High Catalytic Activity in CO Oxidation over MnO x Nanocrystals

Abstract

Manganese oxides of various stoichiometry were prepared via Mn-oxalate precipitation followed by thermal decomposition in the presence of oxygen. A nonstoichiometric manganese oxide, MnO x (x = 1.61…1.67) was obtained by annealing at 633 K and demonstrated superior CO oxidation activity, i.e. full CO conversion at room temperature and below. The activity gradually decreased with time-on-stream of the reactants but could be easily recovered by heating at 633 K in the presence of oxygen. CO oxidation over MnO x in the absence of oxygen proved to be possible with reduced rates and demonstrated a Mars-van Krevelen-type mechanism to be in operation. A TEM structural analysis showed the MnO x phase to form microrods with large aspect ratio which broke up into nanocrystalline manganese oxide (MnO x ) particles with diameters below 3 nm and a BET specific surface area of 525 m 2 /g. Annealing at 798 K rather than 633 K produced well crystalline Mn 2 O 3 which showed lower CO oxidation activity, i.e. 100% CO conversion at 335 K. The catalytic performance in CO oxidation of various Mn-oxides either studied in this work or elsewhere was compared on the basis of specific reaction rates.

Formic Acid Modified Co3O4-CeO2 Catalysts for CO Oxidation

“…However, the high cost of noble materials is a concern. As alternatives, transition metal oxides and their mixed oxides have then been studied for CO oxidation, such as MnO x and CuO-CeO 2 [3,4].…”

Study on the hydrothermal and SO2 stability of Al2O3-supported manganese and iron oxide catalysts for lean CO oxidation

“…Furthermore, prospective CO oxidation activity was also shown for manganese oxide [7][8][9][10] and iron oxide catalysts [11][12][13]. Recently, we evaluated a series of ␥-Al 2 O 3 -supported manganese and iron oxide catalysts for the oxidation of CO under O 2 -rich conditions by systematically varying the metal loading as well as preparation procedure [14,15].…”

Co–Mn-oxide spinel catalysts for CO and propane oxidation at mild temperature

“…According to the reaction conditions the product was reported as Mn 3 O 4 [34], Mn 2 O 3 [22,35], MnO 2 [26] or amorphous MnO x [36].…”

“…ing mixed oxides with very high surface area (300-500 m 2 /g) [12,13]. Moreover this easy and inexpensive method is also very convenient to obtain mixed oxides [14].…”