Recent progress in catalytic NO decomposition

Abstract

a b s t r a c tRecent progress in catalytic direct NO decomposition is overviewed, focusing on metal oxide-based catalysts. Since the discovery of the Cu-ZSM-5 catalyst in the early 1990s, various kinds of catalytic materials such as perovskites, C-type cubic rare earth oxides, and alkaline earth based oxides have been reported to effectively catalyze direct NO decomposition. Although the activities of conventional catalysts are poor in the presence of coexisting O 2 and CO 2 , some of the catalysts reviewed in this article possess significant tolerance toward these coexisting gases. The active sites for direct NO decomposition are different depending on the types of metal oxide-based catalysts. In the case of perovskite type oxides, oxide anion vacancies act as catalytically active sites on which NO molecules are adsorbed. C-type cubic rare earth oxides contain oxide anion vacancies with large cavity space, enabling easy access of NO molecules and their subsequent adsorption. Surface basic sites on alkaline earth based oxides participate in NO decomposition as active sites on which NO molecules are adsorbed as NO 2 À species. The reaction mechanisms of direct NO decomposition are also discussed.

Co-Mn-Al Mixed Oxides Promoted by K for Direct NO Decomposition: Effect of Preparation Parameters

“…Haneda [22,58] proposed that over alkali metal doped Co 3 O 4 catalysts, NO 2 − species probably react with another NO adspecies resulting in the formation of N 2 O x intermediates, which decompose very fast into gaseous N 2 and adsorbed oxygen species. In the literature, it was most often considered that oxygen desorption is the rate determining step; however, some other steps like the attack of second NO molecule on the oxygen vacancy, NO 2 formation, N 2 O formation and decomposition were also considered by different authors [59,60]. Anyway, the suggestion that the formation of N 2 is directly caused from the collision of two activated nitrogen atoms and that formation of O 2 is combined by the two adsorbed oxygen atoms is valid across a lot of different studies [60].…”

Precipitated K-Promoted Co–Mn–Al Mixed Oxides for Direct NO Decomposition: Preparation and Properties

“…The direct decomposition of nitric oxide has been studied and described in some publications [6]. Apart from metals (Pt, Pd, Ag, Rh, Ni, Cu, Mo, Co, Au), metal oxides like Co 3 O 4 , Fe 2 O 3 , NiO, CuO, and ZrO 2 ; lanthanides; perovskites; and mixed oxides were also studied for direct NO decomposition [7][8][9][10].…”

“PdO vs. PtO”—The Influence of PGM Oxide Promotion of Co3O4 Spinel on Direct NO Decomposition Activity

“…Nitrogen oxides (NOx) formed by combustion from fixed and mobile sources cause severe detrimental environmental problems, such as acid rain and photochemical smog [1][2][3]. Effectively controlling the emission of NOx is the topic of much research and has led to the introduction of many new catalyst technologies, such as three-way catalysts (TWC), NOx storage-reduction (NSR), and selective catalytic reduction (SCR) for NOx gas removal from mobile sources, and SCR and selective non-catalytic reduction (SNCR) for NOx gas removal from fixed sources [4][5][6]. Among various deNOx strategies, direct decomposition of NO (NO→1/2O 2 + 1/2N 2 ) has been considered to be the most desirable method because this reaction is thermodynamically favorable at low temperatures and does not need any reductants, such as NH 3 , H 2 , CO, or hydrocarbons.…”

“…Among various deNOx strategies, direct decomposition of NO (NO→1/2O 2 + 1/2N 2 ) has been considered to be the most desirable method because this reaction is thermodynamically favorable at low temperatures and does not need any reductants, such as NH 3 , H 2 , CO, or hydrocarbons. However, kinetic studies have indicated that the reaction needs to overcome a large activation energy (~335 kJ mol −1 ) barrier [4][5][6][7][8][9][10][11][12][13][14][15]. Accordingly, there is an apparent need for a suitable catalyst to decompose NOx at a given temperature, and therefore, significant research has been undertaken towards development of active and stable catalysts.…”

“…Since the pioneering work of Jellinek on the catalytic decomposition of NO in 1906, much research has been reported on NO direct decomposition over several materials, including perovskites, rare earth oxides, and Cu-zeolites [2][3][4][5][6][7]. Numerous metal oxides have also been examined as candidates for NO decomposition catalysts [16] and Co 3 O 4 is often recognized as a significant component in many active catalysts at higher reaction temperatures [17][18][19][20][21].…”