DEVELOPMENT OF Cu- AND Fe-DOPED ZEOLITE-COATED CERAMIC FOAMS AS FUNCTIONAL CATALYSTS FOR AUTOMOTIVE NOx REDUCTION

Rajakrishnamoorthy P.; M. Bakkiyaraj; P. Premkumar; Premnath Muthuvelu

doi:10.17222/mit.2025.1596

Rajakrishnamoorthy P. Department of Mechanical Engineering, Meenakshi Ramaswamy Engineering College, 621804 Ariyalur, Tamil Nadu, India
M. Bakkiyaraj Department of Mechanical Engineering, Rajalakshmi Institute of Technology, Chennai, 600124 Tamil Nadu, India
P. Premkumar Department of Mechanical Engineering, St. Joseph's College of Engineering, Chennai, 603112 Tamil Nadu, India
Premnath Muthuvelu Faculty of Mechanical Engineering, Annamalai University, Chidambaram, 608002 Tamil Nadu, India

DOI: https://doi.org/10.17222/mit.2025.1596

Keywords: ZSM-5 zeolite, catalyst, ceramic foam filter, NOx emission reduction

Abstract

The effective control of nitrogen oxides (NO_x) from gasoline engines remains a critical challenge for sustainable emission management, as conventional three-way catalytic converters (TWCs) exhibit limited NO_x conversion efficiency under oxygen-rich exhaust conditions. This study presents the development and evaluation of metal-doped zeolite-based catalysts – Cu-ZSM-5 and Fe-ZSM-5 – coated onto ceramic foam substrates as advanced alternatives to conventional noble-metal honeycomb monoliths. The catalysts were synthesized via ion-exchange methods and characterized using XRF, SEM, and XRD to confirm successful metal incorporation without compromising the zeolite’s MFI crystalline framework. Engine tests were conducted on a twin-cylinder, 624 cm³ spark ignition engine to compare the catalytic performance of the laboratory-fabricated converters with a commercial TWC. Results demonstrated superior NO_x reduction efficiencies of 71 % and 76 % for Cu- and Fe-doped zeolite converters, respectively, at maximum load conditions. Fe-ZSM-5 exhibited enhanced high-temperature NO_x conversion (up to 79 %), whereas Cu-ZSM-5 showed better low-temperature activity. Both catalysts also achieved higher CO (up to 89 %) and HC (up to 95 %) conversion efficiencies compared to the commercial system. Although a minor decrease in brake thermal efficiency was observed due to the increased backpressure of the ceramic foam substrate, the overall performance indicates that metal-doped zeolite-coated ceramic converters provide a cost-effective, thermally stable, and environmentally sustainable alternative to noble-metal TWCs. This work advances the practical application of zeolite-based catalysts for next-generation automotive emission control systems.

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