HDA Kinetic Aspects

FIGURE 8.1 HDA change from kinetic control to thermodynamic control as reactor temperature is increased. 

For HDA reactions, if raising the reactor temperature decreases product aromatics levels, the reaction is said to be under kinetic control, (i.e., the rate of the forward hydrogenation reaction, kh has been increased and is high relative to the reverse). Conversely, if raising the reaction temperature causes an increase in aromatics, the rate k2 of the reverse reaction has increased and k2 kh and the reaction is under thermodynamic control.  

To pursue this subject more generally and with more detailed background of what is involved in HDA we need to have information on a number of aspects of the reactions  

The overall objective is to develop ways to model the reactions, eventually leading to predictive technologies. Several excellent reviews of aromatics saturation are available.4 6 

FIGURE 8.2 Discrete steps in the hydrotreatment of typical aromatic structures. 

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