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Titolo:
Sol-gel synthesis of alumina modified by phosphorus: a solid state NMR characterization study
Autore:
Quartararo, J; Guelton, M; Rigole, M; Amoureux, JP; Fernandez, C; Grimblot, J;
Indirizzi:
Univ Sci & Technol Lille, Catalyse Lab, UPRESA 8010, F-59655 Villeneuve Dascq, France Univ Sci & Technol Lille Villeneuve Dascq France F-59655 e Dascq, France Univ Sci & Technol Lille, Lab Dynam & Struct Mat Mol, CNRS, URA 801, F-59655 Villeneuve Dascq, France Univ Sci & Technol Lille Villeneuve Dascq France F-59655 e Dascq, France Univ Caen, Catalyse & Spectrochim Lab, ISMRA, UMR 6506, F-14050 Caen, France Univ Caen Caen France F-14050 Lab, ISMRA, UMR 6506, F-14050 Caen, France
Titolo Testata:
JOURNAL OF MATERIALS CHEMISTRY
fascicolo: 10, volume: 9, anno: 1999,
pagine: 2637 - 2646
SICI:
0959-9428(199910)9:10<2637:SSOAMB>2.0.ZU;2-8
Fonte:
ISI
Lingua:
ENG
Soggetto:
HYDROTREATING CATALYST PRECURSORS; QUADRUPOLAR NUCLEI; MAS NMR; MO; MQMAS; RESONANCE; GENESIS; SITES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
Citazioni:
22
Recensione:
Indirizzi per estratti:
Indirizzo: Grimblot, J Univ Sci & Technol Lille, Catalyse Lab, UPRESA 8010, Batiment C3, F-59655 Villeneuve Dascq, France Univ Sci & Technol Lille Batiment C3 Villeneuve Dascq France F-59655
Citazione:
J. Quartararo et al., "Sol-gel synthesis of alumina modified by phosphorus: a solid state NMR characterization study", J MAT CHEM, 9(10), 1999, pp. 2637-2646

Abstract

A sol-gel method using aluminium tri(sec-butoxide) and orthophosphoric acid, H3PO4, as the Al and P sources respectively, 2-butanol as the solvent and 1,3-butanediol as the chelating agent has been extensively used to prepare P-alumina catalytic supports. The study was particularly focused on the influence of the step of phosphorus introduction during the sol-gel procedure, on the amount of incorporated phosphorus and on the temperatures of drying and calcination of the gels to obtain the final mixed oxides. In addition to the classical chemical composition determinations and measurements of specific surface area, characterisations were mainly performed by using solid state Al-27 and P-31 MAS NMR. More precise determinations of the nature of aluminium sites were also obtained by Al-27 MQMAS NMR. XRD was also usedto a lesser extent. Poorly crystallised boehmite is present in the dried samples with aluminium mainly localised in octahedral sites whereas phosphorus is detected as monomeric and polymeric phosphates whose proportions depend on the phosphoruscontent. For the highest P/Al ratio (P/Al=0.2) and when phosphorus is introduced with the hydrolysis water, the NMR data reveal the presence of bridged entities such as Al-tetra-O-P. After calcination at 500 degrees C, badly crystallised gamma-alumina is formed with octahedral, pentacoordinate and tetrahedral aluminium sites. For the highest phosphorus loading, a new aluminium site corresponding to the presence of AlPO4 is observed. The values of the second order quadrupolar effect for each species depend on the preparation procedure and characterise the degree of distortion of the aluminium sites. The drying temperature up to 200 degrees C does not modify the gel structure whereas transformation of boehmite into alumina occurs above 350 degreesC and, for the highest phosphorus content, there is partial destruction ofalumina to form aluminium phosphate when the temperature of calcination isincreased. Such an increase also has a non-negligible influence on the specific surface area which, however, remains as high as 350 m(2) g(-1) after calcination at 700 degrees C.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/12/20 alle ore 10:07:56