reaction follows LH kinetics, with the intrinsic 

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