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>Modification of CrCeOx with Mo: improved SO2 resistance and N-2 selectivity for NH3-SCR at medium-low temperatures
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Modification of CrCeOx with Mo: improved SO2 resistance and N-2 selectivity for NH3-SCR at medium-low temperatures
NH3-SCR at medium and low temperatures is an effective method for the removal of nitrogen oxides (NOx) in industrial furnaces. Chromium (Cr) and cerium (Ce) based catalysts exhibit excellent NH3-SCR potential at medium and low temperatures, but their sulfur resistance and N-2 selectivity need to be further improved. In this manuscript, the Mo(0.3)-CrCeOx catalyst was synthesized via the citric acid method, and showed high catalytic activity with excellent sulfur resistance and N-2 selectivity. The mechanism of Mo doping was investigated. The highly dispersed amorphous MoO3 was found, forming a Mo-O-Ce structure and generating more strong acid sites. The mechanism of Mo doping for enhanced SO2 resistance and N-2 selectivity was further investigated by in situ DRIFTS. By effectively modulating the catalyst basicity, the generation of the active intermediate cis-N2O22- species was promoted. The change from the E-R to L-H mechanism is the key. The strong oxidation of Cr6+ species was appropriately suppressed, thus the N-2 selectivity was improved. It also prevents SO2 from competing for basic sites on Cr species. In a word, all the improved performances were attributed to Mo doping. Finally, the SCR process is proposed.
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