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Non-Hydrolytic Sol-Gel Synthesis of Hybrid Metallosilicates for Ethanol Dehydration



Year of publication 2018
Type Conference abstract
Description Metallosilicates are used as catalysts in epoxidation of alkenes, cracking, isomerization reactions, etc. [1]. Nowadays they are applied in the biomass and biofuel sector as well [2]. However for this modern purpose the performance of metallosilicates is not fully satisfactory, mainly due to their low stability in the presence of water [3]. To tackle these challenges we propose to introduce hydrophobic organic groups into metallosilicate materials. As a synthetic route, non-hydrolytic sol-gel preparation is used. It allows for the synthesis of highly porous and amorphous metallosilicates with homogeneous distribution of active metal sites within the silicate matrix [4,5]. The introduction of organic groups (R) takes place during the polycondensation reactions (eq. 1 and 2). ?(R-)Si-Cl + R´-O-M? › ?(R-)Si-O-M? + R´Cl (1) ?(R-)Si-OAc + R´2N-M? › ?(R-)Si-O-M? + R´2NAc (2) Influence of several parameters on hydrothermal stability, porosity (Figure 1), acidity, and activity in ethanol dehydration is studied. These are particularly (i) the synthetic route chosen (alkyl halide vs. acetamide elimination, eq. 1 and 2, respectively), (ii) the metal (M) introduced (Al vs. Nb), and (iii) the amount and nature of organic groups (R) incorporated within the silicate matrix (terminal vs. bridging, aryl- vs. alkyl-). Prepared materials are characterized by N2-physisorption, NH3-TPD, XPS, TGA, SS NMR, and IR spectroscopy. The influence of hydrophobic organic groups is established by hydrothermal stability tests (flow in water-saturated air, fixed bed). These hybrid metallosilicates exhibit activities and hydrothermal stabilities that are comparable to or better than well–known acidic catalysts (ß-zeolite and commercial silica-alumina). References 1. Ciriminna, R.; Cara, P. D.; Sciortino, M.; Pagliaro, M. Adv. Synth. Catal. 353, 677 (2011). 2. Behrens, M.; Datye, A. K. Catalysis for the Conversion of Biomass and Its Derivatives, Edition Op.; (2013). 3. Zapata, P. A.; Faria, J.; Ruiz, M. P.; Jentoft, R. E.; Resasco, D. E. J. Am. Chem. Soc. 134, 8570 (2012). 4. Debecker, D. P.; Mutin, P. H. Chem. Soc. Rev. 41, 3624 (2012). 5. Styskalik, A.; Skoda, D.; Barnes, C.; Pinkas, J. Catalysts 7, 168 (2017).

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