Yuzuncu Yil University

Van, Turkey
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Herein, the employment of PVP-protected Pt-Ru bimetallic nanoparticles (3.2 ± 1.4 nm) as highly efficient catalysts in the hydrolysis of ammonia borane for hydrogen generation is reported. They were prepared by co-reduction of two metal ions in ethanol/water mixture by an alcohol reduction method and characterized by TEM-EDX analysis, UV-vis spectroscopy, and X-ray photoelectron spectroscopy. They are recyclable and highly active for hydrogen generation from the hydrolysis of ammonia borane even at very low concentrations and temperature, providing a record numbers of average TOF value (308 mol H 2 molcat -1 min-1) and maximum hydrogen generation rate (9884 L H2 min-1 (mol cat)-1) for ammonia borane. PVP-protected Pt-Ru bimetallic nanoparticles provide activation energy of 56.3 ± 2 kJ mol-1 for the hydrolysis of ammonia borane. © 2014 Elsevier B.V.

Dincer F.,Yuzuncu Yil University
Renewable and Sustainable Energy Reviews | Year: 2011

The Republic of Turkey, located in Southeastern Europe and Southwestern Asia (that portion of Turkey west of the Bosporus is geographically part of Europe). Nowadays, Turkey with its young population and growing energy demand per person, its fast growing urbanization, and its economic development, has been one of the fast growing electrical energy markets of the world for the last two decades. Unfortunately, Turkey's energy is largely dependent on foreign countries and the country's energy is imported spending billions of dollars each year. On the other hand, the effects on global and environmental air quality of pollutants released into the atmosphere from fossil fuels in electric power plants provide strong arguments for the development of renewable energy resources. Solar energy is one of the best available among renewable energy sources. There are possess many advantages of solar energy such as relativity, viability, silent, non-polluting, little maintenance, suitable for remote site application, not require any fuel and independent from electricity network. Turkey has advanced a great deal in the generation of electricity from solar energy because of much higher solar energy potential than lots of developed countries on solar energy applications. This study is taken into account that overview of the photovoltaic technology status and perspective in Turkey and the contains of photovoltaic power systems utilization and potential status in the world, energy consumption and demand in Turkey, geographic description of the solar energy in Turkey, PV industry current and potential status in Turkey, solar energy legislation framework in Turkey, R&D status of photovoltaic industry in Turkey, future strategy of PV industry in Turkey, current and future status photovoltaic power systems economics in the world. Also, this paper on the basis of this subjects is analyzed the SWOT of Turkey's photovoltaic industry, its advantages, weaknesses, opportunities and threats. © 2011 Elsevier Ltd. All rights reserved.

Conventional slow pyrolysis of Eremurus spectabilis samples has been performed in a fixed-bed tubular reactor with (tincal, colemanite and ulexite) and without catalyst in the temperature range between 350 and 550 °C with heating rates of 10, 30, 50 °C/min. The yields of bio-char, bio-oil and gas produced, as well as the compositions of the resulting bio-oils were determined by elemental analysis, Fourier transform infrared spectroscopy (FT-IR) and gas chromatography/mass spectrometry (GC-MS). The effects of pyrolysis parameters such as heating rate, temperature, catalyst type, sweeping gas flowrate and particle size (Dp) on product yieldswere investigated. The results show that temperature and catalyst are the main factors that effect the conversion of E. spectabilis into solid, liquid and gaseous products. The highest liquid yield of 38.14% including aqueous phase was achieved with ulexite catalyst at 500 °C temperature at a heating rate of 50 °C/min when 0.224 > Dp > 0.150 mm particle size raw material and 100 mL/min of sweeping gas flow rate were used. Ninety-one and ninety-seven different compounds have been identified by GC-MS in bio-oils obtained at 350 and 550 °C respectively. © 2014 Elsevier B.V. All rights reserved.

Camadan E.,Yuzuncu Yil University
Renewable and Sustainable Energy Reviews | Year: 2011

Promotion of renewable energy sources is a widely adopted policy since they are accepted to positively contribute to ensure the security of energy supply, mitigate CO2 emissions and meet the increasing energy demand. In parallel with that global thought, wind energy has been a hot topic in Turkish energy agenda although the share of wind energy in total energy resources of the country is still low. In this framework, the policies and applications regarding wind energy in Turkey are examined, the short-term and long-term priorities are evaluated and some suggestions are provided in this paper. © 2011 Elsevier Ltd. All rights reserved.

Aysu T.,Yuzuncu Yil University
Biomass and Bioenergy | Year: 2012

Conversion of milled Phalaris arundinacea stalk to liquid products has been performed with organic solvents (methanol, ethanol, acetone and 2-butanol) with catalysts (NaOH or Na 2CO 3) and without catalyst in an autoclave at temperatures of 530, 550 and 570 K. The liquid products obtained were extracted by liquid-liquid extraction with benzene and diethyl ether. The percentage of yields (liquid products) from supercritical extraction by methanol, ethanol, 2-butanol and acetone conversions were 51.7%, 57.2%, 59.8% and 72.8% at 570 K respectively. The highest conversion in the catalytic run was obtained by using ethanol with NaOH at the same temperature (570 K). Some of selected yields of conversion were analyzed by GC-MS. The purpose of present study was to obtain an alternative for petroleum derived fuels or chemical raw materials. © 2012 Elsevier Ltd.

