Hydroquinone Oxidation Kinetics in Adsorptive Liquid Chromatographic Beds

摘要

Catalytic properties of chromatographic silicas modified with ferric ions using abatch preparation process are compared with those modified in situ in a column on the basis of the hydroquinone oxidation to benzoquinone in a liquid chromatographic reactor. This is done through application of a statistical moment method for kinetic parameter estimation from reactor chromatograms. The first absolute moment of the overall elution profile is utilized to evaluate the pseudo-first order rate constants for oxidation both with and without consideration of hydroquinone sorption processes. In general, hydroquinone adsorption processes are found to have a significant role in the overall process and affect the intrinsic reaction rate measurements. On comparing the two modified silicas. It is found that the influence of adsorption in models is less pronounced with the batch-treated material. The decrease in reaction rate effects with the material prepared by a batch process can be attributed to increased quenching of strongly adsorptive sites on the silica surface as a result of prolonged exposure to metal ions in solution. Retention behavior is consistent with a decrease in the influence of hydrogen bonding hydroxyl groups on the batch-treated material.