Ag+ -Exchanged LSX (Ag-LSX: Ag96 Al96 Si96 O384 ⋅n H2 O), a large pore low silica analogue (Si/Al=1.0) of faujasite, was prepared and post-synthetically modified using pressure and temperature in the presence of various pore-penetrating fluids. Using high-resolution synchrotron X-ray powder and single crystal diffraction we derive structural models of the as-prepared and post-synthetically modified Ag-LSX materials. In the as-prepared Ag-LSX model, we located 96 silver cations and 245 H2 O molecules distributed over seven and five distinctive sites, respectively. At 1.4(1) GPa pressure and 150 °C in ethanol the number of silver cations within the pores of Ag-LSX is reduced by ca. 47.4 %, whereas the number of H2 O molecules is increased by ca. 40.8 %. The formation of zero-valent silver nanoparticles deposited on Ag-LSX crystallites depends on the fluid present during pressurization. Ag-nanoparticle-Ag-zeolite hybrid materials are recovered after pressure release and shown to have different chemical reactivity when used as catalysts for ethylene epoxidation.
Keywords: ag-lsx; auto-reduction; catalyst; ethylene epoxidation; post-synthesis; pressure/ temperature.
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