The Selection of Fluid Catalytic Cracking Catalysts and Additives: The Significance of Attrition Studies

Abstract

Fluid catalytic cracking (FCC) is an important secondary conversion process in refinery that converts heavier gas oils and residues to valuable petroleum products. In the present and future crude oil availability scenario demand for FCC process that increases the refinery margins is growing. Continuous attempts are being made to improve FCC margin through process optimization, selection and use of improved catalysts and additives as well as hardware modifications. Refiners often face challenging task of judiciously selecting and switching to improved catalysts and additives for maximizing profits without violating hardware constraints. It is very difficult to select catalyst or additives based on vendor's claims and testing the catalyst directly in the plant is also risky business. It is important to match the plant performance closely to understand unit constraints and exploit the new catalyst capabilities to full extent. Detailed study with respect to catalyst deactivation, microactivity studies, complete characterization, and prediction of performance on the commercial scale, as well as economic evaluation, are key steps in catalyst or additive selection. Catalyst attrition is key issue now days due to heavy losses observed in the plant and frequent shut downs of the CO boiler units. In riser and regenerator reactor of FCC process, catalyst undergoes attrition due to various reasons such as inherent characteristics of catalyst/additive or due to process environment. Poor attrition of either catalyst/additive result into catalyst loss, fouling, and plugging of down stream units. In this communication the attrition behavior of different catalysts and additives and combined effect of base fluid catalytic cracking catalyst along with different additives in various proportions have been evaluated using an ASTM method in laboratory. Attrition behavior of different FCC additives such as CO combustion promoter, Octane and LPG booster and gasoline sulfur reduction additives were measured in isolation as well as by mixing with base catalyst in different proportion. Certain when studied alone exhibited higher attrition when compared with others. It is observed that even though absolute attrition strength of certain additives such as gasoline sulfur is poor, when used along with base catalyst in desired proportion the loss due to attrition was minimized. This study in combination with VGO cracking activity results helps to select suitable catalyst/additive for enhancing FCC process profits.