Optimising alcohol dehydration catalysts for light olefin production through investigating ethanol and propanol interactions with zeolitic Brønsted acid sites

Light olefins such as ethene and propene are essential to the chemical industry but are currently produced from fossil feedstocks. Bio-derived alcohols e.g. ethanol and propanol offer a more sustainable route via catalytic alcohol dehydration to olefins, possible using existing infrastructure. Zeolites are excellent catalysts for this, due to their thermal stability, tuneable acidity, and shape-selective pores. Their Brønsted acid sites drive the initial protonation step, which is preceded by strong H-bonding between the alcohol and the acid site. This H-bonding significantly impacts low-energy vibrational modes, such as the OH in-plane bend, which INS—and especially TOSCA—is uniquely suited to probe.

Our recent QENS study (OSIRIS-RB2310031) examined ethanol/propanol diffusion in H-ZSM-5 and H-Y, revealing jump diffusion with distinct lengths and residence times for each catalyst. To explore these interactions further, we will use INS to probe the vibrational spectra of ethanol and propanol adsorbed in these zeolites.

These spectra will be modelled using QM phonon calculations of the alcohol–zeolite systems (as in our soon-to-be-published work on aromatic alcohols), enabling us to identify favourable adsorption geometries and quantify acid site interactions. This will advance our understanding of alcohol–zeolite interactions and support the optimisation of alcohol dehydration for sustainable olefin production.