Toward the Synthesis of New Zeolite Structures in the Presence of Cesium: Zeolite MMU-1

Abstract

Nanosized small-pore zeolites RHO and MMU-1 (a new Cs-Na modification of an EDI-type zeolite structure) were prepared in the presence of cesium hydroxide by changing the molar composition of the precursor zeolite solution. XRD, Raman, and FTIR results indicated that Cs had a structure-directing effect and controlled the formation of the respective zeolite phases. The presence of water played a crucial role, and when the amount of water was under a certain level, the zeolite cancrinite was formed. Solvent-free syntheses were attempted, and the results confirmed the conclusions drawn based on the water-mediated syntheses, namely that both Cs and water determine the nature of the product formed. The structure of the new zeolite MMU-1 was resolved by Rietveld refinement. MMU-1 was found to exhibit tetragonal symmetry, space group P 21 c (No. 114), and its framework is composed of four-membered and eight-membered TO4-rings. The results reported suggest that there is the potential to synthesize other novel small-pore zeolite structures in the presence of cesium hydroxide by modifications of the chemical composition of the zeolite precursor solution.

Vapor-Assisted Synthesis of Nanosized Beta-Zeolite from Natural Ores and Using as Efficient Catalysts for Baeyer–Villiger Oxidation

“…Figure b displays the high-resolution Sn XPS spectra in sample Sn-Beta-100. Two signal peaks at 487.5 and 495.7 eV were indexed to the Sn 3d5/2 and Sn 3d3/2, and these bands can be ascribed to the tetrahedral coordination framework Sn(IV) species . The presence of extra-framework octahedral coordination Sn(VI) could be ruled out in the Sn-Beta-100 sample because we did not find any XPS peaks at 486.0 and 494.4 eV.…”

The Current Understanding of Mechanistic Pathways in Zeolite Crystallization

“…Most cases with multiple SDAs demonstrate cooperative effects that promote zeolite products with improved properties compared to cases involving only a single SDA. Selected cases with multiple ISDAs include studies showing reduced crystal sizes or more rapid crystallization kinetics. ,, The most common examples with multiple SDAs involve combinations of OSDAs and ISDAs to either control synthesis pathways or reduce organic content. Davis and co-workers discussed that soluble inorganic and organic species can interact when their overlapping hydration spheres are commensurate with van der Waals radii.…”

Zeolite Crystal Engineering

“…The number of variables in zeolite synthesis is a daunting task for experimental design. Many studies have examined the role of key reagents, including the selection of silica/alumina sources, inorganic/organic structure-directing agent cations, and corresponding anions. − Seed-assisted syntheses are being more commonly recognized as versatile approaches in zeolite crystal engineering. For instance, interzeolite transformation (IZT) from an initial (parent) to a final (daughter) crystal , can often produce materials with properties that cannot be achieved by conventional methods.…”