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(264a) Novel Three-Phase Zeolite Intergrowth (CHA/ERI/OFF) Control with a Single Organic Structure-Directing Agent (SDA)

Roman, Y., MIT
Schwalbe-Koda, D., Massachusetts Institute of Technology
Willhammar, T., Stockholm University
Gomez-Bombarelli, R., Massachusetts Institute of Technology
Olivetti, E., Massachusetts Institute of Technology
Moliner, M., ITQ (CSIC-UPV)
Zeolites have been widely used in industry as catalysts due to their intrinsic micropore structures including cages, cavities, and channels. The topological diversity of interconnections between tetrahedral atoms makes the shapes and microstructures of zeolites versatile and unique. Since the zeolite synthesis is controlled with complicated synthetic parameters, the resultant phase occasionally results in physical mixtures or intergrowths of two crystals rather than phase-pure zeolites.

Recently, zeolite intergrowth structures have gained attraction since they showed prolonged catalytic lifetime and enhanced selectivity due to their extraordinary geometries of channels and active sites, compared to their pure phases or physical mixtures. Many of the zeolite intergrown structures are synthesized with the dual-template synthesis method, where each organic structure-directing agent (SDA) plays a role in the synthesis of the pure phase respectively. However, the requirement of two costly SDAs and the uncertainty of the final product phase resulted in only tens of zeolite intergrowths reported in the literature. Also, up to our knowledge, only two-phase intergrowth with limited control has been reported so far.

Here, for the first time, we introduce a novel way to selectively control the three-phase intergrowth family of CHA/ERI/OFF with a single organic SDA. The amount of each phase in the intergrown system has been controlled with the ratio of organic SDA and inorganic alkaline cations in the precursor gel. Powder X-ray diffraction and iDPC-STEM analysis reveal the anatomy of the unique intergrown structures. DFT simulations give insights into the control mechanism supporting the stabilization effect of organic SDAs and inorganic cations of cages inside the zeolites. We envision this new structure can show outstanding performance in methanol-to-olefin and deNOx reactions.