Metal-acid bifunctional catalysts based on porous aromatic frameworks for tandem alkylation-hydrogenation of phenolics with furanics.

Noble metal catalysts based on porous aromatic frameworks modified with sulfo groups were studied in tandem alkylation-hydrogenation reaction between lignocellulose-derived furanic (furfural, furfuryl alcohol and 5-hydroxymethylfurfural) and phenolic compounds (phenol, m-cresol, guaiacol) to produce high-density fuel precursors. Platinum catalysts were synthesized based on PAF-30-SO3H-3 and PAF-30-SO3H-5 supports with 3 and 5 % of sulfur, respectively, and both with 0.8 % of platinum. Hydroalkylation of mixtures of two substrates was performed. The reaction of guaiacol with furfuryl alcohol is characterized by the highest yields of long-chain products. The influence of substrates ratio, H2 pressure, reaction temperature and time on selectivity and activity of the catalysts was studied. The highest yield (77 %) of long-chain oxygenates among all experiments was achieved under the following reaction conditions: 2 MPa H2, 4 h, 130 °C and 1:8 mol/mol furfuryl alcohol-guaiacol ratio. Catalysts Pd-PAF-30-SO3H-3 (with 1.1 % of palladium) and Ru-PAF-30-SO3H-3 (with 0.3 % of ruthenium) were tested in the tandem process to evaluate the impact of metal on reaction. To our knowledge, tandem alkylation-hydrogenation between biomass-derived furanics and phenolics over bifunctional catalysts based on organic polymers is reported for the first time. Moreover, some products of hydroalkylation (e.g., tricyclic oxygenates) haven't yet been described.