Deactivation of a Pt/Silica-Alumina Catalyst and Effect on Selectivity in the Hydrocracking of n-Hexadecane

The deactivation behavior of a bifunctional catalyst consisting of platinum on amorphous silica-alumina was studied in the hydrocracking of n-hexadecane. The initial decline in activity and the change in selectivity were monitored at the following reaction conditions: pressure = 30 bar; temperature = 310 A degrees C; hydrogen-to-hexadecane feed molar ratio = 10. Initially, hexadecane conversion and selectivity to cracking products decreased rapidly with time-on-stream, and stabilized after 40 h on stream. This could be related to an initial loss of metal surface area, which decreased the activity of monofunctional hydrogenolysis generating cracking products. The acidic function seemed to be unaffected under these reaction conditions. The stable catalyst was exposed to a lower hydrogen-to-hexadecane ratio to accelerate deactivation by coking. A decline in the activity of both functions was observed. The activity of the acidic function could be almost completely recovered by oxidative regeneration, while the metal activity was only partially recovered.