Dealumination and characterization of chabazite for catalytic application.

Dealumination of the small-pore zeolite chabazite (CHA) was performed with ammonium hexafluorosilicate under solid and liquid-state conditions to increase the Si-to-Al ratio from 2.0 to 6.0. In the solid state, the mesopore fraction increased with repeating hydrothermal synthesis at 423 K, which was confirmed by nitrogen adsorption-desorption. In the liquid state, the formation of mesopores decreased substantially and the resulting CHA had an Si-to-Al ratio of ca. 5. The result of desorption of NO-NO from the Cu ion-exchanged dealuminated CHA in the solid state indicated that the presence of mesopores reduced NO-NO adsorption and desorption of NO occurred at 383 and 683 K whereas for the high-silica analog SSZ-13 desorption of NO occurred mostly at 473 and at 673 K. [ABSTRACT FROM AUTHOR]