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International audience; Objectives: To evaluate the reliability of attenuation values of the liver parenchyma and focal liver lesions on virtual unenhanced images from arterial (VUEart) and portal venous phases (VUEport) compared to native unenhanced (NU) attenuation values in patients referred for assessment of malignant liver lesions.Methods: Seventy-three patients with confirmed primary or metastatic liver tumors who underwent a multiphase contrast-enhanced rapid-switching kVp dual-energy CT (rsDECT) were included in this IRB-approved retrospective study. Both qualitative and quantitative analyses - including the lesion-to-liver contrast-to-noise ratio (LL-CNR) - were performed and compared between NU and both VUEart and VUEport images.Results: The mean liver attenuation values were significantly lower in VUEart images (56.7 ± 6.7 HU) than in NU images (59.6 ± 7.5 HU, p = 0.008), and were comparable between VUEart and VUEport images (57.9 ± 6 UH, p = 0.38) and between VUEport and NU images (p = 0.051). The mean liver lesions attenuation values were comparable between NU, VUEart and VUEport images (p = 0.60). Strong and significant correlations values were found both in liver lesions and tumor-free parenchyma (r = 0.82-0.91, p < 0.01). The mean LL-CNR was significantly higher in VUEart and VUEport images than in NU images (1.7 ± 1 and 1.6 ± 1.1 vs 0.9 ± 0.6; p < 0.001), but was comparable between VUEart and VUEport images (p > 0.9). Lesion conspicuity was significantly higher in VUEport images than in NU images (p < 0.001).Conclusion: VUEport images derived from 3rd generation rsDECT could confidently replace NU images in patients undergoing assessment for malignant liver lesions. These images provide comparable attenuation values in both liver lesions and liver parenchyma while reducing the radiation dose and scanning time.

Introduction Pulmonary fibrosing sarcoidosis is associated with increased mortality. This study was aimed to explore the prognosis value of a panel of parameters for predicting mortality. Methods This retrospective study included 216 patients with confirmed stage 4 pulmonary sarcoidosis. Stage 4 diagnosis date served as baseline. The following information was systematically present at baseline: epidemiological characteristics; treatments; pulmonary function; composite physiologic index (CPI); systolic pulmonary artery pressure at echocardiography; pulmonary fibrosis extent, main pulmonary artery/ascending aorta diameters ratio (MPAD/AAD) and MPAD/body surface area (BSA) measured and calculated using computed tomography, Walsh's algorithm based on CPI, lung fibrosis extent and MPAD/AAD ratio, and modified Walsh's algorithm with MPAD/BSA replacing MPAD/AAD allowed to estimate good or bad prognosis profiles. The primary outcome of the study was all cause mortality and lung transplantation. The value of baseline parameters was tested as predictors of mortality using univariate and multivariate analyses. Results Median follow-up was 105 months. There were 41 deaths and 5 transplantations. At multivariate analysis, survival was independently predicted by several parameters including CPI, lung fibrosis extent, pulmonary hypertension at echography or MPAD/BSA ratio, Walsh's algorithm, and geographic origin. The modified Walsh's algorithm was most highly predictive. Conclusion Survival was best predicted by geographic origin, lung fibrosis extent, PH at echography or MPAD/BSA ratio, as well as by various scores among them the modified Walsh's algorithm had very high predictive value thanks to MPAD/BSA ratio which accurately predicted mortality.

The impact of recycling unconverted residue on slurry-phase hydroconversion performance was investigated in a continuous microscale pilot unit operated in once-through (OTOM) and recycling (ROM) op...

International audience; A detailed distributed lumped kinetic model for slurry phase Vacuum Residue hydroconversion process (boiling range 525 + °C) has been constructed. Simulated distillation and Gel Permeation Chromatography analysis results were combined to estimate feedstock and product compositions over the whole boiling range. The model uses 21 distributed lumps to represent the hydrocarbons, takes hydrogen consumption into account and calculates reaction rates using molar concentrations. Vapour liquid mass transfer resistances and vapour-liquid equilibrium are also accounted for. The resulting model represents the evolution of the reaction mixture physical properties well and provides a good fit with the experimental data. From estimated parameters, it is deduced that thermally activated and catalytic reactions in cascade occur simultaneously and also that material boiling above 750 °C is converted in a different manner to lighter material.

