Structural Engineering of Pd/C Catalyst for Selective Hydrogenation of Bulky Quinone to Biphenol

Abstract

Tetra-tert-butyldiphenol (TBBP) is a key intermediate for synthesizing advanced materials, including liquid crystals, specialty polymers, and epoxy resins. Its conventional production relies on stoichiometric inorganic reductants, a process that generates substantial saline wastewater and suffers from operational inefficiencies.Herein, we report a green and efficient catalytic route for the selective hydrogenation of tetra-tert-butyldiphenoquinone (TBDPQ) to TBBP using a structurally engineered Pd/C catalyst. A series of Pd/C catalysts were prepared via incipient wetness impregnation, and the effects of the active metal, support, reduction protocol, Pd loading, and reaction conditions were systematically investigated. The optimized 1 wt% Pd/C catalyst exhibited exceptional performance, achieving 98.50% TBDPQ conversion and 99.00% TBBP selectivity under mild conditions (100 °C, 3 MPa H₂).The catalyst retained high activity over five consecutive cycles without significant deactivation. Comprehensive characterization (XRD, TEM, XPS, H₂-TPR, BET) revealed that the high surface area and suitable metal-support interaction of the activated carbon support facilitated the formation and stabilization of well-dispersed Pd nanoparticles (~4.1 nm), which were crucial for the high activity and selectivity. The product was unambiguously identified as TBBP by melting point, FT-IR, NMR, and HPLC analyses. This work provides a sustainable, waste-minimized alternative to conventional TBBP synthesis and offers fundamental insights into the design of supported metal catalysts for the hydrogenation of sterically hindered quinones.