Periana R A, Taube D J, Evitt E R, Löffler D G, Wentrcek P R, Voss G, Masuda T
Science. 1993 Jan 15;259(5093):340-3. doi: 10.1126/science.259.5093.340.
A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a methane conversion of 50 percent, 85 percent selectivity to methyl bisulfate ( approximately 43 percent yield; the major side product is carbon dioxide) was achieved at a molar productivity of 10(-7) mole per cubic centimeter per second and Hg(II) turnover frequency of 10(-3) per second. Separate hydrolysis of methyl bisulfate and reoxidation of the sulfur dioxide with air provides a potentially practical scheme for the oxidation of methane to methanol with molecular oxygen. The primary steps of the Hg(II)-catalyzed reaction were individually examined and the essential elements of the mechanism were identified. The Hg(II) ion reacts with methane by an electrophilic displacement mechanism to produce an observable species, CH(3)HgOSO(3)H, 1. Under the reaction conditions, 1 readily decomposes to CH(3)OSO(3)H and the reduced mercurous species, Hg(2)(2+) The catalytic cycle is completed by the reoxidation of Hg(2)(2+) with H(2)SO(4) to regenerate Hg(II) and byproducts SO(2) and H(2)O. Thallium(III), palladium(II), and the cations of platinum and gold also oxidize methane to methyl bisulfate in sulfuric acid.
报道了一种通过硫酸氢甲酯将甲烷选择性催化氧化为甲醇的均相体系。由汞离子Hg(II)催化的净反应是甲烷被浓硫酸氧化生成硫酸氢甲酯、水和二氧化硫。该反应效率很高。在甲烷转化率为50%时，硫酸氢甲酯的选择性达到85%（产率约为43%；主要副产物是二氧化碳），摩尔生产率为10⁻⁷摩尔每立方厘米每秒，Hg(II)的周转频率为每秒10⁻³。硫酸氢甲酯的单独水解以及用空气将二氧化硫再氧化，为用分子氧将甲烷氧化为甲醇提供了一种潜在可行的方案。对Hg(II)催化反应的主要步骤进行了单独研究，并确定了反应机理的基本要素。Hg(II)离子通过亲电取代机理与甲烷反应生成可观察到的物种CH₃HgOSO₃H，即1。在反应条件下，1很容易分解为CH₃OSO₃H和还原态的亚汞物种Hg₂²⁺。通过用H₂SO₄将Hg₂²⁺再氧化以再生Hg(II)以及生成副产物SO₂和H₂O，从而完成催化循环。铊(III)、钯(II)以及铂和金的阳离子也能在硫酸中将甲烷氧化为硫酸氢甲酯。
