Synthesis and characterization of Mo-SBA-1 cubic mesoporous molecular sieves

A series of Mo-SBA-1 (Pm (3) over capn) cubic mesoporous molecular sieves w ith various H2O/HCl and Si/Mo molar ratios have been synthesized at 0 degre esC using cetyltriethylammonium bromide, tetraethyl orthosilicate, ammonium heptamolybdate and hydrochloric acid. It was found that the Mo-SBA-1 parti cles synthesized at 0 degreesC for 4 days were of a characteristic shape ha ving fifty-four, seventy-four, or more crystal faces. Synthesis conditions have been optimized to introduce high percentage of Mo into the well-ordere d cubic mosoporous structure. The microstructure. of Mo centers has been in vestigated by diffuse reflectance UV-visible and laser Raman spectroscopies . Both techniques reveal that, in the absence of water, Mo species consist of tetrahedrally and octahedrally coordinated monomers and polymers. The te trahedral Mo centers were converted to octahedral Mo centers in the presenc e of moisture partially in directly synthesized Mo-SBA-1 samples and comple tely in impregnated Mo/SBA-1 samples. It is concluded that the impregnated samples were better dispersed than the directly synthesized samples.