Study of K/Mn-MgO Supported Fe Catalysts with Fe（CO）5 and Fe（NO3）3 as Precursors for CO Hydrogenation to Light Alkenes

Two K/Mn-MgO supported catalysts were prepared by Fe（CO）5 and Fe（NO3）3 as precursor respectively. The obtained Fe-K/Mn-MgO catalysts were tested for CO hydrogenation to light alkenes and characterized by X-ray powder diffraction （XRD）, X-ray photoelectron spectra （XPS）, H2 temperature-programmed reduction （H2-TPR）, H2 CO and CO2 temperature-programmed desorption （H2, CO/CO2-TPD） and transmission electron microscope （TEM） The results indicated that the catalyst with 10 wt% Fe loading prepared by Fe（CO）5 as precursor showed better performance in syngas to light alkenes than ones obtained from Fe（NO3）3 as precursor, where the CO conversion was 62.50% and the selectivity was 55.95% at 350 ℃, 1.5 MPa and 1000 h^-1, respectively.

The kinetic study of light alkene syntheses by CO_(2) hydrogenation over Fe-Ni catalysts

A kinetics model of CO_(2) hydrogenation over iron-nickel catalysts was developed based on the detailed mechanism of alkenes re-adsorption and secondary reaction.The corresponding kinetical experiments are conducted in a continuous fixed bed reactor.The effect of reaction conditions on catalyst performance was analyzed according to the results of orthogonal experiments.The results of the experiments show that more methane in products can be obtained with iron-nickel catalysts,the trend of which is consistent with the thermodynamic analysis.However,the content of alkenes in products is equivalent with that of alkanes.This shows that the reaction is controlled by kinetics.In all,the results of the experiments also substantiate that the model can give a good representation of the reaction mechanism of CO_(2) hydrogenation over iron-nickel catalysts.The parameters of this model give a better explanation for the question why the iron-nickel catalysts have a higher selectivity toward alkenes compared with other iron-based catalysts.

Effect of Fe content on FeMn catalysts for light alkenes synthesis

The effect of Fe content on FeMn/MgO catalysts for light alkenes synthesis through CO hydrogenation was investigated.Catalysts were prepared by a conventional co-impregnation method,characterized using BET,X-ray powder diffraction(XRD)and Temperature-programmed reduction(H_(2)-TPR)techniques.High activity was obtained over the catalyst with 9 wt-%Fe content,over which CO conversion and the selectivity of C2^(=)-C4^(=)reached 91.36%and 58.48%,respectively.With the increase of Fe content,both the conversion and the selectivity were improved within a certain range and then decreased.The results show that the surface area of the catalyst played an important role in the catalytic reaction.With the increase of Fe loading,the interaction action between Fe and Mn was enhanced and FeMn solid solution was formed.

Promotion of Mn Doped Co/CNTs Catalysts for CO Hydrogenation to Light Olefins

With various contents, Mn was introduced into carbon nanotubes （CNTs） supported cobalt catalysts and the obtained Mn-Co/CNTs catalysts were investigated for CO hydrogenation to light alkenes and characterized by N2 ad- sorption, X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, H2 temperature programmed reduction （TPR）, CO temperature programmed desorption （TPD） and transmission electron microscope （TEM）. The results indicate that the addition of a small amount of Mn （0.3 wt%） to CNTs-supported Co catalyst significantly increased the selectivity of C2--C4 olefins and decreased the selectivity of CH4. However, with further addition of Mn to the cobalt catalysts, the CH4 selectivity decreased obviously along with the increase of the C5 selectivity. Compared with the unpromoted catalysts, the Mn-promoted cobalt catalysts increased the C2=-C4=/C20- C40 molar ratio.