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International audience; Recent advances in instrumentation for high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have enabled access to ∼70 »000 unique molecular formulas in broadband mass spectral characterization of unfractionated/whole asphaltenes. The results accumulated over a decade highlight the need for an asphaltene molecular model that acknowledges the coexistence of (1) monofunctional and polyfunctional species; (2) island and archipelago structural motifs; and (3) heteroatom-depleted/highly aromatic compounds, as well as atypical species with low aromaticity but increased heteroatom content. Collectively, results from FT-ICR MS, preparatory-scale separations (extrography/interfacial material), gel permeation chromatography, precipitation behavior in heptane:toluene, thermal decomposition, and aggregate microstructure by atomic force microscopy (among other techniques), suggest that the strong aggregation of asphaltenes results from the synergy between several intermolecular forces: π-stacking, hydrogen bonding, London forces, and acid/base interactions. This review presents general features of asphaltene molecular composition reported over the past five decades. We focus on mass spectrometry characterization and expose the reasons why early results supported the dominance of single-core motifs. Then, the discussion shifts to recent advances in instrumentation for high-field FT-ICR MS, which have enabled the detection of thousands of species in asphaltene samples, whose molecular composition and fragmentation behavior in ultrahigh vacuum agree with the coexistence of single-core and multicore structural motifs. Furthermore, evidence that highlights the limitations of commercially available/custom-built ion sources and selective ionization effects is presented. Consequently, the limitations require separations (e.g., chromatography, extrography) to gain more-comprehensive molecular-level insights into the composition of these complex organic mixtures. The final sections present evidence for the role of aggregation in selective ionization and suggest that advanced characterization by both thermal desorption/decomposition and liquid chromatography with online FT-ICR MS detection can be employed to mitigate the effects of aggregation and provide unique insights in molecular composition/structure.

To satisfy the global demand, more and more high quality fuels pure or converted from heavy oil cuts, such as vacuum gas oil (VGO), into highly refined fuels, are demanded1. To meet this increasing...

International audience; Solid circulation in chemical looping combustion (CLC) is very important and affects the mass and heat balance and autothermal operation of a CLC system. A key task in developing CLC technology is to control the solid circulation. In this work, the solid circulation characteristic of a 1.5 MWth CLC cold flow model is reported. The solid circulation between the fuel reactor and the simplified air reactor riser is controlled by the overflow method. Three kinds of quartz sands are selected as fluidized particles, and their median particle diameters are 392, 249, and 122 μm, respectively. A reasonable pressure profile is obtained in the 1.5 MWth CLC cold flow model. The effects of operational parameters, including the fuel reactor gas velocity, loop seal gas velocity, simplified riser gas velocity, particle size, and static bed height, on the solid circulation and hydrodynamic characteristics are measured and analyzed. The maximum solid circulation rate can approach 130 kg/(m2·s), and this value satisfies the requirements of mass and heat balance in the CLC system. The static bed height in the fuel reactor should be higher than the overflow port to prevent it from becoming a constraint factor on the solid circulation rate. An overflow model is developed to predict the solid circulation rate, and the relative errors between the predicted result and the experimental data are within 25%.

Slurry phase hydroconversion is a developing technology with the potential to completely upgrade Vacuum Residues (VR). In this work we use data from a continuous pilot plant with recycle to test and extend an existing distributed lumped kinetic model. The new data includes results from 134 steady state experiments with a Heavy Iran VR, including some at very high conversion, and allows sediment production rates to be quantified as well as sulphur removal in the form of H2S. The purpose of the work is to study the impact of the deep conversion reaction conditions and feedstock on the reaction kinetics. The model uses nineteen distributed lumps to represent the heavy hydrocarbons undergoing hydroconversion and hydrodesulphurisation with VR defined as the boiling range > 525°C. Reaction rates are based on molar concentrations. Hydrogen consumption and sediment production are taken into account in the model, as well as vapour liquid mass transfer resistances and vapour-liquid equilibrium. Parameter estimation has been carried out and the model provides a good fit with the experimental data. The modelling exercise found that, at very high conversions, thermal reactions give way to a cascade of catalytic reactions. The model gave a moderate fit for hydrogen consumption rates, which are strongly dependent on feedstock. Accumulation of sediment at high conversions was identified and well represented and the description of hydrodesulfurisation rates as proportional to cracking rates was validated.

