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A study is performed of samarium-modified Fe-containing catalysts on aluminum–magnesium spinel (MgAl2O4) supports. Data on the adsorption and reduction properties of the catalysts, determined via in situ magnetometry and IR spectroscopy of adsorbed CO, are compared. The IR spectroscopy of adsorbed CO shows that the main Fe species which forms a bond with CO in unpromoted Fe/MgAl2O4 is Fe2+ cations on the surfaces of nucleation centers in both the oxide and the metal phase, while the contribution from complexes with Fe0 atoms is negligible. It is found that promotion with samarium in a ratio of Sm : Fe = 1 : 100 inside the catalyst contributes to the effective reduction of iron oxides. It is shown that the reduction of iron is greatest for the catalyst synthesized by depositing samarium on the surface of a Fe-containing catalyst. [ABSTRACT FROM AUTHOR]

Hydrogenation of carbon monoxide (Fischer–Tropsch synthesis) is a promising route to ultraclean motor fuels, base oils and petrochemicals on the basis of non-petroleum feed such as natural gas, coal and biomass. Although cobalt-based industrial catalysts for this process are in operation for many years, they still need to be improved in terms of specific activity and selectivity to target hydrocarbons. This paper describes the effect of catalyst support coating with carbon on the formation of cobalt active phase and catalytic performance in CO hydrogenation. Carbonization of Mg–Al spinel was performed by impregnating with aqueous glucose solution followed by thermal treatment in inert atmosphere. Thus prepared carbonized material was used for cobalt deposition by incipient wetness impregnation method. The catalysts were characterized by N2 adsorption–desorption, scanning electron microscopy, thermoanalytical measurements combined with mass spectrometry of released gases, X-ray diffraction and in situ magnetic measurements during activation in H2 flow. Catalytic performance in Fischer–Tropsch synthesis was assessed at T = 210 °C, P = 20 bar. The size of Co3O4 crystallites in calcined catalysts and metallic cobalt in activated catalysts decreases with carbon content in the support. Cobalt precursor is reduced completely to metal within 2 h in typical activation conditions for FTS cobalt catalysts: H2 flow, 450 °C. Activity in CO hydrogenation decreases while selectivity to higher hydrocarbons increases with carbon content. High proportion of olefins in synthesized light hydrocarbons (> 65%) is a remarkable feature of the elaborated catalysts. [ABSTRACT FROM AUTHOR]

A study is performed of cobalt/MgAl2O4 catalysts promoted with glucose at Co/C molar ratios of 16.5, 3.2, and 1.6 via sequential deposition and codeposition. Magnetometry and IR spectroscopy of adsorbed CO show that raising the content of carbon in the catalyst contributes to the reduction of cobalt, regardless of how Co is introduced. Infrared spectroscopy reveals the main adsorption sites are cobalt cations and metallic Co. A strong contribution from adsorption sites characteristic of large Co particles is observed in systems synthesized via codeposition. Adsorption sites attributed to Co2+ and Coδ+ are structurally more homogeneous than ones attributed to metallic Co. [ABSTRACT FROM AUTHOR]

The influence of carbon on the genesis of the active phase of cobalt in aluminum–magnesium spinel supported catalysts on their catalytic properties in the synthesis of hydrocarbons from CO and H2 has been studied. Promotion with carbon was carried out by two independent methods: in the first one, carbon was deposited on a spinel support by thermolysis of glucose followed by the deposition of cobalt; in the second one, the catalyst was prepared by coimpregnation of the support with a solution of cobalt nitrate and glucose followed by thermolysis. The catalysts were characterized by simultaneous thermal analysis in combination with mass spectroscopy of evolved gases, in situ magnetic measurements, low-temperature nitrogen adsorption, and transmission electron microscopy. The modified catalysts showed a significantly higher CO conversion rate (turnover frequency) and selectivity for target liquid hydrocarbons compared to the unpromoted catalyst. [ABSTRACT FROM AUTHOR]

The effect of N-layer-by-layer promotion (N = 0, 1, 5, 10 layers) of Co/MgAl2O4 catalysts (MgAl2O4 is aluminum-magnesium spinel with Ssp = 23 m2/g) with glucose on the textural and physicochemical properties of the catalyst was studied. For Co-supported catalysts, the dispersity of cobalt increased significantly after promotion of the MgAl2O4 support with glucose (N > 1). For cobalt catalysts prepared by impregnation of the support with both cobalt nitrate and glucose, the dispersity of cobalt did not change. [ABSTRACT FROM AUTHOR]