Abstract
This work aimed to determine and compare the apparent activation energy, involved in thermal decomposition of CTMA+ from the pores of Ti-MCM-41 synthesized by two different source of silica in order to evaluate their influence in the template removal. The molecular sieves Ti-MCM-41 were synthesized using rice husk ash (RHA), as alternative low cost source of silica, and commercial silica gel, obtaining two mesoporous material by hydrothermal synthesis of gel molar composition of: 1.0 CTMABr: 4.0 SiO2: X TiO2: 1.0 Na2O: 200.0 H2O. The samples were characterized to compare its properties by X-ray diffraction, IR spectroscopy, BET method and thermogravimetric analysis (TGA). The kinetic study using the model proposed by Flynn and Wall to determine the apparent activation energy for CTMA+ removal was performed using TGA data. The thermogravimetric analysis results of the material obtained from RHA confirmed intrinsic properties of mesoporous MCM-41 as the synthesized with commercial silica gel, such as high specific area, mesoporous range of pore diameter and hexagonal structure. According to the kinetics results the RHA showed similar chemical interaction to commercial silica gel, which makes it an interesting material, since it is a low cost source of natural silica from agricultural waste.
Highlights
IntroductionIntensive research activity has been focused on mesoporous materials like MCM-411-6
During the recent years, intensive research activity has been focused on mesoporous materials like MCM-411-6
This work aims the use of the rice husk ash (RHA) and commercial silica gel (SG) as alternatives source of silica in the synthesis of Ti-MCM-41, performing the kinetic study of surfactant cetyltrimethyl ammonium bromide (CTMA+) removal, using the model proposed by Flynn‐Wall, trough thermogravimetric analysis data, relating the apparent activation energy with the chemical interaction of silica sources and the template CTMA+ used in synthesis of this material
Summary
Intensive research activity has been focused on mesoporous materials like MCM-411-6. The MCM-41 shows no considerable acidity, limiting their direct use in catalytic reactions. Due to its high specific area, they are excellent catalyst supports, which can generate acid/base sites during or after synthesis either by impregnation or by isomorphous substitution of heteroatom in the MCM-41, especially metals incorporation such as Al, Ti, Zr, B, V, etc[7]. The iso and nonisomorphic substitutions usually enhance catalytic activity in processes of commercial interest such as: hydrocarbon catalytic cracking isomerization, hydrodesulphurization, oxidation reactions, hydroxylation and epoxidation of aromatics, olefins and phenols[9]. Many authors[10,11,12] have used the rice husk ash (RHA) as silica source in the synthesis of various mesoporous
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