CATALYST ACCESSIBILITY: A NEW FACTOR ON THE PERFORMANCE OF FCC UNITS

摘要

Accessibility has been recently claimed as an important characteristic of the FCC catalysts. This property is specially raised when diffusion limitation becomes a critical issue. This is the case when one takes into account the new trends in FCC operation such as the processing of heavier and lower cost feedstock and the reduction in contact time between catalyst and hydrocarbon vapor. Manufacturing technologies have been developed aiming at enhancing porosity and accessibility and commercially proven advantages have been achieved with these new generation of catalysts. However, the accessibility behavior of the catalysts after entering the commercial unit is not fully understood since different phenomena occur in the FCC process that results in substantial alteration of the original accessibility of the fresh catalyst. Primarily, steam and contaminant metals play an important role on defining the accessibility of the final equilibrium catalyst. In the regeneration conditions, steam cause pore structure opening and some contaminant metals can promote surface blockage, thus generating opposed effects on the catalyst accessibility. In the present work, catalysts from different FCC units at Petrobras, including two RFCC units, were characterized focusing on the accessibility aspect. The results were related to the type of catalyst, to the influence of hydrothermal conditions and presence of contaminants in the unit. The consequences on the commercial performance have also been discussed.