Science2014-07-01 2:11 PM

分解天然气以获取其产品的新方法 Main-Group Compounds Selectively Oxidize Mixtures of Methane, Ethane, and Propane to Alcohol Esters

论文摘要 

据一项新的研究报告,科学家们发现了廉价的材料,其能将天然气在温和的条件下转变为有用的化学物质。这种新的方法最终可与目前的、用于从石油中产生相同化学物质的技术进行竞争。由水力压裂或液压破碎法所发掘的天然气供应的迅速增长促使人们探索改善将其组分(甲烷、乙烷和丙烷)转变成为日用化学品的方法。目前的技术代价过于昂贵,尤其是在与从石油产生的产品进行竞争时是这样。这在很大程度上是因为转变天然气——天然气具有高度的化学惰性——所需的方法很复杂。天然气大体上是由烷烃组成的,而烷烃本身是由通过某些化学中已知的最强固的化学键保持在一起的碳与氢原子组成的。科学家们曾经试图用由诸如铂和铑等贵金属制备的催化剂来开启天然气的反应性。现在,Brian G Hashiguchi及其同事对1990年代的有关较重的主族金属的初步工作进行了重温并发现铅和铊盐——它们都是简单、常见且廉价的化学品——不仅能有效地将天然气中的甲烷而且还能将乙烷和丙烷转变为日用燃料。对这些材料的进一步研发可带来用于其它烃类转换的新化学。

Abstract 

Much of the recent research on homogeneous alkane oxidation has focused on the use of transition metal catalysts. Here, we report that the electrophilic main-group cations thallium(III) and lead(IV) stoichiometrically oxidize methane, ethane, and propane, separately or as a one-pot mixture, to corresponding alcohol esters in trifluoroacetic acid solvent. Esters of methanol, ethanol, ethylene glycol, isopropanol, and propylene glycol are obtained with greater than 95% selectivity in concentrations up to 1.48 molar within 3 hours at 180°C. Experiment and theory support a mechanism involving electrophilic carbon-hydrogen bond activation to generate metal alkyl intermediates. We posit that the comparatively high reactivity of these d10 main-group cations relative to transition metals stems from facile alkane coordination at vacant sites, enabled by the overall lability of the ligand sphere and the absence of ligand field stabilization energies in systems with filled d-orbitals.

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