Browsing by Author "Zahmakiran, Mehmet"

Now showing 1 - 20 of 25

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: 27
Amine-Functionalized Graphene Nanosheet-Supported Pdauni Alloy Nanoparticles: Efficient Nanocatalyst for Formic Acid Dehydrogenation
(Royal Soc Chemistry, 2018) Bulut, Ahmet; Yurderi, Mehmet; Kaya, Murat; Aydemir, Murat; Baysal, Akin; Durap, Feyyaz; Zahmakiran, Mehmet; Chemical Engineering
Formic acid (HCOOH), a major by-product of biomass processing with high energy density, stability and non-toxicity, has a great potential as a safe and a convenient liquid hydrogen (H-2) storage material for combustion engines and fuel cell applications. However, high-purity hydrogen release from the catalytic decomposition of aqueous formic acid solution at desirable rates under mild conditions stands as a major challenge that needs to be solved for the practical use of formic acid in on-demand hydrogen generation systems. Described herein is a new nanocatalyst system comprised of 3-aminopropyltriethoxysilane-functionalized graphene nanosheet-supported PdAuNi alloy nanoparticles (PdAuNi/f-GNS), which can reproducibly be prepared by following double solvent method combined with liquid-phase chemical reduction, all at room temperature. PdAuNi/f-GNS selectively catalyzes the decomposition of aqueous formic acid through the dehydrogenation pathway (similar to 100% H-2 selectivity), in the absence of any promoting additives (alkali formates, Bronsted bases, Lewis bases, etc.). PdAuNi/f-GNS nanocatalyst provides CO-free H-2 generation with a turnover frequency of 1090 mol H-2 mol metal(-1) h(-1) in the additive-free dehydrogenation of formic acid at almost complete conversion (>= 92%) even at room temperature. The catalytic activity provided by PdAuNi/f-GNS nanocatalyst is higher than those obtained with the heterogeneous catalysts reported to date for the additive-free dehydrogenation of formic acid. Moreover, PdAuNi/f-GNS nanoparticles show high durability against sintering, clumping and leaching throughout the catalytic runs, so that the PdAuNi/f-GNS nanocatalyst retains almost its inherent catalytic activity and selectivity at the end of the 10th recycle.
Citation - WoS: 50
Citation - Scopus: 53
Atomic Layer Deposition-sio₂ Layers Protected Pdconi Nanoparticles Supported on Tio₂ Nanopowders: Exceptionally Stable Nanocatalyst for the Dehydrogenation of Formic Acid
(Elsevier Science Bv, 2017) Caner, Nurdan; Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Kivrak, Hilal; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
TiO2 nanopowders supported trimetallic PdCoNi alloy nanoparticles were simply and reproducibly prepared by wet-impregnation followed by simultaneous reduction method, then to enhance their stability against to sintering and leaching atomic layer deposition (ALD) technique was utilized to grow SiO2 layers amongst these surface bound PdCoNi alloy nanoparticles (PdCoNi/TiO2-ALD-SiO2). These new nanomaterials are characterized by the combination of complimentary techniques and sum of their results exhibited that the formation of ALD-SiO2 layers protected well-dispersed and highly crystalline PdCoNi alloy nanoparticles (ca. 3.52 nm) supported on TiO2 nanopowders. The catalytic performance of the resulting PdCoNi/TiO2-ALD-SiO2 in terms of activity, selectivity and stability was investigated in the dehydrogenation of aqueous formic acid (HCOOH), which has recently been suggested as a promising hydrogen storage material with a 4.4 wt% hydrogen capacity, solution under mild conditions. The results collected from our systematic studies revealed that PdCoNi/TiO2-ALD-SiO2 nanomaterial can act as highly active and selective nanocatalyst in the formic acid dehydrogenation at room temperature by providing an initial turnover frequency (TOF) value of 207 mol H-2/mol metal;: h and >99% of dehydrogenation selectivity at almost complete conversion. More importantly, the catalytic reusability experiments separately carried out with PdCoNi/TiO2-ALD-SiO2 and PdCoNi/TiO2 nanocatalysts in the dehydrogenation of formic acid under more forcing conditions pointed out that PdCoNi/TiO2-ALD-SiO2 nanocatalyst displays unprecedented catalytic stability against to leaching and sintering throughout the reusability experiments it retains almost its inherent activity, selectivity and conversion even at 20th reuse, whereas analogous PdCoNi/TiO2 completely lost its catalytic performance. (C) 2017 Elsevier B.V. All rights reserved.
