A copper-impregnated BEA zeolite for adsorption and oxidation of aromatic species during vehicle cold starts

Abstract

In this study, we prepared an effective cold-start hydrocarbon (HC) trap by impregnating BEA zeolites with copper. The resulting Cu-impregnated BEA zeolites allowed for effective HC trapping and, more desirably, low-temperature HC oxidation. An optimal Cu content (∼5 wt%) resulted in the highest cold-start test (CST) performance with respect to two representatives HCs, propene and toluene. The preferential adsorption of propene under wet conditions was key to achieving high efficiency (∼79 %). We found that the presence of Cu+ ions allowed the preferential adsorption of HCs, especially propene, and the CuO particles on the exterior surface (∼1−2 nm in size) could oxidize HCs at low temperatures (starting from ∼210 °C). Finally, a severe hydrothermal treatment at 800 °C was used to simulate long-term driving; the CST performance revealed that the adsorption ability for propene was dramatically decreased, whereas those of toluene, along with the oxidation ability, were still preserved. © 2021 Elsevier B.V.