Rate enhancement via micelle encapsulation for room temperature metal catalyzed Ce(IV) oxidation of formaldehyde to formic acid in aqueous medium at atmospheric pressure: A kinetic approach

Oxidation kinetics of formaldehyde by Ce(IV) in aqueous medium in the presence of surfactants has been carried out to observe the micellar effect on rate. The oxidation kinetics was studied by UV-VIS spectrophotometry. Three catalysts Cu(II), Cr(III), and Ag(I) are used. Both Cr(III) and Ag(l) are active catalysts for the formaldehyde oxidation in the presence and absence of anionic surfactants, but Cu(II) is not an effective catalyst in this reaction. There are no roles of hetero-aromatic N-bases: picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen) as rate enhancement agents rather they inhibit the oxidation reaction. The presence of micelles was found to accelerate the reaction rate and this effect has been explained by the partitioning of the reactants in micelle and also by considering the hydrophobic and electrostatic interactions between the surfactants and reactants. The effect of sodium dodecyl sulfate (SOS) on the rate also indicate that Ce(SO4)(2+) was the main reactive form of cerium(IV). The main product formic acid was identified by the NMR spectroscopy and spot test. The probable mechanism is proposed and rate constants are calculated. The combination of Cr(III) and SDS is the most suitable combination for the conversion of formaldehyde to formic acid. (C) 2013 Elsevier B.V. All rights reserved.