Removal of dilute nitrous oxide from gas streams using a cyclic zeolite adsorption–plasma decomposition process.

Removal of dilute N 2 O from gas streams by a cyclic adsorption–decomposition using Ca13X (Ca 2+ exchanged 13X) in combination with N 2 nonthermal plasma was studied in this work. Zeolite 13X was found to be the best for N 2 O uptake among tested commercial zeolites including 4A, H-β and 13X. By modifying 13X with Ca 2+ cation using ion-exchange method, the N 2 O adsorption capacity was greatly enhanced from ca. 3.5 × 10 −6 to 80 × 10 −6 mol g zeolite - 1 due to the stronger interaction of N 2 O with Ca 2+ cation than that with Na + cation. Ca. 96% of N 2 O removal efficiency at a SIE eq (equivalent specific input energy) of 1116 J L −1 was obtained under the cyclic operation of 60-min N 2 O adsorption (initial concentration: 510 ppm, gas flow rate: 0.5 L min −1 ) over Ca13X followed by 20-min plasma decomposition of adsorbed N 2 O in stationary N 2 atmosphere. In comparison, a similar performance was reached at a relatively high SIE of 1700 J L −1 as the reactor was operated under continuous plasma condition. The time period of plasma step and therefore the energy consumption could be reduced by properly circulating N 2 gas in the reactor. Also, SIE eq was found to decrease with increasing the adsorption time, whereby ca. 95% of N 2 O removal efficiency could be achieved at a SIE eq of 298 J L −1 as the adsorption time was 180 min. The regeneration of N 2 O-adsorbed Ca13X by N 2 plasma was initiated by plasma-induced desorption of adsorbed N 2 O followed by decomposing the desorbed N 2 O in plasma gas phase. [ABSTRACT FROM AUTHOR]