Efficient NH3-SCR removal of NOx with highly ordered mesoporous WO3(χ)-CeO2 at low temperatures

Abstract

To eliminate nitrogen oxides (NOx), a series of highly ordered mesoporous WO3(χ)-CeO2 nanomaterials (χ represents the mole ratio of W/Ce) were synthesized by using KIT-6 as a hard template, which was used for selective catalytic reduction (SCR) to remove NOx with NH3 at low temperatures. Moreover, the nanomaterials were characterized by TEM, XRD, Raman, XPS, BET, H2-TPR, NH3-TPD and in situ DRIFTS. It can be found that all of the prepared mesoporous WO3(χ)-CeO2 (χ = 0, 0.5, 0.75, 1 and 1.25) showed highly ordered mesoporous channels. Furthermore, mesoporous WO3(1)-CeO2 exhibited the best removal efficiency of NOx, and its NOx conversion ratio could reach 100% from 225 ° C to 350 ° C with a gas hourly space velocity of 30 000 h−1, which was due to higher Ce3+ concentrations, abundant active surface oxygen species and Lewis acid sites based on XPS, H2-TPR, NH3-TPD and in situ DRIFTS. In addition, several key performance parameters of mesoporous WO3(1)-CeO2, such as superior water resistance, better alkali metal resistance, higher thermal stability and N2 selectivity, were systematically studied, indicating that the synthesized mesoporous WO3(1)-CeO2 has great potential for industrial applications.

Insight into the Synergism between Copper Species and Surface Defects Influenced by Copper Content over Copper/Ceria Catalysts for the Hydrogenation of Carbonate

“…Figure a shows the Ce 3d, O 1s, and Cu LMM spectra of the reduced catalysts. The peaks u 1 and 1 correspond to the 3d 10 4f 1 electronic state of the Ce 3+ ions, whereas the peaks u , u 2, u 3, , 2, and 3 are the main representatives of the 3d 10 4f 0 state corresponding to Ce 4+ . The amount of Ce 3+ increases gradually from 12.7 % until it hits a maximum at 18.4 % and then decreases to 17.8 % (Table ).…”

Molybdenum modified Montmonrillonite clay as an efficient catalyst for low temperature NH3‐SCR

“…The NO x conversion rate (X NO , %) and the N 2 selectivity rate (S N2 , %) were attained by the following Eq. (1) and (2) …”

Improving the Diagnosis Accuracy of Hydrothermal Aging Degree of V2O5/WO3–TiO2 Catalyst in SCR Control System Using an GS–PSO–SVM Algorithm

“…Figure 7 illustrates the rough selection results of the main parameters in a SVM classifier (C and g) through the GS method. It is obvious that in the range of C[2 4 2 ], the classification accuracy of training data samples can be more than 98%; that is, the optimal c and g are probably to be located within these two ranges. Hence, as in the procedure mentioned above, the PSO algorithm is utilized to search precisely in the range of C[2 4 2 ].…”

“…It is obvious that in the range of C[2 4 2 ], the classification accuracy of training data samples can be more than 98%; that is, the optimal c and g are probably to be located within these two ranges. Hence, as in the procedure mentioned above, the PSO algorithm is utilized to search precisely in the range of C[2 4 2 ]. Then, the optimal c and g, which are obtained through PSO, will be applied in the SVM model to verify the diagnosis effect on hydrothermal aging of the SCR catalyst by testing the data samples.…”

“…Therefore, the reduction of NO x emissions from diesel engine becomes one of the most important objectives for the after-treatment system. In order to solve this problem, a urea based selective catalytic reduction (Urea-SCR) is regarded as the most promising and efficient technique for NO x reduction [1][2][3][4], which can control the NO x emission through the SCR reaction between NH 3 (decomposed from urea) and NO x . Nevertheless, owing to the fact that NH 3 is also a kind of pollutant, the trade-off between NO x conversion efficiency and NH 3 leakage should be taken into consideration.…”