Nonoxidative dehydrogenation of alkanes is an important chemical reaction, as it can be used for production of olefins, commonly used as building blocks for a range of plastics and chemicals. Several metal oxides, including γ-Al₂O₃, have exhibited dehydrogenation activity, showing promise as candidates for the upgrade of alkanes. In this work we use computational chemistry methods to investigate the mechanism of ethane, propane, n-butane, and i-butane dehydrogenation pathways on strong Lewis acid–base sites of γ-Al₂O₃. On the basis of our calculations, it was shown that a concerted dehydrogenation mechanism is energetically preferred with the formation of a carbenium-ion-like transition state. An alkane dehydrogenation model was developed on the basis of methodology previously applied in structure–activity relations (SAR) for alcohol dehydration on metal oxides. The carbenium ion stability (CIS), shown to be a descriptor in alcohol dehydration, was used as a quantitative descriptor in alkane dehydrogenation and was found to correlate with the calculated activation energy barriers for the hydrocarbons in question. Increased hydrocarbon substitution (branching) was found to decrease the calculated reaction barriers, on the basis of the CIS at the transition state. Importantly, SARs developed for alcohol dehydration on various metal oxides were found to accurately capture the catalytic activity trends in alkane dehydrogenation, accounting for catalyst acid–base surface properties and the CIS of intermediates at the transition state. These results highlight that identifying the appropriate physicochemical descriptors of catalysts can accurately describe a different set of reactions (alcohol dehydration vs alkane dehydrogenation) as long as these reactions progress with similar transition states. Such models can accelerate the discovery of highly active metal oxide catalysts for the production of olefins.

中文翻译：

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于理解烷烃脱氢通过酒精脱水的γ-Al ₂ ö ₃

烷烃的非氧化脱氢是重要的化学反应，因为它可用于生产烯烃，通常用作一系列塑料和化学品的基础材料。几种金属氧化物，包括γ-Al系₂ ö ₃，已经表现出脱氢活性，显示出有希望成为烷烃的升级候选。在这项工作中，我们使用计算化学的方法来研究乙烷，丙烷，机制ñ丁烷，和我对强路易斯酸碱场所丁烷脱氢途径的γ-Al ₂ Ø ₃。根据我们的计算，表明在形成碳正离子的过渡态时，在能量上优选协同的脱氢机理。在先前应用于结构-活性关系（SAR）的金属氧化物上进行醇脱水的方法的基础上，开发了烷烃脱氢模型。碳氢离子稳定性（CIS）在醇类脱水中显示为描述符，在烷烃脱氢中用作定量描述符，并发现与所讨论的烃的活化能垒相关。基于过渡态的CIS，发现增加的碳氢化合物取代（支化）可减少计算的反应势垒。重要的，已发现为在各种金属氧化物上进行醇脱水而开发的SAR可准确捕获烷烃脱氢中的催化活性趋势，这考虑了催化剂的酸碱表面性质和过渡态中间体的CIS。这些结果表明，只要催化剂以相似的过渡态进行反应，确定合适的催化剂物理化学指标就可以准确描述一组不同的反应（酒精脱水与烷烃脱氢）。这样的模型可以加速发现用于生产烯烃的高活性金属氧化物催化剂的发现。这些结果表明，只要催化剂以相似的过渡态进行反应，确定合适的催化剂物理化学指标就可以准确描述一组不同的反应（酒精脱水与烷烃脱氢）。这样的模型可以加速发现用于生产烯烃的高活性金属氧化物催化剂的发现。这些结果表明，只要催化剂以相似的过渡态进行反应，确定合适的催化剂物理化学指标就可以准确描述一组不同的反应（酒精脱水与烷烃脱氢）。这样的模型可以加速发现用于生产烯烃的高活性金属氧化物催化剂的发现。