The determination of acidity in Fluid Cracking Catalysts (FCCs) from adsorption microcalorimetry of probe molecules

摘要

The introduction of fluid cracking catalysts (FCCs) for the transformation of crude oil into gasoline and other fuel products has revolutionized the petroleum refining industry. It is generally admitted that the initial step in a cracking reaction is the formation of a carbocation. Consequently, in the field of catalytic cracking of petroleum by zeolite-containing catalysts, the terms "active site" and "acid site" are synonymous [1]. All FCC catalysts, regardless of their specific applications, are designed to have the following catalytic properties: activity, selectivity, and stability [2]. Catalytic activity is due to the presence of acidic sites, and is determined by the zeolite content and by the types of zeolite and matrix in the FCC catalyst. Catalytic selectivity is determined by the zeolite type, the nature (Bronsted or Lewis), strength, concentration and distribution of the acid sites, the pore size distribution, the matrix surface area and activity, and the presence of additives or contaminants. Stability is affected by both the composition and the structural characteristics of the catalyst components [2].