Operation of FCC with mixtures of regenerated and deactivated catalyst

The operation of FCC with mixtures of coked and regenerated catalyst was st udied with a riser simulator reactor on two equilibrium catalysts at 550 de greesC. The coked catalysts maintain an activity level that enables them to be used in the mixtures. The catalytic performances of the regenerated cat alysts were used as references against which the behaviors of 25:75 and 50: 50 (coked:regenerated) mixtures were compared. It was observed that overall catoil has to be increased to maintain conversion. While the yields of gas es, gasoline and LCO showed to be independent of the operative mode, change s were observed in the selectivity to Light olefins C4-C6 that are mainly d ue to changes in the yields of the isoparaffins in the groups. In turn, the se changes could be the consequence of the resulting density of paired acid sites in the zeolite components on hydrogen transfer reactions, due to the contributions by the coked and regenerated portions of catalysts. Coke yie lds in mixtures of coked and regenerated catalysts are not higher, which wo uld allow increasing catalyst circulation without impacting on heat balance . The particularities of this new operation of FCC are very dependent on ca talyst properties. (C) 2001 Elsevier Science B.V. All rights reserved.