Key Laboratory for Green Chemical Technology of Ministry of Education, R&D Center for Petrochemical Technology, Tianjin University, Tianjin 300072, P. R. China.
Phys Chem Chem Phys. 2018 May 9;20(18):12970-12978. doi: 10.1039/c7cp08620b.
Density functional theory (DFT) calculations have been used to elucidate the influence of the surface properties of Zr-SBA-15 on the conversion of ethanol to 1,3-butadiene at the molecular level. To identify the critical reactive intermediates of ethanol catalysis to catalytically form 1,3-butadiene on the Zr-SBA-15 surface, the model of Zr-SBA-15 was first built. The overall enthalpy energy surface was explored for the highly-debated reaction mechanisms, including Toussaint's aldol condensation mechanism and Fripiat's Prins mechanism. It was found that ethanol dehydration to form ethylene possessed a lower energy barrier than dehydrogenation to yield acetaldehyde, which means they are competing reactive pathways. C-C bond coupling to form acetaldol (3-hydroxybutanal) proceeds with a 2.15 eV forward reaction barrier. Direct reaction of ethylene and acetaldehyde proceeds with a free energy barrier of 2.90 eV suggesting that Prins condensation hardly occurs. The results here provide a first glimpse into the overall mechanism of 1,3-butadiene formation on Zr-SBA-15 reactive sites in light of the variety of proposed mechanistic pathways mostly based on conventional homogenous organic chemistry reactions.
密度泛函理论（DFT）计算已被用于阐明 Zr-SBA-15 的表面特性对乙醇转化为 1,3-丁二烯的分子水平的影响。为了在 Zr-SBA-15 表面上确定乙醇催化转化为催化形成 1,3-丁二烯的关键反应中间体，首先构建了 Zr-SBA-15 的模型。探索了备受争议的反应机制的整体焓能表面，包括 Toussaint 的 aldol 缩合机制和 Fripiat 的 Prins 机制。结果发现，乙醇脱水形成乙烯的能量势垒低于脱氢生成乙醛，这意味着它们是竞争反应途径。C-C 键偶联形成乙缩醛（3-羟基丁醛）的正向反应势垒为 2.15 eV。乙烯和乙醛的直接反应具有 2.90 eV 的自由能势垒，表明 Prins 缩合几乎不会发生。这些结果根据大多数基于传统均相有机化学反应的提议的机制途径，为在 Zr-SBA-15 反应性位点上形成 1,3-丁二烯的总体机制提供了初步了解。
