Changes in Powerforming

Powerforming is basically a conversion process in which catalytically promoted chemical reactions convert low octane feed components into high octane products. The key to a good reforming process is a highly selective dual-function catalyst. The dual nature of this catalyst relates to the two separate catalyst functions atomically dispersed platinum to provide 

The dehydrogenation reaction is an extremely rapid endothermic reaction which converts alkylcyclohexanes to aromatics almost quantitatively. It is promoted by the catalyst platinum function and is so rapid that it is normally limited by diffusion into the catalyst particle. 

The isomerization reaction, which is acid-site controlled, includes the conversion of alkylcyclopentanes into alkylcyclohexanes, which, in turn, are quickly converted to aromatics by dehydrogenation. In addition, isomerization also includes the conversion of feed n-paraffms into higher octane I-paraffins. 

Dehydrocyclization refers to the conversion of feed paraffins into alkylcyclohexane and alkylcyclopentane naphthenes. These, in turn, are subsequently converted by isomerization and dehydrogenation into aromatics. Dehydrocyclization is controlled by both acid and platinum functions and is the most sensitive indicator of catalyst selectivity. 

All of the above reactions are reversible, with the exception of hydrocracking, so that thermodynamic equilibrium limitations are important considerations. To the extent possible, therefore, operating conditions are selected which will minimize equilibrium restrictions on conversion to aromatics. This conversion is favored at higher temperatures and lower operating pressures. 

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