RELATIONSHIP BETWEEN ZEOLITE STRUCTURE AND HYDROGEN-TRANSFER REACTIONS IN NAPHTHENES AND PARAFFINS CRACKING

The limitation of hydrogen-transfer reaction in FCC units, when zeolitic additives are used, is desired to maximize the olefins production and to limit aromatics content of gasoline. In this work, the influence of zeolite structure on H-transfer reactions which occur during the cracking of n-hexane and a light gasoline cut (70-140 degrees C) from hydrocracking, composed of a mixture of naphthenes and paraffins, was studied. The results obtained show that there is a link between the zeolite structure and the importance of H-transfer reactions in naphthenes and paraffins cracking. Such reactions appear as being dominant when using Y zeolite, and minimized when using MFI zeolite. Beta and Mordenite zeolites are intermediate and H-transfer reactions are less important in the case of Mordenite in comparison with Beta zeolite. The influence of the Si/Al ratio on the H-transfer reaction is also discussed.