Browsing by Author "Celebi, Metin"

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Citation - WoS: 80
Citation - Scopus: 81
Amine Grafted Silica Supported Craupd Alloy Nanoparticles: Superb Heterogeneous Catalysts for the Room Temperature Dehydrogenation of Formic Acid
(Royal Soc Chemistry, 2015) Yurderi, Mehmet; Bulut, Ahmet; Caner, Nurdan; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Herein we show that a previously unappreciated combination of CrAuPd alloy nanoparticles and amine-grafted silica support facilitates the liberation of CO-free H-2 from dehydrogenation of formic acid with record activity in the absence of any additives at room temperature. Furthermore, their excellent catalytic stability makes them isolable and reusable heterogeneous catalysts in the formic acid dehydrogenation.
Citation - WoS: 135
Citation - Scopus: 140
Carbon Dispersed Copper-Cobalt Alloy Nanoparticles: a Cost-Effective Heterogeneous Catalyst With Exceptional Performance in the Hydrolytic Dehydrogenation of Ammonia-Borane
(Elsevier, 2016) Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Herein, we report the development of a new and cost-effective nanocatalyst for the hydrolytic dehydrogenation of ammonia-borane (NH3BH3), which is considered to be one of the most promising solid hydrogen carriers due to its high gravimetric hydrogen storage capacity (19.6 wt%) and low molecular weight. The new catalyst system consisting of bimetallic copper-cobalt alloy nanoparticles supported on activated carbon was simply and reproducibly prepared by surfactant-free deposition-reduction technique at room temperature. The characterization of this new catalytic material was done by the combination of multi-pronged techniques including ICP-MS, XRD, XPS, BFTEM, HR-TEM, STEM and HAADF-STEM-line analysis. The sum of their results revealed that the formation of copper-cobalt alloy nanoparticles (d(mean) =1.8 nm) on the surface of activated carbon (CuCo/C). These new carbon supported copper-cobalt alloy nanoparticles act as highly active catalyst in the hydrolytic dehydrogenation of ammonia-borane, providing an initial turnover frequency of TOF = 2700 h(-1) at 298 K, which is not only higher than all the non-noble metal catalysts but also higher than the majority of the noble metal based homogeneous and heterogeneous catalysts employed in the same reaction. More importantly, easy recovery and high durability of these supported CuCo nanoparticles make CuCo/C recyclable heterogeneous catalyst for the hydrolytic dehydrogenation of ammonia-borane. They retain almost their inherent activity even at 10th catalytic reuse in the hydrolytic dehydrogenation of ammonia-borane at 298K. (C) 2015 Elsevier B.V. All rights reserved.
Citation - WoS: 18
Citation - Scopus: 20
Cobalt nanoparticles supported on alumina nanofibers (Co/Al₂O₃): Cost effective catalytic system for the hydrolysis of methylamine borane
(Pergamon-elsevier Science Ltd, 2019) Baguc, Ismail Burak; Yurderi, Mehmet; Bulut, Ahmet; Celebi, Metin; Kanberoglu, Gulsah Saydan; Zahmakiran, Mehmet; Baysal, Akin
Amongst different amine-borane derivatives, methylamine-borane (CH3NH2BH3) seems to be one of the capable aspirants in the storing of hydrogen attributable to its high hydrogen capacity, stability and aptitude to generate hydrogen through its catalytic hydrolysis reaction under ambient conditions. In this research paper, we report that cobalt nano-particles supported on alumina nanofibers (Co/Al2O3) are acting as active nanocatalyst for catalytic hydrolysis of methylamine-borane. Co/Al2O3 nanocatalyst was fabricated by double-solvent method followed with wet-chemical reduction, and was characterized by utilizing various spectroscopic methods and imaging techniques. The results gathered from these analyses showed that the formation Al2O3 nanofibers supported cobalt(0) nanoparticles with a mean diameter of 3.9 +/- 1.2 nm. The catalytic feat of these cobalt nanoparticles was scrutinized in the catalytic hydrolysis of methylamine-borane by considering their activity and durability