Date of Award
Doctor of Philosophy
Fluid catalytic cracking of heavy gas oils and similar stocks has captured the attention of refiners, because of the fast changing of crude oil sources and its characteristics. The changing feeds for riser reactors are responsible for undesirable effects like accelerated catalyst deactivation, reduction of gasoline yields, and increment of gas and coke production, mainly due to the contamination effects of nickel and vanadium.;The unsteady state pulse technique has been applied with several commercial catalysts and feedstocks. Equilibrium catalyst was simulated by steaming in a fluidized bed, artificial impregnation with metal naphthenates under vacuum, and calcination. B.E.T. surface area experiments, Scanning Electron Microscopy, and Secondary Ion Mass Spectroscopy analysis confirmed the effectiveness of the artificial aging method.;Experimental runs were performed in a microcatalytic fixed bed. In between injections the bed was fluidized to avoid coke profiles and reactant channeling. In a typical run 10 injections of 5 microlitres were cracked at different temperatures and carrier gas flows, keeping the cumulative catalyst-oil contact time under 20 seconds, to closely mimic the conditions of commercial FCC riser reactors.;The poisoning effects of nickel and vanadium have been demonstrated on different catalysts through the changes obtained in overall conversions, and product selectivities.;Experimental results were analyzed with two kinetic models: (a) a three lump model, featuring gas oil, gasoline, and gas plus coke; (b) a five lump model, where gas oil was split into paraffins, naphthenes, and aromatics. The kinetic constants evaluated clearly showed a decreasing trend with the increment of metal loading from 0 to 5000 ppm of nickel equivalent.;The activation energies calculated presented a consistent trend, decreasing from 18 to 5 Kcal/mol, with increasing metal concentration.;It was also found that the catalyst deactivation process could be represented by a power decay function, with an exponent of 0.25, equivalent to a decay order of five.;It was concluded that the pulse technique is a quite adequate method for testing cracking catalyst, for the attainment of reliable data for design purposes, and for the evaluation of kinetic parameters as a function of nickel and vanadium concentration on the catalyst. (Abstract shortened with permission of author.)
Larocca, Miguel, "Fast Catalytic Cracking Of Heavy Feeds With Nickel And Vanadium Contaminants (volumes I And Ii)" (1988). Digitized Theses. 1762.