Single-Atom Ru-zeolite isomerization catalysis for a bio-based route towards terephthalates from muconic acid

Abstract The search for sustainable polymers requires new ways for accessing monomers from biomass as raw materials. Cis,cis-muconic acid (ccMA), derived from glucose, stands as a potential intermediate to produce valuable monomers, including terephthalic and adipic acids. However, to access terephthalic acid through Diels-Alder cycloaddition, an additional isomerization of ccMA into ttMA (trans,trans-isomer) is required. In this work, we develop a single-atom low-loaded Ru catalyst (0.2 wt.%), supported on *BEA zeolite, that produces tt-muconate in ethanol with total conversion (to equilibrium) and selectivity >95%. We reached productivity rates of 427 mM.h-1 (≈85 g.L-1.h-1), surpassing, by an order of magnitude, the highest values reported for biobased production of 17 mM.h-1 of ccMA, thus making the latter the rate-determining step if both processes were linked. Furthermore, we demonstrate the direct production of terephthalate intermediates with high yields (78%) and selectivity (80%) in a one-pot isomerization/Diels-Alder reaction. This single atom Ru-zeolite isomerizes dienes via a hydride mechanism and could serve the isomerization of other value-added alkenes.