Chapter 5 Correlation Between Catalyst Formulation and Catalytic Properties

Abstract

This chapter discusses the correlation between catalyst formulation and catalytic properties. Modern Fluid Catalytic Cracking (FCC) catalysts consist, in general, of two major components: zeolite and matrix. Some catalysts also contain a third component: one or several additives, designed to boost gasoline octane, increase catalyst metal resistance, reduce SOx emissions, or facilitate CO oxidation. The additive can be incorporated into the catalyst particle or be used as a distinct physical particle. The zeolites used in FCC catalysts are mostly synthetic, faujasite type zeolites: Y and high-silica Y zeolites. Regarding the main applications, commercial FCC catalysts can be broadly classified in three categories: (1) gasoline FCC catalysts, (2) octane FCC catalysts, and (3) resid FCC catalysts. All FCC catalysts, regardless of their specific applications, are designed to have the following catalytic properties: activity, selectivity, and stability. Catalytic activity is because of the presence of acidic sites in the catalyst. It is determined by zeolite content and type, by matrix type, and by the zeolite/matrix activity ratio. Catalytic selectivity is determined by several factors: (1) zeolite type, (2) acid site type (Broensted and/or Lewis), strength, concentration and distribution, (3) pore-size distribution in both matrix and zeolite, (4) matrix surface area and activity, (5) additives present, and (6) contaminants present.