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In ethylbenzene dehydrogenation industrial applications, Fe-K based especially Fe-K-Ce and Fe-K-Ce-Mo based mixed oxides are the most widely used catalysts. But the corresponding reaction mechanism for promoters are still unclear. Herein, the model Fe-K, Fe-K-Ce, Fe-K-Ce-Mo catalysts were prepared by wet granulation method and the insights into promotional effects were clarified by using various characterizations and in situ DRIFTs studies. Our results suggest that Ce addition improved catalytic activity and Mo modification increased styrene selectivity. The Fe-K-Ce showed outstanding redox ability profited from abundant active oxygen species and reducible species. The Fe-K-Ce-Mo achieved optimal activity and selectivity because of the moderate redox behavior. The ethylbenzene adsorption at low temperature form coke deposits and enhanced oxidizing ability of modified catalysts facilitate CO 2 producing thus improve catalyst coke resistance. Besides, the activation induction periods of modified catalysts were shortened based on accelerated formation of main active phase and redox equilibrium. Moreover, the steam significantly promoted styrene species generation and further shorten activation induction periods, which was involved in real reactions instead of just eliminating coke. [Display omitted] • Fe-K, Fe-K-Ce, Fe-K-Ce-Mo mixed oxide catalysts were prepared by wet granulation method. • Ce addition improved catalytic activity and Mo modification increased the styrene selectivity. • Activation induction periods of Fe-K-Ce and Fe-K-Ce-Mo catalysts were shortened. • Fe-K-Ce catalysts had excellent redox ability and Mo addition enhanced ethylbenzene adsorption. • Steam was involved in dehydrogenation reactions instead of just eliminating carbon deposits. [ABSTRACT FROM AUTHOR]

A series of MnO x -MO y /Ce 0.75 Zr 0.25 O 2 (M = Fe, Co, Ni, Cu) catalysts were synthesized by an impregnation method and used for selective catalytic reduction (SCR) of NO x with NH 3 . The catalytic performances of various MnO x -MO y /Ce 0.75 Zr 0.25 O 2 catalysts were studied. It was found that MnO x -FeO y /Ce 0.75 Zr 0.25 O 2 catalyst showed excellent low-temperature activity and a broad temperature window. The catalysts were characterized by N 2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). Characterization of the catalyst confirmed the addition of iron oxide can enhance the NO oxidation ability of the catalyst which results in the outstanding low-temperature SCR activity. Meanwhile, iron oxides were well dispersed on catalyst surface which could avoid the agglomeration of active species, contributing to the strong interaction between active species and the support. More importantly, in situ DRIFTS results confirmed that bidentate nitrates are general active species on these catalysts, whereas the reactivity of gaseous NO 2 and bridged nitrates got improved because of the addition of Fe. [ABSTRACT FROM AUTHOR]

To improve propane combustion activity and illustrate the promotional effects of molybdenum doping, Pt-Mo/ZSM-5 catalysts with different Mo amounts were prepared by the co-impregnation method. XRD, Raman, H2-TPR, NH3-TPD, in situ DRIFTs, XPS and other characterizations were performed. The results indicated that the concentration of Pt0 in Pt/ZSM-5 catalyst increased after the doping of Mo and the content of Pt0 had a positive correlation with the reaction turnover frequency value. The propane combustion activity of Pt/ZSM-5 catalyst was significantly improved after the doping of molybdenum species. Among all the catalysts, Pt-6Mo/ZSM-5 catalyst (Pt/ZSM-5 with 6 wt.% Mo modification) showed the lowest T50 and T90 for propane catalytic combustion. Moreover, the Pt-Mo/ZSM-5 catalyst exhibited outstanding catalytic stability. [ABSTRACT FROM AUTHOR]

• The Fe-OMS-2 catalysts exhibited improved alkali-resistant NO x reduction. • The trapped K+ ions in Fe-OMS-2 could make the catalyst structure more stable. • Fe doping could enhance adsorption of NH 3 species and NOx species. • The formed intermediates on the Fe-OMS-2 catalysts were more reactive. • Improved redox species and more acid sites were demonstrated. Currently, selective catalytic reduction (SCR) of NO x with NH 3 in the presence of alkali metal ions by using vanadium-free catalysts is still a big challenge for the removal of NO x for stationary sources. In this work, improved reduction of NO x with NH 3 in the presence of alkali metal ions over novel Fe-doped manganese oxide octahedral molecular sieve (OMS-2) catalysts has been demonstrated and the promotional effects of Fe have been clarified. The Fe-doped OMS-2 (Fe-OMS-2) catalysts exhibited excellent NH 3 -SCR activity, improved N 2 selectivity and enhanced alkali resistance. The X-ray absorption fine structure spectroscopy (XAFS) results indicated that the trapped K+ ions could make the catalyst structure more stable. In situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) results revealed that the Fe doping could enhance adsorption of NH 3 species and adsorb various types of NO x species namely monodentate nitrate, bridged nitrate, bidentate nitrate and chelating nitrite. These formed intermediates on the Fe-OMS-2 catalysts were more reactive and thus more effectively participated in the SCR reactions. Superior alkali resistance of the Fe-OMS-2 catalysts was due to improved redox species, more acid sites and stronger adsorption of NO x species. The present investigations in this work may lead to an alternative development of high-performance non-vanadium catalysts for alkali-resistant NO x reduction. [ABSTRACT FROM AUTHOR]