Concurrent catalytic removal of typical volatile organic compound mixtures over Au-Pd/α-MnO₂ nanotubes

α-MnO₂ nanotubes and their supported Au-Pd alloy nanocatalysts were prepared using hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. Their catalytic activity for the oxidation of toluene/m-xylene, acetone/ethyl acetate, acetone/m-xylene and ethyl acetate/m-xylene mixtures was evaluated. It was found that the interaction between Au-Pd alloy nanoparticles and α-MnO₂ nanotubes significantly improved the reactivity of lattice oxygen, and the 0.91wt.% Au_0.48Pd/α-MnO₂ nanotube catalyst outperformed the α-MnO₂ nanotube catalyst in the oxidation of toluene, m-xylene, ethyl acetate and acetone. Over the 0.91wt.% Au_0.48Pd/α-MnO₂ nanotube catalyst, (i) toluene oxidation was greatly inhibited in the toluene/m-xylene mixture, while m-xylene oxidation was not influenced; (ii) acetone and ethyl acetate oxidation suffered a minor impact in the acetone/ethyl acetate mixture; and (iii) m-xylene oxidation was enhanced whereas the oxidation of the oxygenated VOCs (volatile organic compounds) was suppressed in the acetone/m-xylene or ethyl acetate/m-xylene mixtures. The competitive adsorption of these typical VOCs on the catalyst surface induced an inhibitive effect on their oxidation, and increasing the temperature favored the oxidation of the VOCs. The mixed VOCs could be completely oxidized into CO₂ and H₂O below 320°C at a space velocity of 40,000mL/(g·hr). The 0.91wt.% Au_0.48Pd/α-MnO₂ nanotube catalyst exhibited high catalytic stability as well as good tolerance to water vapor and CO₂ in the oxidation of the VOC mixtures. Thus, the α-MnO₂ nanotube-supported noble metal alloy catalysts hold promise for the efficient elimination of VOC mixtures.