178 research outputs found
Expression of the nociceptin precursor and nociceptin receptor is modulated in cancer and septic patients
No full textA role of nociceptin and its receptor (NOP) in pain and immune function has been suggested. The hypothesis was that mRNA expression of NOP and the nociceptin precursor pre-pronociceptin (pN/OFQ) in peripheral blood cells differs in end-stage cancer patients suffering from chronic pain and septic intensive care unit (ICU) patients compared with healthy controls
Bimetallic CoMoS Composite Anchored to Biocarbon Fibers as a High-Capacity Anode for Li-Ion Batteries
No full textOur work reports the hydrothermal
synthesis of a bimetallic composite
CoMoS, followed by the addition of cellulose fibers and its subsequent
carbonization under Ar atmosphere (CoMoS@C). For comparison, CoMoS
was heat-treated under the same conditions and referred as bare-CoMoS.
X-ray diffraction analysis indicates that CoMoS@C composite matches
with the CoMoS4 phase with additional peaks corresponding
to MoO3 and CoMoO4 phases, which probably arise
from air exposure during the carbonization process. Scanning
electron microscopy images of CoMoS@C exhibit how the CoMoS material
is anchored to the surface of carbonized cellulose fibers. As anode
material, CoMoS@C shows a superior performance than bare-CoMoS. The
CoMoS@C composite presents an initial high discharge capacity of ∼1164
mA h/g and retains a high specific discharge capacity of ∼715
mA h/g after 200 cycles at a current density of 500 mA/g compared
to that of bare-CoMoS of 102 mA h/g. The high specific capacity and
good cycling stability could be attributed to the synergistic effects
of CoMoS and carbonized cellulose fibers. The use of biomass in the
anode material represents a very easy and cost-effective way to improve
the electrochemical Li-ion battery performance
Sorbitol Derived Carbon Coated Alumina Composite as a Promising Support for CoMoS Hydrotreating Catalyst
No full textThe beneficial impact of carbon coated
alumina (C@Al2O3) implemented as support for
the CoMoS hydrotreating
catalyst has been demonstrated. A series of C@Al2O3 supports with varying carbon contents were obtained by pyrolysis
of sorbitol preliminarily impregnated in alumina from an aqueous solution.
It was found that carbon coating positively affects the formation
of the high-active CoMoS phase. However, control of the carbon content
from 2.3 to 11.3 wt % is essential to maintain the sulfide particles
dispersion and textural properties. CoMoS/C@Al2O3 catalysts demonstrated superior hydrodesulfurization activity compared
with CoMoS/Al2O3. The hydrodenitrogenation activity
of most CoMoS/C@Al2O3 samples is similar to
CoMoS/Al2O3 but decreases when the carbon content
in the support exceeds 11.3 wt %. The determining factor in improving
the CoMoS/C@Al2O3 hydrodesulfurization activity
is the formation of defective graphene fragments, which partially
cover the alumina surface and help to reduce the support acidity and,
therefore, metal–support interaction while maintaining the
textural characteristics
Hydrodeoxygenation of guaiacol Part II: Support effect for CoMoS catalysts on HDO activity and selectivity
No full text3-4 Van Ngoc Bui Laurenti, Dorothee Delichere, Pierre Geantet, ChristopheBio-oils coming from ligno-cellulosic biomass are suitable material for the production of second generation biofuels. The oxygenated compounds have to be eliminated to confer good properties to these bio-oils and to permit their addition to traditional fuels. Hydrodeoxygenation (HDO) process which allows O-elimination by C-O bond cleavage under H-2 can be realized with the same type of catalysts as those used in HDS, supported CoMoS or NiMoS phases. In this work, the support effect associated with CoMoS catalysts has been investigated in guaiacol HDO reaction. Zirconia and titania supports have been compared with the traditional industrially used gamma-alumina and it appeared that zirconia as support gave very efficient conversion of guaiacol into deoxygenated hydrocarbons with a totally different selectivity. The difference in selectivity allowed us to propose a different reaction scheme compared to gamma-alumina and titania supported CoMoS. (c) 2010 Elsevier B.V. All rights reserved
Composite surfactants aided solvothermal synthesis and catalytic hydrogenation property of oil soluble bimetallic CoMoS nanoparticles
No full textOil-soluble bimetallic CoMoS nanoparticles were successfully synthesized by a composite-surfactants-aided-solvothermal process. The surface hydrophilicity and functionality of the products were investigated through transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, and Ultraviolet (UV) spectra analysis. The catalytic performance of hydrogenation on the CoMoS nanoparticles was studied with naphthalene as a model compound. It was found that CoMoS catalysts supported on active carbon (AC) was more active than conventional MoS2/γ-Al2O3. The activity of CoMoS/AC can be tailored through the change of the Co/(Co+Mo) atomic ratio.Department of Applied Physic
First in situ temperature quantification of CoMoS species upon gas sulfidation enabled by new insight on cobalt sulfide formation
No full textInternational audienceInsights into the cobalt sulfide formation upon sulfidation (10% H2S/H2) of cobalt-based materials with 4 wt % CoO supported on alumina or silica were obtained by Quick-X-ray absorption spectroscopy monitoring analysed by multivariate curve regression analysis. A common pathway is evidenced involving the formation of supported defective CoS2 species transformed around 200-250°C into supported Co9S8 species. Upon cooling down under sulfiding atmosphere, a reverse transition towards CoS2 was observed by XAS multivariate analysis and supported by Raman analysis. This reverse transition is sensitive to the Co9S8 crystallite size: the smaller the Co9S8 nanoparticles the higher the amount of formed CoS2 after cooling. The knowledge gained on the sulfidation of monometallic cobalt-based catalysts has been used in order to isolate the X-ray absorption spectrum of the CoMoS active species formed during the sulfidation of a calcined cobalt-promoted HDS catalyst. The evolution of the concentration of the CoMoS species upon temperature increase is determined for the first time, together with those of the pristine oxidic CoMo catalyst and CoS2 and Co9S8 supported species. Although the conversion of Co9S8 into CoS2 is still observed for the HDS catalyst when temperature is decreased under H2S/H2 atmosphere, no change of the CoMoS percentage is evidenced
