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Direct decomposition of N2O and the reduction of N2O with CH4 over Ga/H-ZSM-5 and Mo/Ga/H-ZSM-5 (Si/Al = 40) catalysts in a plug flow reactor under steady-state conditions as well as by temperature programmed surface reaction (TPSR) have been investigated. Ga ions were ion-exchanged from liquid phase while Mo was deposited onto the Ga/H-ZSM-5 sample using incipient wetness technique. The catalysts were characterized by means of XRF, XPS, TPR, CO chemisorption, TEM and EDS. The N2O forms redox centers in the Mo/Ga/H-ZSM-5 catalysts at elevated temperatures, which are extremely active in the reaction with CH4 already at around 373 K. Addition of Mo to the Ga/H-ZSM-5 decreased the T50 temperature in the N2O decomposition and reduction of N2O with CH4 from 819 to 787 K and from 755 to 646 K, respectively. The oxidation/reduction of the Mo/Ga/H-ZSM-5 sample is more favoured in the interaction with N2O/CH4 as compared to that using O2/H2 and the mechanism of the redox reactions might also be different. The reduction of N2O with CH4 cannot be described with the Mars–van Krevelen redox mechanism, but by the participation of CH4 via MoGa–OCH3 species in a complex oxygen transfer mechanism is proposed at which N2O does not directly reoxidise the reduced active centers. |
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