Operando characterisation by DRX-DRIFT-GC of cobalt catalysts during the Fischer Tropsch synthesis

International @ INGENIERIE+LBC:YSCInternational audienceNon

How does activation affect the cobalt crystallographic structure? An in situ XRD and magnetic study

INGENIERIE+LBC:ELA:YSCFischer-Tropsch synthesis uses cobalt catalysts to convert syngas into linear hydrocarbons. Activation is the key step generating and impacting the active phase and more precisely the crystallographic structure of the metallic cobalt particles. This study investigates the selective crystallographic orientation of cobalt-supported catalysts and its impact on the degree of reduction. Three catalysts supported on alumina and silica with various particle sizes were prepared and characterized by ex situ techniques. They underwent two kinds of reduction processes carried out under different atmospheres. A carbidisation-decarbidisation cycle was also performed on reduced catalysts. The evolution of the active phase under reactive conditions was followed by in situ X-Ray Diffraction and magnetic measurements. The different reduction processes gave rise to the formation of metallic cobalt with mainly a face-centered cubic structure. The degree of reduction was also affected by the type of reduction process. Carbidisation-decarbidisation had no global impact on the reduction extent and allowed the formation of mainly hexagonal closed packed metallic cobalt. (C) 2013 Elsevier B.V. All rights reserved

Operando characterisation by DRX-DRIFT-GC of cobalt catalysts during the Fischer Tropsch synthesis

International @ INGENIERIE+LBC:LDR:YSCInternational audienceNon

Innovative low temperature regenerable zinc based mixed oxide sorbents for synthesis gas desulfurization

SSCI-VIDE+ECI2D+CGEInternational audienceZinc oxide-based materials are commonly used for the final desulfurization of synthesis gas in IGCC and Fischer-Tropsch based XTL processes. The formation of large amount of solid waste is the major issue of this process. In-situ oxidative regeneration is a promising way to reduce this waste formation and enhance desulfurization process efficiency and economics. However, previous studies showed that one of the major drawbacks of oxidative regeneration of sulfided oxides relies in the high operating temperature range required to overcome the formation of inhibitory sulfate phases. A preliminary work of the authors focused on single oxides identified that regeneration temperature of zinc oxide-based sorbent could be reduced through the addition of molybdenum oxide. Two composites oxides - a single oxides mixture (ZnO and MoO3) and a mixed oxide (ZnMoO4) - were synthesized and characterized. Their sulfidation and oxidative regeneration properties were investigated through thermogravimetry and in-situ characterizations. Sulfidation of the single oxides mixture was shown to be similar to the combination of the sulfidation of both independent single oxides. Mixed oxide sulfidation leads to ZnMoO4 phase demixing into ZnS, MoS2 and ZnMoO3. The oxidative regenerations of the sulfided single oxide mixtures and mixed oxide are initiated, respectively, at 350 degrees C and 300 degrees C. These temperatures are 250 degrees C and 300 degrees C lower than the regeneration temperature of a pure ZnS. For the sulfided mixed oxide regeneration is even complete at 500 degrees C under isothermal conditions. Regeneration of sulfided oxides mixture and mixed oxide was thus shown to exhibit synergetic effects, resulting from exothermic oxidative reactions of molybdenum phases. Heat energy released during these reactions is assumed to enhance ZnS oxidation kinetics at a temperature lower than the previously measured one. (C) 2014 Elsevier Ltd. All rights reserved

An X-ray diffractometer coupled with diffuse reflectance infrared Fourier transform spectroscopy and gas chromatography for in situ and in operando characterization: an innovative analytical laboratory instrument

INGENIERIE+LBC:YSCIn heterogeneous catalysis, chemical reactions take place at the surface of the material and can be influenced by its structure. To understand better the impact of the material surface and structure on catalytic properties, it is important to characterize them simultaneously. The association of X-ray diffraction and diffuse reflectance infrared Fourier transform spectroscopy, combined in a single dedicated high-temperature and high-pressure reaction cell with an online gas chromatograph, could be the answer to this challenge. For the first time, such an analytical tool has been developed for laboratory applications. The use of this device is illustrated, and it is validated through the in situ study of the thermal decomposition of calcium oxalate