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: 144
Citation - Scopus: 147
Carbon Supported Trimetallic Pdniag Nanoparticles as Highly Active, Selective and Reusable Catalyst in the Formic Acid Decomposition
(Elsevier Science Bv, 2014) Yurderi, Mehmet; Bulut, Ahmet; Zahmakiran, Mehmet; Kaya, Murat; Chemical Engineering
Trimetallic PdNiAg nanoparticles supported on activated carbon were simply and reproducibly prepared by wet-impregnation followed by simultaneous reduction method without using any stabilizer at room temperature. The characterization of the resulting material was done by the combination of complimentary techniques and the sum of their results shows that the formation of well-dispersed 5.6 +/- 2.2 nm PdNiAg nanoparticles in alloy form on the surface of activated carbon. These carbon supported PdNiAg nanoparticles were employed as heterogeneous catalyst in the catalytic decomposition of formic acid, which has great potential as a safe and convenient hydrogen carrier for fuel cells, under mild conditions. It was found that PdNiAg/C can catalyze the dehydrogenation of formic acid with high selectivity (similar to 100%) and activity (TOF = 85 h(-1)) at 50 degrees C. More importantly, the exceptional stability of PdNiAg nanoparticles against to agglomeration, leaching and CO poisoning make PdNiAg/C reusable catalyst in the formic acid dehydrogenation. PdNiAg/C catalyst retains almost its inherent activity (>94%) even at 5th reuse in the dehydrogenation of formic acid with high selectivity (similar to 100%) at complete conversion. The work reported here also includes the compilation of kinetic data for PdNiAg/C catalyzed dehydrogenation of formic acid depending on catalyst [PdNiAg], substrate [HCOOH], promoter [HCOONa] concentrations and temperature to determine the rate expression and the activation parameters (Ea, Delta H-#, and Delta S-#) of the catalytic reaction. (C) 2014 Elsevier B.V. All rights reserved.
Citation - WoS: 7
Citation - Scopus: 8
Chromium Based Metal-Organic Framework Mil-101 Decorated Palladium Nanoparticles for the Methanolysis of Ammonia-Borane
(Royal Soc Chemistry, 2020) Caner, Nurdan; Yurderi, Mehmet; Bulut, Ahmet; Kanberoglu, Gulsah Saydan; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Palladium nanoparticles stabilized by an MIL-101 metal-organic framework (Pd@MIL-101) are synthesized by a novel synthesis approach. A Pd@MIL-101 catalyst facilitates H(2)generation from the methanolysis of ammonia-borane with record catalytic activity (TOF = 1080 min(-1)) at room temperature. Moreover, the exceptional stability of Pd@MIL-101 makes it a reusable heterogeneous catalyst in this catalytic transformation.
