EFFECT OF WATER IN THE PERFORMANCE OF THE SOLID PHOSPHORIC-ACID CATALYST FOR ALKYLATION OF BENZENE TO CUMENE AND FOR OLIGOMERIZATION OF PROPENE

The solid phosphoric acid catalyst has been utilized industrially for a long time for the synthesis of cumene by benzene alkylation, as well as for the oligomerization of propene to liquids utilized for gasoline blendings. This paper describes the effect of the water content in the feedstock on the catalytic performance of the solid phosphoric acid catalyst, both in terms of activity/selectivity and of the overall life. The water was found to affect the activity strongly in the case of the propene oligomerization, the highest activity was achieved in the case of complete hydrolysis of the P2O5/H2O, constituting the active phase of the catalyst, to the ortho-phosphoric acid. In the case of the benzene alkylation, instead, complete hydrolysis led to a decrease in both the activity and the selectivity to alkylaromatics. However, the main influence of water was on catalyst lifetime: more than 200 ppm water in the feed led to a quick destruction of the catalyst, with loss of the mechanical properties. This phenomenon was found to be due to the hydrolysis of the main catalyst components, the silicon phosphates. A remarkable improvement in lifetime of the solid phosphoric acid catalyst was achieved by making the system more resistant to hydrolysis through a modification in the preparation procedure.