An Insight on the Role of Pd/Cu Ratio in PdxCuy/TiO2 Bimetallic Catalysts for the Hydrogenation of Muconic Acid

Biomass-derived muconic acid (MA) is a promising platform molecule for the sustainable production of a range of valueadded chemicals, including adipic acid (AdA), hexenedioic acids, and muconolactone (Mlac). AdA is a key precursor in the synthesis of nylon 6,6. A renewable route to AdA via MA hydrogenation offers a greener alternative, aligning with the goals of circular and carbon-neutral chemical manufacturing. In this work, we explore the selective hydrogenation of MA over PdxCuy/TiO2 catalysts, focusing on the tunable production of three distinct compounds of industrial relevance. Pd-rich catalysts exhibit high activity and selectivity toward full hydrogenation to AdA. With increasing Cu content, a shift in selectivity is observed, favoring the formation of 2- and 3-hexenedioic acids, which are of interest for modifying polymer properties. At high Cu loading, the reaction pathway leads predominantly toMlac, a versatile intermediate for fine chemical synthesis. Catalyst structure–function relationships were investigated using transmission electron microscopy and highangle annular dark-field scanning transmission electron microscopy, revealing that the nature and distribution of Cu relative to Pd significantly influence the reaction selectivity. These findings demonstrate the potential of catalyst engineering to steer biomass-derived feedstocks toward multiple high-value chemical products, offering a flexible and sustainable platform for green chemical synthesis.