Tuning of Acid/Base Functionalities in the MgAlO System for Ethanol Upgrade to n-Butanol

Hydrotalcite-derived mixed metal oxides (MgAlO)-based catalysts are used for the catalytic upgrade of ethanol to butanol which adjust the catalyst structure and number of relevant active sites through changes in the Mg/Al ratio. By performing a series of reaction activity tests, kinetic experiments, FTIR characterization, CO2-TGA analysis, and in situ active center titration, qualitative and quantitative relationships between catalyst structure and catalytic performance are obtained. We found the MgAlO mixed metal oxide system can catalyze the ethanol-to-butanol process through a Guerbet reaction pathway, though the process is kinetically limited. The data suggest that strong basic centers hosted in Mg-O sites are the most catalytically relevant function in the MgAlO material, as they control enolate formation, which is likely the rate limiting step of the aldol condensation stage in the Guerbet reaction.