Mutable Lewis and Bronsted Acidity of Aluminated SBA-15 as Revealed by NMR of Adsorbed Pyridine-(15)N

0365144 - ÚFCH JH 2012 RIV US eng J - Journal Article
Gurinov, A. A. - Rozhkova, Yu. A. - Zukal, Arnošt - Čejka, Jiří - Shenderovich, I, G.
Mutable Lewis and Bronsted Acidity of Aluminated SBA-15 as Revealed by NMR of Adsorbed Pyridine-(15)N.
Langmuir. Roč. 27, č. 19 (2011), s. 12115-12123. ISSN 0743-7463
R&D Projects: GA AV ČR KAN100400701; GA ČR GA203/08/0604
Institutional research plan: CEZ:AV0Z40400503
Keywords : 15N NMR * post-synthesis alumination * phase Beckmann rearrangement
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 4.186, year: 2011

1H and variable-temperature (15)N NMR techniques have been used to study the effect of the gradual alumination of SBA-15 on the structure and adsorption properties of this mesoporous material. The interpretation of experimental spectra suggests that aluminum chlorhydrol most effectively reacts with silica surfaces in the confinement of the cavities of rough mesopore walls, instead of forming a homogeneous aluminum film. This first leads to a gradual filling of the cavities and finally results in aluminum islands on the inner surfaces of mesopores. In the sample with a Si/Al atomic ratio of 4.1, up to half of the inner surface area of the mesopores is covered with aluminum. The alumination produces Bronsted acid sites attributed to silanol groups interacting with aluminum but does not affect the proton-donating ability of isolated silanol groups. At high Si/Al ratios, the surface contains only one type of Lewis site attributed to tetracoordinated aluminum.
Permanent Link: http://hdl.handle.net/11104/0006580