Selective catalytic oxidation of toluene with O2 to benzyl alcohol and benzaldehyde over bimetallic NiCu/MgAlO catalyst in solvent-free and additive-free conditions

Abstract

In this work, a stable bimetallic hydrotalcite-derived NiCu/MgAlO catalyst and O₂ as oxidant were used for the toluene oxidation to produce the valuable benzyl alcohol (PhCH₂OH) and benzaldehyde (PhCHO) under solvent-free and additive-free conditions. This strategy gave 7.2% toluene conversion with 70.7% selectivity to PhCH₂OH & PhCHO. Multiple characterizations showed that highly dispersed metallic Cu and Ni were anchored on the support surface and a chemical bonding interaction occurred between the metallic Ni and the MgAlO. The metal–support interaction contributed to the formation of active Ni⁰ species and NiCu alloy with abundant oxygen defects, resulting in excellent catalytic activity and acceptable stability. A plausible reaction mechanism for the catalytic oxidation of toluene over NiCu/MgAlO catalyst has been proposed. The attractive feature of the present catalytic oxidation system compared to conventional methods was its ability to achieve high selectivity for the desired target product. The further advantage of NiCu/MgAlO catalyzed toluene oxidation was that the reaction temperature and time could be below 180 °C and 2 h, thereby minimizing energy consumption and reducing effluent wastewater, which has potential application prospects.