Supported copper and cobalt oxides on activated carbon for simultaneous oxidation of toluene and cyclohexane in air

Abstract

Copper and cobalt oxides supported on almond shell derived activated carbon (AC) with different loadings were synthesized by sequential and co-deposition–precipitation methods leading to Cu(shell)/Co(core)/AC, Co(shell)/Cu(core)/AC and Cu–Co(mixed)/AC catalysts that were subsequently used for catalytic oxidation of gaseous mixtures of toluene and cyclohexane in air in a tubular flow reactor. The catalysts and the support were characterized by Boehm test, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP), and thermogravimetric analysis (TGA). Catalyst efficiency for toluene and cyclohexane oxidation, both separately and in a mixture, was higher over the mixed metal oxides catalysts compared with the core–shell catalysts. An increase in the cobalt loading on the support led to a decrease in the metal oxide crystallite size and a change in the catalyst morphology. The best performance was obtained for the Cu₂–Co₆(mixed)/AC sample (Removal Efficiency >99.9%). Agglomeration of copper oxide over cobalt oxide crystallites for Cu(shell)/Co(core)/AC samples resulted in catalysts with the worst performance for complete oxidation of VOCs. Results indicated a negligible deterrence effect of toluene on cyclohexane oxidation. Furthermore, the addition of water (humid air) decreased the conversion of hydrocarbons.