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Removal of organic template from mesoporous MCM-41

The removal of cetyltrimethylammonium bromide from as-synthesized MCM-41 in different methods has been investigated. The removal of template from MCM-41 precursors was conducted by reflux, Soxhlet extraction and magnetic stirring extraction at ambient room temperature in ethanol and ethanol-containing hydrochloride solvents. The obtained materials were characterized by TG-DSC, XRD, SEM, TEM and isotherm of adsorption/desorption of nitrogen. The results show that the treatment of MCM-41 precursor in the C2H5OH-HCl-H2O system allows a complete removal of organic template in range of 5-60 minutes at room temperature. The obtained MCM-41 materials possess highly ordered mersoporous structure. | JOURNAL OF SCIENCE, Hue University, Vol. 69, No. 6, 2011 REMOVAL OF ORGANIC TEMPLATE FROM MESOPOROUS MCM-41 Pham Dinh Du1, Dinh Quang Khieu2 and Tran Thai Hoa2 1 2 Kontum teachers’ training College College of Sciences, Hue University Abstract. The removal of cetyltrimethylammonium bromide from as-synthesized MCM-41 in different methods has been investigated. The removal of template from MCM-41 precursors was conducted by reflux, Soxhlet extraction and magnetic stirring extraction at ambient room temperature in ethanol and ethanol-containing hydrochloride solvents. The obtained materials were characterized by TG-DSC, XRD, SEM, TEM and isotherm of adsorption/desorption of nitrogen. The results show that the treatment of MCM-41 precursor in the C2H5OH-HCl-H2O system allows a complete removal of organic template in range of 5-60 minutes at room temperature. The obtained MCM-41 materials possess highly ordered mersoporous structure. 1 Introduction Mesoporous silica materials of MCM-41 type are synthesized from the surfactant micellar template addition of an inorganic silica source [1]. Cetyltrimethylammonium bromide (CTA+ Br -) is most commonly used as template. It is necessary to remove the occluded organic molecules to make the sieves porous for adsorption and catalysis. In general, the template molecules are burned off by calcination at 500-600°C in air or oxygen. Although calcination is largely satisfactory, it occasionally leaves carbonaceous residue in the molecular sieves. Sometimes the situation may be ameliorated by slow and/or step heating. However, there are at least three inherent problems associated with the calcination process that is frequently used to remove template molecules from molecular sieves. (1) The sample in question may not be stable at the temperature at which the organic molecules are removed, eg. Organo functionalized MCM-4l; (2) the sample may be stable at a high temperature at which the organic molecules are removed, but the removal