N₂O Decomposition over Perovskite Catalysts

Abstract

Four perovskite catalysts LaBO3 (where B = Cr, Mn, Fe, and Co) were prepared via a highly exothermic and self-sustaining reaction, the so-called “solution combustion synthesis (SCS)”, and characterized by means of X-ray diffraction, BET, field-emission scanning electron microscopy−energy-dispersive spectrometry, and H2-temperature-programmed reduction (TPR) analyses. The performance of these catalysts toward the decomposition of N2O to N2 and O2 was evaluated in a temperature programmed reaction (TPRe) apparatus in the absence and the presence of different oxygen concentrations. Among the catalysts screened, LaCoO3 showed the best performance, with 50% conversion of N2O at 455 °C and 490 °C in the absence and presence of 5% of oxygen, respectively. The LaCoO3 catalyst was deposited by in situ SCS directly over a ceramic honeycomb monolith and then tested in a lab-scale test rig. The coated ceramic monolith gave 50% N2O conversion performance similar to that obtained on powder for GHSV values of industrial interest (10 000−30 000 h-1). The correlation between the observed oxygen inhibition and the proposed N2O decomposition mechanism as well as the relationship between the observed activity and the reducibility of the B site, determined from TPR experiments, is discussed.

A comprehensive investigation of influences of NO and O2 on N2O-SCR by CH4 over Fe-USY zeolite

“…In each test, 0.10 g catalyst (sieve fraction: 0.25-0.5 mm) was placed into a quartz reactor (4 mm i.d.) and pretreated in He at 600 8C for 1 h. After the reactor was cooled down to 200 8C, the reactant gas mixture (N 2 O, CH 4 and other gases, He balance) was fed into the catalytic reactor with the total flow rate at 60 ml min À1 , i.e. GHSV = $30,000 h À1 .…”

“…Although most zeolite catalysts suffer the activity loss during the operation under these practical conditions, we have luckily found that Fe-USY zeolite shows a high activity and a high hydrothermal stability for N 2 O decomposition in our previous studies under the similar conditions [11,12]. Therefore, the objective of this paper was to examine the catalytic behaviors of N 2 O-CH 4 4 -derived intermediates. The negative effect of NO is very prominent, inhibiting the N 2 O conversion by strongly occupying the active sites and gradually moving the reaction pathways from N 2 O-CH 4 SCR to NO-assisted N 2 O decomposition, where the former is more efficient than the latter for N 2 O decomposition under the same operation conditions.…”

“…To this end, various kinds of catalysts, such as metal oxides [3][4][5], supported noble metals [6] and transition metal-exchanging zeolites (Co-zeolite, Fe-zeolite, etc.) [7][8][9][10][11][12][13], have been intensively investigated for N 2 O direct decomposition.…”

“…Methane is the main component of natural gas and also present in some combustion exhaust. Compared with NH 3 -SCR of N 2 O, CH 4 SCR is more advantageous in transportation, storage, equipment corrosion, etc. Therefore, CH 4 SCR of N 2 O is thought as a practical method to eliminate N 2 O in terms of the efficiency and the cost.…”

A study on N2O catalytic decomposition over Co/MgO catalysts

“…supported noble metals [3][4][5], mixed oxides with different structure [6][7][8][9][10], iron zeolites [11][12][13][14][15], have been investigated for N 2 O decomposition. Supported cobalt catalysts have received considerable attention due to high activity [16][17][18][19][20][21][22][23][24][25][26].…”