Hydrogen storage in nickel doped MCM-41

Hydrogen as an energy carrier is one of the best environmentally friendly alternatives to fossil fuel sources. The potential use of hydrogen results with increasing demand to hydrogen production and storage. Recent studies show that materials having high surface area, large pore size and high affinity to hydrogen have high hydrogen storage capacity. MCM-41 is silica based material having such properties and its hydrogen sorption properties can be improved by doping transition metals to the structure. Ni was chosen for this purpose as it is known with its hydrogen affinity. In this study, different amounts of Ni doped in MCM-41 that was produced by microwave heating to examine hydrogen storage capacity of Ni doped MCM-41 systems. The morphology and structure of the material was characterized by scanning electron microscope and X-ray diffraction analysis. Thermal stability of MCM-41 was examined by thermogravimetric analysis and it was seen that MCM-41s are hydrothermally stable. Surface area, pore size and adsorption capacity of MCM-41 were measured by Brunauer-Emmett-Teller (BET) method. It was observed that the material had large surface area around 1000 m2/g and roughly 2 nm pore size. It was found materials have uniform pore structure with hexagonal well-ordered arrangement. BET surface area, pore volume and pore diameters decreased as the metal loading increased. The hydrogen adsorption capacity measurements were achieved by the Intelligent Gravimetric Analyzer at room temperature and up to 10 bar pressure. It was observed that the hydrogen storage capacity of MCM-41 is strongly affected by metal doping

Hydrogen storage in single wall carbon nanotubes produced on iron catalyst

Hydrogen is a promising clean energy alternative to conventional energy sources. Hence, increasing demand on hydrogen as energy carrier enhances studies in hydrogen storage. Hydrogen should be safely and efficiently stored in order to overcome existing barriers in hydrogen usage. Single wall carbon nanotube (SWCNT) is an eligible material for hydrogen storage. In this study, SWCNTs were produced by catalytic chemical vapor deposition (CCVD) of acetylene (C2H2) on MgO powder substrate impregnated with Fe. Catalysts were prepared with Fe to MgO ratio of 5:100 using iron nitrate (Fe(NO3)3•9H2O) solution as Fe source. SWCNTs were synthesized at 800°C for 60 minutes. Nitric acid (HNO3), was used for purification of synthesized SWCNT. The aim of the research was to investigate hydrogen storage capacity of as produced and purified SWCNTs synthesized on Fe-MgO catalyst. The morphology and structure of the SWCNTs were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. Thermal gravimetric analysis (TGA), and Raman spectroscopy were used for further characterization. Hydrogen storage capacities of SWCNTs were measured by high pressure volumetric analyzer using volumetric method at the cryogenic temperature and gas pressure up to 90 bar. It was found that the hydrogen adsorption capacities of these materials were around 1.9 and 5.3 wt% for as produced and purified SWCNTs respectively. With the fact that DOE target for 2015 is 5.5 wt%, it was seen that SWCNTs produced on Fe-MgO catalyst have good potential as hydrogen storage material

Propolisteki fenolik bileşiklerin farklı biyotransformasyon koşullarındaki değişimi

