A DFT study of the aldol condensation reaction in the processing of ethanol to 1,3-butadiene on a MgO/SiO2 surface

Abstract

MgO/SiO₂ is a significant catalyst system for the production of 1,3-butadiene from ethanol, in which the aldol condensation reaction is a key step. In this work, density functional theory was used to study the interaction mechanism between MgO and SiO₂, in which it was significant to study the MgO/SiO₂ composite oxide model constructed, and its surface structure, electronic properties as well as acid–base properties. The reaction barrier of aldol condensation was calculated. We found that SiO₂ as a structural promoter can keep MgO highly dispersed, and SiO₂ as an electronic promoter affects the electronic properties and acid–base properties of MgO components. On the surface of different catalyst structures, the difficulty of the aldol condensation reaction is different. When MgO is supported on SiO₂, the Lewis acidity of Mg ions is strong, while the basicity of O anions is weak, which is beneficial towards balancing the reaction barrier of the enolization step and the proton return step, and further lowers the reaction barrier of the entire reaction.