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: 3
Citation - Scopus: 3
Comparative Performance Study of Acidic Pumice and Basic Pumice Inclusions for Acrylonitrile-Butadiene Composite Filaments
(Mary Ann Liebert, inc, 2024) Tayfun, Umit; Tirkes, Seha; Dogan, Mehmet; Tirkes, Suha; Zahmakiran, Mehmet; Chemical Engineering
This study aims to evaluate the effective use of porous pumice powder as an additive in acrylonitrile-butadiene-styrene (ABS)-based composite materials. The influence of pumice addition on mechanical, thermomechanical, thermal, and physical properties of ABS filaments was reported. Two types of pumice, namely acidic pumice (AP) and basic pumice (BP), were melt compounded with ABS at loading levels of 5%, 10%, 15%, and 20% by weight using the melt extrusion preparation method. Composites were shaped into dog bone test specimens by the injection molding process. The physical properties of pumice powders were investigated by particle size analysis and X-ray spectroscopy techniques. Mechanical, thermomechanical, thermal, melt flow, and morphological behaviors of ABS/AP and ABS/BP composite filaments were proposed. According to test results, pumice addition led to an increase in the mechanical response of ABS up to a filling ratio of 10%. Further inclusion of pumice caused sharp reduction due to the possible agglomeration of pumice particles. Composites filled with AP yielded remarkably higher mechanical performance in terms of tensile, impact, and hardness strength compared with BP-loaded composites. According to thermal analyses, ABS exhibited higher thermal stability after incorporation of AP and BP. Pumice addition also resulted in raising the glass transition temperature of ABS. Melt flow index (MFI) findings revealed that addition of two types of pumice led to an opposite trend in the melt flow behavior of ABS filaments. Homogeneous dispersion of pumice particles into the ABS matrix when adding low amounts, as well as reduction in dispersion homogeneity with high amounts, of AP and BP was confirmed by scanning electron microscopy (SEM) micrographs.
Citation - WoS: 19
Citation - Scopus: 20
Complete Dehydrogenation of Hydrazine Borane on Manganese Oxide Nanorod-Supported Ni@ir Core-Shell Nanoparticles
(Amer Chemical Soc, 2020) Yurderi, Mehmet; Top, Tuba; Bulut, Ahmet; Kanberoglu, Gulsah Saydan; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Hydrazine borane (HB; N2H4BH3) has been considered to be one of the most promising solid chemical hydrogen storage materials owing to its high hydrogen capacity and stability under ambient conditions. Despite that, the high purity of hydrogen production from the complete dehydrogenation of HB stands as a major problem that needs to be solved for the convenient use of HB in on-demand hydrogen production systems. In this study, we describe the development of a new catalytic material comprised of bimetallic Ni@Ir core-shell nanoparticles (NPs) supported on OMS-2-type manganese oxide octahedral molecular sieve nanorods (Ni@Ir/OMS-2), which can reproducibly be prepared by following a synthesis protocol including (i) the oleylamine-mediated preparation of colloidal Ni@Ir NPs and (ii) wet impregnation of these ex situ synthesized Ni@Ir NPs onto the OMS-2 surface. The characterization of Ni@Ir/OMS-2 has been done by using various spectroscopic and visualization techniques, and their results have revealed the formation of well-dispersed Ni@Ir core-shell NPs on the surface of OMS-2. The catalytic employment of Ni@Ir/OMS-2 in the dehydrogenation of HB showed that Ni-0.22@Ir-0.78/OMS-2 exhibited high dehydrogenation selectivity (>99%) at complete conversion with a turnover frequency (TOF) value of 2590 h(-1) at 323 K, which is the highest activity value among all reported catalysts for the complete dehydrogenation of HB. Furthermore, the Ni-0.22@Ir-0.78/OMS-2 catalyst enables facile recovery and high stability against agglomeration and leaching, which make it a reusable catalyst in the complete dehydrogenation of HB. The studies reported herein also include the collection of wealthy kinetic data to determine the activation parameters for Ni-0.22@Ir-0.78/OMS-2-catalyzed dehydrogenation of HB.
Citation - WoS: 99
Citation - Scopus: 103
Copper(0) Nanoparticles Supported on Silica-Coated Cobalt Ferrite Magnetic Particles: Cost Effective Catalyst in the Hydrolysis of Ammonia-Borane With an Exceptional Reusability Performance
(Amer Chemical Soc, 2012) Kaya, Murat; Zahmakiran, Mehmet; Ozkar, Saim; Volkan, Murvet; Chemical Engineering
Herein we report the development of a new and cost-effective nanocomposite catalyst for the hydrolysis of ammonia-borane (NH3BH3), which is considered to be one of the most promising solid hydrogen carriers because of its high gravimetric hydrogen storage capacity (19.6% wt) and low molecular weight. The new catalyst system consisting of copper nanoparticles supported on magnetic SiO2/CoFe2O4 particles was reproducibly prepared by wet-impregnation of Cu(II) ions on SiO2/CoFe2O4 followed by in situ reduction of the Cu(II) ions on the surface of magnetic support during the hydrolysis of NH3BH3 and characterized by ICP-MS, XRD, XPS, TEM, HR-TEM and N-2 adsorption-desorption technique. Copper nanoparticles supported on silica coated cobalt(II) ferrite SiO2/CoFe2O4 (CuNPs@SCF) act as highly active catalyst in the hydrolysis of ammonia-borane, providing an initial turnover frequency of TOF = 2400 h(-1) at room temperature, 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, they were easily recovered by using a permanent magnet in the reactor wall and reused for up, to 10 recycles without losing their inherent catalytic activity significantly, which demonstrates the exceptional reusability of the CuNPs@SCF catalyst.
