AMBIENTUM BIOETHICA BIOLOGIA CHEMIA DIGITALIA DRAMATICA EDUCATIO ARTIS GYMNAST. ENGINEERING EPHEMERIDES EUROPAEA GEOGRAPHIA GEOLOGIA HISTORIA HISTORIA ARTIUM INFORMATICA IURISPRUDENTIA MATHEMATICA MUSICA NEGOTIA OECONOMICA PHILOLOGIA PHILOSOPHIA PHYSICA POLITICA PSYCHOLOGIA-PAEDAGOGIA SOCIOLOGIA THEOLOGIA CATHOLICA THEOLOGIA CATHOLICA LATIN THEOLOGIA GR.-CATH. VARAD THEOLOGIA ORTHODOXA THEOLOGIA REF. TRANSYLVAN
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STUDIA CHEMIA - Ediţia nr.1-2 din 2002 | |||||||
Articol: |
ADSORPTION OF AMMONIA AND PYRIDINE ON COAPO-5 SINGLE CRYSTALS STUDIED BY IN SITU FT-IR MICRO-SPECTROSCOPY. Autori: J. BÓDIS, G. MÜLLER, J. KORNATOWSKI, J.A. LERCHER. |
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Rezumat: Direct spectroscopic evidence for the existence of Brønsted acid sites in CoAPO-5 single crystal molecular sieves is reported. Compared with unsubstituted AlPO4-5 single crystals, the cobalt substituted samples exhibit well developed bands of isolated bridging hydroxyl groups and a broad absorption band indicating the existence of hydrogen bonded OH groups. Ammonia and pyridine interact with the bridging OH groups. This seems to involve simultaneous interactions with Lewis and Brønsted acid sites. Upon adsorption of pyridine new hydroxyl groups (νOH = 3682 and 3590 cm-1) were observed in parallel to pyridine bonding to Lewis acid sites. This suggests opening framework metal-oxygen bonds during sorption of pyridine. | |||||||