Abstract
C-H bond breaking is important for industrial commodity and specialty chemical transformations, including the upgrading of alcohols. Small primary alcohols – methanol and ethanol – are used industrially as precursors for the corresponding aldehydes at industrial scales. However, upgrading these primary alcohols involves C-H bond breaking and the processes are run at elevated temperatures (> 200 °C). In this work, new understanding from temperature programmed reaction (TPR) studies with methanol over a CeO2(111) surface show the C-H bond breaking and the subsequent desorption of formaldehyde, even below room temperature. This is of particular interests because CeO2 is a naturally abundant, inexpensive metal oxide. We combine density functional theory (DFT) and kinetic Monte Carlo (KMC) to simulate the TPR of methanol on CeO2. Our simulations show that the low temperature C H bond breaking occurs via disproportionation of adjacent methoxy species to form methanol and formaldehyde which each then desorb. We further show from DFT calculations that the same transition state with comparably low activation energies should be possible for other sustainable primary alcohols, with ethanol, 1-propanol, and 1-butanol having been explicitly calculated. These findings point out a new class of transition states to search for in seeking low temperature C-H bond breaking over inexpensive metal oxides.
