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Improving alkane dehydrogenation activity on γ-Al2O3 through Ga doping
Catalysis Science & Technology ( IF 5 ) Pub Date : 2020-09-10 , DOI: 10.1039/d0cy01474e
Mona Abdelgaid 1, 2, 3, 4 , James Dean 1, 2, 3, 4 , Giannis Mpourmpakis 1, 2, 3, 4
Affiliation  

Nonoxidative alkane dehydrogenation is a promising route to produce olefins, commonly used as building blocks in the chemical industry. Metal oxides, including γ-Al2O3 and β-Ga2O3, are attractive dehydrogenation catalysts due to their surface Lewis acid–base properties. In this work, we use density functional theory (DFT) to investigate nonoxidative dehydrogenation of ethane, propane, and isobutane on the Ga-doped and undoped (100) γ-Al2O3 via the concerted and stepwise mechanisms. We revealed that doping (100) γ-Al2O3 with Ga atoms has significant improvement in the dehydrogenation activity by decreasing the C–H activation barriers of the kinetically favored concerted mechanism and increasing the overall dehydrogenation turnover frequencies. We identified the dissociated H2 binding energy as an activity descriptor for alkane dehydrogenation, accounting for the strength of the Lewis acidity and basicity of the active sites. We demonstrate linear correlations between the dissociated H2 binding energy and the activation barriers of the rate determining steps for both the concerted and stepwise mechanisms. We further found the carbenium ion stability to be a quantitative reactant-type descriptor, correlating with the C–H activation barriers of the different alkanes. Importantly, we developed an alkane dehydrogenation model that captures the effect of catalyst acid–base surface properties (through dissociated H2 binding energy) and reactant substitution (through carbenium ion stability). Additionally, we show that the dissociated H2 binding energy can be used to predict the overall dehydrogenation turnover frequencies. Taken together, our developed methodology facilitates the screening and discovery of alkane dehydrogenation catalysts and demonstrates doping as an effective route to enhance catalytic activity.

中文翻译:

Ga掺杂改善γ-Al2O3上烷烃的脱氢活性

非氧化烷烃脱氢是生产烯烃的有前途的途径,通常在化学工业中将其用作结构单元。金属氧化物,包括γ-Al系2 ö 3和的β-Ga 2 ö 3,是有吸引力的脱氢催化剂由于其表面的路易斯酸-碱特性。在这项工作中,我们使用密度泛函理论(DFT)来调查乙烷,丙烷和异丁烷的上掺杂Ga和非氧化性脱氢未掺杂的(100)的γ-Al 2 ö 3 经由协同和逐步的机制。我们发现,掺杂(100)的γ-Al 2 ö 3带有Ga原子的化合物通过降低动力学上受促进的协同机制的C–H激活壁垒并增加总体脱氢转换频率,可以显着改善脱氢活性。我们确定解离的H 2结合能作为烷烃脱氢的活性描述子,说明了路易斯酸的强度和活性位点的碱性。我们证明了解离的H 2之间的线性关系协同和逐步机制的结合能和速率决定步骤的激活障碍。我们进一步发现,碳鎓离子的稳定性是定量的反应物类型的描述子,与不同烷烃的C–H活化势垒相关。重要的是,我们开发了一种烷烃脱氢模型,该模型可以捕获催化剂酸碱表面性质(通过解离的H 2结合能)和反应物取代(通过碳正离子的稳定性)的影响。此外,我们证明了离解的H 2结合能可用于预测总体脱氢转换频率。综上所述,我们开发的方法有助于筛查和发现烷烃脱氢催化剂,并证明了掺杂是增强催化活性的有效途径。
更新日期:2020-09-16
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