The structural comparison between Al-MCM-41 and B-MCM-41

A series of mesoporous aluminosilicate and borosilicate molecular sieves with the MCM-41 structure have been synthesized with different SiO2/Al2O3 or SiO2/B2O3 mass ratios of 5, 10, 25, 50, 70 and 150. The samples were synthesized using the direct method with a duration of 48 h. As silica source colloidal silica (ludox 40%, Prolabo), as aluminium source sodium aluminates and boric acid as the boron source were used in these syntheses. All samples were characterized by X-ray diffraction (XRD), ATR-FT-IR, N2 gassorption and elemental analysis by electron microscopy.XRD revealed that the characteristic MCM-41 structure is obtained for both mass ratios greater than 10. B-MCM-41 gives a better organization of the structure than Al-MCM-41. The B substitution in MCM-41 gives a tetrahedral configuration as proven by ATR-FT-IR. The pore diameter is very similar in both samples.