Study on the NaNp/Al2O3-SiO2 system.
Sodium naphthenide (NaNp) deposited on aluminosilicate gels yields systems that exhibit signals in EPR spectra, the multiplicity, g values, and intensities of which depend on the gel composition. The symmetrical singlets (I) of a g(1) value of 2.00 were assigned to the complexed naphthalene anion radicals on the centers occurring on the surfaces of the alumina and silica phases of the gels studied. Those radicals complexed on surface Lewis acid sites are of hard acid/hard base type according to Pearson theory, and are bonded to the sites by ionic forces. The asymmetrical singlets (II) described by the value g(2)=1.95 were assigned to naphthalene anion radicals, which are complexed by the centers of the aluminosilicate phase of the gels studied. Those radicals, complexed on surface Lewis acid sites of this phase, are of soft acid/soft base type and are bonded to the sites by covalent bonds. The highest intensity of the singlet (I) was recorded for the system containing alumina gel. The highest intensity of the singlet (II) was recorded for the system containing Al(2)O(3) in 30 wt%. The structures of Lewis acid sites on aluminosilicate phases are postulated to be different from those on alumina or silica phases.
Maksimowski
Paweł
P
Faculty of Chemistry, Warsaw University of Technology (Politechnika), Noakowskiego 3, 00-664 Warsaw, Poland.
Skupiński
Wincenty
W
D000537:Aluminum Oxide / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005782:Gels / Q000737:chemistry; D009281:Naphthalenes / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
D005782:Gels; D009281:Naphthalenes; D012822:Silicon Dioxide; D000537:Aluminum Oxide