Neutron Rietveld refinement of a synthetic low silica ferrierite in deuterium form was performed in the Immm space group This space group is different from that of as-synthesized form (which is P2(1)/n), and its cell volume (V=1977 Angstrom(3)) is slightly smaller (V=1984 Angstrom(3)). These differences do not cause noticeable modifications in the framework. Two Bronsted acid sites were recognized. The first was on framework oxygen O4, which bridges T1 and T3 tetrahedron cations, and headed towards the center of the ferrierite cage. The other was on the framework oxygen O6, which bridges two T4 tetrahedron cations, and headed towards the 10-ring channel parallel to [001], not far from the center of the 8-ring of the ferrierite cage facing towards the channel. Both deuterium sites were occupied in about 15% of cases. Three other extraframework sites, at great distances from the extraframework oxygens and weakly occupied, were recognized in D-ferrierite, and were attributed to residual ND4 groups. (C) 1999 Elsevier Science B.V. All rights reserved.
Location of Bronsted sites in D-ferrierite by neutron powder diffraction
MARTUCCI, Annalisa;ALBERTI, Alberto;CRUCIANI, Giuseppe;
1999
Abstract
Neutron Rietveld refinement of a synthetic low silica ferrierite in deuterium form was performed in the Immm space group This space group is different from that of as-synthesized form (which is P2(1)/n), and its cell volume (V=1977 Angstrom(3)) is slightly smaller (V=1984 Angstrom(3)). These differences do not cause noticeable modifications in the framework. Two Bronsted acid sites were recognized. The first was on framework oxygen O4, which bridges T1 and T3 tetrahedron cations, and headed towards the center of the ferrierite cage. The other was on the framework oxygen O6, which bridges two T4 tetrahedron cations, and headed towards the 10-ring channel parallel to [001], not far from the center of the 8-ring of the ferrierite cage facing towards the channel. Both deuterium sites were occupied in about 15% of cases. Three other extraframework sites, at great distances from the extraframework oxygens and weakly occupied, were recognized in D-ferrierite, and were attributed to residual ND4 groups. (C) 1999 Elsevier Science B.V. All rights reserved.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