performances. They achieve releasing of 3.0 equivalent of H-2 via methylamine-borane hydrolysis at room temperature (initial TOF = 297 mol H-2/mol metal x h). Along with activity the catalytic durability of Co/Al2O3 was also studied by carrying out recyclability tests and it was found that these supported cobalt nanoparticles have good durability during the course of the catalytic recycles so that Co/Al2O3 preserves almost its innate activity at 5th catalytic recycle. The studies presented here also contains kinetic investigation of Co/Al2O3 catalyzed methylamine borane hydrolysis depending on the temperature, cobalt and methylamine borane concentrations, which were used to define rate expression and the activation energy of the catalytic reaction. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Citation - WoS: 15
Citation - Scopus: 15
Keggin Type-Polyoxometalate Decorated Ruthenium Nanoparticles: Highly Active and Selective Nanocatalyst for the Oxidation of Veratryl Alcohol as a Lignin Model Compound
(Wiley-v C H verlag Gmbh, 2017) Baguc, Ismail Burak; Saglam, Serif; Ertas, Ilknur Efecan; Keles, Muhammed Nuri; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Described herein is a new nanocatalyst system that efficiently works in the aerobic oxidation of veratryl alcohol (VA), which is formed by cleavage of beta-O-4 linkages in lignin, to veratraldehyde (VAL) under mild reaction conditions. The new nanocatalyst system comprised of ruthenium(0) nanoparticles supported on the Keggin type polyoxometalate (POM; K-3[PMo12O40]) network (Ru/POM) can simply and reproducibly be prepared by the dimethylamine-borane ((CH3)(2)NHBH3) reduction of ruthenium(III) chloride trihydrate (RuCl3.3H(2)O) in isopropanol solution of K-3[P Mo12O40] at room temperature. The characterization of Ru/POM by the combination of various analytical techniques reveals that the formation of well-dispersed ruthenium(0) nanoparticles with a mean diameter of 4.7 +/- 1.2nm on the surface of POM network structure. This new Ru/POM nanocatalyst displays remarkable activity (TOF=7.5mol VAld/mol Ru x h) at high selectivity (> 98%) and almost complete conversion (98%) in the aerobic oxidation of VA to VAld under mild conditions.
Citation - WoS: 8
Citation - Scopus: 8
Nanohydrotalcite Supported Ruthenium Nanoparticles: Highly Efficient Heterogeneous Catalyst for the Oxidative Valorization of Lignin Model Compounds
(Wiley-v C H verlag Gmbh, 2017) Baguc, Ismail Burak; Celebi, Metin; Karakas, Kadir; Ertas, Ilknur Efecan; Keles, Muhammed Nuri; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
The catalytic transformation of lignocellulosic biomass derived chemicals into value-added chemicals under mild conditions remains a challenge in the fields of synthetic chemistry and catalysis. Herein, we describe a new heterogeneous catalyst system that efficiently works in the oxidative valorization of lignin model compounds. This new heterogeneous catalyst system comprised of nano-sized hydrotalcite (n-HT; Mg6Al2 (CO3)(OH)(16)) supported ruthenium(0) nanoparticles (Ru/ n-HT) was prepared by ion-exchange of [Ru(OH2)Cl-5](2-) anions with the extraframework CO32- anions of n-HT followed by their borohydride reduction (NaBH4) in water at room temperature. The characterization of Ru/n-HT was done by the combination of various spectroscopic and the sum of their results revealed that the formation of well-dispersed ruthenium(0) nanoparticles with a mean diameter of 3.2 +/- 0.9 nm on the surface of n-HT structure. The catalytic performance of Ru/n-HT in terms of activity, selectivity and stability was tested in the aerobic oxidation of cinnamyl, veratryl and vanillyl alcohols, which are important lignin model compounds used to mimic the propyl side chain, the phenolic and non-phenolic, respectively functional groups of lignin. We found that Ru/ n-HT nanocatalyst displays remarkable activity at high selectivity and almost complete conversion in these catalytic transformations under mild reaction conditions (at 373 K under 3 bar initial O-2 pressure).
