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The adsorption and reaction properties of heterogeneous zeolite catalysts (e.g. for catalytic cracking of petroleum, partial oxidation of natural gas) depend strongly on the types and distributions of Al heteroatoms in the aluminosilicate frameworks. The origins of these properties have been challenging to discern, owing in part to the structural complexity of aluminosilicate zeolites. Herein, combined solid‐state NMR and synchrotron X‐ray powder diffraction analyses show the Al atoms locate preferentially in certain framework sites in the zeolite catalyst Al‐SSZ‐70. Through‐covalent‐bond 2D 27Al{29Si} J‐correlation NMR spectra allow distinct framework Al sites to be identified and their relative occupancies quantified. The analyses show that 94 % of the Al atoms are located at the surfaces of the large‐pore interlayer channels of Al‐SSZ‐70, while only 6 % are in the sub‐nm intralayer channels. The selective siting of Al atoms accounts for the reaction properties of catalysts derived from SSZ‐70. [ABSTRACT FROM AUTHOR]

A literature survey reveals a prominent reduction in the concentration of Brønsted acid sites in hierarchically organized zeolites with increasing mesoporous or external surface area independent of the framework type or synthesis route; this suggests a common fundamental explanation. To determine the cause, nature, and impact of the underlying changes in aluminum speciation, this study combines a multitechnique analysis that integrates basic characterization, a detailed synchrotron XRD and multiple-quantum NMR spectroscopy assessment, and catalytic tests to correlate evolution of the properties with performance during successive steps in the preparation of hierarchical MFI-type zeolites by desilication. The findings, subsequently generalized to FAU- and BEA-type materials, identify the crucial impact of calcination on the protonic form, which is an integral step in the synthesis and regeneration of zeolite catalysts; on aluminum coordination; and the associated acidity trends. [ABSTRACT FROM AUTHOR]

A combination of advanced powder diffraction and NMR techniques have allowed the structure of the novel microporous aluminophosphate IST-1 (|(CH3NH2)4(CH3NH3+)4(OH−)4|[Al12P12O48]) to be elucidated. The framework structure was determined in the non-centrosymmetric space group Pca21 (a=9.61523(1) A˚, b=8.67024(1) A˚, c=16.21957(2) A˚) from high-resolution synchrotron powder diffraction data using the program FOCUS. Extra framework species were then located on difference electron density maps. A hydroxyl group was found to bridge between two of the framework Al atoms, and one methylamine species, presumably protonated, could be located in the channels where it H-bonds to three framework oxygens. The most unusual feature of the structure is the second methylamine molecule, which bonds directly to a framework Al atom. The structure is entirely consistent with 31P and 27Al MAS NMR studies, which showed there to be three P (all 4-coordinate) and three Al (one 4-, one 5- and one 6-coordinate) sites, and with 13C MAS NMR, which showed there to be two different types of methylamine species in equal amounts. Assignment of the 31P, 27Al and 13C MAS NMR signals could be deduced from the crystallographic data,31P-27Al HETCOR spectra and ab initio calculations. [Copyright &y& Elsevier]

Analysisof the structure of the zeolite ferrierite (frameworktype FER) synthesized using a combination of tetramethylammonium(TMA) and pyrrolidine as organic structure-directing agents (|((CH3)4N)0.4((CH2)4NH)3.6H1.7|[Si33.9Al2.1O72]) has revealed that TMA ions reside exclusively inthe [586682] cavities of the FERframework, whereas pyrrolidine species are found in boththe [586682] cavities and the main10-ring channel. A similar, but not identical, arrangement of pyrrolidinemolecules was found for a sample synthesized with pyrrolidine as theonly SDA (|((CH2)4NH)4.2H2.2|[Si33.8Al2.2O72])). A comparisonof the two structures shows the influence of TMA on the location ofpyrrolidine and the framework Al. Pyrrolidine species establish strongerinteractions with the zeolitic framework than does TMA, suggestinga different ability of the amine to exert an influence on the aluminumdistribution of the zeolite. These findings have implications in thecatalytic performance of the samples. [ABSTRACT FROM AUTHOR]