Influence of pretreatment methods on adsorption and catalytic characteristics of toluene over heterogeneous palladium based catalysts |
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Authors: | Wang Geun Shim Hyun Chul Kang Jae Wook Lee Hee Moon |
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Institution: | a Faculty of Applied Chemical Engineering and Center for Functional Nano Fine Chemicals (BK21 CFN), Chonnam National University, Gwangju 500-757, Republic of Korea b Department of Environmental Education, Mokpo National University, #61 Dorim-ri, Chungkye-myon, Muan 534-729, Republic of Korea c Department of Chemical Engineering, Seonam University, Namwon 590-170, Republic of Korea |
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Abstract: | The adsorption and catalytic characteristics of heterogeneous palladium based catalyst and its modified catalysts with gases (air and hydrogen) and acidic aqueous solution (HCl) were studied for evaluating the influence of pretreatment methods for toluene. The structural and energetic adsorption properties of the parent and pretreated catalysts were analyzed by means of nitrogen adsorption isotherms and gravimetric methods. The light-off curve and the XPS investigation were used for analyzing the catalytic activity and the surface state of palladium. It was clearly shown from the experimental results that hydrogen pretreated catalysts having metallic surface state exhibited the highest adsorption capacity and catalytic activity compared to that of parent and modified catalysts. The adsorption equilibrium data for toluene were obtained at three different temperatures and correlated successfully with the two-site Langmuir molecular isotherm model (L2m). It was also found that the palladium phase has more adsorption affinity for toluene molecules than the alumina support. The isosteric heat of adsorption calculated by using the Clausius-Clapeyron equation significantly changed with the coverage and the lateral interactions between the adsorbate-adsorbate molecules control the system. Furthermore, comparative analysis of the adsorption energy distribution revealed that the parent and its modified catalysts have different types of surface energetic heterogeneities. |
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Keywords: | Adsorption Catalytic oxidation Palladium Pretreatment VOCs |
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