ACTIVITY AND DURABILITY OF FE ZSM-5 CATALYSTS FOR LEAN BURN NOX REDUCTION IN THE PRESENCE OF WATER-VAPOR/

A novel method for the preparation of superior Fe/ZSM-5 catalysts is d escribed. FeCl3 is sublimed into the cavities of H/ZSM-5, where it rea cts chemically with the acid sites of the zeolite. With this method, F e/ZSM-5 with an iron loading as high as Fe/Al=1 can be easily achieved . This preparation method is less sensitive to the origin of the zeoli te and its synthesis history than the conventional ion-exchange method . HRAEM, FTIR, H-2-TPR and CO-TPR results show that iron is located at the exchange sites of the zeolite. An oxygen bridged binuclear iron c omplex is a plausible prototype for the active iron species. The iron is reduced from +3 to +2 below 800 degrees C. These catalysts are very active and selective in the catalytic reduction of NO, with iso-butan e; they have a high durability under conditions simulating vehicular e mission. A conversion of NO to N-2 Of about 76% was observed near 350 degrees C. Remarkably and in contrast to most other M/ZSM-5 catalysts, the performance of the new catalysts was not impaired when 10% H2O wa s added to the feed. H2O actually enhances the NOx conversion at low t emperatures. CO and CO2 are both true primary products of NOx SCR over Fe/ZSM-5 catalysts. (C) 1998 Elsevier Science B.V. All rights reserve d.