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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}
}
  • Molecular sieves are extensively used in the chemical and petrochemical industry as catalysts, absorbents, and ion exchangers. New molecular sieve structures have the potential to improve the performance of these materials. We have discovered a new microporous material, EMM-3, prepared in both aluminophosphate and silicoaluminophosphate compositions by use of N,N,N,N{prime},N{prime},N{prime}-hexamethyl-1,6-hexanediammonium as a template at 160 C in 20 h. The structure of EMM-3 has been solved and refined from powder data by use of synchrotron X-ray radiation. The unit cell for the calcined AlPO form of EMM-3 has monoclinic space group symmetry, I2/m11, with cell dimensions a = 10.3132(2), bmore » = 12.6975(3), and c = 21.8660(4) and {alpha}= 89.656(1). The microporous structure contains 12-ring, sinusoidal, unidimensional channels with pore openings of 6.1 x 6.5 Angstroms. This new framework contains two new building chains, not observed in other known framework structures. The {sup 31}P and {sup 27}Al NMR spectra of the calcined/dehydrated form are in agreement with a fully connected tetrahedral structure containing five unique phosphorus and five unique aluminum atoms. The material is stable upon calcination and absorbs 9-10 wt % hydrocarbons.« less
  • A new chiral one-dimensional (1D) aluminophosphate chain compound [d-Co(en){sub 3}][AlP{sub 2}O{sub 8}].6.5H{sub 2}O (designated AlPO-CJ22) has been hydrothermally synthesized by using the optically pure d-Co(en){sub 3}I{sub 3} complex as the template. Single-crystal structural analysis reveals that its structure is built up from alternating connection of AlO{sub 4} and PO{sub 2}(=O{sub 2}) tetrahedra to form corner-shared Al{sub 2}P{sub 2} four-membered ring (4-MR) chains. The d-Co(en){sub 3}{sup 3+} complex cations extended along the 2{sub 1} screw axis interact with the inorganic chains through hydrogen-bonds of N...O atoms in a helical fashion. Optical rotation measurement shows that AlPO-CJ22 is chiral as with d-Co(en){submore » 3}{sup 3+} complex cations. Crystal data: orthorhombic, I2{sub 1}2{sub 1}2{sub 1}, a=8.5573(8)A, b=22.613(2)A, c=22.605(2)A, Z=8, R{sub 1}=0.067, wR{sub 2}=0.1291, and Flack parameter: -0.02(3). CCDC number: 254179. -0.02(3). CCDC number: 254179.« less
  • An aluminophosphate with a layer structure has been synthesized hydrothermally. The ratio P/Al = 2 for the framework; its structure consists of Al-centered tetrahedra and P-centered tetrahedra as basic building units to form a two-dimensional layer structure. The protonated ethylenediamine molecules are located in the interlayer space and sustain the framework. The water molecules are located in the space between two layers. Layers are joined together by van der Waals force to form a three-dimensional structure which crystallizes in the space group Pbnb, with a = 8.052(6), b = 8.760(2), c = 17.037(7) {angstrom}, and V = 1201.88 {angstrom}{sup 3}.more » The crystal structure has been refined to yield values of R = 0.0418, R{sub w} = 0.0447.« less
  • Three sodium aluminophosphate glasses proposed for the immobilization of high- and medium-level radioactive wastes were studied by IR and ESR spectroscopy. This study involves the effect of Cs{sub 2}O, SrO, CoO, CaO, Fe{sub 2}O{sub 3}, SO{sub 3}, and NaCl on the anionic motic of the glasses. It is shown that the structural network of sodium aluminophosphate glasses consists of interlinked [PO{sub 4}] and [AlO{sub 4}] groups. The addition of Cs{sub 2}O (instead of Na{sub 2}O) and Fe{sub 2}O{sub 3} (instead of Al{sub 2}O{sub 3}) does not cause any appreciable changes in glass structure. The addition of SrO, CoO, CaO, SO{submore » 3}, NaCl, and simulated high-level radioactive waste oxides somewhat reduces the degree of polymerization of the structural network.« less
  • The local structure of cerium in two systematic compositional series of glasses, nominally CeP{sub 3}O{sub 9}-AlP{sub 3}O{sub 9} and CeP{sub 3}O{sub 9}-SiP{sub 2}O{sub 7}, was interrogated using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy. XPS revealed that, for glasses melted in air, {>=}95% of cerium ions are Ce{sup 3+}. This was independently confirmed using X-ray absorption near edge spectroscopy (XANES). Ce K-edge extended X-ray absorption fine structure (EXAFS) has been used to determine the local structure of Ce{sup 3+}. Near the metaphosphate composition, cerium was found to have an average cerium coordination number of {approx}7.0 andmore » an average cerium-oxygen bond length of 2.41 {angstrom}. The average cerium coordination number and average cerium-oxygen bond distance were found to increase with decreasing cerium concentration in both compositional series. Rare-earth clustering is suggested based on numerical calculations for glasses containing {>=}14 and {>=}15 mol% Ce{sub 2}O{sub 3} for the aluminophosphate and silicophosphate series, respectively.« less