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To minimize greenhouse gas emissions, efficient carbon dioxide capture and utilization need to be addressed. In this study, to determine the structure–activity interplay, three different promising catalytic systems for the CO2 hydrogenation process were synthesized using mesoporous silica SBA-15 as a support material: copper-based catalyst with zinc, indium-based catalyst with palladium and iron-based catalyst with potassium. The role of metal–metal oxide interaction has been showed. The use of Cu/Zn catalytic system and SBA-15 allowed to obtain very small crystallite size of tenorite and zinc oxide, good dispersion of active phases with strong basic sites. In order to find the most effective catalyst providing the maximal methanol yield and selectivity, these catalytic systems were compared under the same reaction conditions (250 °C, 20 bar, H2 to CO2 molar ratio 4 to 1) using fixed-bed tubular micro-activity reactor. Results showed that the highest methanol yield can be obtained with Cu/Zn/SBA-15 catalyst as might be expected according to obtained characterization. [ABSTRACT FROM AUTHOR]

A series of multicomponent oxide catalysts (CuO/ZnO/MemOn/ZrO2/SiO2, with Me = Mg, Ce, or La) was synthesized through a one-pot soft-template approach and used for CO2 hydrogenation to methanol. In the case of the La-containing catalysts, additional samples were prepared with CuO contents in the range 40–60 wt%. The influence of the catalyst composition on the physicochemical properties as well as the effect on the catalytic performance were investigated. The fresh catalysts were characterized in terms of composition, structure, textural properties, dispersion of the oxidic phases, and reducibility. On the reduced samples, structural and acid–base properties were also investigated, as well as specific metal surface area and dispersion of Cu0. After in situ H2-treatment at 250 °C, the catalysts activity was tested in a bench scale plant at 250 °C and 3.0 MPa, using a gas hourly space velocity of 24,000 Ncm3 h−1 gcat−1 and a H2/CO2 molar ratio equal to 3. It was found that the production of methanol is particularly favored by the introduction of La2O3, the highest value of methanol space–time yield (413 mg CH 3 OH h - 1 g cat - 1 ) being obtained on the CuO/ZnO/La2O3/ZrO2/SiO2 catalyst containing 50 wt% of copper oxide. [ABSTRACT FROM AUTHOR]

Nanosized NiO, CeO2 and NiO-CeO2 mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method. All the samples were characterized by different techniques as to their chemical composition, structure, morphology and texture. On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined. NiO and CeO2 nanocrystals of about 4 nm in size were obtained, regardless of the Ni/Ce molar ratio. The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO2 interface, where Ni species are in strong interaction with the support. The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that, unlike metallic nickel, CeO2 is able to effectively adsorb CO2, forming carbonates and hydrogen carbonates. After reduction in H2 at 400 °C for 1 h, the catalytic performance was studied in the CO and CO2 co-methanation reaction. Catalytic tests were performed at atmospheric pressure and 300 °C, using CO/CO2/H2 molar compositions of 1/1/7 or 1/1/5, and space velocities equal to 72000 or 450000 cm3·h−1·gcat−1. Whereas CO was almost completely hydrogenated in any investigated experimental conditions, CO2 conversion was strongly affected by both the CO/CO2/H2 ratio and the space velocity. The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO2 methanation. On a selected sample, the influence of the reaction temperature and of a higher number of space velocity values, as well as the stability, were also studied. Provided that the Ni content is optimized, the NiCe system investigated was very promising, being highly active for the COx co-methanation reaction in a wide range of operating conditions and stable (up to 50 h) also when submitted to thermal stress. [ABSTRACT FROM AUTHOR]