A Study on the Reaction Characteristics of Vanadium-Impregnated Natural Manganese Oxide in Ammonia Selective Catalytic Reduction

Figures & data

Table 1a. Chemical properties of NMO

Component	Mn	SiO2	Al2O3	Fe	CaO	MgO	Balance O2 of Mn and Fe
wt %	51.85	3.13	2.51	3.86	0.11	0.25	38.33

Table 1b. Physical properties of NMO

Mean particle size	0.359 mm
Density	3980 kg/m^3
Pore volume	0.0369 cm^3/g
Surface area	23.29 m^2/g

Table 2. Physicochemical properties and NO_x conversion over NMO and V/NMO

	NMO	1% V/NMO	1% V/NMO OA	2% V/NMO	2% V/NMO OA
Mn atom (atoms/cm^3)	78.14	69.53	59.09	59.38	52.52
Vatom (atoms/cm^3)	–	9.76	9.98	10.63	11.22
V/Mn atomic ratio	–	0.14	0.17	0.17	0.21
Surface area (m^2/g)	23.29	22.13	22.40	17.30	15.60
pH in solution (NMO or NMO +V)	5.48	6.74	4.48	6.85	3.82
NOx conversion (%) at 175 °C	62.87	54.45	46.53	49.50	43.56

Figure 1. XRD patterns of NMO and V/NMO.

Figure 2. Effect of V loading and OA addition on NO_x conversion over NMO (space velocity [SV] = 60,000 hr⁻¹, NO = 190 ppm, NO₂ = 20 ppm, water vapor = 8%, O₂ = 15%, NO_x/NH₃ = 1).

Figure 3. Effect of temperature on NH₃ oxidation over NMO and V/NMO (SV = 60,000 hr⁻¹, NH₃ = 225 ppm, water vapor = 8%, O₂ = 15%, NO = 0, NO₂ = 0).

Figure 4. Effect of temperature on NH₃ oxidation over NMO as detected by mass spectroscopy (SV = 60,000 hr⁻¹, NH₃ = 225 ppm, water vapor = 8%, O₂ = 15%, NO = 0, NO₂ = 0).

Figure 5. Effect of temperature on NO oxidation over NMO and V/NMO (SV = 60,000 hr⁻¹, NO = 190 ppm, NO₂ = 20 ppm, water vapor = 8%, O₂ = 15%).

Figure 6. NH₃ TPD profiles of NMO.

Figure 7. Comparison of NO_x conversion with all desorbed nitrogen compounds from (a) B and (b) total acid sites over various samples.

Figure 8. Comparison of NO_x conversion with all desorbed nitrogen compounds from L acid sites over various samples.

Figure 9. Decrease in NO_x conversion with time after O₂ on-off over NMO (SV = 60,000 hr⁻¹, NO = 190 ppm, NO₂ = 20 ppm, water vapor = 8%, O₂ = 15%, NO_x/NH₃ = 1).

Figure 10. Decrease in NO_x conversion with time after O₂ on-off over NMO, 1%V/NMO, and 2%V/NMO (SV = 60,000 hr⁻¹, NO = 190 ppm, NO₂ = 20 ppm, water vapor = 8%, O₂ = 15%, NO_x/NH₃ =1 at 200 °C).

Table 3. Relative amount of active lattice oxygen in NMO and V/NMO

	NMO	1%V/NMO	2%V/NMO
Relative amount of active lattice oxygen	1	0.34	0.33