Comparative analysis of sorption of small molecule hydrocarbons and polar substances in polish hard coals
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Comparative analysis of sorption of small molecule hydrocarbons and polar substances in polish hard coals Grzegorz Jodłowski • Marta Wo´jcik
Received: 15 November 2012 / Accepted: 16 February 2013 / Published online: 16 March 2013 Ó The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract The subject of the article is the thermodynamic analysis of the sorption of aliphatic hydrocarbons in hard coals from polish mines. The analysis is based on a Multisorption model designed for describing small molecule sorption in different types of carbonaceous materials (e.g. hard coals, lignites or active carbons). Experimental isotherms of hydrocarbons: hexane, heptane, octane and benzene, in hard coals of different rank, together with water and methanol vapor isotherms measured at room temperature (25 °C), are taken as comparative data for simulations. Results of the analyses reveal the complicated behavior of linear molecules in the sorption system. The location of molecules on the sorbent surface brings a spectrum of problems associated with the incomplete filling of pores, the coiling up of chains, the formulation of plates or globules, and the blocking of micropores. All these effects have an influence on the level and character of sorption, often in opposing ways. The sorption of small inorganic molecules is taken into account in the objective of achieving a more precise identification of the structure of coal. Semi-simultaneous computations for all types of sorbates have already been carried out. Keywords Sorption Adsorption Absorption Modeling Hard coal Organic solvent
G. Jodłowski (&) M. Wo´jcik AGH-University of Science and Technology, Faculty of Energy and Fuels, Al.A.Mickiewicza 30, 30-059 Krako´w, Poland e-mail: [email protected] M. Wo´jcik e-mail: [email protected]
1 Introduction Investigations of vapor recovery from hydrocarbon solvents or air purification from hydrocarbons have been carried out for many years (Fugassi et al. 1958; Shimizu et al. 1998; Breus et al. 2006; Belov et al. 2009; Shi et al. 2011). However there are not many publications explaining the principles behind the phenomenon of aliphatic molecules locating themselves on the surface of porous materials, especially geosorbents like hard coals. The aim of the investigations was to obtain knowledge about the character of the phenomenon of sorption of chain hydrocarbons in carbonaceous sorbents as ‘‘chip sorbents’’ in comparison to the sorption of cyclic ones. A secondary objective of the work is to check the applicability of the multiple sorption model (MSM) and its adequacy when applied to such complicated systems, in particular because it uses a model based on the spherical representation of sorption space at atomic scale (Duda and Milewska-Duda 1995). It is a known fact that a partial elastic material (like hard coal) shows both adsorption and absorption in contact with small molecules. It is obvious that some intermediate phenomena occur in such a material. All the spectrum of sub-processes is
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