Kinetic study of the reduction of cobalt(II) by carbon monoxide in an aqueous system

A study of the catalyzed reduction of cobalt(II) to metal by carbon monoxide from aqueous, ammoniacal solutions between 180 and 230 °C and from 0 to 50 atm CO is reported.The reaction proceeds through the intermediate formation of a cobalt carbonyl anion. Under the conditions of this study this intermediate is produced homogeneously and also heterogeneously in the presence of cobalt sulfide. Metal formation occurs only in the presence of cobalt sulfide.The stoichiometry of the production of cobalt carbonyl anion is consistent with the equation[Formula: see text]Metal formation follows the stoichiometry of the equation[Formula: see text]A mechanism that is consistent with the kinetic observations is presented.

Kinetics and mechanisms of the reaction between carbon monoxide and copper(II) in aqueous solution

The kinetics of the reduction of copper(II) to copper(I) by carbon monoxide in aqueous solutions have been investigated at 120 °C and carbon monoxide pressures up to 1360 atm. The reaction is homogeneous and proceeds by two paths, one of which is virtually independent of carbon monoxide pressure due to the formation of a stable cuprous carbonyl complex Cu(CO)+. The second reaction path contains both a pH-dependent and pH-independent component. The rate-determining step in both paths appears to be the decomposition of a carbon monoxide insertion complex by a cupric ion. Complexing ligands such as acetate were observed to have a minor inhibiting effect on the overall reaction.

THE KINETICS AND MECHANISM OF THE Cu++-CATALYZED REDUCTION OF CrVI BY HYDROGEN IN AQUEOUS SOLUTIONS

The kinetics of the Cu++-catalyzed reduction of CrVI by H2 in aqueous perchlorate solutions have been investigated between 160° and 200 °C. The mechanism proposed to account for the kinetics gives rise to a rate law of the form[Formula: see text]where[Formula: see text]As a consequence of these studies an important anomaly between the previously published rate law for dichromate reduction and a more recent kinetic study of the cupric-perchlorate-catalyzed hydrogen–oxygen recombination has been resolved.

EFFECT OF COMPLEXING ON THE HOMOGENEOUS CATALYTIC ACTIVATION OF HYDROGEN BY CUPRIC SALTS

The effects of various organic and inorganic complex-forming reagents on the homogeneous catalytic activation of H2 by Cu++ in aqueous solution have been determined. The catalytic activities of the cupric complexes decrease in the order: butyrate, propionate > acetate > SO4− > Cl− > H2O (i.e. the uncomplexed Cu++ ion) > glycine, ethylenediamine. The mechanism of the activation process is discussed.

KINETICS OF THE CUPRIC ACETATE CATALYZED HYDROGENATION OF DICHROMATE IN AQUEOUS SOLUTION

In aqueous solution, cupric acetate was found to act as a homogeneous catalyst for the reduction of dichromate by hydrogen, i.e.[Formula: see text]

The paper describes a kinetic study of this reaction. Rates were determined at temperatures between 80° and 140 °C. and hydrogen partial pressures up to 27 atmospheres. The rate is independent of the dichromate concentration but varies directly with the partial pressure of hydrogen and is nearly proportional to the concentration of cupric acetate. The activation energy is 24,600 calories per mole. Cupric acetate, apparently acting as a true catalyst, activates the hydrogen through formation of a complex with it. An extension of the mechanism proposed earlier for the reaction of cupric acetate itself with hydrogen also accounts for the kinetics of the dichromate reaction.