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A series of double-perovskite LaAMnNiO6 (A = La, Pr, Sm) catalysts with mesoporous morphology was prepared by a sol–gel method and further applied into photothermal synergistic degradation of gaseous toluene. Transmission electron microscopy and Brunauer–Emmett–Teller characterizations confirmed that double-perovskite LaAMnNiO6 (A = La, Pr, Sm) had obvious mesoporous structure, which can provide a larger specific surface area and further enhancing the reactivity of catalyst. UV-vis and X-ray photoelectron spectroscopy characterization illustrated that LaSmMnNiO6 possessed higher adsorption oxygen content and light absorption capacity, which contribute to the occurrence of catalytic oxidation in the Mars–van Krevelen redox cycle mechanism. A group of active tests showed that the double-perovskite LaSmMnNiO6 catalyst had a lower reaction initiation temperature (starting reaction at 75 °C) and a lower activity temperature of optimal reaction (more than 90% at 255 °C). Moreover, the research on reaction kinetics of the catalyst demonstrated that LaAMnNiO6 (A = La, Pr, Sm) had lower activation energy and thus exhibited better catalytic activity. The results of the study indicate that the double-perovskite LaAMnNiO6 (A = La, Pr, Sm) has broad application prospects in the field of volatile organic pollutant degradation.
A series of metal oxides (MnFeOx, MnCrOx, MnTiOx, and MnFeTiOx) supported on attapulgite (ATP) were synthesized by coprecipitation for the low-temperature selective catalytic reduction (SCR) of NOx with NH3. Then, they were subjected to appropriate characterizations for their properties (XRD, TEM, BET, XPS, etc.). The catalytic activity of MnFeTiOx/ATP catalyst was over 95% NOx conversion within a wide temperature window between of 175 and 300 °C, and 88% N2 selectivity. Moreover, MnFeTiOx/ATP presented excellent potassium resistance relative to the traditional V–W–Ti catalyst, and its denitration performance was significantly improved. The NOx conversion rate could be restored to nearly 90% at 210 °C after removing potassium via washing of K–MnFeTiOx/ATP. In addition, the MnFeTiOx/ATP showed better SO2 resistance and stability than the traditional V–W–Ti catalyst. Therefore, the MnFeTiOx/ATP catalyst has been proved to have broad prospects in NH3-SCR.
In the new generation of Global Navigation Satellite Systems (GNSS), dual-frequency constant envelope multiplexing is widely desired and is becoming an important subject in signal design. Considerable work has been devoted to multiplexing for the Alternative Binary Offset Carrier (AltBOC)-like signal model, for which each sideband consists of two or fewer signal components. In this paper, a phase-aligned dual-frequency constant envelope multiplexing technique is proposed for a general dual-frequency signal model. This multiplexing technique can be used to combine two constant-envelope-modulated signals in two sidebands into a composite signal with a constant envelope, where the constant-envelope-modulated signal in each sideband consists of an arbitrary number of signal components with an arbitrary power ratio and phase relationship among the signal components. A Lookup Table (LUT)-based signal generation method is also proposed, for which the required driving clock rate of the signal generator can be flexibly adjusted to meet the requirements of the satellite payload. Applications for the AltBOC-like signal model and a general dual-frequency signal model in the Beidou B1 band validate the flexibility and high multiplexing efficiency of our method. Specifically, AltBOC is a special case of the proposed method.