High-Performance Na-CH₃ONa/γ-Al₂O₃ Catalysts for High-Efficiency Conversion of Phenols to Ethers

An efficient alkaline catalyst with a porous structure (Na-CH₃ONa/γ-Al₂O₃) was prepared by the melting method. The wastewater from the semicoke plant (WW_SCP) was extracted multiple times with isometric dimethyl carbonate (DMC)-cyclohexane mixed solvent at room temperature to obtain an organic phase (OP) with a high concentration of phenols. Ether (OPCP) was obtained by catalytic conversion of OP over catalyst Na-CH₃ONa/γ-Al₂O₃ at 210 °C and with a reaction time of 2.5 h. Both OP and OPCP were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and a quadrupole Exactive Orbitrap mass spectrometer (QPEOTMS). The results showed that only DMC, phenol, o-cresol, and other monohydric phenols were detected in OP, and only other saturated ethers such as anisole and O-methylanisole were detected in OPCP. Through the study of the catalytic conversion of the WW_SCP-related model compound, it was found that Na-CH₃ONa/γ-Al₂O₃ could effectively activate (deprotonate) phenol into phenate, and the strong nucleophilic oxyanion of phenate would attack the methyl carbon and carbonyl carbon on DMC to obtain methyl and methoxy groups. Thereby, phenate can be combined with methyl and methoxy groups to acquire the product anisole. In addition, the catalyst Na-CH₃ONa/γ-Al₂O₃ was found to still have high catalytic activity after 10 repeated cycles. It was speculated that this was related to the abundant microporous and mesoporous structure of the catalyst Na-CH₃ONa/γ-Al₂O₃.