Synthesis of SBA-15/MCM-41 bimodal mesoporous silica
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Synthesis of SBA-15/MCM-41 bimodal mesoporous silica Leyla Y. Jaramillo 1,3, Wilson A. Henao2 and Elizabeth Pabón-Gelves3 1
Grupo Calidad, Metrología y Producción, Instituto Tecnológico Metropolitano, 050015, Medellín, Colombia 2 Grupo Materiales Avanzados y Energía, Instituto Tecnológico Metropolitano, 050015, Medellín, Colombia 3 Grupo Ciencia de Materiales Avanzados, Universidad Nacional de Colombia. Medellín, Colombia ABSTRACT Nanostructured silica materials with different morphologies and adjustable pore size have been studied by researches worldwide for several applications such as catalysis, separation, adsorption, and templates for new materials. The main interest in the development of these materials is to obtain a structure with a specific combination of pore sizes for a particular application. The morphology and textural properties of pores can be easily changed with the modification of the synthesis parameters, among these, the choice of surfactant or structure directing agent (SDA). Accordingly, in this work, three types of nanostructured silica with different mesoporosity were synthesized by using of CTAB and Pluronic 123 as structure directing agents: SBA-15 and MCM-41 unimodal mesoporous silica and SBA-15/MCM-41 bimodal mesoporous silica. To evaluate the effect of surfactant on the morphology and textural properties of pores, the materials were characterized by scanning electron microscopy (SEM), X-ray Diffraction (XRD) and nitrogen sorption (BET). INTRODUCTION Recently, mesoporous silica materials (MSMs) have attracted attention of many researchers due to their unique surface, structural and bulk properties. These properties can be used in applications such as adsorbents, ion exchange, separation, catalysis, sensors and drugs delivery [1]. Because of the properties of MSMs vary depending on the size, arrangement and shape of their pores, as well as the porosity (the ratio of the total pore volume relative to apparent volume of the material) and composition of the material itself, there has been numerous effort focused on understanding how changing the synthesis parameters can lead to mesoporous structures with specific properties of interest [2-4]. Particularly, MSMs with a bimodal pore size distribution, have a potential advantage for applications requiring that the pores are not too small to obstruct the transport of bulky molecules neither too large to affect the surface area and size-selectivity. About this topic, the literature shows that the most common way to generate bimodal mesoporous systems is through the mixture of surfactants with different chain length and polarity, based on adding a block copolymer and a small surfactant or ionic cosolvent to sol-gel solution [5-7].
In this work, the effect of surfactant on the morphology and textural properties of mesoporous silica is evaluated. EXPERIMENTAL DETAILS Synthesis of SBA-15 mesoporous silica SBA-15 mesoporous silica was obtained according to the sol-gel procedure described by Zhao et al [8]. For this, 4 g of Pluronic123 triblock copoly
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