Dehydration of 1,3-butanediol to butadiene over medium-pore zeolites: Another example of reaction intermediate shape selectivity

Abstract

Here we compare the catalytic properties of the proton form of 11 medium-pore zeolites, with different framework topologies and/or compositions for the dehydration of biomass-derived 1,3-butanediol at 300 °C under excess water conditions (H2O/1,3-butanediol = 45). It was found that high-silica H-ferrierite (Si/Al = 130) with intersecting 10- and 8-ring channels exhibits the highest butadiene yield, together with the best durability, among the zeolites tested. Due to its highly inactive nature, however, 3-buten-1-ol, one of the butenol reaction intermediates in 1,3-butanediol dehydration, also remained a major by-product. IR spectroscopy with adsorbed 3-buten-1-ol shows that intramolecularly hydrogen-bonded 3-buten-1-ol exists predominantly in H-ZSM-5 with two intersecting 10-ring channels, while the one with no intramolecular hydrogen bonding is another species found not only in H-ferrierite but also in the one-dimensional 10-ring zeolite H-ZSM-22. By combining both experimental and theoretical results, we conclude that 1,3-butanediol dehydration over medium-pore zeolites may constitute another example of reaction intermediate shape selectivity.