Table 1
The physico-chemical properties of the prepared zeolite catalysts.
| Zeolite catalyst | Method of preparation | Si/Al ratio | Copper content [wt.%] | Surface area [m2·g−1] | Pore volume [cm3·g−1] |
|---|---|---|---|---|---|
| Cu-MFIa | ion exchange | 40 | 1.92 | 395.2 | 0.175 |
| Cu-MFIb | ion exchange | 28 | 3.65 | 425.6 | 0.193 |
| Cu,Al-MFIc | direct hydrothermal synthesis | 40 | 3.65 | 0.56 | 0.160 |
| Cu,Al-MFId* | direct hydrothermal synthesis | →∞ | 1.39 | 423.6 | 0.209 |
Fig. 1
SEM images of zeolite samples: (a) Cu-MFIa, (b) Cu-MFIb (c) Cu,Al-MFIc, (d) Cu,Zn-MFId.
Fig. 2
X-ray diffraction patterns of the zeolite samples Cu,Zn-MFId, Cu,Al-MFIc, Cu-MFIb and Cu-MFIa. Vertical arrows represent the peak positions of the reported powder patterns for the corresponding material (JCPDS-ICDD Card No. 37-0361).
Fig. 3
EPR spectra of hydrated Cu-MFI at room temperature: (a) Cu-MFIa, (b) Cu,Al-MFIc, (c) Cu,ZnMFId.
Table 2.
Evaluated parameters obtained from the prominent peaks position in EPR spectra for corresponding Cu+ centers.
| Zeolite catalyst | A║ [mT] | g║ | g⊥ | Intensity of EPR catalyst signal [a. u.] |
|---|---|---|---|---|
| Cu-MFIa | 12.0 | 2.371 | 2.129 | 17.25 |
| Cu,Al-MFIc | 12.4 | 2.372 | 2.072 | 2.53 |
| Cu,Zn-MFId | 12.4 | 2.392 | 2.081 | 1.83 |
Fig. 4
Dependence of NO conversion for obtained different flow rates of the reactant gas 723 K for fresh and reused Cu-MFIa catalyst.
Fig. 5
Influence of the pre-reaction thermal treatment of the catalyst at different calcination temperatures on the molar fraction of nitrogen in the reaction products for Cu-MFIa catalyst at different normalized residence times.
Fig. 6
Molar fraction of NO in the reaction products as a function of normalized residence times at temperatures lower than 623 K.
Fig. 7
Molar fraction of NO in the reaction products as a function of normalized residence times at different reaction temperatures (Cu,Zn-MFIdzeolite).
Fig. 8
Comparison of different catalysts in NO decomposition at higher reaction temperature (> 723 K).