Accelerated Construction of High-Silica RHO and CHA Zeolites via Interzeolite Transformation and Their NH3-SCR Performances after Copper Exchange

Rapid and selective synthesis of high-silica zeolites, including topologies of RHO and CHA, has been realized by interzeolite transformation process. The XRD patterns and morphology images collected within the whole procedure of aging and reaction suggest that the interzeolite transformation from FAU to RHO zeolite proceeds in a way of directly reassembling the locally ordered FAU-derived species, but as quasi-amorphous domains, on the surface of the RHO moieties. Therefore, the crystallization process could be remarkably accelerated by circumventing the incipient nucleation from the fundamental Si/Al species. Thenceforth, the high-silica descendant zeolites obtained by interzeolite transformation were all employed in the NH3-SCR process after copper ion exchange to a similar level. Therein, the RHO zeolite achieves fine trade-off between the activity and durability even after hydrothermal treatment at 800 degrees C, which indicates that the durability issue involved could be validly fixed by this zeolite and once again highlights the advantages of the interzeolite conversion process