Aqueous-phase hydrodeoxygenation of highly oxygenated aromatics on platinum

Abstract

Utilization of renewable sugars from biomass by a hybrid chemical process produces highly oxygenated aromatic compounds, such as phloroglucinol, which require catalytic reduction for desirable aromatic products. Aqueous phase hydrodeoxygenation of phloroglucinol on carbon-supported platinum produces resorcinol, phenol, cyclohexanol, cyclohexanone, and 1,3-cyclohexanediol by combinations of carbon–oxygen bond cleavage and carbon–carbon double bond hydrogenation. Carbon–carbon σ-bond cleavage was not observed. Hydrodeoxygenation was the primary reaction of phloroglucinol, leading to the production of resorcinol in the overall rate-limiting reaction, with an activation energy barrier of E_a = 117 kJ mol⁻¹. Subsequent reactions of resorcinol produced 1,3-cyclohexanediol and phenol with similar energy barriers, E_a = 46 and E_a = 54 kJ mol⁻¹, respectively. Further hydrogenation of phenol (E_a = 42 kJ mol⁻¹) occurs through the intermediate, cyclohexanone, which is further reduced (E_a = 14 kJ mol⁻¹) to the dominant product, cyclohexanol.