OL负载Cu催化剂及其催化氧化CO及乙酸乙酯性能

采用氧化还原法合成了层状锰氧化物(OL),并以OL为载体采用离子交换法制备了不同Cu负载量的Cu_x/OL催化剂。利用X射线衍射(XRD)、电子扫描电镜(SEM)、N_2吸附/脱附、H_2~-程序升温还原(H_2-TPR)、TG(热重)、X射线光电子能谱(XPS)、O_2-程序升温脱附(O_2-TPD)等技术对所制催化剂进行结构和织构表征,并对其催化氧化CO及乙酸乙酯活性进行了评价。结果表明,OL具有典型的层状锰氧化物结构,适量掺杂Cu对OL的结构和织构影响不大,但Cu的掺杂明显影响Cu_x/OL的还原性、氧移动性及催化剂表面Cu~(2+)/CuO、(Mn~(2+)+Mn~(3+))/Mn~(4+)和Oads/Olatt的比例。Cu_x/OL的催化性能与以上因素密切相关。在Cu_x/OL样品中,Cu_5/OL催化剂具有最佳的催化活性(CO催化氧化,T_(50)=70°C和T_(90)=100°C;乙酸乙酯催化氧化T50=160°C,T90=200°C)。同时,Cu_5/OL催化剂具有最佳的还原性能、氧移动性能和最多的Cu~(2+)、(Mn~(2+)+Mn~(3+))和表面吸附氧浓度。Cu_x/OL催化性能与铜锰之间相互作用、还原性和氧移动性能密切相关。

Cu-Doped Octahedral Layered Birnessites Catalysts for the Catalytic Oxidation of CO and Ethyl Acetate

Octahedral layered birnessite (denoted as OL) was synthesized by the oxidation-reduction method and a series of Cu_x/OL catalysts were prepared by the ion exchange method with various Cu loadings. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ adsorption-desorption, hydrogen temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and.oxygen temperature-programmed desorption (O₂-TPD) techniques, and their catalytic activities for CO and ethyl acetate oxidation were evaluated. The results show that OL is a typical octahedral layered structure, and the doping of Cu hardly affects the structure of OL. Moreover, Cu_x/OL samples had different reducibility, oxygen mobility, and atomic ratio of Cu²⁺/CuO, (Mn²⁺+Mn³⁺)/Mn⁴⁺, and O_ads/O_latt after the addition of Cu to OL. Among the Cu_x/OL samples, the Cu₅/OL sample showed the best activity for the catalytic oxidation of CO and ethyl acetate (T₅₀=70 and T₉₀=100℃ for CO oxidation; T₅₀=160℃ and T₉₀=200℃ for ethyl acetate oxidation). Cu₅/OL showed the best reducibility, most isolated Cu²⁺ species, highest surface (Mn²⁺+Mn³⁺)/Mn⁴⁺ atomic ratio, highest chemisorbed oxygen species, and lowest O₂ desorption temperature. Hence, factors such as the strong interaction between copper and manganese, good reducibility, and oxygen mobility were responsible for the excellent catalytic activity of Cu₅/OL.