The activity decay of cracking catalysts: chemical and structural deactivation by coke

The deactivation of cracking catalysts by coking with vacuum gas oils (VGO) is studied in relation to the chemical deactivation due to site coverage, and with the increase of diffusional limitations. These two phenomena are taken into account by a simple deactivation function versus catalyst coke content. The parameters of this function are discussed in relation to feedstock analysis and change of effective diffusivity with catalyst coke content.