Hard x-ray photon-in-photon-out spectroscopy with lifetime resolution – of XAS, XES, RIXSS and HERFD

Spectroscopic techniques that aim to resolve the electronic configuration and local coordination of a central atom by detecting inner-shell radiative decays following photoexcitation using hard X-rays are presented. The experimental setup requires an X-ray spectrometer based on perfect crystal Bragg optics. The possibilities arising from non-resonant (X-Ray Emission Spectroscopy - XES) and resonant excitation (Resonant Inelastic X-Ray Scattering Spectroscopy – RIXSS, High-Energy-Resolution Fluorescence Detected (HERFD) XAS) are discussed when the instrumental energy broadenings of the primary (beamline) monochromator and the crystal spectrometer for x-ray emission detection are on the order of the core hole lifetimes of the intermediate and final electronic states. The small energy bandwidth in the emission detection yields line-sharpened absorption features. In transition metal compounds, electron-electron interactions as well as orbital splittings and fractional population can be revealed. Combination with EXAFS spectroscopy enables to extent the k-range beyond unwanted absorption edges in the sample that limit the EXAFS range in conventional absorption spectroscopy

Nanocomposite MFI-alumina and FAU-alumina Membranes: Synthesis, Characterization and Application to Paraffin Separation and CO2 Capture

Rouleau, L. Pirngruber, G. Guillou, F. Barrere-Tricca, C. Omegna, A. Valtchev, V. Pera-Titus, M. Miachon, S. Dalmon, J. A.International audienceIn this work, we report the preparation of thermally and mechanically resistant high-surface (24-cm2) nanocomposite MFI-alumina and FAUalumina membranes by pore-plugging synthesis inside the macropores of α-alumina multilayered tubular supports. The MFI membranes were prepared from a clear solution precursor mixture being able to easily penetrate into the pores of the support. The MFI membranes were evaluated in the separation of n-/i-butane mixtures. The synthesis reliability was improved by mild stirring. The most selective MFI membranes were obtained for supports with mean pore sizes of 0.2 and 0.8 μm. The MFI effective thickness could be reduced to less than 10 μm by impregnating the support with water prior to synthesis and by diluting the synthesis mixture. The best MFI membrane offered an excellent tradeoff between selectivity and permeance at 448 K, with separation factors for equimolar n-butane/i-butane mixtures up to 18 and n-butane mixture permeances as high as 0.7 μmol$\cdot$s-1$\cdot$m-2$\cdot$Pa-1.Furthermore, a novel nanocomposite FAU membrane architecture has been obtained by an original synthesis route including in situ seeding using a cold gel-like precursor mixture, followed by growth of the FAU material by hydrothermal synthesis in two steps using a clear solution of low viscosity. This new membrane showed interesting performance in the separation of an equimolar CO2/N2 mixture at 323 K, with CO2/N2 separation factors and mixture CO2 permeances up to 12 and 0.4 μmol$\cdot$s-1$\cdot$m-2$\cdot$Pa-1,respectively

Caffeine Prevents Transcription Inhibition and P-TEFb/7SK Dissociation Following UV-Induced DNA Damage

Background: The mechanisms by which DNA damage triggers suppression of transcription of a large number of genes are poorly understood. DNA damage rapidly induces a release of the positive transcription elongation factor b (P-TEFb) from the large inactive multisubunit 7SK snRNP complex. P-TEFb is required for transcription of most class II genes through stimulation of RNA polymerase II elongation and cotranscriptional pre-mRNA processing. Methodology/Principal Findings: We show here that caffeine prevents UV-induced dissociation of P-TEFb as well as transcription inhibition. The caffeine-effect does not involve PI3-kinase-related protein kinases, because inhibition of phosphatidylinositol 3-kinase family members (ATM, ATR and DNA-PK) neither prevents P-TEFb dissociation nor transcription inhibition. Finally, caffeine prevention of transcription inhibition is independent from DNA damage. Conclusion/Significance: Pharmacological prevention of P-TEFb/7SK snRNP dissociation and transcription inhibitio

Mineralogical and geochemical analysis of Fe-phases in drill-cores from the Triassic Stuttgart Formation at Ketzin CO₂ storage site before CO₂ arrival