Citation - WoS: 34
Citation - Scopus: 37
Hydroxyapatite-Nanosphere Supported Ruthenium(0) Nanoparticle Catalyst for Hydrogen Generation From Ammonia-Borane Solution: Kinetic Studies for Nanoparticle Formation and Hydrogen Evolution
(Royal Soc Chemistry, 2014) Durak, Halil; Gulcan, Mehmet; Zahmakiran, Mehmet; Ozkar, Saim; Kaya, Murat; Chemical Engineering
The development of readily prepared effective heterogeneous catalysts for hydrogen generation from ammonia-borane (AB; NH3BH3) solution under mild conditions still remains a challenge in the field of "hydrogen economy". In this study, we report our finding of an in situ generated, highly active ruthenium nanocatalyst for the dehydrogenation of ammonia-borane in water at room temperature. The new catalyst system consists of ruthenium(0) nanoparticles supported on nanohydroxyapatite (RuNPs@nano-HAp), and can be reproducibly prepared under in situ conditions from the ammonia-borane reduction of Ru3+ ions exchanged into nanohydroxyapatite (Ru3+@nano-HAp) during the hydrolytic dehydrogenation of ammonia-borane at 25 +/- 0.1 degrees C. Nanohydroxyapatite-supported ruthenium(0) nanoparticles were characterized by a combination of advanced analytical techniques. The sum of their results shows the formation of well-dispersed ruthenium(0) nanoparticles with a mean diameter of 2.6 +/- 0.6 nm on the surface of the nanospheres of hydroxyapatite by keeping the host matrix intact. The resulting RuNPs@nano-HAp are highly active catalyst in the hydrolytic dehydrogenation of ammonia-borane with an initial TOF value of 205 min(-1) by generating 3.0 equiv. of H-2 per mole of ammonia-borane at 25 +/- 0.1 degrees C. Moreover, they are sufficiently stable to be isolated and bottled as solid materials, which can be reused as active catalyst under the identical conditions of first run. The work reported here also includes the following results: (i) monitoring the formation kinetics of the in situ generated RuNPs@nano-HAp by hydrogen generation from the hydrolytic dehydrogenation of ammonia-borane as the reporter reaction. The sigmoidal kinetics of catalyst formation and concomitant dehydrogenation fits well to the two-step, slow nucleation, followed by autocatalytic surface growth mechanism, P -> Q (rate constant k(1)) and P + Q -> 2Q (rate constant k(2)), in which P is Ru3+@nano-HAp and Q is the growing, catalytically active RuNPs@nano-HAp; (ii) the compilation of kinetic data for the RuNPs@nano-HAp catalyzed hydrolytic dehydrogenation of ammonia-borane depending on the temperature and catalyst concentration to determine the dependency of reaction rate on catalyst concentration and activation parameters (E-a, Delta H-#, and Delta S-#) of the reaction.