Propolis, kompleks içeriğe sahip bir değerli bir arı ürünüdür. Propolis, çeşitli bitki kaynaklarından bal arıları (Apis mellifera L.) tarafından toplanan reçinemsi maddedir. Arılar bitkilerin farklı kısımlarından topladıkları maddeleri kovana taşırlar. Arıların çeneleri yardımıyla topladıkları bu maddeleri tükürük salgıları ve balmumu ile karıştırmaları sonucunda propolis meydana gelir. Bu tezde propolisin içerdiği fenolik bileşenlerin biyotransformasyondan sonra daha kullanışlı hale gelebileceği ve farklı uygulama alanlarında kullanılabileceği düşüncesi ile yola çıkılarak propolisteki fenolik bileşenlerin farklı biyotrasformasyon koşullarındaki değişimi incelenmiştir. Biyotransformasyonda sırasında farklı çözücüler (etanol, polietilen glikol ve su), farklı inokülasyon oranları (%1,5, %2,5, %3,5), farklı kültürler (Lactobacillus plantarum İŞLG–2, Lactobacillus plantarum ATCC® 8014, Lactobacillus plantarum Visbyvac) ve ultrason uygulaması (5 dk, 10 dk, 15 dk) kullanılmıştır. Farklı biyotransformasyon koşullarına tabii tutulalan propolis örneklerinin UPLC/MS-MS yöntemi fenolik bileşen analizi, Folin Ciocalteu yöntemi ile toplam fenolik bileşik analizi ve troloks eşdeğeri antioksidan aktivite (TEAC), 2,2-difenil-1-pikrilhidrazil radikal süpürücü antioksidan aktivite (DPPH) ve demir (III) iyonu indirgeyici antioksidan aktivite (FRAP) yöntemi ile analizler yapılmıştır. Çalışmanın sonucunda, fenolik bileşenler üzerinde farklı çözücülerin, kültürlerin ve ultrason uygulamalarının etkileri değişmekle birlikte hedef fenolik bileşene göre seçilecek her bir parametrenin kalitatif olarak bir etki yaratabileceği ortaya çıkmıştır.Propolis is a valuable bee product with complex content. Propolis is a resinous material collected by honeybees (Apis mellifera L.) from various plant sources. The bees carry the materials to hive which they collect from different parts of the plants. Propolis comes to as a result of mixing these substances with salivary secretions and wax with the help of the jaws of the bees. In this thesis, the change of phenolic components in propolis under different biotrasformation conditions was investigated by considering the fact that the phenolic compounds contained in propolis can become more useful after biotransformation and can be used in different application areas. Different solvents (ethanol, polyethylene glycol and water), different inoculation rates (1.5%, 2.5%, 3.5%), different cultures (Lactobacillus plantarum ISLG-2, Lactobacillus plantarum ATCC® 8014, Lactobacillus plantarum Visbyvac) and ultrasound application (5 min, 10 min, 15 min) were used during biotransformation. Propolis samples subjected to different biotransformation conditions were analyzed by UPLC/MS-MS method, total phenolic compound analysis by Folin Ciocalteu method and antioxidant activity analysis by trolox equivalent antioxidant activity (TEAC), 2,2-diphenyl-1-picrylhydrazyl radical scavenging antioxidant activity (DPPH) and iron (III) reducing antioxidant activity (FRAP) method. As a result of the study, the effects of different solvents, cultures and ultrasound applications on phenolic compounds have changed and it was found that each parameter selected according to the target phenolic component could have a qualitative effect

Synthesis and characterization of metal loaded mcm-41 zeotypes and their utilization in hydrogen storage

In this study, we investigated the hydrogen storage behavior of MCM-41 that is a mesoporous material with high surface area and uniform pore size, which makes it a good candidate for gas adsorption applications. To improve the hydrogen storage capacity of MCM-41, the samples were loaded with Pd and Ni that are known with their affinities to hydrogen. MCM-41 samples were synthesized by microwave irradiation and metals were loaded before the samples were calcined. The effect of loading metals (Pd and Ni) and microwave power (90 and 120 W) to the structure of MCM-41 were investigated. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analyzer, BET analyzer, and X-ray photoelectron spectroscopy. The hydrogen storage capacities of the samples were measured by Intelligent Gravimetric Analyzer (IGA) at 298 K and up to 10 bar. The kinetics behavior and computational modeling of the hydrogen storage of MCM-41 were also investigated. It was seen that loading Pd and Ni to MCM-41 enhanced the hydrogen uptake of the material. The highest adsorption capacities were measured as 0.98, 1.34, 1.74 for Pd-Ni, Ni, and Pd loaded MCM-41, respectively. The textural properties of the samples were affected by the microwave power used during the synthesis. The kinetics investigation and the review of the experimental results with the findings of the computational studies were novel contributions to the literature

Mesoporous MCM-41 material for hydrogen storage: a short review

Decreasing supply of fossil fuels and concerns about environmental issues makes hydrogen a good alternative to fossil fuel sources as it is an environmentally friendly energy carrier. However, the storage of hydrogen is the main challenge to its effective use. For the utilization of hydrogen, the development of safe, effective and high capacity storage media is needed. MCM-41 that is most commonly used in catalytic applications has been also considered for hydrogen storage due to its high surface area, uniform pore size and good adsorption properties. There are a number of researches in which MCM-41 is now also considered as hydrogen storage media with a maximum reported hydrogen uptake of 2.01 wt%. However, there is not any review specifically on the hydrogen storage of MCM-41. Therefore, the present review highlights the recent studies on the use of MCM-41 as hydrogen storage media as well as its synthesis conditions and the effect of loading metal on the storage capacity