The effect of trivalent framework heteroatoms in Cu-CHA on the Selective Catalytic Reduction of NO

• Published in: Applied catalysis. A, General Vol. 626; p. 118326
• Main Authors: Tomkins, Patrick, Marler, Bernd, McGuire, Robert, Müller, Ulrich, Feyen, Mathias, Parvulescu, Andrei-Nicolae, Zhang, Weiping, Yokoi, Toshiyuki, Xiao, Feng-Shou, Gies, Hermann, Kolb, Ute, Zhao, Haishuang, Valvekens, Pieterjan, De Baerdemaeker, Trees, De Vos, Dirk
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.09.2021; Elsevier Science SA
• Subjects: Ammonia; Borosilicate; Catalytic activity; Chabazite; Chemical reduction; Copper; Gallosilicate; Heteroatom substitution; Hydrophobicity; Low temperature; NH3 breakthrough; NO oxidation; Oxidation; SCR; Selective catalytic reduction; Selectivity; Speciation; Zeolites; Chabazite; Borosilicate; SCR; Heteroatom substitution; NH3 breakthrough; Gallosilicate; NO oxidation; Zeolites
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2021.118326

[Display omitted] •B- or Ga-substituted CHA zeolites were used as hosts for Cu2+ in deNOx SCR.•Activity of Cu-Ga-CHA is on par with that of the Al-analogue.•The stability of the Cu-Ga-CHA can be adjusted via the Si/Ga ratio.•Remarkably, N2O make by Cu-Ga-CHA is significantly lower than on Cu-Al-CHA. The effect of the trivalent framework atoms (Si4+/M3+ = 13-105) in Cu exchanged CHA-type zeolites was investigated for the selective catalytic reduction of NO with NH3. While the increased hydrophobicity of B-CHA compared to Al-CHA could make it a good candidate for low temperature SCR, the material was too unstable under reaction conditions and the exchanged Cu2+ did not remain isolated. Consequently a lower activity and selectivity than for Al-CHA were observed. Ga-CHA on the other hand showed a similar Cu2+ speciation as Al-CHA at similar Si4+/M3+ ratios. The difference in catalytic activity was remarkably small. While Ga-CHA was less stable upon hydrothermal aging, this was markedly improved by increasing the Si/Ga ratio and by inserting the Cu2+ during the synthesis of the zeolite. Remarkably, the Cu-loaded Ga-CHA catalysts demonstrated a consistently lower selectivity to N2O by-product formation compared to Al-CHA because of a lower tendency for NO oxidation.