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: 78
Citation - Scopus: 83
Methylene Blue Photocatalytic Degradation Under Visible Light Irradiation on Copper Phthalocyanine-Sensitized Tio₂ Nanopowders
(Elsevier Science Bv, 2017) Cabir, Beyza; Yurderi, Mehmet; Caner, Nurdan; Agirtas, Mehmet Salih; Zahmakiran, Mehmet; Kaya, Murat; Chemical Engineering
Described herein is a new photocatalytic material that shows remarkable catalytic performance in terms of activity and reusability in the photocatalytic degradation of methylene blue (MB) in water. The new catalyst system comprised of copper phthalocyanine modified titanium(IV) oxide (TiO2) nanopowders (CuPc-TiO2\) was prepared by the wet chemical impregnation method to improve the photocatalytic activity of TiO2 and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-Vis, FTIR, FE-SEM, SEM-EDX, BFTEM, HRTEM and N-2-adsorption-desorption techniques. The photocatalytic performance of the resulting CuPc-TiO2 in terms of activity and stability was evaluated by the photocatalytic degradation of MB in aqueous solution under mild conditions. Our results revealed that CuPc-TiO2 photocatalyst displayed remarkable activity (TOF = 3.73 mol MB/(mol CuPc + mol TiO2) x h) in the complete (100%) photocatalytic degradation of MB under visible light irradiation (150 W). Moreover, CuPc-TiO2 photocatalyst showed excellent stability against to sintering and clumping throughout the reusability experiments and it retained >80% of its initial activity even at 5th reuse, which makes it reusable photocatalyst in the photocatalytic degradation of MB. (C) 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 124
Mno_x< Pdag Alloy Nanoparticles for the Additive-Free Dehydrogenation of Formic Acid at Room Temperature
(Amer Chemical Soc, 2015) Bulut, Ahmet; Yurderi, Mehmet; Karatas, Yasar; Say, Zafer; Kivrak, Hilal; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Formic acid (HCOOH) has a great potential as a safe and a convenient hydrogen carrier for fuel cell applications. However, efficient and CO-free hydrogen production through the decomposition of formic acid at low temperatures (<363 K) in the absence of additives constitutes a major challenge. Herein, we present a new heterogeneous catalyst system composed of bimetallic PdAg alloy and MnOx nanoparticles supported on amine-grafted silica facilitating the liberation of hydrogen at room temperature through the dehydrogenation of formic acid in the absence of any additives with remarkable activity (330 mol H-2 center dot mol catalyst(-1)center dot h(-1)) and selectivity (>99%) at complete conversion (>99%). Moreover this new catalytic system enables facile catalyst recovery and very high stability against agglomeration, leaching, and CO poisoning. Through a comprehensive set of structural and functional characterization experiments, mechanistic origins of the unusually high catalytic activity, selectivity, and stability of this unique catalytic system are elucidated. Current heterogeneous catalytic architecture presents itself as an excellent contender for clean hydrogen production via room-temperature additive-free dehydrogenation of formic acid for on-board hydrogen fuel cell applications.
Citation - WoS: 23
Citation - Scopus: 27
Nanocrystalline Metal Organic Framework (mil-101) Stabilized Copper Nanoparticles: Highly Efficient Nanocatalyst for the Hydrolytic Dehydrogenation of Methylamine Borane
(Elsevier Science Sa, 2018) Baguc, Ismail Burak; Ertas, Ilknur Efecan; Yurderi, Mehmet; Bulut, Ahmet; Zahmakiran, Mehmet; Kaya, Murat; Chemical Engineering
The copper nanoparticles stabilized by nanocrystalline MIL-101 framework (Cu/nano-MIL-101) was reproducibly prepared by following double solvent method combined with liquid phase chemical reduction technique. The characterization of the resulting new material was done by using various analytical techniques including ICP-OES, P-XRD, N-2-adsorption-desorption, XPS, FE-SEM, SEM-EDX, BFTEM and HAADF-STEM; the summation of their results reveals that the formation of well-dispersed and very small sized (0.8 nm) copper nanoparticles within nanocrystalline MIL-101 framework. The catalytic performance of Cu/nano-MIL-101 in terms of activity and stability was tested in the hydrolytic dehydrogenation of methylamine borane (CH3NH2BH3), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage. Cu/nano-MIL-101 catalyzes the hydrolytic dehydrogenation of methylamine borane with high activity (turnover frequency; TOF = 257 mot H-2/mol Cu x h) and conversion ( > 99%) under air at room temperature. Moreover, these nano-MIL-101 framework stabilized copper nanoparticles show great durability against to sintering and leaching, which make Cu/nano-MIL-101 reusable nanocatalyst in the hydrolytic dehydrogenation of methylamine-borane. Cu/nano-MIL-101 nanocatalyst retains 83% of its inherent activity at complete conversion even at 10th recycle in the hydrolytic dehydrogenation of methylamine borane.