Citation - WoS: 40
Citation - Scopus: 44
Palladium Nanoparticles Decorated Graphene Oxide: Active and Reusable Nanocatalyst for the Catalytic Reduction of Hexavalent Chromium(vi)
(Wiley-v C H verlag Gmbh, 2017) Celebi, Metin; Karakas, Kadir; Ertas, Ilknur Efecan; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Today, the catalytic reduction of Cr(VI) to Cr(III) stands one of the most important challenges in the environmental chemistry and catalysis due to highly stable, contaminant and toxic nature of Cr(VI). In this study, we show that a new nanocatalyst system comprised of 3-aminopropyltriethoxysilane (APTS) stabilized palladium(0) nanoparticles grafted onto the surface of graphene oxide (Pd/GO) efficiently works in the catalytic reduction of Cr(VI) to Cr(III) under mild reaction conditions. Pd/GO nanocatalyst was reproducibly prepared through two-steps procedure: (i) H-2 reduction of Pd(dba)2(dba= dibenzylideneacetone) in the presence of APTS in THF to synthesize colloidal APTS stabilized palladium(0) nanoparticles and then (ii) the deposition of 3-aminopropyltriethoxysilane stabilized palladium 0) nanoparticles onto the surface of graphene oxide (GO) by impregnation. The characterization of Pd/GO was carried out by advanced analytical techniques. The summation of the results acquired from these analyses reveals that the formation of well-dispersed and highly crystalline palladium(0) nanoparticles on the surface of GO. The catalytic performance of the resulting Pd/GO in terms of activity and stability was assessed in the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid (HCOOH) as a reducing agent. We found that Pd/GO nanocatalyst exhibits high activity (TOF= 3.6 mol Cr2O72-/mol Pdxmin) and reusability (> 90% at 5th reuse) in this catalytic transformation at room temperature.
Citation - WoS: 195
Citation - Scopus: 206
Palladium Nanoparticles Supported on Amine-Functionalized Sio₂ for the Catalytic Hexavalent Chromium Reduction
(Elsevier Science Bv, 2016) Celebi, Metin; Yurderi, Mehmet; Bulut, Ahrnet; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Hexavalent chromium (Cr(VI)) is commonly identified acutely toxic, a proven mutagen and carcinogen heavy metal pollutant in the aquatic environment, whereas Cr(III) is believed to be an essential element. In the present study, we show that palladium(0) nanoparticles supported on 3-aminopropyltriethoxysilane (APTS) functionalized silica (Pd@SiO2-NH2) effectively catalyze the reduction of Cr(VI) to Cr(III) by using formic acid (HCOOH) as reducing agent under mild conditions (at room temperature under air). Pd@SiO2-NH2 catalyst was reproducibly prepared by deposition-reduction technique and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-vis, XPS, BFTEM, HRTEM and TEM-EDX techniques. The sum of their results is indicative of the formation of well-dispersed palladium(0) nanoparticles (d(mean) = 3.7 nm) on the surface of APTS-functionalized SiO2. The catalytic performance of the resulting palladium(0) nanoparticles in terms of activity and stability was evaluated by the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid as a reducing agent. Our results reveal that Pd@SiO2-NH2 catalyst displays unprecedented activity (TOF = 258 mol Cr2O72-/mol Pd min) and reusability (<85% at 5th reuse) for the reduction of Cr(VI) to Cr(III) at room temperature. The present study reported here also includes the compilation of wealthy kinetic data for Pd@SiO2-NH2 catalyzed the reduction of Cr(VI) to Cr(III) in aqueous formic acid (HCOOH)-sodium formate (HCOONa) solution depending on substrate [Cr2O72-], catalyst [Pd@SiO2-NH2], surface grafted amine [APTS], formic acid [HCOOH], sodium formate [HCOONa] concentrations, temperature and type of support material (Al2O3, C, unmodified SiO2) to understand the nature of the catalytic reaction and determine the rate expression and activation parameters. (C) 2015 Elsevier B.V. All rights reserved.