International audience; Mineral base oils are used to produce commercial lubricants and are obtained from refining vacuum residue. Lubricants are used to reduce friction in industry devices, so their viscosity is a key characteristic that needs to be optimized throughout the process. The purpose of this study is to show how global chemical characterization of samples from the base oil production chain can facilitate a better understanding of the molecular impacts of processing and their effect on macroscopic properties like viscosity. Eight different samples were characterized by different analytical techniques, including liquid chromatography and mass spectrometry techniques, to understand their chemical evolution through the different process units at the molecular level. Furthermore, a statistical treatment allowed for the identification of parameters that influence viscosity, mainly sulfur and polyaromatics content. This study demonstrates the importance and effectiveness of cross-checking results from different complementary analytical techniques to acquire valuable data on lubricating oil base samples.

International audience; Asphaltenes, as the heaviest and most polar fraction of petroleum, have been characterized by various analytical techniques. A variety of fractionation methods have been carried out to separate asphaltenes into multiple subfractions for further investigation, and some of them have important reference significance. The goal of the current review article is to offer insight into the multitudinous analytical techniques and fractionation methods of asphaltene analysis, following an introduction with regard to the morphologies of metals and heteroatoms in asphaltenes, as well their functions on asphaltene aggregation. Learned lessons and suggestions on possible future work conclude the present review article.

International audience; Asphaltenes are among the most challenging components in petroleum processing because they contain high amounts of heteroatoms (i.e., S, N, O, V, and Ni) thought to be responsible for strong aggregation tendencies, precipitation, and fouling problems. The role of vanadium- and nickel-containing petroleum compounds (i.e., petroporphyrins) in aggregation and fouling is not completely understood because asphaltene composition and structure is still a subject of debate in the petroleum chemistry community. Characterization of asphaltenes, namely, molecular analysis that employs no chromatographic separation, often fails to reveal their comprehensive composition. The work herein presents asphaltene fractionation by (1) solid/liquid extraction, which allows for separation of single-core (“island”) and multicore (“archipelago”) structural motifs and by (2) high-performance thin layer chromatography (HPTLC) with cellulose as the stationary phase and DCM/MeOH as the eluent, which facilitates access to petroporphyrins. Characterization is performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI FT-ICR MS). The results demonstrate that even with multiple separation steps, a large quantity of vanadyl porphyrins remains inaccessible for molecular analysis by MALDI FT-ICR MS, which raises the question of what portion of a complex sample of asphaltene can be revealed by ultrahigh resolution mass spectrometry. Furthermore, the results show that easily accessible porphyrins migrate with the solvent front in HPTLC. Thus, HPTLC can be used to isolate and identify “free” porphyrins not locked into asphaltene aggregates; however, further development of separation methods is required to access the most difficult and problematic asphaltene fractions, which do not migrate and impose analytical challenges due to their stronger aggregation tendency.

International audience; The numerical simulations on the large-scale fluidized beds still remain challenging due to the computational limitation and experimental validation. In the present work, a CFD study of a large-scale fluidized bed is investigated using the NEPTUNE_CFD code based on an Eulerian n-fluid modeling approach. A SubGrid Scale (SGS) drag model based on the filtered approach is used to take into account the effect of very small solid structures unresolved with the coarse mesh. The numerical results are compared with the experimental data carried out in a pilot-scale fluidized bed unit and provided by Particulate Solid Research Inc (PSRI). By applying the SGS drag model without any specific or empirical tuning, mesh-independent numerical results are obtained. The flow regimes inside the fluidized bed are well predicted for all the superficial gas velocities studied here. The bed density profiles and the solid entrainment fluxes are also in good agreement with the experimental measurement.  The large-scale fluidized bed simulations are validated against PSRI experiments for different flow regimes from turbulent to fast fluidization.  A SGS drag model based on the filtered approach is using without any specific or empirical tuning which shows certain universality.  The gas-solid flows inside the fluidized bed with different gas velocities are characterized.  The validation in this study is a critical step toward industrial-scale fluidized bed simulations. Gas-solid fluidized bed simulations using the filtered approach: Validation against pilot-scale experiments Abstract The numerical simulations on the large-scale fluidized beds still remain challenging due to the computational limitation and experimental validation. In the present work, a CFD study of a large-scale fluidized bed is investigated using the NEPTUNE CFD code based on an Eulerian n-fluid modeling approach. A SubGrid Scale (SGS) drag model based on the filtered approach is used to take into account the effect of very small solid structures unresolved with the coarse mesh. The numerical results are compared with the experimental data carried out in a pilot-scale fluidized bed unit and provided by Particulate Solid Research Inc (PSRI). By applying the SGS drag model without any specific or empirical tuning, mesh-independent numerical results are obtained. The flow regimes inside the fluidized bed are well predicted for all the superficial gas velocities studied here. The bed density profiles and the solid entrainment fluxes are also in good agreement with the experimental measurement.

