Axel Löfberg

Nickel ferrite spinel as catalyst precursor in the dry reforming of methane：Synthesis,characterization and catalytic properties

Abstract Dry reforming of methane by CO2 using nickel ferrite as precursor of catalysts was investigated. Nickel ferrite crystalline particles were prepared by coprecipitation of nitrates with NaOH or ammonia followed by calcination, or by hydrothermal synthesis without calcination step. The textural and structural properties were determined by a number of analysis methods, including X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), among which X-ray diffraction (XRD) was at room and variable temperatures. All synthesized oxides showed the presence of micro or nanoparticles of NiFe2O4 inverse spinel, but Fe2O3 (hematite) was also present when ammonia was used for coprecipitation. The reducibility by hydrogen was studied by temperature-programmed reduction (TPR) and in situ XRD, which showed the influence of the preparation method. The surface area (BET), particle size (Rietveld refinement), as well as surface Ni/Fe atomic ratio (XPS) and the behavior upon reduction varied according to the synthesis method. The catalytic reactivity was investigated using isopropanol decomposition to determine the acid/base properties. The catalytic performance of methane reforming with CO2 was measured with and without the pre-treatment of catalysts under H2 in 650-800 °C range. The catalytic conversions of methane and CO2 were quite low but they increased when the catalysts were pre-reduced. A significant contribution of reverse water gas shift reaction accounted for the low values of H2/CO ratio. No coking was observed as shown by the reoxidation step performed after the catalytic reactions. The possible formation of nickel-iron alloy observed during the study of reducibility by hydrogen was invoked to account for the catalytic behavior.

Elucidating the genesis of Bi2MoO6 catalyst by combination of synchrotron radiation experiments and Raman scattering

Combination of in situ Raman scattering with high-resolution XRD and XAS techniques has proven to be a powerful tool to elucidate the crystal growth of gamma-Bi2MoO6 under hydrothermal conditions.

Catalytic dense membranes of doped Bi4V2O11 (BIMEVOX) for selective partial oxidation: chemistry of defects versus catalysis

A catalytic dense membrane reactor (CDMR) is used to physically separate the reaction step from the reoxidation of the catalyst. By decoupling the redox mechanism prevailing in mild oxidation of hydrocarbons, the operating conditions may be optimized resulting in an increase of selectivity. The membranes are made up of BIMEVOX oxides, obtained by partial substitution of V in γ-Bi4V2O11 by ME (Co, Cu, Ta). Experiments performed on BIMEVOX dense membranes using propene and propane are described in terms of, (i) active sites on polished or unpolished surfaces, (ii) operating conditions (T, pO2 in the high oxygen partial pressure compartment), which determine the selectivity, either to mild oxidation products (acrolein, hexadiene, CO), or to partial oxidation products (CO, H2), and, (iii) nature of ME cations and relative properties. The discussion deals with the respective role of electronic versus oxide ion conductivities which depend on defects in the structure as well as on the redox properties of cations.

The pivotal role of catalysis in France: selective examples of recent advances and future prospects

The Review describes the most significant results achieved in France in the field of heterogeneous catalysis over the last 10 years and placed in the context of international research. The focus lies on the research conducted in French academic laboratories, often in close collaboration with industrial partners. A wide range of heterogeneous catalysis is covered, including ab initio calculations, biomass conversion, catalytic cracking, catalyst characterization, CO2 conversion, Fischer–Tropsch, pollution abatement, power‐to‐gas and kinetics.