Investigating the state of Fe and La in MCM-41 mesoporous molecular sieve materials

Fe-containing, La-containing, siliceous and aluminum silicate MCM-41 mesoporous materials were synthesized using water glass as silica source. The states of Fe(III) and La(III) species were investigated by thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), framework infrared (FTIR), electron spin resonance (ESR) and Mossbauer spectroscopic techniques. It was shown that Fe(III) or La(III) species was incorporated into framework. Because the Fe-O or La-O bond is longer than Si-O bond, Fe(III) or La(III) species was limited to insert into framework and transformed from tetrahedrally coordinated state to octahedrally coordinated state upon calcination to remove template. (C) 2001 Elsevier Science B.V. All rights reserved.