Influence of the process variables on the product distribution and catalyst decay during cracking of paraffins

The influence of the partial pressure of the hydrocarbon, reaction temperature, time on stream and the presence of olefins on the product distribution and the kinetics and decay during the cracking of n-heptane on an REHY zeolite were studied. It was found that the isomerization to cracking ratio depends on the hydrocarbon partial pressure. The active sites for cracking and isomerization are not the same and those for cracking decay faster, the selectivity changing with the degree of decay of the zeolite. The protolytic to β-cracking ratio, and therefore the paraffin to olefin ratio, are a function of the partial pressure of n-heptane. Both reactants and products have a marked influence on catalyst decay.