Determination of the basic strength of solid catalysts in water by means of a kinetic tracer

The kinetic analysis of the isomerization of glucose into fructose in the presence of solid basic catalysts, cation-exchanged zeolites and anion-modified hydrotalcites, has been performed in order to evaluate the basicity of those solids in water as the solvent and under working reaction conditions. A standardization curve is established by plotting the logarithms of the rate constants of isomerization of glucose against pH for a series of sodium hydroxide solutions at different dilutions. It was then possible to calculate the corresponding pH value of solid basic catalysts from the measurement of their reaction rate constants and extrapolation on the previously established standardization plot. For 1 g of catalyst in 50 ml of water, pH values of 11 were calculated for NaA, Na- and Cs-exchanged X zeolites, and hydrotalcite in its carbonated form, whereas the pH value of meixnerite, the hydroxide form of the hydrotalcite precursor, was close to 12.4, thus confirming its higher basic properties. Moreover, from the determination of pH values after a 24 h-pre-equilibrium of solid catalysts in water, it was also possible to evaluate the percentage of the cationic species passed into solution which well agrees with the percentage obtained from elemental analyses. © 2006 Elsevier B.V. All rights reserved.

Bibliographic Details

Main Authors:	Moreau, Claude, Lecomte, Jérôme, Roux, Alain
Format:	article biblioteca
Language:	eng
Subjects:	Q60 - Traitement des produits agricoles non alimentaires,
Online Access:	http://agritrop.cirad.fr/535641/ http://agritrop.cirad.fr/535641/1/535641.pdf
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