Reactive iron (Fe) oxides and sheet silicate-bound Fe in reservoir rocks may affect the subsurface storage of CO2 through several processes by changing the capacity to buffer the acidification by CO2 and the permeability of the reservoir rock: (1) the reduction of three-valent Fe in anoxic environments can lead to an increase in pH, (2) under sulphidic conditions, Fe may drive sulphur cycling and lead to the formation of pyrite, and (3) the leaching of Fe from sheet silicates may affect silicate diagenesis. In order to evaluate the importance of Fe-reduction on the CO2 reservoir, we analysed the Fe geochemistry in drill-cores from the Triassic Stuttgart Formation (Schilfsandstein) recovered from the monitoring well at the CO2 test injection site near Ketzin, Germany. The reservoir rock is a porous, poorly to moderately cohesive fluvial sandstone containing up to 2–4 wt% reactive Fe. Based on a sequential extraction, most Fe falls into the dithionite-extractable Fe-fraction and Fe bound to sheet silicates, whereby some Fe in the dithionite-extractable Fe-fraction may have been leached from illite and smectite. Illite and smectite were detected in core samples by X-ray diffraction and confirmed as the main Fe-containing mineral phases by X-ray absorption spectroscopy. Chlorite is also present, but likely does not contribute much to the high amount of Fe in the silicate-bound fraction. The organic carbon content of the reservoir rock is extremely low (<0.3 wt%), thus likely limiting microbial Fe-reduction or sulphate reduction despite relatively high concentrations of reactive Fe-mineral phases in the reservoir rock and sulphate in the reservoir fluid. Both processes could, however, be fuelled by organic matter that is mobilized by the flow of supercritical CO2 or introduced with the drilling fluid. Over long time periods, a potential way of liberating additional reactive Fe could occur through weathering of silicates due to acidification by CO2

Metal phosphides and zeolite-like mesoporous materials as catalysts

Two new classes of materials, which we developed and use in our catalytic research, are described. Metal phosphides are studied for their use as model compounds for hydrodenitrogenation catalysis. M41S type materials contain mesopores, which enhance diffusion and, thus, the effectiveness of zeolitic materials in liquid-phase reactions. After grafting with sulfonic acid groups, they are used as wide-pore solid acids

Post-Combustion CO

Simulation results in the literature suggest that Vacuum Swing Adsorption (VSA) processes using physisorbents might largely outperform the current state-of-the-art post-combustion CO2 capture technologies based on amine solvents in terms of energy consumption. Most studies consider the zeolite NaX as adsorbent. NaX has a very strong affinity for CO2 but is difficult to regenerate and very sensitive to the presence of water in the flue gas. By tuning the polarity of the adsorbent, it might be possible to find a better compromise between adsorption capacity, regenerability and sensitivity to H2O. In the present contribution, we therefore screen the performance of a series of zeolites as physisorbents in a VSA process for CO2 capture. The adsorbents are tested by breakthrough experiments of a dry and wet model flue gas, in once-through and cyclic operation. The most interesting material, zeolite EMC-1, is selected for numerical simulations of a full VSA cycle, in comparison with zeolite NaX. Both solids satisfy the performance targets in terms of recovery (> 90%) and purity of CO2 (> 95%) but the very low pressure required for regeneration of the adsorbents will be a serious handicap for the deployment of this technology on a large scale

kinetic study of the support acidity effects of nimo sulfide catalysts on quinoline hydrodenitrogenation

