In Situ Spectroscopic Insights on the Molecular Structure of the MgO/SiO2 Catalytic Active Sites during Ethanol Conversion to 1,3-Butadiene

Abstract

Ethanol is an important renewable chemical that allows for sustainable high-value product, such as 1,3-butadiene, catalytic synthesis. The MgO/SiO2 catalyst is typically utilized in a single-step ethanol-to-1,3-butadiene catalytic conversion, and the (by)product yields were shown to depend on the type, structure, and strength of the catalytic active sites. The fundamental factors describing the molecular structure and binding properties of these sites are thus of critical importance but not yet fully understood. We utilized a multimodal approach, including temperature-programmed surface-sensitive infrared mass spectrometry using probe molecules, such as CO2, NH3, and pyridine and propionic acids, to unravel the structure and persistence of these catalytic sites in situ. In particular, Mg–O–Mg, Mg–O(H)–Mg, Mg–O–Si, and Mg–O(H)–Si surface site binding configurations were proposed and scrutinized using spectroscopic methods in combination with density functional theory (DFT) calculations. A combination of NH...