International audience; In this work, Arabian light atmospheric residue and Safaniya vacuum residue were hydroconverted in a slurry phase semi-batch stirred tank reactor at 15 MPa for a wide range of temperatures (420–440 °C) and reaction times up to 4 h. Experimental data was used to develop a semi-batch reactor model including vapor-liquid equilibrium, gas-liquid mass transfer and gas phase hydrodynamics. Mass transfer and kinetic parameters were estimated by minimizing not only the total masses of products but also the outlet gas flow dynamics. Mass transfer and hydrogen consumption were compared against former studies using a batch reactor, a continuous stirred tank reactor and work by other authors, reported in the literature. Higher hydrogen consumption was achieved with the semi-batch reactor and no hydrogen mass transfer limitation was observed. Therefore, it was concluded that this setup is more suited and reliable for studying the chemical kinetics of slurry-phase hydroconversion of petroleum residues and permits improved representation of the role of hydrogen compared with current models.

MICROSCOPIE+ECI2D+MTF:MLA:DGO:MAO:RBA:PAF:CGE; International audience; Hydroconversion of an atmospheric residue (AR) was performed in an autoclave with Mo, Ni, V compounds applied as precursors of the dispersed sulfide catalysts. The reaction was conducted at 450 degrees C, residence time 1 h and the catalyst concentration in the range of 300-900 ppm. AR conversions were compared for the reaction carried out in the presence of sole metals and for the mixtures of two metals. By mixing of the Ni and Mo precursor salts together, improvement in the total conversion and hydrodesulfurization (HDS) degree of the AR was observed, indicating on a significant synergy between Ni and Mo dispersed sulfides. By contrast, in the case of V and Mo precursors mixture the total activity was just a sum of the contributions from two respective metals. With the support provides by high resolution microscopy (HRTEM) and core-hole X-ray absorption spectroscopy (XAS) it was concluded that in the case of mixed Ni-Mo catalyst, MoS2 slabs were deposited on the surface of Ni3S2 crystallites, providing a reverse synergistic effect. (C) 2015 Elsevier Ltd. All rights reserved.

An in situ time-resolved XRD/XANES/EXAFS investigation combined with on-line evaluation of catalytic performance indicates considerable structural transformations of the conventional Pt-promoted alumina supported cobalt catalyst under the realistic conditions of Fischer–Tropsch synthesis. Cobalt and platinum are reduced into metallic states after pre-treatment in hydrogen at 623 K and form Co–Pt bimetallic nanoparticles. Depending on catalyst and reaction conditions, the metallic nanoparticles can undergo sintering, carbidisation, and fcc–hcp phase transformations. The observed changes in the catalyst structure significantly affect the performance in the Fischer–Tropsch reaction. Cobalt hcp phase seems more active in Fischer–Tropsch synthesis than cobalt fcc metal phase.

The structure of alumina-supported cobalt catalysts promoted with platinum and their catalytic performance in Fischer–Tropsch synthesis were investigated under realistic reaction conditions ( P = 20 bar, T = 493 K) using in situ time-resolved X-ray diffraction with simultaneous analysis of reaction products. The catalysts were prepared via incipient wetness impregnation and characterized by a wide range of ex situ techniques. Direct in situ measurements were indicative of considerable versatility of alumina-supported cobalt catalysts during Fischer–Tropsch synthesis. Cobalt sintering occurred at the first hours of the reaction and resulted in a significant drop of the catalytic activity. In addition to sintering, partially oxidized catalysts containing smaller cobalt particles (mean particle size 2 C cobalt carbide. Cobalt carbidization followed by hydrogenation selectively led to cobalt hcp metallic phase, which seems to be more active in Fischer–Tropsch synthesis than cobalt fcc phase. Cobalt oxidation by water was not significant in the catalysts with metal particles larger than 5 nm even at high water concentrations.

The structure–activity relations in the alumina-supported cobalt catalysts are studied at the realistic conditions of Fischer-Tropsch synthesis using in situ time-resolved XRD and catalytic measurements. Cobalt sintering during the first 3–5 h of the reaction and cobalt carbidisation at a longer time on stream (>8 h) coincide with catalyst deactivation.

