Introducing nanocrystalline CeO2 as heterogeneous environmental friendly catalyst for the aerobic oxidation of para-xylene to terephthalic acid in water

Abstract

CeO₂ nanoparticles exposed in (100) and (111) surfaces have been synthesized and explored as a heterogeneous catalyst for the first time in the oxidation of para-xylene to terephthalic acid. The synthesis and catalysis reaction was environmental friendly, where water was used as the solvent. Ceria nanoparticles were synthesized with controlled size of 15 nm and high surface area of 268 m² g⁻¹ magnitude. These particles were exploited as a novel heterogeneous catalyst for aqueous phase oxidation of para-xylene to bypass all the hazardous steps involve in the manufacture of industrially important terephthalic acid. The result shows the formation of 30–40% terephthalic acid under mild reaction condition, i.e. at 70 °C in water, by avoiding the corrosive bromide promoter and acetic acid solvent. The recyclability studies reveal that the recovered ceria catalyst retained its activity in para-xylene conversion without the change in the fluorite crystal structure, crystallite size and morphology of CeO₂. At last, a radical mechanism for this particular catalytic activity of the catalysis reaction has been proposed based on the high surface area and the corresponding available exposed active (100) and (111) surfaces.