Activity and coke deposition on a composite acid catalyst and its components

Deactivation of a composite acid catalyst during cracking of n-hexadecane was studied by using a thermogravimetric analysis system operating as a pulse microreactor, followed by a gas chromatograph. The composite catalyst, which contains a silica-alumina component and a zeolite component, was compared to the separate, catalytically active components with respect to activity, surface area, acidity, and coke laydown. A Partitioned-Flow model, which postulates a zeolite contact fraction depending on coke level, is the simplest model that can relate the performance of the composite in terms of the component performances. The contact fraction decreases rapidly with coke level and then levels off.