Manganese and Cobalt Doped Hierarchical Mesoporous Halloysite-Based Catalysts for Selective Oxidation of p-Xylene to Terephthalic Acid

Abstract

Bimetallic MnCo catalyst, supported on the mesoporous hierarchical MCM-41/halloysite nanotube composite, was synthesized for the first time and proved its efficacy in the selective oxidation of p-xylene to terephthalic acid under conditions of the AMOCO process. Quantitative yields of terephthalic acid were achieved within 3 h at 200–250 °C, 20 atm. of O2 and at a substrate to the Mn + Co ratio of 4–4.5 times higher than for traditional homogeneous system. The influence of temperature, oxygen, pressure and KBr addition on the catalyst activity was investigated, and the mechanism for the oxidation of p-toluic acid to terephthalic acid, excluding undesirable 4-carboxybenzaldehyde, was proposed.