Styrene adiabatic dehydrogenation processes

Both the isothermal and the adiabatic dehydrogenation processes are applied in industrial styrene production. The flow diagram for the BASF dehydrogenation process is shown in Figure 5.6. 

The use of steam has a number of other advantages in the styrene process. The most important of these is that it acts as a source of internal heat supply so that the reactor can be operated adiabatic-ally. The dehydrogenation reaction is strongly endothermic, the heat of reaction at 560°C being (- AH) - 125,000 kJ/kmoL It is instructive to look closely at the conditions which were originally worked out for this process (Fig. 1.7). Most of the.steam, 90 per cent of the total used, is heated separately from the ethylbenzene stream, and to a higher temperature (7I0SC) than is required at the inlet to the... 

The dehydrogenation reaction is an endothermic reaction, with the heat source supplied either by superheated steam (800—950 °C) mixed with preheated ethylbenzene feedstock prior to exposure to the catalyst (the adiabatic process), or by indirect heat exchange design (the isothermal process). For every mole of ethylbenzene, the process produces one mole of each styrene and hydrogen. This process accounts for over 90% of the total worldwide production of styrene. 

The dehydrogenation of ethyl benzene is endothermic so that heat must be sup-pUed during operation. The two commercial styrene processes either incorporate several adiabatic beds with interbed heat exchange/steam addition or isothermal tubular reactors with a siritable heating mediirm in order to maintain operating... 

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