2007_6_Nr6_EEMJ

Chirila et al /Environmental Engineering and Management Journal 6 (2007), 6, 549-553
Conversia NO x
[%]
100
90
80
70
60
50
40
30
20
10
0
600 °C
800 °C
1000 °C
150 200 250 300 350 400 450 500 550 600 650
Oxygen lack in synthetic gas mixture leaded to
important changes of conversion curves for both
propane oxidation and nitrogen oxides reduction.
Fig.6 displays, reduction reaction was favored, while
oxidation reaction has kept constant values in whole
temperature range in which tests were performed. The
higher values for oxidation reaction belong to
perovskite sample calcined at 600 o C which proves to
be again the most efficient perovskite in propane
oxidation while LaMnO 3 sample calcined at 800°C
presented lower values, almost negligible.
Temperatura [°C]
100
100
90
90
80
Conversia C 3
H 6
[%]
80
70
60
50
40
30
20
10
0
600
800
1000
150 200 250 300 350 400 450 500 550 600 650
Temperatura [°C]
Conversiea NO x
[%]
70
60
50
40
30
20
10
0
600
800
1000
150 200 250 300 350 400 450
Temperature [°C]
Fig. 4. Nitrogen oxides (a) and propene (b) conversion for
the LaMnO 3 perovskite samples (propene 600 ppm, NOx
600 ppm)
Conversia NO x
[%]
Conversia C 6
H 8
[%]
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
600 °C
800 °C
1000 °C
150 200 250 300 350 400 450
Temperatura [°C]
600 °C
800 °C
1000 °C
150 200 250 300 350 400 450
Temperatura [°C]
Fig. 5. Nitrogen oxides (a) and propane (b) conversion for
the LaMnO 3 perovskite samples (propane 400 ppm, NOx
600 ppm, 5% O 2 )
Conversia C 6
H 8
[%]
100
90
80
70
60
50
40
30
20
10
0
600 °C
800 °C
1000 °C
150 200 250 300 350 400 450
Temperatura [°C]
Fig. 6. Nitrogen oxides (a) and propane (b) conversion for
the LaMnO 3 perovskite samples (propane 400 ppm, NOx
600 ppm)
4. Conclusions
The characterization by presented physicochemical
methods confirmed that the synthesized
samples are perovskite structures with a high
homogeneity and crystallinity. The calcination
process has leaded to three different symmetry of
LaMnO 3 perovskite due to octahedral distortion.
It is well known that perovskites present a
certain small surface comparing with other catalysts.
The BET specific surface of LaMnO 3 perovskite was
found 24m 2 /g corresponding to the sample obtained at
600 o C and decreases once with the calcinations
temperature rising up to 2.5m 2 /g in the case of
calcinations sample at 800 o C. The oxidation state of
the manganese from the LaMnO 3 perovskite leaded to
552