Optimum catalyst, kinetic considerations

In addition to Mo co-catalyst, PtSn formulations have received considerable attention. The co-catalytic activity of Sn for the enhancement of CO oxidation has been well documented and the optimum catalyst composition was found to be Pt Sn = 3 1 (atomic ratio) [76-78]. Ross and co-workers proposed the following mechanism for Sn promotion in the framework of Langmuir-Hinshelwood kinetics, also implicating surface S11O2 in H2O dissociation [76] ... 

Kinetic Considerations of Optimum Catalyst for Two-Step Sequence... 

Several researchers have experimentally demonstrated the inhibiting influence of hydrogen sulfide (H2S) on HDS. This inhibiting influence is expected from simple and kinetic and equilibrium considerations. Refiners take great care to keep H2S in commercial hydrotreaters at an optimum level. For example, hydrogen—used in excess in a hydrotreater—is recirculated after scrubbing out the H2S by-product carefully. The recycle stream needs to contain an optimum level of H2S to keep the catalyst as a sulfide and thus maintain its activity and selectivity. Sie has described other process options to minimize inhibition effects by H2S, e.g., countercurrent flow reactors and monolithic catalyst systems. ... 

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