MICROACTIVITY TEST (MAT) STUDY OF THE ZSM-5 ADDITION EFFECTS ON FCC PRODUCT YIELDS AND GASOLINE COMPOSITION

A commercial ZSM-5 containing additive was tested at a MAT unit and the derived results concerning product distribution as well as gasoline composition shifts have been interpreted by means of changes in the rates of certain secondary reactions occurring during catalytic cracking. The most important results of the ZSM-5 addition are gasoline yield decrease, LPG alkenes increase and RON gain. The gasoline composition changes include a significant decrease of the C6-C-9 alkanes yield, lighter gasoline formation through increase of the C5 hydrocarbons yields, increased branching in the light alkenes and a small decrease in the naphthenes and aromatics yields. Most of the above effects have been interpreted by taking into account the enhanced alkenes reactivity on ZSM-5. A comparison of the present results with those from pilot plants and commercial units reveal that the shifts imposed by ZSM-5 either to the product yield distribution or to gasoline composition are in very good agreement, despite the significant differences of the absolute yields.