Effect of the adsorbent/catalyst preparation method and plasma reactor configuration on the removal of dilute ethylene from air stream

• High ethylene adsorption capacity of Ag ion-exchanged 13X zeolite.
• Oxidative transformation of adsorbed ethylene to CO2 by ozone-induced atomic oxygen.
• Fast oxidation of adsorbed ethylene by short-lived oxidizing species.
• High performance of the hybrid reactor for oxidative removal of adsorbed ethylene.

13X zeolite-supported Ag was employed as the dual-functional adsorbent/catalyst for the plasma-catalytic abatement of dilute ethylene. The adsorbent/catalyst prepared by ion exchange (Ag-EX/13X) exhibited better adsorption capability than the parent 13X and Ag-IM/13X prepared by the impregnation method. The oxidative transformation of the adsorbed ethylene was then performed by using three different reactor configurations such as one-stage (i.e., adsorbent/catalyst in direct contact with plasma), two-stage (i.e., adsorbent/catalyst located downstream of the plasma region), and the combination of the two (hybrid). The oxidation of the adsorbed ethylene to CO2 in the two-stage configuration can be explained by the diffusion of ozone into zeolite micro-pores, which was, however, much slower than in the one-stage and hybrid configurations. When compared at an identical applied voltage of 20 kV (inlet ethylene: 200 ppm; adsorption time: 100 min; plasma oxidation time: 20 min), the mineralization efficiency of the hybrid reactor was greater than the sum of those of one- and two-stage reactors, i.e., 63, 42, and 10%, respectively. Using the hybrid configuration, ozone and other reactive species were more effectively produced, thereby shortening the oxidation time of ethylene and therefore achieving a higher energy efficiency which was evaluated to be ca. 2.4 g (kWh)−1.

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