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Preparation of activated carbons from Zonguldak region coals by physical and chemical activations for hydrogen sorption

Kopac T. | Toprak A.

Article | 2007 | International Journal of Hydrogen Energy32 ( 18 ) , pp.5005 - 5014

Activated carbons were prepared by physical and chemical activations from coals collected from two mines (Kilimli and Armutcuk) in Zonguldak region, Turkey under different conditions. Ash content was reduced considerably by use of HCl and HF treatments. Pyrolytic thermal treatments in a temperature range of 600-900 {ring operator} C under N2 flow and chemical treatments using different chemical agents such as KOH, NH4Cl, ZnCl2 were applied to the coal samples from the two mines. N2 adsorption isotherms were obtained at 77.4 K for the thermally and the chemically treated samples and the data were used for the evaluation of the specif . . .ic surface area, total pore volumes and the average pore sizes of the samples. Higher surface area values were obtained from Kilimli coal samples than Armutcuk. The BET surface area of the Kilimli coal samples which were initially have a value of 1.20 m2/g were increased to 52.62 m2/g after pyrolytic heat treatments at 800 {ring operator} C and increased to a value of 830.5 m2/g by treating the coals with KOH + NH4 Cl mixture at 750 {ring operator} C followed by oxidation of the samples mixed with ZnCl2. The activated carbon samples were prepared for the purpose of their evaluation in hydrogen sorption studies. © 2007 International Association for Hydrogen Energy Daha fazlası Daha az

Temperature and alkaline hydroxide treatment effects on hydrogen sorption characteristics of multi-walled carbon nanotube-graphite mixture

Kopac T. | Erdogan F.O.

Article | 2009 | Journal of Industrial and Engineering Chemistry15 ( 5 ) , pp.730 - 735

Temperature and alkaline hydroxide treatment effects on the surface area and pore structure of the cathode deposit multi-walled carbon nanotube (MWCNT)-graphite mixture were investigated in a temperature range of 600-800 °C. Hydrogen sorption properties of the MWCNT-graphite mixture samples were studied by varying the alkaline hydroxide-activation temperature. Pore characterization of modified MWCNT-graphite mixture was performed with the observation of adsorption-desorption isotherms of N2 at 77 K. Hydrogen sorption of the non-treated and treated MWCNT-graphite mixture was carried out using a volumetric apparatus at 77 K. The highe . . .st surface area of the sample was obtained as 275 m2 g-1 by treatments with KOH at 600 °C. The increase in the specific surface area of MWCNT-graphite sample mixture was about 13 times. The maximum amount of hydrogen adsorbed on the MWCNT-graphite sample mixture was found as 0.75 and 0.54 wt.% by chemical treatments with KOH at 600 °C and NaOH at 700 °C, respectively whereas it was 0.01 wt.% for the original sample. The hydrogen sorption capacity was enhanced considerably by KOH treatments at 600 °C. © 2009 The Korean Society of Industrial and Engineering Chemistry Daha fazlası Daha az

Dynamic analysis of sorption of hydrogen in activated carbon

Erdogan F.O. | Kopac T.

Article | 2007 | International Journal of Hydrogen Energy32 ( 15 SPEC. ISS. ) , pp.3448 - 3456

Hydrogen storage and adsorption studies in carbon materials have been of great concern in recent years. Hydrogen is thought to be an ideal energy source because of causing no pollutants or greenhouse gases during combustion unlike the fossil fuels. In this study, sorption characteristic of H2 and N2 gases in activated carbon having three different particle sizes were investigated in a temperature range of 303-473 K using a dynamic technique. The experimental procedure consist of introducing a pulse of H2 and N2 on the inlet of a column packed with activated carbon samples and measuring the concentration versus time response peak lea . . .ving the other end of the column. Adsorption equilibrium constants were evaluated using the moment analysis of the chromatographic peaks. At 473 K, the adsorption equilibrium constant for H2 on activated carbon having 4.76-0.85 mm particle size (ACI) was found to be 7.92 × 10- 4, whereas it has value of 1.83 × 10- 3 m3 / kg at 303 K. Heats of adsorption of H2 and N2 on ACI were determined as - 4.8 and - 11.6 kJ mol- 1, respectively. The values of heat of adsorption obtained indicate physical adsorption of H2 and N2 gases on the activated carbon samples used. © 2007 International Association for Hydrogen Energy Daha fazlası Daha az

Effect of thermal treatments and palladium loading on hydrogen sorption characteristics of single-walled carbon nanotubes

Kocabaş, Sefa | Kopaç, Türkan | Doğu, Gülsen | Doğu, Timur

Article | 2008 | International Journal of Hydrogen Energy33 ( 6 ) , pp.1693 - 1699

The effects of thermal treatments and palladium loading on sorption characteristics of single-walled carbon nanotube (SWCNT) samples were investigated. The thermal treatment experiments were carried out in a temperature range of 300-800 °C. The sorption characteristics of nitrogen and hydrogen on the original, heat treated and the palladium loaded samples were investigated. Analyzing the nitrogen adsorption isotherms on these samples at 77.4 K, the highest specific surface area of 2230 m2 / g was obtained at 575 °C, while the original samples had a specific surface area of 230 m2 / g. The highest surface area samples obtained at 575 . . . °C were loaded by 3.3, 6.3 and 10.1 wt% palladium and hydrogen adsorption isotherms on these samples were obtained at 77.4 K. The hydrogen sorption capacities of the original and the 10.1 wt% palladium loaded samples were found to be 0.76 and 1.66 wt%, respectively. It was shown that by controlling the temperature of heat treatment, the specific surface area of the samples could be increased and the spillover effect of palladium could enhance the hydrogen sorption. © 2008 International Association for Hydrogen Energy Daha fazlası Daha az

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