Recent advances in the deactivation of FCC catalysts by cyclic propylene steaming (CPS) in the presence and absence of contaminant metals

The deposition and ageing of contaminant metals on FCC catalysts in circulating pilot units best simulates the equilibration of FCC catalysts in commercial units. However, these units are expensive and time consuming to operate and are not suited fur screening large numbers of catalysts. Thus, the deactivation of FCC catalysts in small-scale units following metals impregnation has been the industry workhorse for a number of years. A major advancement in the deactivation of metallated catalysts on a small-scale that better simulated the performance of commercial FCC catalyst, was the introduction by Grace Davison of the cyclic propylene steaming (CPS) method. In the CPS protocol, FCC catalyst is impregnated with vanadium and nickel prior to deactivation in reduction-oxidation cycles. This provides significant advantages over traditional methods such as the Mitchell approach. Nevertheless, recent investigations have shown that, in certain situations, the contribution of vanadium to catalyst deactivation is over-emphasised in the CPS method. This paper describes a number of modifications that have been made to the CPS method to further attenuate the destructive effects of vanadium on the FCC catalyst during deactivation. This includes exposing the metallated catalyst to pre-stabilisation steps with reduction-oxidation cycles and changing the ratio of the time the catalyst spends in reducing and oxidising environments during the CPS cycles. These investigations have also shown that the use of reduction-oxidation cycles better simulates the deactivation of FCC catalysts in the absence of contaminant metals. (C) 2000 Elsevier Science B.V. All rights reserved.