Synthesis of Renewably Sourced Monomers: Hydrogenation of 2,5-Furandicarboxylic Acid Using Pt and Pd Supported Catalysts

Recent efforts to reduce industrial reliance on fossil fuels have focused on developing renewably sourced production routes for key monomers. This study investigates the selective hydrogenation of 2,5-furandicarboxylic acid (FDCA) to produce tetrahydrofuran-2,5-dicarboxylic acid (THFDCA), a polyester monomer and an intermediate to adipic acid (AA). Platinum (Pt) and palladium (Pd) catalysts supported on silica (SiO₂) and titania (TiO₂) were used at 5% wt. loading of the noble metal. All reactions were carried out at 34.5 bar H₂, for 4 hrs (100% conversion). Pd catalysts achieved yields of 98% (5% wt. Pd/SiO₂) and 90% (5% wt. Pd/TiO₂) towards THFDCA at 60ºC, while Pt catalysts achieved yields of only 13% (5% wt. Pt/SiO₂) and 17% (5% wt. Pt/TiO₂) THFDCA. Interestingly, Pt catalysts showed preference for reductive ring opening, with 5% wt. Pt/SiO₂ achieving an 85% yield of 2-hydroxyadipic acid (2-HAA), an intermediate in the HDO of THFDCA and valuable research compound. Similarly, 5% wt. Pt/TiO₂ formed 2-HAA in 74% yield. At 24 hrs of reaction time, the product distribution of 5% wt. Pd/SiO₂ remained unchanged from 4 hrs, implying distinct reaction pathways for Pd and Pt. Increasing the temperature of reaction from 60ºC to 100ºC led to decreased yield of the more selective product, and decreasing the temperature to 40ºC did not have a significant impact on yields. Further studies will test the hypotheses that differences in selectivity arise from differences in adsorption modes of FDCA onto the surface of the catalyst, the presence of different hydrogen species (H^* vs H⁺), or a difference in electron transfer between the noble metal and support.