Different nanocomposites silica-resin based were prepared and characterized in order to achieve a porous monolith that contains bentonite and allows the flow of aqueous systems. The bentonite used to prepare the nanocomposites was a good adsorbent for various molecules in aqueous media in stirred tank reactor. But the challenge was the obtention of porous bentonite composite columns for industrial applications. The primary composite, silica-resin, was prepared by the sol-gel precursor mixture of the tetraethylorthosilicate (TEOS) and a phenolic resin, made up the gel which is then dried and cured at 180 °C. Bentonite was added to the precursor mixture obtaining the, silica-resin-bentonite composite, and also other potencial adsorbent, carbon, was added obtaining the silica-resin-bentonite-carbon composite. The different composites were mineralogical and structurally evaluated by X-ray diffraction, Infrared spectroscopy with Fourier transform, Differential thermal analyses and thermogravimetric analyses. The textural characterization was performed by Adsorption of nitrogen (Sg-BET), Mercury intrusion porosimetry and Scanning electron microscopy. The comparison of the characteristics and properties between the composites evidenced that the addition of bentonite modify the solgel process and interferes in the composite cured process, so that, modify the mesoporosity and macroporosity of the composite. But, there is a maximum clay limit to obtain an homogeneous monolith. The addition of carbon decreases the porosity of the composite to a greater extent when the granulometry is greater.
Activated bentonites are low-cost acid catalysts used in several reactions. However, their application at an industrial scale is affected by the formation of colloidal suspensions when these bentonites are in aqueous solutions. In order to overcome these limitations, this work proposes obtaining a catalyst based on a composite containing natural bentonite within a silica–resin structure, which allows separating and re-utilizing the catalyst more easily and without centrifugal filtration requirements. By means of characterization techniques, the present study determined that the activated bentonite composite presented a total specific surface area of ~360 m2 g−1, ~4 mmol of acid sites per gram of bentonite, and sites with strong acid strength, all of which bestowed activity and selectivity in the solketal synthesis reaction from glycerol and acetone, reaching equilibrium conversion within a short reaction time. Furthermore, the present work developed a Langmuir–Hinshelwood–Hougen–Watson kinetic model, achieving an activation energy of 50.3 ± 3.6 kJ mol−1 and a pre-exponential factor of 6.4 × 106 mol g−1 L−1 s−1, which are necessary for reactor design.
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