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首页> 外文期刊>Chemistry: A European journal >Selective Oxidation of Alkanes with Molecular Oxygen and Acetaldehyde in Compressed (Supercritical) Carbon Dioxide as Reaction Medium
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Selective Oxidation of Alkanes with Molecular Oxygen and Acetaldehyde in Compressed (Supercritical) Carbon Dioxide as Reaction Medium

机译：压缩态（超临界）二氧化碳中分子氧和乙醛对烷烃的选择性氧化

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摘要

The oxidation of cyclo-alkanes or alkylarenes with molecular oxygen and acetaldehyde as sacrificial co-reductant occurs efficiently in compressed (supercritical) carbon dioxide (scCO_2) under mild multiphase conditions.No catalyst is required and high-pressure ATR-FTIR online measurements show that a radical reaction pathway is heterogeneously initiated by the stainless steel of the reactor walls.For secondary carbon atoms,high ketone to alcohol ratios are observed (3.5-7.9),most probably due to fast consecutive oxidation of alcoholic intermediates.Since C-C scission reactions are detected only to a very small extent,tertiary carbon atoms are transformed into the corresponding alcohols with high selectivity.Detailed analysis of the product distributions and other mechanistic evidence suggest that acetaldehyde acts not only as the sacrificial oxygen acceptor,but also as an efficient H-atom donor for peroxo and oxo radicals and as a crucial reductant for hydroperoxo intermediates.In comparison to other inert gases such as compressed N_2 or Ar,the use of carbon dioxide was shown to increase the yields of alkane oxygenates under identical reaction conditions.
机译：在温和的多相条件下，压缩的（超临界）二氧化碳（scCO_2）中，分子氧和乙醛作为牺牲性共还原剂，可以有效地发生环烷烃或烷基芳烃的氧化反应，无需催化剂，高压ATR-FTIR在线测量表明自由基反应途径是由反应器壁的不锈钢异质引发的。对于仲碳原子，观察到较高的酮与醇比（3.5-7.9），这很可能是由于醇中间体的快速连续氧化所致。仅在很小的程度上检测到，叔碳原子就可以高选择性地转化为相应的醇。对产物分布的详细分析和其他机理证据表明，乙醛不仅可以作为牺牲性的氧受体，而且还可以作为高效的H-过氧和氧自由基的原子供体，也是氢过氧中间体的关键还原剂。与其他惰性气体（例如压缩的N_2或Ar）相比，在相同的反应条件下，使用二氧化碳可提高烷烃氧化物的收率。

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