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

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.