(211a) Catalytic Ethanol Conversion to 1,3-Butadiene on MgO/SiO2: Reactive Catalyst Surface Structure and Reaction Mechanisms

Biomass can serve as a sustainable and renewable carbon source to generate chemicals. Ethanol is relatively inexpensive and widely available and can its catalytic upgrading has been proposed as a viable route of indirect biomass valorization. 1,3-butadiene, the most important monomer for synthetic rubber, has been produced via catalytic processing of ethanol during World War II by USSR and USA, using Lebedev and Ostromislensky processes, respectively. The former utilized catalytic conversion of ethanol to 1,3-butadiene in one-step over MgO/SiO₂ catalysts, while the latter utilized a two-step process with the first step of ethanol dehydrogenation to acetaldehyde over Cu/SiO₂ catalysts and transforming acetaldehyde into 1,3-butadiene over a tantalum-based catalyst during the second step. Recent abundance of shale gas resulted in a different catalytic cracker product distribution dominated by ethylene. This caused a worldwide shortage of C4 hydrocarbons, such as 1,3-butadiene. Since ethanol can be produced using variety of biomass processing routes, including fermentation and gasification, it recently reemerged as the green route to catalytically form 1,3-butadiene but improvements in yields are necessary.

In this study, we identified the reaction mechanisms of ethanol on MgO surface by combining both theoretical and experimental study by means of DFT, in-situ FTIR, TPSR and fixed bed reactor studies. A complex mechanism involving acetaldehyde, crotyl species as well as unexpected pathway via ethylene are discussed.