Abstract
A series of Pd-TiO2/Pd-Ce/TiO2 catalysts were prepared by an equal volume impregnation method. The effects of different Pd loadings on the catalytic activity of chlorobenzene (CB) were investigated, and the results showed that the activity of the 0.2%-0.3% Pd/TiO2 catalyst was optimal. The effect of Ce doping enhanced the catalytic activity of the 0.2% Pd-0.5% Ce/TiO2 catalyst. The characterization of the catalysts using BET, TEM, H2-TPR, and O2-TPD showed that the oxidation capacity was enhanced, and the catalytic oxidation efficiency was improved due to the addition of Ce. Ion chromatography and Gas Chromatography-Mass Spectrometer results showed that small amounts of dichlorobenzene (DCB) and trichlorobenzene (TCB) were formed during the decomposition of CB. The results also indicated that the calcination temperature greatly influenced the catalyst activity and a calcination temperature of 550 °C was the best. The concentration of CB affected its decomposition, but gas hourly space velocity had little effect. H2-TPR indicated strong metal–support interactions and increased dispersion of PdO in the presence of Ce. HRTEM data showed PdO with a characteristic spacing of 0.26 nm in both 0.2% Pd /TiO2 and 0.2% Pd-0.5% Ce/TiO2 catalysts. The average sizes of PdO nanoparticles in the 0.2% Pd/TiO2 and 0.2% Pd-0.5% Ce/TiO2 samples were 5.8 and 4.7 nm, respectively. The PdO particles were also deposited on the support and they were separated from each other in both catalysts.
Highlights
Volatile organic compounds (VOCs) contribute greatly to air pollution, such as chemical smog and atmospheric haze, and seriously affect the health of the population
The temperature of the reactor was measured using a thermocouple located at the surface of the catalyst, and the effluent gases were analyzed by an on-line gas chromatograph (GC) equipped with a flame ionization detector (FID) (6890N, Agilent, Palo Alto, CA, USA)
A series of Pd/Pd-Ce/TiO2 catalysts were prepared by an impregnation method, and their catalytic activities were analyzed
Summary
Volatile organic compounds (VOCs) contribute greatly to air pollution, such as chemical smog and atmospheric haze, and seriously affect the health of the population. The key to catalytic oxidation is to obtain a high activity and stability, and catalysts with few by-products, strong anti-poisoning characteristics, and low prices have been developed [10]. Many studies [12,13,14,15] have reported that noble metal catalysts with good oxidation properties can help reduce the CO selectivity, reduce the temperature of the Deacon reaction, and prevent the accumulation of HCl on the catalyst surface, which can improve the stability of the Catalysts 2020, 10, 347; doi:10.3390/catal10030347 www.mdpi.com/journal/catalysts. The stability of the active component was increased by adding auxiliaries and reducing the surface area of carbon in the catalyst. The catalytic oxidation activity and reaction conditions of low concentrations of CB were investigated. The catalyst performance was evaluated by analyzing both the catalytic activity and by-product formation
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