The conversion of ethanol to form 1,3-butadiene (BD) over heterogeneous Lewis acid catalysts is a complex multi-step process involving various intermediates and catalyst functionalities. Typical steady-state spectroscopic studies will lead to crowded spectra that are difficult to interpret. Hence, more sophisticated spectroscopic tools are required to gain molecular level insights. Here we use a modulation approach that enables us to better understand the dynamic processes involved and the origin of consecutive reaction products. We developed an operando DRIFTS-MS setup that allows for precise control and simultaneous analysis of changes in the gas-phase composition as well as surface species.<sup>1</sup><br/><br/>Performing modulation experiments with our setup revealed a reaction intermediate with a vibrational frequency of 1690 cm-1 that is likely involved in the production of BD. Further experiments using isotope modulation finally helped us proposing a molecular level reaction mechanism for the production of BD over Ta-BEA. This mechanism also explains why a high ethanol concentration is required in the two-step process and might have consequences for the design of novel catalysts for this reaction.

Elucidating the mechanism of the Lewis acid catalyzed production of 1,3-butadiene from ethanol with modulated DRIFTS-MS

253rd National Meeting (2017)

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