Catalytic Pyrolysis of Waste Epoxy Resin over Phosphorus-Modified Activated Carbon for Selective Production of Phenolic Compounds

Epoxy resin (ER) is difficult to degrade naturally and it poses significant environmental risks. In this study, walnut shell (WS) was used to prepare phosphorus-doped activated carbon (PAC), which was employed in ER catalytic pyrolysis aimed at phenolic compound production. The effects of PAC preparation (H₃PO₄/WS ratio) and pyrolysis conditions (pyrolysis temperature, PAC/ER ratio) on the yields and selectivity of phenolic compounds were systematically explored. The results indicated that PAC, which possessed a large specific surface area and abundant oxygen-containing functional groups, could initially catalyze ER decomposition to produce phenol and 4-isopropenylphenol, and then further promote the hydrogenation of 4-isopropenylphenol to produce 4-isopropylphenol. When the H₃PO₄/WS ratio was 3, the pyrolysis temperature was set at 500 °C, and the PAC/ER ratio was 1, the total yield and selectivity of phenol and 4-isopropylphenol reached 32.41 wt % and 50.48%, respectively, greatly surpassing the 11.76 wt % and 17.32% observed from ER direct pyrolysis. This study presents a novel approach for the secure and efficient management of waste ER.