The nature of the active sites in the reactions of cumene on HY and LaY catalysts

The secondary reactions which accompany cumene cracking have been studied at 360°, 430°, 500°C, over an HY zeolite catalyst using a tubular packed bed reactor. The concept of “Optimum Performance Envelope” was used in order to identify which of the observed reaction products are primary and which are secondary. In this way, benzene, ethylbenzene, n‐propylbenzene, cymene, m‐ and p‐diisopropylbenzene, as well as propylene, i‐butene, and butene have been found to be primary products, while methane, ethylene, ethane, toluene, ethyl toluene, and i‐ and n‐butane are identified as secondary products. The initial selectivities for the primary products have been calculated, and from these, the initial kinetic rate constants. These values, as well as the activation energies of primary product formation, are compared with those obtained using a LaY zeolite catalyst. The observed differences are discussed in terms of the nature and number of the active sites on the catalyst and lead us to conclude tthat LaY and HY have identical active sites but differ in site concentration.