Kinetics and Mechanism of Paraffin Cracking with Zeolite Catalysts

Acid catalyzed cracking of simple paraffins at high temperature and low partial pressure does not occur by the classical bimolecular carbenium chain reaction, but by protonation of the paraffins to produce penta-coordinated carbonium ion intermediates. Under limiting conditions, the kinetics of the two reaction paths both follow a first order rate law, although with very different activation energies. In the intermediate regime, the kinetics is quite complex. Hexane cracking offers several advantages as a means to characterize acid catalysts, and is best carried out at high temperature and low partial pressure.