Determination of adsorption entropies on solid surfaces by reversed-flow gas chromatography

Dremetsika, Assimina V.; Siskos, Panayotis A.; Katsanos, Nicholas A.

doi:10.1016/j.jhazmat.2007.06.108

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…The pre-exponential factor K 0 ′ of the van't Hoff equation is related to the adsorption entropy. Although the exact form of the relationship between the pre-exponential factor and the adsorption entropy is the subject of debate, [63][64][65][66] analysis of the chain length dependency of the pre-exponential factor yields information on the evolution of adsorption entropy with chain length, regardless of the form of the equation. One possible expression is given below 67…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The pre-exponential factor K 0 ′ of the van’t Hoff equation is related to the adsorption entropy. Although the exact form of the relationship between the pre-exponential factor and the adsorption entropy is the subject of debate, − analysis of the chain length dependency of the pre-exponential factor yields information on the evolution of adsorption entropy with chain length, regardless of the form of the equation. One possible expression is given below K 0 ′ = exp true[ Δ S 0 , l o c a l Θ R + true( n T 2 p Θ true) true] The subscript 0 refers the zero coverage limit, p θ to the standard state of the gas phase (chosen as 1 atm), and n T equals the number of adsorption sites.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Cage and Window Effects in the Adsorption of n-Alkanes on Chabazite and SAPO-34

et al. 2008

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The adsorption of C 1 -C 14 n-alkanes on SAPO-34 and Na-CHA zeolites was studied at low surface coverage using the pulse chromatographic method. On both isostructural materials, containing cages interconnected via small windows, the Henry adsorption constant K′ varies in a nonmonotonous way with carbon number. K′ increases more or less exponentially with carbon number from methane to n-hexane. On Na-CHA, K′ decreases from n-hexane, reaches a minimum at n-octane, and then increases again. On SAPO-34, a minimum is attained at n-decane. From this point on, K′ increases till the longest alkane studied, i.e., n-tetradecane. On SAPO-34, the increase in zero coverage adsorption enthalpy per additional methylene group in the alkane chain becomes smaller for carbon numbers between 5 and 11. A local minimum in adsorption enthalpy occurs at n-undecane. A compensation plot between adsorption entropy and enthalpy shows a pronounced discontinuity at n-undecane for SAPO-34. The present observations provide additional proof for the existence of "window effects". Given their molecular length, C 1 -C 6 alkanes adsorb in a relatively unhindered way in the SAPO-34 cages. C 7 -C 10 alkanes adopt a coiled configuration inside the cage, which strongly affects their adsorption enthalpy and entropy. From n-undecane onward, the alkanes are no longer fitting within the cage and protrude the small windows connecting the cages. The presence of cations on Na-CHA results in stronger energetic interactions compared to SAPO-34, which shifts the window protrusion to lower chain lengths.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Cage and Window Effects in the Adsorption of n-Alkanes on Chabazite and SAPO-34

et al. 2008

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“…In this way, a repeated sampling of slow rate processes taking place within the chromatographic column can be carried out. Using suitable mathematical analysis of the experimentally obtained chromatographic data, a big amount of physicochemical parameters have been estimated among the others: adsorption equilibrium constants, gas diffusion coefficients in binary and ternary mixtures, activity coefficients, mass transfer coefficients on solids and liquids, solubility and interaction parameters in polymer-solvent systems, molecular diameters and critical volumes in gases, Lennard-Jones parameters, as well as rate constants and activation parameters [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51].…”

Section: Introductionmentioning

confidence: 99%

Determination of Lewis Acid Base Properties of Poly(α-n-alkyl) Methacrylates Adsorbed on Silica by Inverse GC

Hamieh

2011

Chromatographia

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In this paper, the acid base properties in the Lewis terms of poly(a-n-alkyl) methacrylates and when they are adsorbed on silica, were determined. The acid base constants K A and K D of various polymers were calculated by testing the classical model and proposed a new model giving K A and K D and a third constant K reflecting the amphoteric character of our solid substrates and obtaining more precise and quantified results. When the length of alkyl group in side chain of poly(a-n-alkyl) methacrylates changes, the surface properties of such polymers also change and consequently affect all superficial characteristics and especially the acid base constants and the transition phenomena. It was also proved that the specific enthalpy was directly correlated to the acid base constants, the carbon atom number in the side chain of poly(a-n-alkyl) methacrylates and the acceptor AN and donor DN numbers of electrons of polar organic molecules, by the following relationship: DH sp = DH sp (AN, DN, K D , K A , n SC ).

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“…As far as air pollutants are concerned an important process which contributes to the damage of artworks is pollutant deposition and adsorption. Adsorption is a pure physicochemical phenomenon [3,4].…”

Section: Introductionmentioning

confidence: 99%