Selective Catalytic Oxidation of Ammonia to Nitrogen on CuO-CeO2 Bimetallic Oxide Catalysts

Abstract

This study addresses the performance of the selective catalytic oxidation (SCO) of ammonia to N 2 over a CuO-CeO 2 bimetallic oxide catalyst in a tubular fixed-bed reactor (TFBR) at temperatures from 423 to 673 K in the presence of oxygen. CuO-CeO 2 bimetallic oxide catalyst was prepared by co-precipitation with Cu(NO 3 ) 2 and Ce(NO 3 ) 3 at various molar concentrations.This study tested operational stability and investigated how the influent NH 3 concentration (C 0 = 500-1000 ppm) influences the capacity to remove NH 3 . The catalysts were characterized using XRD, FTIR, PSA, SEM and EDX. Ammonia was removed by oxidation in the absence of CuO-CeO 2 bimetallic oxide catalyst, and the formation of copper (II) and cerium (IV) oxide active sites was confirmed. Additionally, the effects of the NH 3 content of the carrier gas on the catalyst's reaction rate (r) were observed. The results revealed that the extent of catalytic oxidation of ammonia in the presence of a CuO-CeO 2 bimetallic oxide catalyst was a function of the molar ratio Cu:Ce in the bimetallic catalyst. The kinetics of catalyzed NH 3 oxidation are described using the rate expression of the Eley-Rideal kinetic model. Also, experimental results indicate a reasonable mechanism for the catalytic oxidation of ammonia.

Advances in selective catalytic oxidation of ammonia to dinitrogen: a review

“…An interesting concept of the catalyst for the lowtemperature ammonia oxidation, based on CuO-CeO 2 oxide system was proposed by Hung. 117,118 Cerium dioxide in copper catalyst can be assumed to promote the formation of the active phase of CuO under the conditions of ammonia oxidation. Moreover, CeO 2 -based materials, due to the Ce 3+ -Ce 4+ redox couple, can act as oxygen buffers by storing/releasing O 2 .…”

“…Moreover, CeO 2 -based materials, due to the Ce 3+ -Ce 4+ redox couple, can act as oxygen buffers by storing/releasing O 2 . 119 The samples with different CuO : CeO 2 molar ratios (6 : 4, 7 : 3, 8 : 2 and 9 : 1) were prepared by co-precipitating copper nitrate and cerium nitrate using K 2 CO 3 as precipitating agent, followed by calcination of the obtained precipitates at 773 K. 117,118 The highest ammonia conversion (99% at 673 K) and selectivity to N 2 was obtained for the sample with the CuO : CeO 2 molar ratio of 6 : 4. Author reported that the efficiency of ammonia conversion increased with reaction temperature and as the residence period was reduced.…”

“…One of the main drawbacks of the co-precipitated CuO-CeO 2 studied by Hung was their relatively low surface area that limited the rate of ammonia conversion. 117,118 This problem was solved by Wang et al, who studied CuO-CeO 2 oxide system obtained by the surfactant directed method. 120 Cetyltrimethyl ammonium bromide (CTAB) was used as surfactant, while Cu(NO 3 ) 2 and Ce(NO 3 ) 3 solutions were used as precursors of mixed metal oxides.…”

Removal of Gaseous Ammonia in Pt-Rh Binary Catalytic Oxidation

“…The most promising and widely used technology for solving NH 3 pollution is the selective catalytic oxidation (SCO) of ammonia (SCO-NH 3 ) to produce N 2 and H 2 O (Hung, 2006;Hung, 2008a;Cui et al, 2010;Hung, 2010;Hung, 2011b). This important heterogeneous catalytic process has attracted significant attention in materials chemistry and the effectiveness of the oxidation process has been improved by using high-performance catalysts, which potentially shorten the reaction time of the oxidation and allow the reaction to proceed under milder operating conditions.…”

Preparation Methods and Applications of CuO-CeO2 Catalysts: A Short Review

“…Reactions of other importance are concerned with the selective oxidation of ammonia to nitrogen [68] and lower hydrocarbon reforming into synthetic gas [69]. Further, Cu/CeO2 composite catalytic electrodes are used for direct oxidation of various fuels in fuel cells [70][71][72][73].…”