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Title: Structure of an Aluminophosphate EMM-8: a Multi-Technique Approach

Abstract

The crystal structure of an aluminophosphate, EMM-8 (ExxonMobil Material No. 8), was determined in its calcined, anhydrous form from synchrotron powder diffraction data using the computer program FOCUS. A linkage of double four-ring (D4R) building units forms a two-dimensional framework with 12-MR and 8-MR channels, and differs from a similar SAPO-40 (AFR) framework only by the relationship between paired D4R units. Rietveld refinement reveals a fit of the model to the observed synchrotron data by R{sub 2p} = 0.1118, R(F{sup 2}) = 0.1769. Local environments of the tetrahedral phosphorus and aluminium sites were established by solid-state NMR, which detects distinct differences between as-synthesized and calcined materials. Distinct, reversible changes in the local symmetry of the P and Al atoms were observed by NMR upon calcination and subsequent hydration. These NMR data provided important constraints on the number of tetrahedral (T) atoms per unit cell and the connectivities of the T atoms. Detailed local structural information obtained by solid-state NMR thereby guided the ultimate determination of the structure of AlPO EMM-8 from the powder data. Comparisons are made to the recently published crystal structure of the fluoride-containing, as-synthesized SSZ-51, indicating that the unit-cell symmetry, axial dimensions and framework structure are preservedmore » after calcination.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930331
Report Number(s):
BNL-81042-2008-JA
Journal ID: ISSN 0108-7681; ASBSDK; TRN: US200904%%625
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Crystallographica Section B: Structural Science; Journal Volume: 63
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM; ATOMS; CALCINATION; CRYSTAL STRUCTURE; DIFFRACTION; DIMENSIONS; HYDRATION; PHOSPHORUS; SYMMETRY; national synchrotron light source

Citation Formats

Cao,G., Afeworki, M., Kennedy, C., Strohmaier, K., and Dorset, D.. Structure of an Aluminophosphate EMM-8: a Multi-Technique Approach. United States: N. p., 2007. Web. doi:10.1107/S0108768106040109.
Cao,G., Afeworki, M., Kennedy, C., Strohmaier, K., & Dorset, D.. Structure of an Aluminophosphate EMM-8: a Multi-Technique Approach. United States. doi:10.1107/S0108768106040109.
Cao,G., Afeworki, M., Kennedy, C., Strohmaier, K., and Dorset, D.. Mon . "Structure of an Aluminophosphate EMM-8: a Multi-Technique Approach". United States. doi:10.1107/S0108768106040109.
@article{osti_930331,
title = {Structure of an Aluminophosphate EMM-8: a Multi-Technique Approach},
author = {Cao,G. and Afeworki, M. and Kennedy, C. and Strohmaier, K. and Dorset, D.},
abstractNote = {The crystal structure of an aluminophosphate, EMM-8 (ExxonMobil Material No. 8), was determined in its calcined, anhydrous form from synchrotron powder diffraction data using the computer program FOCUS. A linkage of double four-ring (D4R) building units forms a two-dimensional framework with 12-MR and 8-MR channels, and differs from a similar SAPO-40 (AFR) framework only by the relationship between paired D4R units. Rietveld refinement reveals a fit of the model to the observed synchrotron data by R{sub 2p} = 0.1118, R(F{sup 2}) = 0.1769. Local environments of the tetrahedral phosphorus and aluminium sites were established by solid-state NMR, which detects distinct differences between as-synthesized and calcined materials. Distinct, reversible changes in the local symmetry of the P and Al atoms were observed by NMR upon calcination and subsequent hydration. These NMR data provided important constraints on the number of tetrahedral (T) atoms per unit cell and the connectivities of the T atoms. Detailed local structural information obtained by solid-state NMR thereby guided the ultimate determination of the structure of AlPO EMM-8 from the powder data. Comparisons are made to the recently published crystal structure of the fluoride-containing, as-synthesized SSZ-51, indicating that the unit-cell symmetry, axial dimensions and framework structure are preserved after calcination.},
doi = {10.1107/S0108768106040109},
journal = {Acta Crystallographica Section B: Structural Science},
number = ,
volume = 63,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}