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.
Citation - WoS: 24
Citation - Scopus: 28
Palladium(0) Nanoparticles Supported on Hydroxyapatite Nanospheres: Active, Long-Lived, and Reusable Nanocatalyst for Hydrogen Generation From the Dehydrogenation of Aqueous Ammonia-Borane Solution
(Springer, 2014) Karatas, Yasar; Yurderi, Mehmet; Gulcan, Mehmet; Zahmakiran, Mehmet; Kaya, Murat; Chemical Engineering
Among the solidmaterials considered in the chemical hydrogen storage, ammonia-borane (NH3-BH3) appears to be one of the promising candidates as it can release hydrogen throughout hydrolysis in the presence of suitable catalyst under mild conditions. Herein we report, for the first time, the preparation and characterization of palladium(0) nanoparticles supported on nanohydroxyapatite and their catalytic use in the hydrolysis of ammonia-borane under air at room temperature. These new palladium(0) nanoparticles were generated in situ during the catalytic hydrolysis of ammonia-borane starting with palladium(II) immobilized nanohydroxyapatite. The preliminary characterization of the palladium(0) nanoparticles supported on nanohydroxyapatite was done by the combination of complimentary techniques, which reveals that the formation of well-dispersed Pd(0)NPs nanoparticles (1.41 +/- 0.52 nm) on the surface of hydroxyapatite nanospheres (60-150 nm). The resulting palladium nanocatalyst achieves hydrogen generation from the hydrolysis of ammonia-borane with an initial turnover frequency value (TOF) of 11 mol H-2 mol(-1) Pd x min at room temperature under air. In addition to their high activity, the catalytic lifetime experiment showed that they can also act as a long-lived heterogeneous catalyst for this reaction (TTON = 14,200 mol H-2 mol(-1) Pd) at room temperature under air. More importantly, nanohydroxyapatite- supported palladium(0) nanoparticles were found to be highly stable against to leaching and sintering throughout the catalytic runs that make them isolable, bottleable, and reusable heterogeneous catalyst for the hydrolysis of ammonia-borane.
Citation - WoS: 148
Citation - Scopus: 150
Pd-mno_x< Nanoparticles Dispersed on Amine-Grafted Silica: Highly Efficient Nanocatalyst for Hydrogen Production From Additive-Free Dehydrogenation of Formic Acid Under Mild Conditions
(Elsevier Science Bv, 2015) Bulut, Ahmet; Yurderi, Mehmet; Karatas, Yasar; Zahmakiran, Mehmet; Kivrak, Hilal; Gulcan, Mehmet; Kaya, Murat; Chemical Engineering
Herein we report the development of a new highly active, selective and reusable nanocatalyst for additive-free dehydrogenation of formic acid (HCOOH), which has great potential as a safe and convenient hydrogen carrier for fuel cells, under mild conditions. The new catalyst system consisting of bimetallic Pd-MnOx nanoparticles supported on aminopropyl functionalized silica (Pd-MnOx/SiO2-NH2) was simply and reproducibly prepared by deposition-reduction technique in water at room temperature. The characterization of Pd-mnO(x)/SiO2-NH2 catalyst was done by the combination of multipronged techniques, which reveals that the existence of highly crystalline individually nucleated Pd(0) and MnOx nanoparticles (d(mean) = 4.6 +/- 1.2 nm) on the surface of aminopropyl functionalized silica. These supported Pd-MnOx nanoparticles can catalyze the additive-free dehydrogenation of formic acid with record activity (TOF = 1300 h(-1)) at high selectivity (>99%) and conversion (>99%) under mild conditions (at 50 degrees C and under air). Moreover, easy recovery plus high durability of these supported Pd-MnOx nanoparticles make them a reusable heterogeneous catalyst in the additive-free dehydrogenation of formic acid. (C) 2014 Elsevier B.V. All rights reserved.