Sulfide catalysts reaction selectivity role

Role of Crystal Structure on Reaction Selectivity. The question of selectivity of the HDS reaction and its control by the sulfide catalyst has been little studied. However, the existence of two active sites on M0S2 is well established throughout much of the literature, particularly in the work of Voorhoeve (16). One site is usually described as a direct sulfur removal site and the other as a hydrogenation site. 

In addition to studies focusing exclusively on the catalyst surface, the catalyst support (when employed) can play a major role in enhacing the activity/selectivity via morphologic, electronic, and physico-chemical effects. These factors have been extensively explored in the case of thermochemical heterogeneous reactions where a variety of compounds and structures have been successfully used on an industrial scale as catalyst supports (e.g., oxides, sulfides, meso- and microporous materials (molecular sieves), polymers, carbons [251-256]). In electrocatalysis, on the other hand, the practical choice of support in gas diffusion electrodes has been largely limited thus far to carbon black particles. The high electronic conductivity requirement, combined wifli electrochemical stability and cost effectivness, imposes serious restrictions on the type of materials that could be employed as supports in electrocatalysis. 

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