Altundal, Ömer Faruk
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- PublicationDifferent Zeolite Phases Obtained with the Same Organic Structure Directing Agent in the Presence and Absence of Aluminum: The Directing Role of Aluminum in the Synthesis of Zeolites(American Chemical Society, 2023-05-30) Altundal, Ömer Faruk; León-Rubio, Santiago; Sastre Navarro, German Ignacio; Instituto Universitario Mixto de Tecnología Química; Generalitat Valenciana; Agencia Estatal de Investigación; Ministerio de Ciencia e Innovación[EN] Zeolites are a large family of crystalline microporous materials with, mainly, silicate and aluminosilicate composition. Each topology can only be synthesized in a specific range of aluminum content, Al/(Si + Al), within the interval [0¿0.5], and this interval cannot, in general, be predicted for each structure. Aluminum and organic structure directing agents (OSDAs), among others, act together in obtaining the zeolite phase under each specific synthesis condition. The present study is an attempt to rationalize the role of aluminum as a structure directing agent in the synthesis of zeolites using computational chemistry and based on the criteria of energetic stability using both force field and periodic DFT methods. A proper selection of cases in which, using the same OSDA, different zeolite phases are obtained in the presence and absence of aluminum helps to rationalize how aluminum contributes to the relative stability of the different competing zeolite phases considered.
- PublicationThe Directing Role of Aluminum in the Synthesis of PST-21 (PWO), PST-22 (PWW), and ERS-7 (ESV) Zeolites(American Chemical Society, 2023-07-31) Altundal, Ömer Faruk; Sastre Navarro, German Ignacio; Instituto Universitario Mixto de Tecnología Química; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] Zeolites are a diverse class of crystalline microporousmaterialsof, mainly, aluminosilicate chemical composition. Organic structure-directingagents (OSDAs) are generally utilized in zeolite synthesis to drivethe outcome to a specific zeolite phase. In addition to OSDA, thepresence and content of aluminum in the gel play a role in drivingthe synthesis under specific conditions. The structure-directing roleof aluminum as well as fluoride in zeolite synthesis was exploredthrough the analysis of three recently synthesized aluminosilicatezeolites, PST-21 (PWO), PST-22 (PWW), and ERS-7 (ESV), using a forcefield simulation approach. An updated and recently proposed methodbased on the calculation of "synthesis energy" is usedto predict the stability of zeolites at pure-silica and aluminosilicategel compositions, also able to include fluoride anions as well asOSDAs, and hence largely general. The results are not only demonstratingthat the calculated structures with lowest "synthesis energy"correspond to those experimentally obtained under "standard"(meaning HF/SDA = 1) synthesis conditions but also that new structuresobtained under the recently introduced "excess fluoride approach"are those which follow with energy slightly larger than the lowest,as calculated from the list of competing zeolites. With this method,we were able to rationalize the structure-directing effect of aluminum,in the presence of fluoride and OSDAs, in the synthesis of zeolites.
- PublicationEffect of Intracrystalline Silanol Defects on the Diffusivity of Benzene in Silicalite Zeolite(John Wiley & Sons, 2023-11) Misturini, Alechania; Altundal, Ömer Faruk; García Aznar, Pablo; Kariminasab, Sara; Sastre Navarro, German Ignacio; Instituto Universitario Mixto de Tecnología Química; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] Intracrystalline zeolite silanol defect groups (& EQUIV;SiOH) were modelled in silicalite (silica ZSM-5, MFI) using experimental data. We make a molecular dynamics study on the self-diffusivity of benzene in silicalite with defects. The simulations at three different loadings (1, 3 and 5 benzene per unit cell) and temperatures (298, 348 and 398 K) allow to calculate self-diffusivity, adsorption energy and the activation energy. The results show that benzene self-diffusivity in silicalite is increased by the presence of silanol defects. Previous experimental results support this claim.