INFLUENCE OF PLATINUM ON THE TRANSFORMATION OF AN ETHYLBENZENE-O-XYLENE MIXTURE ON H-ZSM-5

The transformations of pure ethylbenzene and of an ethylbenzene (20 wt .-%)-o-xylene (80 wt.-%) mixture were carried out on acid and bifuncti onal ZSM-5 catalysts under the following operating conditions: fixed b ed reactor, temperature 410 degrees C, 0.96 MPa pressure of hydrogen a nd 0.24 MPa pressure of hydrocarbons, weight of hydrocarbon injected p er weight of catalyst and per hour between 10 and 110, On both catalys ts the main reactions of pure ethylbenzene are dealkylation and dispro portionation, this latter reaction occurring through a dealkylation-al kylation scheme. The main effect of platinum is to increase the rate o f dealkylation and to decrease that of disproportionation, which is du e to the rapid hydrogenation of ethylene. In addition to dealkylation and disproportionation, ethylbenzene mixed with xylenes is also transf ormed into dimethylethylbenzene (transethylation), this latter reactio n decreasing considerably in the presence of platinum. On the acid and bifunctional catalysts o-xylene is very rapidly transformed into p- a nd m-xylenes. Xylenes are also transformed through disproportionation and transethylation. Platinum increases slightly the rate of dispropor tionation at the expense of transethylation.