Bestimmung der Oberflächenacidität von porösem Siliciumdioxid durch Titration im aprotischen Solvens und Vergleich der Ergebnisse mit denen aus infrarotspektroskopischen Messungen und heterogenem Isotopenaustausch mit HTO

Kittelmann, Udo R.; Unger, Klaus K.

doi:10.1007/bfb0117381

Cited by 10 publications

(2 citation statements)

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“…To quantify a liquid in terms of its HBA property or basicity, among others, the following physicochemical parameters have been well established: Gutmann's donor number (DN), which corresponds to the reaction enthalpy of the HBA solvent with SbCl 5 , which serves as the reference electron pair acceptor, measured in 1,2-dichloroethane, , the p K (BH + ) value, the protonation equilibrium constant in water, or the β value introduced by Kamlet and Taft, which results from the solvatochromism of several reference compounds . A critical review of the applicability of the different empirical HBA property parameters is given by Marcus and Gritzner …”

Section: Introductionmentioning

confidence: 99%

“…Several authors have shown that the Kamlet−Taft solvent parameters α, β, and π* are well suited for the quantitative description of solvent−solid interfacial interactions, in chromatographic 12 and adsorption processes, rather than parameters derived using water as the reference liquid. , Furthermore, the advantage of the Kamlet−Taft parameters is that they can be converted by means of multiple LSE relationships into other useful polarity scales, for example, the acceptor number (AN) or donor number (DN) scales of Gutmann 16,17,24 and the E T (30) scale of Reichardt …”

Section: Introductionmentioning

confidence: 99%

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Influence of Chemical Solvent Properties on the External and Internal Surface Polarity of Silica Particles in Slurry

et al. 2002

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Kamlet−Taft's α (hydrogen-bond acidity) and π* (dipolarity/polarizability) parameters of three different silica samples and a siliceous MCM-41 material determined in 17 various solvents are presented. Fe(phen)2(CN)2 [cis-dicyano-bis(1,10)phenanthrolineiron(II), (1)] and Michler's ketone [4,4‘-bis(N,N-dimethylamino)benzophenone, (2)] were used as solvatochromic surface polarity indicators. The UV/vis transmission spectra of the two surface polarity indicators 1 and 2 adsorbed on the silicas from the solvents were measured, and the absorption maxima were used to calculate the α and π* values of the silica surface. α of the silanols on the freely accessible surfaces decreases with increasing HBA (hydrogen-bond accepting) capacity of the solvent whereas the π* term of the solvent only marginally modifies the polarity of the external surface silanol groups. In the mesopores of MCM-41, the UV/vis shift of the solvatochromic dyes shows a different behavior as a function of solvent polarity than that on freely accessible silica surfaces. The dipolarity/polarizability of solvent molecules inside the pores affects significantly the solvatochromic shift of the dye in the pores. The specific polarity properties of the solvent/silica interface at freely accessible surfaces and inside the MCM-41 pores are discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of Chemical Solvent Properties on the External and Internal Surface Polarity of Silica Particles in Slurry

et al. 2002

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Examination and standardisation of amine titration in surface acidity measurements of silicas, aluminas and synthetic zeolites

Unger¹,

Kittelmann²,

Kreis³

1981

J. Chem. Technol. Biotechnol.

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The amine titration method using Hammett and arylmethanol indicators has been examined on selected samples of porous silica, active alumina and synthetic zeolites. On the basis of the successive approximation technique the evaluation of surface acid strength distribution has been standardised. A new method has been developed to assess the total acidity without employing indicators. The distinction between Bronsted and Lewis acidity through measuring the HO and HR acidity distribution function on aluminas and zeolites is shown to be erroneous. The acidity is strongly affected by the size of amine and by the density of surface acid centres-as demonstrated on a series of silicas and on synthetic zeolites. The size dependence can be utilised to detect the acidity of distinct pore size ranges within a given porous solid. Under certain conditions the acidity measurements can be correlated with those obtained from other techniques such as heterogeneous exchange and infrared spectroscopy.

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Examination and standardisation of amine titration in surface acidity measurements of silicas, aluminas and synthetic zeolites

Unger

Kittelmann

Kreis

1981

J. Chem. Technol. Biotechnol.

View full text Add to dashboard Cite

The amine titration method using Hammett and arylmethanol indicators has been examined on selected samples of porous silica, active alumina and synthetic zeolites. On the basis of the successive approximation technique the evaluation of surface acid strength distribution has been standardised. A new method has been developed to assess the total acidity without employing indicators. The distinction between Bronsted and Lewis acidity through measuring the Ho and HR acidity distribution function on aluminas and zeolites is shown to be erroneous. The acidity is strongly affected by the size of amine and by the density of surface acid centres—as demonstrated on a series of silicas and on synthetic zeolites. The size dependence can be utilised to detect the acidity of distinct pore size ranges within a given porous solid. Under certain conditions the acidity measurements can be correlated with those obtained from other techniques such as heterogeneous exchange and infrared spectroscopy.

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Bestimmung der Oberflächenacidität von porösem Siliciumdioxid durch Titration im aprotischen Solvens und Vergleich der Ergebnisse mit denen aus infrarotspektroskopischen Messungen und heterogenem Isotopenaustausch mit HTO

Cited by 10 publications

References 29 publications

Influence of Chemical Solvent Properties on the External and Internal Surface Polarity of Silica Particles in Slurry

Influence of Chemical Solvent Properties on the External and Internal Surface Polarity of Silica Particles in Slurry

Examination and standardisation of amine titration in surface acidity measurements of silicas, aluminas and synthetic zeolites

Examination and standardisation of amine titration in surface acidity measurements of silicas, aluminas and synthetic zeolites

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