Influence of La2O3 promoter on the structure of MnOx/SiO2 catalysts
作者： R. Craciun , N. Dulamita
关键词: Ethylbenzene 、 Oxidation state 、 Chemistry 、 Chemical engineering 、 Heterogeneous catalysis 、 Inorganic chemistry 、 Manganese 、 Atomic ratio 、 Dehydrogenation 、 Calcination 、 Catalysis
摘要: X-ray diffraction (XRD) and photoelectron spectroscopy (XPS) analyses have been used to characterize the structure of a La2O3-promoted MnOx/SiO2 catalyst, before after its utilization in oxidative dehydrogenation ethylbenzene (EB). MnOx/La2O3/SiO2 catalysts were prepared by pore volume impregnation, using aqueous solutions (i) La3+-nitrate at an atomic ratio La/Si = 0.08, (ii) Mn2+-nitrate Mn/Si 0.10, followed drying calcination 500°C air. XRD data show no patterns specific MnOx on calcination. Thus, presence La2O3 apparently favors dispersion manganese oxides during calcination, presumably forming mixed Mn-La oxides. On fresh promoted unpromoted catalysts, XPS indicated that Mn was present mostly as MnO2 Mn2O3. In from catalyst degenerated Mn4+ Mn2+, resulting formation Mn3O4 species, whereas case remained well dispersed It appears precludes EB dehydrogenation, conserving oxidation state.
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