Pd–Au Bimetallic Catalysts for the Hydrogenation of Muconic Acid to Bio-Adipic Acid

The hydrogenation reaction of muconic acid, produced from biomass using fermentative pro-cesses, to bio-adipic acid is one of the most appealing green emerging chemical process. This re-action can be promoted by catalysts based on metal belonging to the platinum-group and the use of a second metal can preserve and increase their activity. PdAu bimetallic nanoparticles samples supported on high temperature heat-treated carbon nanofibers were prepared using sol-immobilization method, changing the Pd-Au molar ratio. These catalysts were characterized by TEM, STEM and XPS analysis and tested in a batch reactor pressurized with hydrogen where muconic acid dissolved in water was converted to adipic acid. The synthesized Au-Pd bimetallic catalysts showed higher activity than monometallic Au and Pd material and better stability during the recycling tests. Moreover, the selectivity toward the mono-unsaturated changes by decreasing the Pd/Au molar ratio: the higher the amount of gold, the higher the selectivity to-ward the intermediates.