CuMg-MOF-74 derived stable Cu/MgO@SiO2 for the hydrogenation of bis(2-hydroxyethyl)cyclohexane-1,4-dicarboxylate

Abstract

Cu-based catalysts play an important role in the hydrogenation of esters, however, their application at high temperatures is limited due to the low Hüttig temperature of Cu. Promoting the activity and stability of Cu catalysts at elevated temperatures remains a challenge. In this work, a highly stable Cu/MgO@SiO₂ was calcined and reduced controllably from CuMg-MOF-74 modified with SiO₂. This catalyst was then applied in the hydrogenation of poly(ethylene terephthalate)-degraded bis(2-hydroxyethyl)cyclohexane-1,4-dicarboxylate (BHCD) to 1,4-cyclohexanedimethanol (CHDM). Characterization results indicated that Cu/MgO@SiO₂ exhibited an enlarged surface area and pore volume (104 m² g⁻¹ and 0.52 cm³ g⁻¹), highly dispersed Cu (22.7%), and abundant basicity (480 μmol g⁻¹). It was confirmed that the conversion of BHCD and the selectivity of CHDM over Cu/MgO@SiO₂ reached 99.2% and 97.1%, respectively, at 260 °C, 2.5 MPa H₂, 0.8 g_BHCD g_cat.⁻¹ h⁻¹, and 155 mol_H2 mol_BHCD⁻¹, which were superior to those over the reference Cu/MgO and other Cu–MgO–SiO₂ catalysts. Furthermore, Cu/MgO@SiO₂ maintained its activity even at 280 °C for 100 h, owing to the MgO-decorated Cu nanoparticles encapsulated by SiO₂ hollow structures in the well-designed Cu/MgO@SiO₂.