Hydrogenolysis and β–elimination mechanisms for C S bond scission of dibenzothiophene on CoMoS edge sites
No full textInternational audienceUnraveling the mechanisms of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and the corresponding active sites represents a scientific challenge to improve the intrinsic performances of Co-promoted MoS2 (CoMoS) catalysts. By using density functional theory calculations, we compare two historical mechanisms for the Csingle bondS bond scission of DBT (direct desulfurization): direct hydrogenolysis of DBT and β–elimination of α,β–dihydro-diobenzothiophene (α,β–DHDBT) on four relevant sites of the two CoMoS M- and S-edges. On the Co promoted M-edge, the α,β–DHDBT is formed through dihydrogenation which is kinetically competing with hydrogenolysis (both exhibiting activation free energies, ΔG‡, smaller than +1.24 eV). On the S-edge, both dihydrogenation and hydrogenolysis exhibit higher ΔG‡ (>+1.78 eV). Interestingly, on the S-edge, the β–elimination (E2 type) on the α,β–DHDBT is found to be kinetically competing (ΔG‡ = +1.14 eV). The elimination of Hβ atom involves a S2 dimer close to the S-vacancy site where DHDBT is adsorbed. Since this leaving Hβ atom is distinct from the one added at dihydrogenation step, this may explain why direct desulfurization of 4,6-alkyl substituted DBT compounds is hampered according to the elimination mechanism. We finally discuss the possible synergy between the two edges of CoMoS for HDS of DBT
Synergy Between the Comos Phase and Supported Or Unsupported Cobalt Sulfide - Existence of a Remote-control Effect
No full textUnsupported Co9S8, MoS2, and CoMoS sulfides (prepared by the HSP method) as well as supported MoS2/Al2O3 and CoSx/C (prepared by impregnation) were used to prepare a series of binary mechanical mixtures of various compositions. A variety of physicochemical techniques (temperature programmed decomposition and sulfidation, both followed by subsequent TPO, XRD, TPR, microelectrophoresis, XPS and AEM) were used to study the samples, verify the formation of the ''CoMoS phase'' in the mixed CoMo sulfide and investigate the existence of interactions between the sulfides forming the mechanical mixtures. The catalytic activity of the supported and unsupported HSP sulfides as well as that of the mechanical mixtures was tested in the hydrodesulfurization of thiophene (HDS) and the hydrogenation of cyclohexene (HYD) at 513 K and 3 MPa. The mechanical mixtures exhibit a synergy in HDS and HYD. This shows that cobalt sulfide (supported or unsupported HSP) can promote the activity not only of molybdenum sulfide, but also of the unsupported HSP ''CoMoS phase''. In addition, XRD and AEM (performed before and after catalytic tests) were used to study the evolution of the unsupported ''CoMoS phase'' during the catalytic reaction, ft was found that this phase is unstable; cobalt segregates from the CoMoS association to form Co9S8, even after a relatively short period in the reactor. These results provide more evidence that the remote control mechanism plays a major role in the synergetic behavior of the CoMo hydrotreating catalysts
Deep hydrodesulfurization of 4,6-dimethydibenzothiophene over CoMoS/TiO2 catalysts: Impact of the TiO2 treatment
No full textMesostructured titania as support for the CoMoS active phase in deep hydrodesulfurization (HDS) of 4,6-dimethydibenzothiophene (4,6-DMDBT) leads to an increase of the intrinsic HDS activity and a higher selectivity for direct desulfurization (DDS) for HDS reaction in contrast with the conventional CoMoS/alumina catalyst. The temperature treatment of the mesostructured TiO2 support, modifies the catalyst’s activity for the transformation of 4,6-DMDBT. The higher total and HDS activities were obtained after treatment at 380 °C corresponding to the higher specific surface area and to a mesostructured TiO2 material with a semi-crystalline anatase framework. Beyond 550 °C, the specific surface area decreases strongly corresponding to a complete crystallization of the mesopores walls into anatase structure. Moreover, the temperature under which the support is treated prior its impregnation has no impact on the selectivity of the transformation routes of the sulfur compound
Deep hydrodesulfurization of 4,6-dimethydibenzothiophene over CoMoS/TiO2 catalysts: Impact of the TiO2 treatment
No full textInternational audienceMesostructured titania as support for the CoMoS active phase in deep hydrodesulfurization (HDS) of 4,6-dimethydibenzothiophene (4,6-DMDBT) leads to an increase of the intrinsic HDS activity and a higher selectivity for direct desulfurization (DDS) for HDS reaction in contrast with the conventional CoMoS/alumina catalyst. The temperature treatment of the mesostructured TiO2 support, modifies the catalyst’s activity for the transformation of 4,6-DMDBT. The higher total and HDS activities were obtained after treatment at 380 °C corresponding to the higher specific surface area and to a mesostructured TiO2 material with a semi-crystalline anatase framework. Beyond 550 °C, the specific surface area decreases strongly corresponding to a complete crystallization of the mesopores walls into anatase structure. Moreover, the temperature under which the support is treated prior its impregnation has no impact on the selectivity of the transformation routes of the sulfur compound
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