Hydrogenation dehydrogenation component

Reforming is the conversion primarily of naphthenes and alkanes to aromatics, but other reactions also occur under commercial conditions. Platinum or platinum/rhenium are the hydrogenation/ dehydrogenation component of the catalyst and alumina is the acid component responsible for skeletal rearrangements. 

The reactions of the various xylenes and ethylbenzene have been studied by Pitts and associates (P7). It was found that isomerization reactions among the three xylenes were catalyzed by acidic catalysts, but that interconversions between the xylenes and ethylbenzene required the presence of a hydrogenation-dehydrogenation component. Furthermore, it was found that the conversion of xylenes to ethylbenzene increased with decreasing temperature. Since lower temperatures are more favorable for hydrogenation, it has been suggested that the reaction proceeds by a sequence of steps such as the following (P7, W3) ... 

Most hydrocracking catalysts of commercial interest are dual functional in nature, consisting of both a hydrogenation-dehydrogenation component and an acidic support. The reactions catalyzed by the individual components are quite different. In specific catalysts, the relative strengths of the two components can be varied. The reactions occurring and the products formed depend critically upon the balance between these two components. 

Bifunctional zeolite catalysts are used in various commercial processes light alkane hydroisomerization (chapter 7), hydrocracking (chapter 6),hydrodewaxing (chapter 8), light alkane aromatization and hydroisomerization of the C8 aromatic cut (chapter 9). The hydrogenation/dehydrogenation components included in zeolite catalysts can be very different and located in different positions ... 

Many hydrocracking catalysts of commercial importance are dualfunctional catalysts containing both a hydrogenation-dehydrogenation component and an acidic component. The reactions catalyzed by the... 

Here we discuss and contrast the chemistry of hydrocracking with two major categories of hydrocracking catalysts (1) dual-functional catalysts in which the acidic component is strong and the hydrogenation component is relatively weak, and (2) nonacidic catalysts with an active hydrogenation-dehydrogenation component. 

An extensive study of the reactions of pure hydrocarbons, including alkanes, cycloalkanes, alkenes and aromatics has been made in the presence of hydrogen, these catalysts are active for (1) isomerization of alkanes, cycloalkanes, and alkyl-aromatics, (2) hydroisomerization of alkylcyclo-pentanes to aromatics, and (4) dehydrogenation of alkanes and cyclohexanes to aromatics. The activity and selectivity of these catalysts are dependent primarily on (1) the hydrogenation-dehydrogenation component used and its concentration, (2) the acidity of the oxide support, and (3) the reaction conditions. The effect of these factors on the conversion of pure hydrocarbons as well as the mechanism of these reactions will be discussed. 

The alkali salts include carbonates, bicarbonates, phosphates, sulphides, bisulphides, silicates, bisulphites, aluminates, hydroxides, acetates, tungstenates, etc. of sodium, potassium, rhodium and caesium. Suitable hydrogenation/ dehydrogenation components can be elements of group V-B, VI-B or group VIII,... 

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