Abstract:
Volatile organic compounds (VOCs), which include benzene, toluene and xylene, are harmful to both human health and the environment. It is important to control and reduce the release of VOCs. Transition-metal oxides have been widely studied due to their low cost and relative high activity for catalyzing VOCs. In this work, manganese oxide was used to coat zeolite molecular sieve, producing the composite by a one-step redox reaction between potassium permanganate and manganese nitrate. By introducing a template agent, the reaction temperature and concentration are optimized to modulate the structure and properties of manganese oxide, producing a layered porous structure that sets free the pore of the zeolite molecular sieve thoroughly. The large special surface area of zeolite molecular sieve facilitates the adsorption of VOCs and the manganese oxide coating promotes the catalytic oxidation of VOCs. The results show that the use of different reaction temperature and catalyst concentration leads to the changes of the morphology of manganese oxide, the specific surface area of the composite, the mole ratio of lattice oxygen to adsorbed oxygen, and the mole ratio of Mn
3+ to Mn
4+ in manganese oxide catalyst. The special surface area of the composite, coating amount, the mole ratio of lattice oxygen to adsorbed oxygen and Mn
3+ to
Mn
4+ together impact the catalytic performance of the composite. An appropriate amount of manganese oxide coated molecular sieve catalyst prepared under ice bath shows the best catalytic performance for toluene (0.26 g/m
3), which the toluene conversion reaches above 90% at 256 °C.