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

Kopaç, Türkan | Kocabaş, Sefa

Article | 2002 | Chemical Engineering and Processing41 ( 3 ) , pp.223 - 230

In this work, the adsorption equilibrium and adsorption rate of sulfur dioxide were investigated on silica gel. A packed bed adsorber 0.1 m in length and 0.0095 m in diameter was used for the adsorption experiments. The adsorption equilibrium experiments were carried out at 473 K constant temperature with an initial sulfur dioxide concentration in the range 430-3400 p.p.m. in nitrogen carrier gas. The experimental adsorption isotherms were compared with the Freundlich, Langmuir, and the linearized form of the Brunauer-Emmett-Teller and the Dubinin-Radushkevitch-Kaganer models by the nonlinear least-squares estimate method. The Freun . . .dlich model gave the best fit with a correlation coefficient greater than 0.98, suggesting a surface adsorption mechanism for sulfur dioxide adsorption on silica gel. The deactivation model was applied to the adsorption rate data. It was found that the adsorption rate data fitted well with the deactivation model. Observed adsorption rate constants and the first-order deactivation rate constants were obtained from the model. The nonlinear least-squares analysis technique was used to estimate the parameters appearing in the deactivation model. The breakthrough experiments were repeated at 1610 p.p.m. constant initial sulfur dioxide concentration in a temperature range of 323-473 K, and the effect of initial sulfur dioxide concentration and the effect of temperature were investigated on the model results. © 2002 Elsevier Science B.V. All rights reserved Daha fazlası Daha az

Kopaç, Türkan | Kocabaş, Sefa

Article | 2003 | Chemical Engineering Communications190 ( 05.Aug ) , pp.1041 - 1054

In this study sulfur dioxide adsorption and rate were investigated on molecular sieve 5A zeolite in a packed bed system at 473 K. The experimental adsorption isotherms were compared with Langmuir, Freundlich, and Dubinin-Radushkevitch-Kaganer (DRK) adsorption isotherm models. The simple Langmuir and the Freundlich models provided a better description of sulfur dioxide sorption on molecular sieve 5A zeolite, so that a selective surface adsorption mechanism for adsorption of sulfur dioxide on molecular sieve 5A zeolite can he suggested. The breakthrough behavior for sulfur dioxide adsorption on molecular sieve 5A was also investigated . . . in this study. The experimental breakthrough curves were compared with deactivation models proposed by Orbey et al., and the recent models of Suyadal et al. and Yaşyerli et al. The deactivation models were found to give good agreement with the experimental results Daha fazlası Daha az

Kopaç, Türkan | Kocabaş, Sefa

Article | 2004 | Advances in Environmental Research8 ( 03.Apr ) , pp.417 - 424

In this work, experimental breakthrough curves for sulfur dioxide adsorption on silica gel were analysed with deactivation models proposed by 'Can. J. Chem. Eng. 60 (1982) 314' and 'Ind. Eng. Chem. Res. 40 (2001) 5206'. The deactivation model of 'Ind. Eng. Chem. Res. 40 (2001) 5206' taking into account the concentration dependence of the deactivation process along the reactor gave the best fit to the experimental breakthrough data for sulfur dioxide adsorption on silica gel. Deactivation rate constant k d values were determined from adsorption experiments done at 473 K temperature with a sulfur dioxide inlet concentration in the ran . . .ge of 0.0443-0.3504 mol/m3. © 2002 Elsevier Science Ltd. All rights reserved Daha fazlası Daha az