Catalytic cracking catalyst deactivation

In addition, salts deactivate reforming and catalytic cracking catalysts. 

Sodium Deactivation of Fluid Catalytic Cracking Catalyst... 

Contaminant-Metal Deactivation and Metal-Dehydrogenation Effects During Cyclic Propylene Steaming of Fluid Catalytic Cracking Catalysts... 

Improved Methods for Testing and Assessing Deactivation from Vanadium Interaction vvith Fluid Catalytic Cracking Catalyst... 

Catalytic cracking catalysts can deactivate by the extended exposure to water vapour at very high temperatures. In a commercial cracking unit such conditions can occur in the regenerator vessel... 

When deactivation occurs rapidly (in a few seconds during catalytic cracking, for instance), the fresh activity can be found with a transport reac tor through which both reac tants and fresh catalyst flow without slip and with short contact time. Since catalysts often are sensitive to traces of impurities, the time-deac tivation of the catalyst usually can be evaluated only with commercial feedstock, preferably in a pilot plant. 

Coking is a severe thermal cracking process designed to handle heavy residues with high asphaltene and metal contents. These residues cannot be fed to catalytic cracking units because their impurities deactivate and poison the catalysts. 

Cracking is an endothermic reaction, implying that the temperature must be rather high (500 °C), with the consequence that catalysts deactivate rapidly by carbon deposition. The fluidized catalytic cracking (FCC) process, developed by Standard Oil Company of New Jersey (1940) (better known as ESSO and nowadays EXXON), offers a solution for the short lifetime of the catalyst. Although cracking is... 

The hydrocarbon catalytic cracking is also a chain reaction. It involves adsorbed carbonium and carbenium ions as active intermediates. Three elementary steps can describe the mechanism initiation, propagation and termination [6]. The catalytic cracking under supercritical conditions is relatively unknown. Nevertheless, Dardas et al. [7] studied the n-heptane cracking with a commercial acid catalyst. They observed a diminution of the catalyst deactivation (by coking) compared to the one obtained under sub-critical conditions. This result is explained by the extraction of the coke precursors by the supercritical hydrocarbon. 

Different procedures can be used in practice to activate the zeolite, and the choice of a particular method will depend on the catalytic characteristics desired. If the main objective is to prepare a very active cracking catalyst, then a considerable percentage of the sodium is exchanged by rare earth cations. On the other hand, if the main purpose is to obtain gasoline with a high RON, ultrastable Y zeolites (USY) with very low Na content are prepared. Then a small amount of rare earth cations is exchanged, but a controlled steam deactivation step has to be introduced in the activation procedure to obtain a controlled dealumination of the zeolite. This procedure achieves a high thermal and hydrothermal stability of the zeolite, provided that silicon is inserted in the vacancies left by extraction of A1 from the framework (1). The commercial catalysts so obtained have framework Si/Al ratios in the... 

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