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The effect of the precursor ageing time on the structure, thermal decomposition, specific surface area, active copper surface area as well as on the morphology of the precursors and catalysts oxide forms was investigated. The hydroxycarbonate precursor, with the composition corresponding to industrial catalysts, was prepared via coprecipitation method from the solutions of copper and zinc nitrate with a mixture of sodium aluminate and sodium carbonate at pH = 7.4 and then aged in the mother liquor. The activity of the prepared catalysts in the LT-WGS reaction was compared under conditions similar to those in the industrial process. The results reveal that the precursor ageing influences the precursor phase composition, the active copper surface area and the catalytic activity. The activity decreases with the increasing ageing period but the activity concerned a single surface copper atom (TOF) is constant and independent of the ageing time. [ABSTRACT FROM AUTHOR]

The effect of a copper modifier on physicochemical properties of coprecipitated precursors and final Ni–Cu/Al 2 O 3 catalysts for benzene to cyclohexane hydrogenation was investigated. Based on the studies of physicochemical properties, the influence of copper on the catalytic activity and selectivity of Ni–Cu/Al 2 O 3 systems was discussed. The addition of copper resulted in a decrease of the specific and nickel surface area, improvement of the selectivity and a slight decrease of the benzene hydrogenation activity compared to the reference catalyst. A decrease of methylcyclopentane and methylcyclohexane by-products formation on the surface of Ni–Cu/Al 2 O 3 catalyst containing 10–17 wt% CuO by, respectively, 70% and 10% was observed. The results reveal a distinct, beneficial effect of the Ni/Al 2 O 3 modification by copper on the catalyst selectivity. However, this effect depends on temperature and is limited to ca. 20 wt% CuO, above this content the activity was found to decrease considerably. [ABSTRACT FROM AUTHOR]

The effect of steam gasification on the surface composition, surface area, pore size distribution as well as on the morphology of the carbon supports has been investigated. Materials have been characterized by nitrogen physisorption, mercury porosimetry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Model samples of the Co–Mo–K catalysts with the same composition have been prepared on carbon supports differing in the temperature of steam gasification process. Catalytic activity measurements have been carried out in a gradientless reactor in a kinetic regime at low partial pressures of reagents. A relationship between textural parameters of the supports and the catalysts activity has been estimated. The highest activity in the SGS process has been determined for the Co–Mo–K/SRO/40.49 supported catalyst. [ABSTRACT FROM AUTHOR]

Ni/La–Al 2 O 3 and Ni/Ce–Al 2 O 3 catalysts with a small amount of promoters intended for prereforming of LNG were characterized by XRF, N 2 adsorption-desorption, XRD, H 2 chemisorption, HRTEM and XPS. The catalytic activity was evaluated in methane steam reforming both in the kinetic and diffusion regime, at temperatures characteristic of pre-reforming. Carbonaceous deposit was analysed by TPO-MS method. The nature and location of the coke were studied by HRTEM. La or Ce addition into Ni–Al system causes the increase of the active surface area of Ni by enhancing its dispersion. Studies at kinetic regime have shown that the promoted catalysts have almost twice the activity than reference Ni–Al catalyst. This effect was not confirmed by measurements in the diffusion regime on whole catalyst tablets. Almost identical textural properties of catalysts and diffusive limitations related to them but not the catalytic properties of the material itself appeared to be crucial factors. The presence of La (but not Ce) causes a significant increase in resistance to coking. [Display omitted] • Ni/Al 2 O 3 and Ni/M/Al 2 O 3 (M = La or Ce) were tested in methane steam reforming. • Catalytic activity was evaluated both in the kinetic and diffusion regime. • The promoters increased the catalytic activity at kinetic regime almost twice. • An effect of additives was not confirmed in diffusive regime. • The addition of La 2 O 3 caused a significant increase in resistance to coking. [ABSTRACT FROM AUTHOR]

Abstract: The Fe2O3-based catalysts have numerous advantages for HT-deN2O process applications. The possibility of enhancing their activity by various metal oxide modifiers addition (Al, Zr, Ce, La, Cu, Cr) has been investigated. The catalysts were prepared by the coprecipitation method and their physicochemical properties were characterized by N2 sorption, XRF and XRD methods. A quartz gradientless reactor was used for activity evaluation at the temperature range of 500–900°C. The modifiers efficiency was compared and the activity of hematite catalysts at 800̊C was found to increase in the following order: Cr