Palladium-based catalysts are known to promote the selective hydrogenation of acetylene to ethylene. Unfortunately, coupling reactions between the numerous surface intermediates generated in this process occur alongside. These side reactions are undesired, generating the so-called “green oil”, i.e., C4+ hydrocarbons that poison the active sites of the catalyst. The current work assesses the energetic and kinetic aspects of C4 side products formation from the standpoint of computational chemistry. Our results demonstrate that the C–C coupling of common surface species, in particular acetylene, vinylidene, and vinyl, is competitive with selective hydrogenation. These C–C couplings are particularly easy for intermediates where the C–Pd bond can largely remain intact during the coupling. Furthermore, the thus formed oligomers tend to be hydrogenated more easily, consuming hydrogen normally spent on acetylene hydrogenation. The analysis of site requirement suggests that isolated Pd2 ensembles are sufficient fo...

International audience; This paper proposes a particular study of the classic internal model control algorithm for a sampled- data system in a generalized context of uncertainty. Besides the usually considered model mismatch, the particularity of the case under consideration is that the measurements available to the control algorithm suffer from large, varying and uncertain delays. The presented study considers a simple SISO nonlinear system. The control algorithm is a sampled nonlinear model-based controller with successive model inversion and bias correction. The main contribution of this article is its proof of global convergence and robustness despite time-varying delays and uncertain measurement dating. In particular, the model error, the varying delays and measurements dating error are treated using monotonicity of the system and a detailed analysis of the closed-loop behaviour of the sampled dynamics, in an appropriate norm.

This article reports the developments of the technology used at TOTAL for estimating, controlling and optimizing the quality of fuels produced in refineries. Some key difficulties and practical problems are discussed along with a schematic description of the developed solutions and on-going research efforts.

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 study, carbon nanotubes (CNTs) were formed on a high-carbon 25Cr35Ni–Nb cast alloy using a laboratory-scale experimental set-up that simulated favorable conditions for CNT growth in the presence of ethane and water vapor. After 45 min of exposure to the reactive atmosphere, the entire sample surface was covered with multiwalled nanotubes with an average diameter of approximately 50 nm, indicating the strong catalytic activity of the alloy surface. Transmission electron microscopy combined with energy-dispersive X-ray spectroscopy analyses revealed the presence of iron-containing Ni3C-based catalytic particles at the nanotubes tip. The origin of the nickel in the system was then investigated via cross-sectional observations and discussed. A mechanism similar to the so-called “ex-solution” process was proposed to explain the presence of catalytic particles, while their stability was attested by thermodynamic considerations. A scenario describing the different steps involved in the CNTs formation on the oxide scale is finally proposed.

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.

The microstructure of a centrifugally cast HP alloy was studied in its as-received state and after ageing at 900 °C. A multi-scale approach combining X Ray Diffraction (XRD), advanced electron microscopy modes (scanning and transmission electron microscopies (SEM, TEM), together with focused ion beam/SEM nanotomography (FIB-nt)) has been carried out to characterize the evolution of niobium carbides during ageing. After thermal treatment, the carbides exhibit a complex microstructure, consisting of a core of untransformed NbC, an intermediate layer of G-phase (Ni16Nb6Si7) with embedded nanometric titanium carbide precipitates, and an outer shell of alternating chromium carbides Cr23C6 and G-phase. A simple diffusion model was used to explain the faster external growth of G-phase compared to the internal NbC dissolution, and to determine a diffusion coefficient of niobium in the G-phase at 900 °C.

Restructuring of alloy surfaces induced by strongly bound adsorbates is a well-established phenomenon occurring in catalysis and membrane science. In catalytic processes, this restructuring can have profound effects because it alters the ensemble distribution between the as-prepared state of the catalyst and the catalytic surface under operando conditions. This work assesses the restructuring of Pd–Ag alloys induced by adsorption of acetylene in the framework of the ensemble formalism. A detailed Ising-type model Hamiltonian of the (111) surface plane is fitted to extensive density functional theory computations. The equilibrium distributions under a realistic environment are then evaluated by a Monte Carlo approach as a function of temperature and alloy composition. Acetylene induces a strong reverse segregation within the relevant range of temperature. Therefore, the surface of Pd–Ag catalysts is almost entirely covered by Pd for bulk ratios

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International audience; Petroleum and its fractions are some of the most complex mixtures found in analytical chemistry. Mass spectrometry currently plays an increasing role in the characterization of these matrices. Since the last review on this topic in 2011, several new approaches have been introduced, and these approaches increasingly use sample fractionation by extraction and/or liquid chromatographic techniques. This review considers molecular mass spectrometry (with special emphasis on the use of ion mobility) and inorganic mass spectrometry. The combination of both techniques paves the way to "petrointeractomic" approaches, which are introduced as a novel, important part of "petroleomic" approaches.

