Synthesis of fly ash-based zeolite and experimentation in catalytic converter for NO_x reduction on diesel engines: a...

This study presents the synthesis of low-cost ZSM-5 zeolite-like materials from hazardous coal fly ash and their application as metal-doped catalysts for nitrogen oxides (NO_x) reduction in diesel engine exhaust. The synthesized zeolite was prepared through acid treatment and hydrothermal crystallization, followed by metal doping with Cu, Fe, and Ce using an ion-exchange method. The catalysts were characterized using SEM, XRF, and XRD. Metal-doped zeolite formulations (Fe-ZSM-5, Cu-ZSM-5, Fe-Ce-ZSM-5, and Cu-Ce-ZSM-5,) were wash-coated onto cordierite monoliths and tested in a four-stroke CRDI diesel engine. The performance of the self-made catalytic converters (CCs) was compared with a commercial catalytic converter (CCC). Results showed that Fe-Ce-ZSM-5 and Cu-Ce-ZSM-5 achieved NO_x reductions of 69% and 71%, respectively, at full load, which were approximately 7% higher than that of the commercial CC. All developed catalysts demonstrated significant reductions in hydrocarbons (HC) and carbon monoxide (CO) emissions, with only minimal influence on brake thermal efficiency (BTE). The findings demonstrate that fly-ash-derived ZSM-5 is a promising sustainable catalyst support for diesel exhaust after-treatment applications.