The luminescent behavior of the steamed EuY zeolite incorporated with vanadium and rare earth passivators

In the present work, the use of rare earth ions as passivating agents to prevent vanadium poisoning of Y zeolite-based cracking catalysts during typical hydrothermal operating conditions of FCC units was studied to establish the capability of each RE3+ passivator used here (RE = La, Gd or Lu) to interact with vanadium in order to protect the zeolite from structural collapse by exploring the photoluminescent properties of the Eu3+ ion as local probe in the zeolitic lattice environment. The Omega; intensity parameters (gimel = 2 and 4) were determined from the emission spectra which showed that Eu3+ ion assumes a stronger covalent character in relation to V attack. In another approach, the formation of orthovanadate ion was determined by means of excitation spectra and related with the intraconfigurational transitions from the Eu3+ ion. It was suggested that the interaction with vanadium could be associated to REVO4 intrinsic thermodynamic values. (C) 2001 Elsevier Science B.V. All rights reserved.