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Cobalt distribution between the external surface and micropores and acidity of the large pore BEA zeolite were controlled by choosing the sequence of impregnation and ion exchange procedures. Higher concentration of ion exchangeable cobalt was observed in the catalyst prepared by ion‐exchange of the zeolite proton form. The presence of Na+ instead of H+ ions in the exchange positions of zeolite favored deposition of cobalt on the external surface. The acid sites in the zeolite micropores can be then restored by subsequent ion exchange of sodium with ammonium nitrate and calcination. The catalytic performance of the cobalt zeolite catalysts prepared using different impregnation and ion exchange procedures was tested in the Fischer‐Tropsch synthesis. Higher reaction rates were observed over the catalysts, which did not contain cobalt ions in the cation sites of the zeolite. Lower methane selectivity, higher selectivity to long chain hydrocarbons and high fraction of isomerized products are observed when cobalt species are located on the zeolite outer surface and acid sites inside the BEA zeolite micropores. Ion launch sequence: Impregnation and ion exchange sequences control metal localization, acidity, diffusion and performance of cobalt‐BEA catalysts for Fischer‐Tropsch synthesis [ABSTRACT FROM AUTHOR]

Mg-Co-Al mixed oxides were synthesized by the precipitation method and evaluated for dry reforming of methane. The samples were characterized by thermal techniques (TGA/DTA, NH3-TPD, H2-TPR, and TPO), specific surface area, and X-ray diffraction (XRD). Activity runs were conducted at atmospheric pressure, temperatures between 400 and 550°C, a CH4/CO2molar ratio of 1, and a space velocity of 6000 NmL CH4/g/h. The partial substitution of Co with Mg increased the surface area and thermal stability and changed the reducibility and acid-base properties of the samples. These modifications led to a higher activity for dry reforming of methane for the catalyst with Mg/Co = 0.5, primarily due to its enhanced thermal stability. However, its higher activity was followed by higher amounts of coke. The different activation procedures highlighted Co3O4as the main active phase rather than the Co-mixed oxides. Therefore, milder activation temperatures are required to properly reduce the Co3O4phase and avoid sintering. [ABSTRACT FROM PUBLISHER]

Abstract: Ni–Mg–Al catalysts prepared by continuous coprecipitation were evaluated for carbon dioxide reforming of methane carried out between 500 and 700°C. The mixed oxides obtained after calcination exhibit higher surface area values and lower crystallinity. The activity results obtained with different samples demonstrated that the catalytic properties of Ni–Mg–Al catalysts are more affected by the MII/MIII ratio than the Ni/Mg ratio. For samples with constant MII/MIII ratio the best results were obtained for 5≥Ni/Mg>1 ratios. Among the thermal pretreatment effects, the reduction temperature was revealed as a strong influence on the activity and selectivity for the CO2 reforming of methane. In contrast, the catalytic properties can be considered practically independent from the calcination temperature, and the influence of this parameter is restricted to the decrease of the surface area values with the increase of the calcination temperature. [Copyright &y& Elsevier]