MECHANISM AND KINETICS OF DIRECT OXIDATION OF METHANE TO METHANOL BY HYDROGEN PEROXIDE ON A BIOMIMETIC CATALYST IN THE CONTEXT OF COHERENTLY SYNCHRONIZED REACTIONS

The biomimetic catalyst penta-FTPhPFe(III)OH/Al2O3 was synthesized by adsorption of the active complex FTPhPFe(III)OH on Al2O3 from a solution in dimethylformamide The active complex concentration relative to the Al2O3 mass was 0.64 mg/g. Activity of penta- FTPhPFe(III)/Al2O3 biomimetic catalyst in the reaction of methane direct conversion into methanol by green oxidant hydrogen peroxide was studied at the t=150-350°C and atmospheric pressure, where methanol yield was 19.2% with methane conversion of 28%. The kinetic investigation of methane biomimetic monooxidation reaction with hydrogen peroxide was carried out based on the established coherently synchronized character of reaction and the proposed most probable mechanism for the methane conversion into its monooxygenates: methanol, formaldehyde and dimethyl ether. The proposed mechanism shows that the formation of CH3OH and CH2O occurs through the formation of an active intermediate complex (penta-FTPhPFe(III)OOH/Al2O3), and the formation of dimethyl ether through a sequential reaction from methanol, through its dehydration under the action of the acid-base sites of the catalyst, similar to the multifunctional actions of enzymes. The kinetic model has been derived for the rate of methane biomimetic monooxygenation with hydrogen peroxide by jointly solving the determinant equation, which characterizes the chemical conjugation in the reaction system, with the equations obtained by the method of stationary concentrations. The rate constants for elementary reactions, the kinetic and thermodynamic parameters for the formation of the intermediate iron complex of the biomimetic ligand have been calculated. By using these rate constants, the theoretical values for the rate of methane consumption into monooxygenates have been calculated, which adequately describe the experimental data