Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Nickel and vanadium poison FCC catalysts with destruction of zeolites. This is reflected by a lower gas oil conversion and lower gasoline selectivity. Ni and V also affect hydrogen transfer resulting in more coke formation and reducing light gases.;New catalysts, so-called FCCT (catalysts for FCC with "in situ metal traps"), were developed in this study to achieve high dispersion of passivators. FCCTs were extensively tested and demonstrated experimentally. On the strength of these results, it can be stated that high dispersion of the metal traps, using the "in situ" mode of preparation with traps "waiting" the contaminants and "shielding" the zeolites, contributed significantly to the results obtained. Catalysts with metal traps can easily be prepared by adding the metal traps, as an extra step, during catalyst manufacturing. In this way the traps will be evenly distributed on the particles and be ready to accommodate, while reacting, metal contaminants present in the feedstock.;The excellent dispersion of the metal traps were confirmed by SIMS. Moreover, high metal dispersion obtained was accompanied with a very small reduction in surface area. TPD analysis also showed that both for Sn and Sb additions reduced total acidity. Studies developed allowed for the determination of Bronsted and Lewis acid sites in FCCTs. TPR results revealed antimony, in a reducible form, at 63.2 wt% while tin was at 87.3 wt%. This further demonstrated the very high degree of Sn and Sb metal trap dispersion achieved in FCCTs.;Experimental results demonstrated that gas oil conversion recovered significantly with FCCTs. It was also proven that the effects of the addition of the "in situ" metal traps were beneficial on gasoline yield, gasoline selectivity and GCRON. There was also an increase in C{dollar}\sb4{dollar}-olefins and this is a most valuable result given C{dollar}\sb4{dollar}-olefins fraction may be used for alkylation and production of "reformulated gasolines". A major contribution of the "in situ" metal traps was an important reduction in coke yield. Consistent with this result a reduced catalyst deactivation was observed with FCCTs.;In the course of this study, the pulse technique with a fixed bed microcatalytic unit has been proven to be very adequate for the evaluation of cracking catalyst. The specific technique adopted do not allow coke profiles to develop in the catalyst bed with particle fluidization in between injections.;A kinetic model constituted by four lumps (gas oil, gasoline, light gases and coke), was found valuable to reproduce the experimental data of catalytic cracking reactions. The proposed mathematical model highlights the importance of separating coke and light gases as two different pseudospecies. Modelling catalyst deactivation in terms of exponential decay law and coke concentration (coke-on-catalyst) was also found to be most appropriate. An important outcome of the mathematical modelling was the determination of the energies of activation and the analysis of their evolution with the levels of metal traps. Thus, with the kinetic parameters and model selected, the model was extensively tested. It was observed that essentially all predictions, resulting for the four lumps of the model were in the {dollar}\pm{dollar}10% interval with very few exceptions deviating from this trend.



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