Partial Oxidation Of Methane In Organic Acid Solvents

In this paper, the performance of oxidants for the liquid-phase partial oxidation of methane to methanol in acetic acid were studied. The acidy and oxidizability of acetic acid system were analyzed with comparison to the oleum system.The thermodynamic and iodine catalytic pathways of liquid-phase partial oxidation of methane in oleum and acetic acid system were calculated by employing Gaussian 09, and the solvent models of oleum and acetic acid system in Gaussian 09 was established, respectively.We find that the conversion of methane to methyl bisulfate in oleum system can occur spontaneously, which is mainly through the reaction of methane, sulfur trioxide and sulfuric acid to produce methyl bisulfate. Our thermodynamic calculations indicate the transformation of methane to methyl acetate is able to accur spontaneously in the acetatic acid, which is mainly through the reaction of methane, acetic acid and potassium permanganate to produce methyl acetate. Comprehensive analysis of thermodynamics calculations between oleum system and acetic acid system, the reaction temperature should be controlled at 473 K. To determine the relative reaction barriers and the rate-determining step for the process of partial oxidation of methane to methanol catalyzed by iodine, we investigated the potential energy of reaction mechanism in oleum system and acetic acid, respectively. We find that the relative reaction barriers of the oxidation step are highest in the catalytic oxidation of methane, suggesting that the oxidation step is rate-determining step for methane thansformation and oxidability is very crucial to the conversion of methne to methanol in the liquid-phase.Based on the results of thermodynamics computations and the studies of reaction mechanism through Gaussian 09, various oxidants including organic and inorganic oxidants were investigated for the partial oxidation of methane to methanol via methyl acetate catalyzed by iodine in acetic acid solvent. Among these inorganic oxidants investigated, potassium permanganate exhibited the higher methane conversion and tert-butyl hydroperioxide (TBHP) exhibited the higher methane conversion among all organic oxidants investigated. Moreover, the influences of various kinetic factors on the oxidability of KMnO4 and TBHP in acetic acid solvent were studied, and the optimized conditions have been obtained, respectively.Under the optimized conditions of KMnO4 in non-aqueous acetic acid medium, the transformation of methane to methanol via methyl acetate catalyzed by iodine was determined as the first order reaction, and the rate equation was established as r=0.377e-11840/RTPCH4.