2,4-dimethylfuran has a rare disubstitution pattern in the five-membered heterocyclic furan ring that is highly interesting chemically but challenging to access synthetically. We present a heterogeneously catalysed route to synthesise 2,4-dimethylfuran from commonly available 2,5-dimethylfuran using a zeolite packed-bed flow reactor. As supported by DFT calculations, the reaction occurs inside the zeolite channels, where the acid sites catalyse proton transfer followed by migration of a methyl group. The zeotype Ga-silicate (MFI type) appears superior to an aluminium-containing ZSM-5 by demonstrating higher selectivities and slower catalyst deactivation. This work provides new opportunities for the continuous valorisation of bio-feedstock molecules in the perspective of the emerging biorefinery era. MFI framework zeolites and zeotypes enable the isomerisation of 2,5-dimethylfuran to 2,4-dimethylfuran through a heterogeneously catalysed route. Incorporating gallium instead of aluminium increases the selectivity and durability of the catalyst. This reaction is promoted by suitable acidity of the catalyst and steric confinement in the micropores. image

The valorization of biomass-derived molecules into commodity chemicals is important for the transition to renewable feedstocks. The model platform molecule 2,5-dimethylfuran (2,5-dmf) can be converted into value-added aromatics such as benzene, toluene, and xylenes (BTX) over zeolite catalysts. To explore the role of the zeolite acid site(s) in BTX selectivity, gallium has been isomorphously substituted into the framework, resulting in a Ga-silicate. Compared to the ZSM-5 counterpart, this modification shows enhanced benzene selectivity as well as resistance to deactivation by coke in continuous catalytic performance tests.

The valorisation of 2,5-dimethylfuran over zeolites under catalytic fast pyrolysis conditions was analysed by on-line FTIR-MS. BTX and olefins correlate and decrease with time on stream, whereas the isomerisation of 2,5-dimethylfuran increases.

On-line composition analysis of complex hydrocarbon mixtures is highly desirable to determine the composition of process streams and to study chemical reactions in heterogeneous catalysis. Here, we show how the combination of time-resolved Fourier transform infrared spectroscopy and ion–molecule-reaction mass spectrometry (IMR-MS) can be used for compositional analysis of processed plant biomass streams. The method is based on the biomass-derived model compound 2,5-dimethylfuran and its potential catalytic conversion to valuable green aromatics, for example, benzene, toluene, and xylenes (BTX) over zeolite β. Numerous conversion products can be determined and quantified simultaneously in a temporal resolution of 4 min–1 without separation of individual compounds. The realization of this method enables us to study activity, selectivity, and changes in composition under transient reaction conditions. For example, increasing isomerization of 2,5-dimethylfuran to 2,4-dimethylfuran, 2-methyl-2-cyclopenten-1-one, and 2-methyl-2-cyclopenten-1-one is observed as the catalyst is exposed to the reactant, while BTX and olefin formation is decreasing.

A visible-light driven Suzuki cross-coupling reaction was performed with colored and bench-stable arylazosulfones in the presence of Ph3PAuCl (5 mol%) as the catalyst. The absence of a photocatalyst, along with the use of commercially available and easy-to-handle arylboronic acids underline the novelty and synthetic usefulness of the protocol. A reaction mechanism involving the generation of an aryl radical as the key intermediate has been proposed on the basis of experimental investigations.