DFT исследование элементарных актов сверхкритического водного окисления на примере каталитической реакции радикальной диссоциации воды с участием модельного кластера Fe4O6

Abstract

This report details aspects of the reactivity of the products of catalytic dissociation of water as applied to the description of the nature of supercritical water oxidation and other oxidative SCF processes in general. It has been shown quantum chemically that the products of thermodynamically nonequilibrium to one degree or another dissociation of water on the surface of a model Fe4O6 cluster of different multiplet nature can act as effective agents for interaction with atmospheric oxygen and organic compounds. The antiferromagnetic forms of iron oxides can actively participate in radical reactions. It is shown using a model cluster Fe4O6 as an example. The radical reactions are able to easily change their multiplet state by simple chemisorption of 3O2 on their surface. In combination with the ability of water to dissociate on the model Fe4O6 cluster by the ionic type, the latter can easily transform into a triplet system, which, accordingly, leads to the emergence of an equilibrium biradical water dissociation formally even at room temperature. Hydrate-oxygen interactions on the surface of the Fe4O6 cluster lead to the generation of either an extremely reactive iron-hydroperoxide complex or a hydroperoxyl radical capable of conducting oxidative processes under SCF conditions in the volume of the corresponding fluid. It is shown the dissociative chemisorption of a water molecule on a Fe4O6 cluster in a triplet state (initiated, for example, by chemisorption of 3O2), in contrast to the heterolytic dissociation of water (whose thermodynamic equilibrium is shifted towards the molecular form of water), is practically a thermodynamically equilibrium process. It is this fact allowed us to consider the hydride-hydroxyl form of the Fe4O6 triplet cluster as one of the real agents for the oxidation of propylene glycol by the example of its first stage of catalytic dehydrogenation.