Selective production of orthoalkyl phenols on Cu0.5Co0.5Fe2O4: a study of catalysis and characterization Original Research Article

Phenol alkylation was carried out on Cu1−xCoxFe2O4 (x = 0–1) by employing various alkylating agents: CH3OH, CH3OCOOCH3 dimethyl carbonate (DMC), C2H5OH, 2-C3H7OH and isobutene (IB), under a wide variety of reaction conditions; a comparative analysis is made. Cu0.5Co0.5Fe2O4 displays the highest phenol alkylation activity, irrespective of the alkylating agents. The catalytic conversion of phenol follows the following order: MeOH ≈ DMC > EtOH > isopropanol ≈ IB. Ortho-dialkylated product formation decreases as the chain length of alkylating agent increases. X-ray photoelectron spectra (XPS) and Auger electron spectroscopy analysis of fresh and spent Cu0.5Co0.5Fe2O4 catalysts revealed a partial reduction of metal ions due to reaction. Valence band studies reveal an increase in the overlap of metal ion 3d bands from fresh to spent catalysts due to a large decrease in the energy gap between them. The high activity observed is attributed to an optimum distribution of Cu-species with hetero-atom neighbors on the surface and a large overlap between the Cu and Co 3d bands. A mechanism involving the reaction of phenol and alcohol molecules adsorbed simultaneously on the same acid–base pair site is supported by IR spectroscopy results from the reactants and pyridine adsorbed on catalyst.