Abstract
The Ni-loaded cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) catalysts (xNi/OMS-2: x = 1, 3, 5, and 10 wt%) were prepared by a pre-incorporation method. Physicochemical properties of the as-synthesized materials were characterized by means of various techniques, and their catalytic activities for CO, ethyl acetate, and toluene oxidation were evaluated.The loading of Ni played an important role in improving physicochemical propertiesof OMS-2. Among all of the samples, 5Ni/OMS-2 exhibited the best catalytic activity, with the T90 being 155 °C for CO oxidation at a space velocity (SV) of 60,000 mL/(g·h), 225°C for ethyl acetate oxidation at an SV of 240,000 mL/(g·h), and 300 °C for toluene oxidation at an SV of 240,000 mL/(g·h), which was due to its high Mn3+ content and Oads concentration, good low-temperature reducibility and lattice oxygen mobility, and strong interaction between the Ni species and the OMS-2 support. In addition, catalytic mechanisms of the oxidation of three pollutants over 5Ni/OMS-2 were also studied. The oxidation of CO, ethyl acetate, and toluene over the catalysts took place first via the activated adsorption, then intermediates formation, and finally complete conversion of the formed intermediates to CO2 and H2O.
Highlights
CO and volatile organic compounds (VOCs) bring about great harmfulness to human health and the atmosphere [1]
The results showed that the loading of Ni could modify the physicochemical property and catalytic activity of OMS-2 due to the strong synergistic action of Ni and manganese oxide
After Ni loading, the vibration absorption superposition of the Ni–O–Mn bonds increased the intensity of the absorption band at 710 cm−1 of the xNi/OMS-2 samples, which was consistent with the formation of the Ni–O–Mn bonds revealed in the X-ray diffraction (XRD) investigations
Summary
CO and volatile organic compounds (VOCs) bring about great harmfulness to human health and the atmosphere [1]. Catalytic oxidation possesses the advantages of low energy consumption, no secondary pollution, good safety, and wide applications, in particular, supported noble metal catalysts show high efficiency in CO and VOCs elimination at low temperatures [4]. The OMS-2 possesses a variety of manganese ions with different valences (Mn2+, Mn3+, and Mn4+) [12], a large number of open interlayer pore structures, and abundant surface hydroxyl groups It shows strong ion exchange ability, large adsorption capacity, and excellent catalytic performance. We report the preparation of a series of Ni/OMS-2 catalysts, their physicochemical properties, and their catalytic activities for the oxidation of CO, ethyl acetate, and toluene.
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