International audience; A 2D G-S pseudo-homogeneous steady-state plug flow, non-isobaric and non-isothermal model is used to investigate the effects of operating conditions and catalyst thermal properties on the behaviour of a multi-tubular fixed bed for Fischer–Tropsch synthesis. This simulator allows observing, quantifying and discussing the influences of the gas velocity, the tube diameter, the type of catalyst used (monolithic foam or extrudates) and the heat conductivity of the support (alumina or silicon carbide). The observed responses are the effective thermal parameters of the catalytic bed, the radial and axial temperature profiles and the global performances of the reactor (yield, productivity and selectivity). Thermal properties of the support exhibit a strong influence when low fluid velocities and/or large tube diameters are employed. Because of the high void fraction of a foam structure these effects are less pronounced than with packed beds. This structural difference allows a wider range of operating conditions in terms of fluid velocity and tube diameter but underlines the necessity to tune the void fraction of a foam bed to obtain the best compromise between its volumetric catalytic activity and a good thermal behaviour.

The use of porous structures with high external surface area represents an important breakthrough in industrial applications. Foam structures receive more and more scientific and industrial interest as catalyst support. Knowledge of pressure drop induced by these foam matrices is essential for successful design and operation of high performance industrial systems. In this context, the aim of this paper is to critically review the relation between permeability and structural parameters of the different foam structures. This work is willing to examine the effect of a large number of structural parameters (struts diameter, porosity, size of pores, specific surface area …) in the prediction of bed permeability based on principals of experimental and theoretical works on the single-phase flow model found in the literature. The state-of-the-art of modeling pressure drop in foams is summarized in Table 1. The goal was to assess and to critically evaluate all available design tools, whether empirical or theoretical.

Foam-structured beds are likely to be the next generation of catalyst supports due to their interesting specific properties (large exchange area, low pressure drop, easy control of external porosity, etc.). Nevertheless, chemical engineering parameters of this new catalyst support types are still not completely clear for the scientific community and many approaches are attempted to solve this problem. SiC foams offer the dual advantages of the interesting properties of structured beds and the intrinsic thermal and mechanical properties of silicon carbide as a catalytic support. In the present work, the problem of pressure drops along foam beds is studied with a new simplistic geometrical model as a first step in the understanding of the peculiar hydrodynamic behavior of SiC foams in chemical processes. The proposed model was successfully validated by experimental results on a relatively large range of parameters which fully confirm the validity of the model.

Reduction of (NH4)2MoS4 with N2H4 in aqueous solution in the presence of alumina suspension leads to the formation of a highly dispersed MoS2 supported on the surface of Al2O3. In the model thiophene desulfurization reaction, these MoS2/Al2O3 catalysts show a linear increase of catalytic activity as a function of Mo content up to 22 wt% of molybdenum. This preparation method makes it possible to efficiently disperse amounts of the active sulfide phase on alumina much higher than those of conventional systems prepared by impregnation. Promoted by Co, these materials exhibit a HDS catalytic activity much higher than that of a commercial CoMo/Al2O3 catalyst used as a reference.

An alumina supported CoMo catalyst was activated in the temperature range 295–773 K with H2/H2S. At several temperatures, elemental analysis, EDX, XPS and TPO techniques were used to measure the degree of sulfidation, expressed as the S/(Co+Mo) atomic ratio. A particular attention was paid to EDX analysis. A remarkable agreement was obtained between elemental analysis, EDX and XPS. No quantitative information but qualitative ones could be obtained from TPO. An attempt was made to relate catalyst sulfidation with the catalytic activity in thiophene and tetralin model reactions of hydrotreatment.

This work reports a systematic study of the changes in the catalytic activities and in adsorptive properties of ruthenium sulphide with sulphur removal. From physicochemical characterization of the reduced samples it is shown that 50% of the initial sulphur content can be eliminated without changing the structure and the morphology of the pyrite phase. The adsorption of CO, NO and H 2 S increases with the degree of reduction of the solid. However, the maximum of adsorption capacities for these probe molecules does not correspond to the maximum of catalytic activity observed for the reactions of H 2 -D 2 exchange and 1-butene hydrogenation. This suggests that distinct sites are required for adsorption and for catalysis. The use of ammonia as probe molecule seems to be a good tool for determining the Bronsted acidic surface sites. From thermoflash desorption of hydrogen, it has been demonstrated that two different species are retained by the catalyst: one adsorbed on surface sulphur atoms and the other one adsorbed on coordinatively unsaturated ruthenium cation. The concentration of the latter correlates fairly well with the catalytic activities.