Research Project: İmidazolyum Türü İyonik Sıvı Yardımlı Destekli Metal Katalizörlerin Performanslarını ve Kullanılabilirlik Koşullarını Belirleyen Yapısal Faktörlerin Sistematik İncelenmesi
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Contributors
Funders
ID
TB.00156
Authors
Uzun, Alper
Faculty Member
Publications
Thermal stability limits of imidazolium ionic liquids immobilized on metal-oxides
(American Chemical Society, 2015) Akçay, Aslı; Babucci, Melike; Balcı, Volkan; Uzun, Alper; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Engineering; Research Center
Thermal stability limits of 33 imidazolium ionic liquids (ILs) immobilized on three of the most commonly used high surface area metal-oxides, SiO2, gamma-Al2O3, and MgO, were investigated. as were chosen from a family of 13 cations and 18 anions. Results show that the acidity of C2H of an imidazolium ring is one of the key factors controlling the thermal stability. An increase in C2H bonding strength of ILs leads to an increase in their stability limits accompanied by a decrease in interionic energy. Systematic changes in IL structure, such as changes in electronic structure and size of anion/cation, methylation on C2 site, and substitution of alkyl groups on the imidazolium ring with functional groups have significant effects on thermal stability limits. Furthermore, thermal stability limits of ILs are influenced strongly by acidic character of the metal-oxide surface. Generally, as the point of zero charge (PZC) of the metal-oxide increases from SiO2 to MgO, the interactions of IL and metal-oxide dominate over interionic interactions, and metal-oxide becomes the significant factor controlling the stability limits. However, thermal stability limits of some ILs show the opposite trend, as the chemical activities of the cation functional group or the electron donating properties of the anion alter IL/metal-oxide interactions. Results presented here can help in choosing the most suitable ILs for materials involving ILs supported on metal-oxides, such as for supported ionic liquid membranes (SLLM) in separation applications or for solid catalyst with ionic liquid layer (SCILL) and supported ionic liquid phase (SILP) catalysts in catalysis.
Controlling catalytic activity and selectivity for partial hydrogenation by tuning the environment around active sites in iridium complexes bonded to supports
(Royal Society of Chemistry (RSC), 2019) Babucci, Melike; Uzun, Alper; Fang, Chia-Yu; Perez-Aguilar, Jorge E.; Hoffman, Adam S.; Boubnov, Alexey; Guan, Erjia; Bare, Simon R.; Gates, Bruce C.; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); KUYTAM (Koç University Surface Science and Technology Center); Yes; College of Engineering; Research Center
Single-site Ir(CO)(2) complexes bonded to high-surface-area metal oxide supports, SiO2, TiO2, Fe2O3, CeO2, MgO, and La2O3, were synthesized by chemisorption of Ir(CO)(2)(acac) (acac = acetylacetonate) followed by coating with each of the following ionic liquids (ILs): 1-n-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4], 1-n-butyl-3-methylimidazolium acetate, [BMIM][Ac], and 1-(3-cyanopropyl)-3-methylimidazolium dicyanamide, [CPMIM][DCA]. Extended X-ray absorption fine structure spectroscopy showed that site-isolated iridium was bonded to oxygen atoms of the support. Electron densities on the iridium enveloped by each IL sheath/support combination were characterized by carbonyl infrared spectroscopy of the iridium gem-dicarbonyls and by X-ray absorption near-edge structure data. The electron-donor/acceptor tendencies of both the support and IL determine the activity and selectivity of the catalysts for the hydrogenation of 1,3-butadiene, with electron-rich iridium being selective for partial hydrogenation. The results resolve the effects of the IL and support as ligands; for example, the effect of the IL becomes dominant when the support has a weak electron-donor character. The combined effects of supports and ILs as ligands offer broad opportunities for tuning catalytic properties of supported metal catalysts.
Tuning the selectivity of single-site supported metal catalysts with ionic liquids
(American Chemical Society (ACS), 2017) Babucci, Melike; Uzun, Alper; Fang, Chia-Yu; Hoffman, Adam S.; Bare, Simon R.; Gates, Bruce C.; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Engineering; Research Center
1,3-Dialkylimidazolium ionic liquid coatings act as electron donors, increasing the selectivity for partial hydrogenation of 1,3-butadiene catalyzed by iridium complexes supported on high-surface-area gamma-Al2O3. High-energy-resolution fluorescence detection X-ray absorption near-edge structure (HERFD XANES) measurements quantify the electron donation and are correlated with the catalytic activity and selectivity. The results demonstrate broad opportunities to tune electronic environments and catalytic properties of atomically dispersed supported metal catalysts.
Effects of interionic interactions in 1,3-dialkylimidazolium ionic liquids on the electronic structure of metal sites in solid catalysts with ionic liquid layer (SCILL)
(Elsevier Science, 2016) Babucci, Melike; Uzun, Alper; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
Well-defined gamma-Al2O3-supported Ir(CO)(2) complexes were coated with various 1,3-dialkylimidazolium ionic liquids (ILs) to elucidate the ligand effect of ILs. Variations in electron density of iridium sites when coated with ILs were probed by the infrared (IR) fingerprints of carbonyl ligands. Results presented here illustrate that IL layer strongly controls the electron density of metal sites; and there is a strong correlation between the interionic interactions in ILs and the degree of electron donation to the metal. These results create opportunities to tune the electronic structure of active metal sites by tailoring the structure of IL for optimum catalytic performance.
Selection rules for estimating the solubility of C4-hydrocarbons in imidazolium ionic liquids determined by machine-learning tools
(Elsevier B.V., 2019) Jalal, Ahsan; Keskin, Seda; Uzun, Alper; Can, Elif; Yıldırım, Ramazan; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); KUYTAM (Koç University Surface Science and Technology Center); Yes; College of Engineering; Research Center
Solubilities of C-4-hydrocarbons, 1,3-butadiene (13BD), trans/cis-2-butene (T2B and C2B), 1-butene (1B), isobutene (i-But), isobutane (i-B), and butane (B), in 3267 different imidazolium-type ionic liquids (ILs) in a temperature range from 273.15 to 373.15 K were estimated by means of the COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) calculations. Simple temperature-dependent mathematical expressions were developed to predict the solubility of 13BD, C2B, T2B, 1B, i-But, i-B, and B at any temperature in a range from 273 to 373 K. The COSMO-RS results for each hydrocarbon considered were then analyzed using machine learning tools, induding association rule mining and decision tree classification, using semi-empirically derived molecular descriptors of ILs. It was found that the polarizabilities of both cation and anion, together with the anion's CPK (space filling model) area, are the most important descriptors for determining the affinity of ILs towards C-4-hydrocarbons. Results also present the selection rules for imidazolium ILs, offering opportunities for the rational design of new ILs by using these simply-determined structural descriptors to meet the desired solubility (or selectivity) requirements for each C-4-hydrocarbon considered.
