Manganese Catalyzed Partial Oxidation of Light Alkanes
Manganese Catalyzed Partial Oxidation of Light Alkanes
复制标题
DOI：
10.1021/acscatal.2c00982
复制
发表时间：
2022-04
期刊：
影响因子：
12.9
通讯作者：
Nathan Coutard;C. Musgrave;Jisue Moon;Nichole S. Liebov;Robert M. Nielsen;J. Goldberg;M. Li;Xiaofan Jia;Sungsik Lee;D. Dickie;W. Schinski;Zi-Shan Wu;J. Groves;W. Goddard;T. Gunnoe
中科院分区：
文献类型：
--
作者：
Nathan Coutard;C. Musgrave;Jisue Moon;Nichole S. Liebov;Robert M. Nielsen;J. Goldberg;M. Li;Xiaofan Jia;Sungsik Lee;D. Dickie;W. Schinski;Zi-Shan Wu;J. Groves;W. Goddard;T. Gunnoe
甲烷的催化部分氧化是在低温(<；200℃)下，使用锰氧化物和锰盐在三氟乙酸和三氟乙酸酐的混合物中实现的。氧气被用作现场终端氧化剂。对于锰氧化物(如MnO2、Mn2O3和Mn3O4)，我们研究了甲烷在HTFA(TFA=三氟乙酸酯)中的化学计量部分氧化。使用三氟乙酸锰盐，在180℃和25psig甲烷下，观察到单氧化产物三氟乙酸甲酯的产物选择性为>；90%，∼为35%，甲烷转化率约为6次。在我们的甲烷催化氧化反应条件下，MeTFA对过氧化反应是稳定的，这解释了可能在转化率>；15%时的高选择性。利用实验研究和密度泛函理论计算相结合的方法，提出了催化循环中包含可溶性和分子锰物种的机理。所提出的反应途径包括氧气对MnII的初始活化，MnIII羟基中间体裂解甲烷C-H键，甲基自由基反弹生成MeTFA，最后起始MnII络合物的再生。该工艺也适用于乙烷的氧化反应，有利于生成单氧化产物三氟乙酸乙酯，∼转化率可达46%。
The catalytic partial oxidation of methane is achieved at low temperatures (<200 °C) using manganese oxides and manganese salts in mixtures of trifluoroacetic acid and trifluoroacetic anhydride. Dioxygen is used as thein situterminal oxidant. For Mn oxides (e.g., MnO2, Mn2O3, and Mn3O4), we studied stoichiometric methane partial oxidation in HTFA (TFA = trifluoroacetate). Using a Mn trifluoroacetate salt, at 180 °C and under 25 psig of methane, product selectivity for the mono-oxidized product methyl trifluoroacetate (MeTFA) is observed to be >90% at ∼35% methane conversion at approximately 6 turnovers. Under our catalytic methane oxidation reaction conditions, MeTFA is stable against overoxidation, which explains the likely high selectivity at conversions >15%. Using combined experimental studies and DFT calculations, a mechanism involving soluble and molecular Mn species in the catalytic cycle is proposed. The proposed reaction pathway involves initial activation of MnIIby dioxygen, cleavage of a methane C–H bond by a MnIIIhydroxo intermediate, rebound of the methyl radical to generate MeTFA, and finally regeneration of the starting MnIIcomplex. Also, this process is shown to be applicable to the oxidation of ethane, favoring the mono-oxidized product ethyl trifluoroacetate (EtTFA) and reaching ∼46% conversion.