International audience; The size distributions of sulfur (S), vanadium (V), and nickel (Ni) compounds in four crude oils, two residues, and their saturate, aromatic, resin, and asphaltene (SARA) fractions were determined using gel permeation chromatography (GPC) coupled to inductively coupled plasma high-resolution mass spectrometry (ICP HR MS). The results show trimodal distributions of V, Ni, and S compounds in the crude oils and residues. V and Ni compounds are present in both resins and asphaltenes. Trimodal distributions are clearly apparent in the resins but not apparent in the asphaltenes. In the latter, the predominant compounds have a high molecular weight (HMW), even when the solution of asphaltenes is diluted by 40000-fold. In the resins, compounds with a medium molecular weight (MMW) were expected; however, HMW compounds were observed, indicating that nanoaggregates or large molecules exist in both the asphaltenes and resins. Low-molecular-weight (LMW) compounds are predominantly present in the resins and do not represent more than 22% of V and Ni present in crude oil. These compounds appear to have molecular weights similar to simple metalloporphyrins.

International audience; The heat capacities at constant pressure of FAMEs were measured within the temperature range of 250-390 K. The measurements were performed on 7 pure saturated fatty acid methyl esters and 5 unsaturated fatty acid methyl esters. These data were then employed to calculate heat capacities of four different biodiesels (rapeseed and soybean origins) through an ideal mixing rule. The calculated and the experimental heat capacity of these biodiesels were then compared and an absolute average deviation of 0.9% was observed.

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SSCI-VIDE+ECI2D+PAL:CGE; International audience; Previously, using a batch reactor, Nguyen et al. (2013) proposed a kinetic model for atmospheric residue hydroconversion wherein residue consumption rate depends on residue and dissolved hydrogen concentrations. In the present work, a new kinetic study was carried out in a semi-batch reactor at 420 and 430°C, total pressure of 15 MPa and different reaction times (0, 30, 60 and 120 min). Nguyen’s kinetic model was improved by introducing a hydrodesulfurization (HDS) reaction and modeling the gas flow dynamics at the outlet of the semi-batch reactor. A new set of kinetic parameters for atmospheric residue hydroconversion has been estimated using a nonlinear least-squares regression on the total mass of products and the dynamics of outlet gas flow. In comparison to Nguyen’s kinetic study performed in a batch reactor, the results of the present work do not show any mass transfer limitation for H2 from gas to liquid in the semi-batch reactor. A high value of kLa was obtained confirming the high efficiency of this kind of apparatus to estimate the kinetic parameters. Moreover, the differences found between the values of kinetic parameters obtained in both batch and semi-batch reactors were explained by a free radical kinetic model.

International audience; The melting temperature of fatty acid methyl esters (FAMEs) have been measured both at atmospheric pressure by using a μDSC calorimeter and at high pressure (up to 80 MPa) thanks to a dedicated microscope. The values obtained at atmospheric pressure have been compared with literature data. The influence of the chain structure on the melting temperatures has been discussed, as well as the slopes of the liquid-solid transition curves in the (T, P) diagram. The experimental results have efficiently allowed predicting the solid molar volume and consequently, the difference between the volume in liquid and solid phases has been evaluated

International audience; A circulating turbulent fluidized bed connected with a riser and an annular carbon stripper (CS) is proposed to be used as a fuel reactor (FR) in chemical looping combustion. The bottom section of the FR is operated under a turbulent fluidization regime, which can achieve enough solid residence time and enhance the mixing of the oxygen carrier with solid fuel. A 1.5 MWth cold model of the FR was designed, constructed, and tested to investigate the hydrodynamics of solid particles with different sizes. Three kinds of quartz sands with different particle sizes (d50 = 122, 249, and 392 μm) were used as bed materials to simulate the oxygen carrier. Continuous operation with a reasonable pressure balance was achieved in the cold model. The effects of important variables, including gas velocity, static bed height, and particle size, on the gas–solid hydrodynamics of the FR were measured and discussed. It was found that the transition velocities from bubbling to turbulent fluidization for different particles of d50 = 122, 249, and 392 μm were measured to be 0.78, 0.95, and 1.06 m/s, respectively, indicating that the transition velocity increased with increasing the particle size. The solid fraction profile along the reactor height and solid circulation rate were affected by gas velocity and static bed height. A modified correlation was proposed to predict the solid fraction of the annular CS dilute phase, and the predicted results agree well with the experimental data under a wide range of operational conditions.