SSCI-VIDE+ECI2D+MNG:MTF:CGEInternational audienceThe improvement of hydrodenitrogenation (HDN) catalytic activity is important due to poisoning effects of nitrogen compounds on acidic catalysts and their inhibiting effects on hydrotreating reactions [1,2]. HDN reaction networks usually comprise a complex set of hydrogenation, ring opening and C-N bond breaking reactions. In order to understand how modifications of HDN catalysts act on this complex reaction network, a detailed kinetic analysis is necessary. In this work we present a very detailed kinetic study of the HDN of quinoline in a batch reactor. The Langmuir-Hinshelwood model includes liquid-vapor mass transfer, which is essential for obtaining reliable kinetic parameters. Each catalyst is tested at different concentrations of quinoline and different temperatures. Thus, 981 experimental points are obtained, which allow the simultaneous estimation of 39 parameters, i.e. activation energies and heat of adsorption. The catalytic tests were carried out over NiMo(P) sulfide catalysts supported on γ-Al2O3 and SiO2-Al2O3. Table 1 summarizes the characteristics and catalytic properties of the two catalysts.Table 1 â Characteristics and catalytic properties of the NiMo catalysts NiMo(P)/Al2O3NiMo(P)/SiO2-Al2O3Weight content of MoO3 / NiO, wt %18.6 / 3.8414 / 2.97Cyclohexane isomerization conversion, %2288NiMoS promoted phase content (mmol/g catal.)0.3260.205Position of NiMoS band in IR Spectroscopy of adsorbed CO (cm-1)21292134Effective rate constant of 14THQ â DHQ step (s-1)0.070.12Effective rate constant of OPA â PB step (s-1)0.0460.173Our kinetic modeling shows that the hydrogenation of 1,2,3,4-tetrahydroquinoline (14THQ) into decahydroquinoline (DHQ) is the determining rate step of the main reaction pathway for both catalysts. The NiMo(P)/SiO2-Al2O3 exhibits a higher rate constant in the hydrogenation of 14THQ and Csp2-N bond cleavage of o-propylaniline (OPA) into propylbenzene (PB). This is attributed to the modification of the electronic properties of promoted phase due to the higher acidity of NiMo(P)/SiO2-Al2O3, as confirmed by Infrared Spectroscopy of CO. The adsorption constants of nitrogen compounds are higher on NiMoP/SiO2-Al2O3 than on NiMoP/γ-Al2O3, which results in higher self-inhibition effects of quinoline and N compounds over NiMoP/SiO2-Al2O3. As a consequence of this higher self-inhibition, the overall activity of the silica-alumina supported catalyst becomes lower than for the alumina-supported catalyst

Vacuum gas oil hydrocracking performance of bifunctional Mo/ Y Zeolite catalysts in a semi-batch reactor

International @ RAFFINAGE+RHE:MTF:PAF:CLOInternational audienceA new approach has been developed to characterize bifunctional catalysts in a complex matrix of hydrotreated vacuum gas oil, 370°C+ using a batch reactor test. Triphasic reactions were carried out in a reactor equipped with a stationary basket, hydrogen injection and products sampling systems. Bifunctional catalysts containing different relative amounts of alumina-supported NiMo sulfide and zeolite were tested at 400°C under 120 bars over different reaction times. The repeatability of the test conditions was validated and the lack of mass transfer limitations at phase interfaces was confirmed. Gas and liquid samples were analyzed by one and two-dimensional gas chromatography (2D-GCGCxGC) respectively to obtain quantitative distributions of linear and branched paraffins, olefins, naphthenes and aromatics. The details of the products distribution provided by the chromatography were analyzed using model kinetic mechanisms of bifunctional catalysis. It has been established that the limiting step defining the total conversion is scission of the hydrocarbon chains on zeolite sites. The increase of the molybdenum to zeolite ratio provided an improvement of selectivity to middle distillate (150-370°C

Vapor-Liquid Equilibrium of Hydrogen, Vacuum Gas Oil, and Middle Distillate Fractions

RAFFINAGE+BBR:RHE:PAF:#30:MTFVapor-liquid equilibrium (VLE) data for hydrogen/hydrocarbon mixtures based on real feedstocks at high temperature and pressure is scarce and is needed to model hydrocracking systems accurately. Experiments with a vacuum gas oil have been used to generate VLE data for real hydrogen/hydrocarbon mixtures under hydrocracking conditions in a semibatch reactor with a range of compositions. Flash calculations were performed using a process simulation program and compared to the experimental results. The data was used to verify the existence of equilibrium conditions in the reactor and to show that the Grayson Streed activity coefficient model, combined with Peng-Robinson equation of state, provides a good estimate of liquid phase and vapor phase compositions and individual component volatility