Catalytic dehydrogenation reactor designs

According to this scheme, the catalyst serves primarily to promote dehydrogenation. Cyclization of the hexatriene was shown years ago (JJ.) to occur thermally in the gas phase at temperatures well below these dehydrocyclization conditions. Thus, the overall reaction is projected to be the combination of several catalytic dehydrogenation steps and a non-catalytic cyclization step. This projection implies that the design of the catalytic reactor may be important in order to optimize the ratio of void space for cyclization and catalyst space for dehydrogenation. 

Methane-steam reaction Hydrogenation of benzene to cyclohexane Dehydrogenation of ethylbenzene to styrene Tarhan Catalytic Reactor Design, McGraw-Hill, 1983) has computer programs and results for these cases ... 

Design a reactor system to produce styrene by the vapor-phase catalytic dehydrogenation of ethyl benzene. The reaction is endothermic, so that elevated temperatures are necessary to obtain reasonable conversions. The plant capacity is to be 20 tons of crude styrene (styrene, benzene, and toluene) per day. Determine the bulk volume of catalyst and number of tubes in the reactor by the one-dimensional method. Assume that two reactors will be needed for continuous production of 20 tons/day, with one reactor in operation while the catalyst is being regenerated in the other. Also determine the composition of the crude styrene product. 

Catalytic reformers are normally designed to have a series of catalyst beds (typically three beds). The first bed usually contains less catalyst than the other beds. This arrangement is important because the dehydrogenation of naphthenes to aromatics can reach equilibrium faster than the other reforming reactions. Dehydrocyclization is a slower reaction and may only reach equilibrium at the exit of the third reactor. Isomerization and hydrocracking reactions are slow. They have low equilibrium constants and may not reach equilibrium before exiting the reactor. 

Unsteady-state reactor operation is traditionally considered to be related to the performance of catalytic processes which are characterized by quick loss in catalyst activity. For such processes as, for example, catalytic cracking (Section B.3.10) or dehydrogenation of alkanes (Section B.4.3), a sequence of reaction and regeneration stages is unavoidable and should be included into the design. 

O. Wolfrath, L. Kiwi-Minsker, A. Renken, Filamenteous catalytic beds for the design of membrane micro-reactor propane dehydrogenation as a case study, in M. Matlosz, W. Ehrfeld, J.P. Baselt (Eds.), Proceedings of the 5th International Conference on Microreaction Engineering (IMRET 5), Springer, Berlin, 2001, p. 191. 

M. Roumanie, V. Meille, C. Pijolat, G. Tournier, C. De Bellefon, P. Pouteau, C. Delattre, Design and fabrication of a structured catalytic reactor at micrometer scale Example of methylcyclohexane dehydrogenation, Catal. Today 110 (2005) 164. 

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