Abstract
Three-dimensionally ordered macroporous (3DOM) NiCe catalysts with different Ni/Ce molar ratio were fabricated using the colloidal crystal templating method. The physic-chemical properties of the samples were characterized by various techniques, including N2 adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, and H2-temperature-programmed reduction (TPR) characterizations. The results revealed that the 3DOM NiCe samples preserved the three-dimensionally ordered macroporous channels with interlinked micro- or mesoporous structure and highly dispersed nickel oxide species in the framework upon different amount of nickel incorporation. In the evaluation of the oxidative dehydrogenation (ODH) of propane, the 3DOM NiCe catalysts exhibited higher selectivity and yield to propene than the amorphous NiCe catalyst. An optimum yield of propene of 11.9% with the 30.3% propane conversion at 375 °C was obtained over the 3DOM 2NiCe catalyst. Combining XRD, TPR, and Raman analysis, it could be found that the nickel incorporation in CeO2 lattice produced a high concentration of oxygen vacancies that were the active sites for the oxidative dehydrogenation of propane. Besides this, the 3DOM structure promoted the rapid diffusion of the reactants and products—favorable for the generation of propene in the ODH of propane.
Highlights
The synthesis of propene from oxidative dehydrogenation (ODH) of propane exhibits the virtue of favorable thermodynamics and less coke deposits compared with the traditional steam cracking of naphtha or direct dehydrogenation of propane, becoming one of the routes with the most potential to produce value-added unsaturated hydrocarbon chemicals [1,2]
The N2 adsorption–desorption isotherms and the textural properties of 3DOM NiCe mixed oxides samples are given in Figure 1 and Table 1
Almost linear isotherms could be seen in the low-pressure portion for 3DOM NiCe samples, characteristic of the unrestrained monoor multilayer adsorption in macroporous structures [26]
Summary
The synthesis of propene from oxidative dehydrogenation (ODH) of propane exhibits the virtue of favorable thermodynamics and less coke deposits compared with the traditional steam cracking of naphtha or direct dehydrogenation of propane, becoming one of the routes with the most potential to produce value-added unsaturated hydrocarbon chemicals [1,2] In this process, vanadium and molybdenum-based catalysts are commonly used for the selective catalytic production of propene [3,4,5]. Using the beneficial features of 3DOM CeO2 , another study reported that the structured catalysts exhibit efficient heat/mass transfer with excellent activity, selectivity, and stability for the catalytic oxidation of methane to syngas [23]. The resulting catalysts were systematically characterized and evaluated in the ODH of propane for the purpose of understanding the effect of the nickel introduction on ODH activity of 3DOM CeO2 -doped Ni catalysts with respect to the modification of structure and redox properties
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