Activity and durability of Fe/ZSM-5 catalysts for lean burn NOx reduction in the presence of water vapor

Hai Ying Chen, Wolfgang M.H. Sachtler

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506 Scopus citations

Abstract

A novel method for the preparation of superior Fe/ZSM-5 catalysts is described. FeCl3 is sublimed into the cavities of H/ZSM-5, where it reacts chemically with the acid sites of the zeolite. With this method, Fe/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 zeolite and its synthesis history than the conventional ion-exchange method. HRAEM, FTIR, H2-TPR and CO-TPR results show that iron is located at the exchange sites of the zeolite. An oxygen bridged binuclear iron complex is a plausible prototype for the active iron species. The iron is reduced from +3 to +2 below 800°C. These catalysts are very active and selective in the catalytic reduction of NOx with iso-butane; they have a high durability under conditions simulating vehicular emission. A conversion of NO to N2 of about 76% was observed near 350°C. Remarkably and in contrast to most other M/ZSM-5 catalysts, the performance of the new catalysts was not impaired when 10% H2O was added to the feed. H2O actually enhances the NOx conversion at low temperatures. CO and CO2 are both true primary products of NOx SCR over Fe/ZSM-5 catalysts.

Original languageEnglish
Pages (from-to)73-83
Number of pages11
JournalCatalysis Today
Volume42
Issue number1-2
DOIs
StatePublished - Jun 18 1998
Externally publishedYes

Funding

Financial support for this research by an unrestricted grant from the Ford Motor Corporation is gratefully acknowledged. We thank Professor W.K. Hall for kindly sending us his papers prior to their publication. We thank Dr. Steve Wilson of UOP, Dr. Arno Tißler of ALSI-Penta Zeolithe GmbH, Dr. Yuejin Li of Air Products and Chemicals and Dr. Armin Pfenninger of Uetikon Chemie A.G. for kindly donating us ZSM-5 samples.

FundersFunder number
Ford Motor Corporation

    Keywords

    • DeNO
    • Fe/ZSM-5
    • HO effect
    • SCR
    • Sublimation

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