Diner F.,Yuzuncu Yil University
Renewable and Sustainable Energy Reviews | Year: 2011

Energy, which is the main agenda of our world, is crucially important for the people. Many countries frequently held meetings and discussions with energy agenda. These countries are working to balance the energy demand and supply. For finding the solution are researched, researches should be attempted to present a more efficient way to use energy as well as renewable energy resources effectively. Photovoltaic energy power systems take place as the most dominant source among renewable energy technologies. The most important reason is that it is unlimited and clean energy of the solar power systems. Many studies show that photovoltaic power systems will have an important share in the electricity of the future. In this study, to generate electricity from solar energy using photovoltaic systems have a leading position in some European countries, United States of America, China and Japan's current status and future policies will be analyzed in various comments were made. © 2010 Elsevier Ltd.

Today, the synthesis of well-defined metal nanoparticles stabilized by the metal-organic frameworks (MOFs), which provide high specific surface areas, tunable pore sizes, and guest interactable organic linkers, and the discovery of their unique properties are still challenging goals. The chemically robust zeolitic imidazole framework (ZIF) is a subclass of MOF. In this study, the microporous sodalite-like ZIF-8 (Zn(MeIM); MeIM = 2-methylimidazole) was selected as host matrix to stabilize guest iridium nanoparticles (IrNPs). The iridium loading was achieved via gas phase infiltration of Ir(COD)(MeCp) (methylcyclopentadienyl)(1,5-cyclooctadiene)iridium(i)) precursor followed by hydrogenolysis of the inclusion compound Ir(COD)(MeCp)@ZIF-8 to form the IrNPs@ZIF-8. The characterization of IrNPs@ZIF-8 by ICP-MS, P-XRD, XPS, 13C MAS NMR, TEM, HRTEM, STEM, STEM-EDX, HAADF-STEM, DR-UV-vis, EA analyses and N 2-adsorption-desorption techniques reveal the formation of well-dispersed iridium nanoparticles (3.3 ± 1.7 nm) within the framework of ZIF-8 (IrNPs@ZIF-8) by keeping the host framework intact. The catalytic application of IrNPs@ZIF-8 in terms of activity, selectivity, reusability and durability was demonstrated in the hydrogenation of cyclohexene and phenylacetylene under mild conditions, in which they were found to be highly active catalysts. Moreover, they show great durability against sintering and leaching throughout the catalytic runs that make them highly reusable catalysts. They retain their inherent catalytic activity even at the fifth catalytic run in the hydrogenation of cyclohexene and phenylacetylene. © 2012 The Royal Society of Chemistry.

The catalytic use of highly efficient poly(N-vinyl-2-pyrrolidone)-stabilized palladium-platinum nanoparticles (4.2 ± 1.9 nm) in the hydrolysis of ammonia-borane is reported. The catalyst is prepared by co-reduction of two metal ions in ethanol/water mixture by an alcohol reduction method and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Vis spectroscopy. They are recyclable and highly active for hydrogen generation from the hydrolysis of ammonia-borane even at very low concentrations and temperature, providing a record numbers of average turnover frequency value (125 mol H2/mol cat.min-1) and maximum hydrogen generation rate (3468 L H2 min-1 (mol cat)-1). They also provide activation energy of 51.7 ± 2 kJ/mol for the hydrolysis of ammonia borane. © 2014 Elsevier B.V. All rights reserved.

Density functional theory (DFT) calculations were carried out in a study of the mechanism of direct oxidation of methanol to formaldehyde by N2O over an extra-framework species in ZSM-5 zeolite represented by a [(SiH 3)4AlO4(Fe) or (FeO)] cluster models. The major difference between these two sites is that in the case of the [Fe]1+ site, a reaction is present that leads to the formation of the thermodynamically highly stable grafted OH and methoxy (OCH3) species. Moreover, the vibrational frequencies for grafted species on the surface match well with the experimental values. The theoretical calculations achieved in this study obviously show that [Fe-O]1+ site in Fe-ZSM-5 catalyst has a significant role on the catalytic oxidation of methanol to formaldehyde by N2O. © 2011 Elsevier Inc. All rights reserved.

The safe and efficient hydrogen storage and production are major obstacles to use hydrogen as an energy carrier. Therefore, significant efforts have been focused on the development of new materials for the chemical hydrogen storage and production. Of particular importance, ammonia-borane (NH 3BH 3) is emerging as one of the most promising solid hydrogen carrier due to its high gravimetric hydrogen storage capacity (19.6 wt.%) and low molecular weight (30.8 g/mol). ammonia-borane can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, the discovery of a new catalytic material, ruthenium nanoparticles stabilized by ZK-4 zeolite framework, for this important reaction has been reported. This new catalyst system was prepared by borohydride reduction of ruthenium(III)-exchanged ZK-4 zeolite in water at room temperature. The characterization of the resulting material by advanced analytical tools shows the formation of ZK-4 zeolite dispersed ruthenium nanoparticles (2.9 ± 0.9 nm). The catalytic performance of the resulting supported ruthenium nanoparticles depending on activity, lifetime and reusability was demonstrated in the hydrolytic dehydrogenation of ammonia-borane. They were found to be highly active (initial TOF = 5410 h -1), long-lived (TTO = 36,700) and reusable catalyst (retaining of >85% of initial activity in the 5th reuse) in this important catalytic reaction at room temperature under air. © 2012 Elsevier B.V. All rights reserved.

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