Search

The quasicrystalline structures of alloys with nominal compositions of Al72Ni13.4Co14.6 and Al72.3Ni7.8Co19.8 were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. For catalytic application, the solids were leached with an alkaline NaOH solution and tested at 373 K with two model reactions under atmospheric pressure: hydrogenation of crotonaldehyde and acetonitrile. The catalytic activities of these leached alloys were compared to that of a Raney nickel reference catalyst. Catalysts prepared from quasicrystals showed high catalytic activities and high selectivities towards butanal (in crotonaldehyde hydrogenation) and ethylamine (in acetonitrile hydrogenation). [ABSTRACT FROM AUTHOR]

Abstract: Two alloys of composition Al59Cu25.5Fe12.4B3 and Al71Cu9.7Fe8.7Cr10.6 were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The latter forms a mixture of imperfect icosahedral phase and cubic phase upon rapid solidification from the liquid state. After heat treatment, this alloy transforms into a decagonal quasicrystalline phase. Both alloys can be used as catalysts precursors and transformed into active metallic phases after alkali leaching with a NaOH solution. These catalysts were used for hydrogen production by steam reforming of methanol between 473 and 773K. The catalytic activities of these treated alloys were compared to that of a reference Cu/ZnO/Al2O3 catalyst. Quasicrystal derived catalysts showed a high catalytic activity for the production of hydrogen. [Copyright &y& Elsevier]

Abstract: Chelating agents enhance the catalytic properties of HDT catalysts. It was evidenced that the presence of this organic compounds delays sulfidation. In the present study, we focused on the interaction of the chelating agent with industrial CoMo on alumina HDT catalysts after impregnation with a diammonium salt of ethylenediaminetetraacetate (diA-EDTA), drying or drying and calcination. X-ray diffraction (XRD) and Raman spectroscopy characterization demonstrate the strong interaction of the chelating agent with CoMoO4. After sulfidation, enhanced catalytic activities are obtained for the treated catalysts. Interaction of model CoMoO4 and CoAl2O4 solids with a solution of diA-EDTA demonstrates that the chelating agent is able to solubilize Co2+ cations from the molybdate but not from the spinel structure. [Copyright &y& Elsevier]

Abstract: In the framework of a two stage process for the hydrotreatment of gas oil, the use of noble metal catalysts in the second stage, where the H2S partial pressure is considerably decreased, was proposed. Thus, the catalytic properties of a series of Pt x Pd100−x (x corresponding to at.% in the alloy) particles supported on zirconia were investigated in tetralin hydrogenation and decahydroquinoline hydrodenitrogenation. TEM micrographs and EDS analysis evidenced the high dispersion of the monometallic and bimetallic composition of the nanoparticles. Whereas a promoting effect is observed in the case of hydrogenation reaction, the introduction of Pd suppressed the catalytic activity in C–N bond scission reaction. This poisoning effect can be simply understood as a linear effect of the segregation of Pd at the surface of PdPt particles. The effect of H2S partial pressure on the HDN activity was investigated and showed that for this reaction thioresistance is not improved by alloying. [Copyright &y& Elsevier]

Abstract: In the field of hydrotreating (HDT) catalysis, density functional theory (DFT) calculations are of great help to explore new active phases on the basis of volcano curve relationships correlating HDT activities and the sulfur–metal (S–M) bond energy chemical descriptor, calculated in transition metal sulfides catalysts. In the present study, we synthesize Mo1−x W x S2 solid solutions supported on γ-alumina. For non-promoted systems, the catalytic tests reveal that a continuous and linear evolution of the catalytic activity is obtained for solid solutions for x varying between 0 and 1. As expected from the calculated S–M bond energy values, no synergy effect is observed in that case. For Ni and Co promoted Mo1−x W x S2 active phases (ternary metal sulfides), the S–M bond energy values determined with an interpolation model of the binary sulfides predict that NiMo1−x W x S2 phases should be more active than NiMoS and NiWS ones. In contrast, CoMo1−x W x S2 phases are expected to develop weak synergetical effect with respect to CoMoS and CoWS ones. Experiments performed on Co and Ni promoted Mo1−x W x S2 active phases confirmed the DFT-volcano curve prediction and an increment of about 30% in HDS catalytic activity is obtained for NiMo0.5W0.5S catalysts in both model molecule conversion and gas oil treatment. [Copyright &y& Elsevier]

Within the framework of volcano curves, a kinetic study of toluene hydrogenation catalyzed by transition metal sulfides highlights the variation of the apparent kinetic parameters as a function of the ab initiosulfur-metal bond energy descriptor and sulfo-reductive reaction conditions. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of hydrated ZrOCl2 in NaNO3–Na2SO4 melt at 673 K produces non-stoichiometric lamellar Na–Zr oxide sulfate. In this water-insoluble solid, Na+ cations can be exchanged with K+, or protons. Reflux with n-pentylamine leads to the reversible intercalation of the amine molecules between the layers with an increase of the interlayer distance. Protonic form of the solid showed high activity in the isooctane hydrocracking reaction. [Copyright &y& Elsevier]

Review: 33 refs. [ABSTRACT FROM AUTHOR]

Abstract: Hindered diffusion and adsorption phenomena of coal asphaltenes inside the porous network of hydrotreating catalysts are discussed in this paper. After solvent extraction from a coal-derived liquid and solubilization in THF, asphaltenes were contacted with a series of mesoporous hydrotreating catalysts and adsorption–diffusion phenomena recorded by UV–Vis spectroscopy measurements. The effect of the porosity of various NiMo(P) catalysts supported on monomodal mesoporous or bimodal (meso–macro) alumina carrier was investigated. The parameters estimations have been performed, discussed and those obtained with the bimodal (meso–macro) alumina catalyst have been compared to petroleum asphaltenes data [31]. The range of studied concentrations corresponds to cluster formation domain. The results evidence that coal asphaltenes aggregates are smaller, have lower molecular weight and exhibit a much higher diffusion coefficient than petroleum asphaltene aggregates. These results bring important insights for the interpretation of the performance of the catalysts during coal-derived liquid upgrading. Concerning adsorption phenomena, the adsorption constants of coal asphaltenes and petroleum asphaltenes have been found equivalent. The adsorption saturation concentration of coal asphaltenes is higher than that of petroleum asphaltenes. The effective diffusion coefficients obtained at ambient temperature were correlated to the catalytic performances observed during coal-derived liquid hydrotreatment. It points out that the conversion of coal-derived liquid into the porous network of our catalyst is a hindered phenomenon, and that pore size distribution of the support has a great influence on the hydroliquefaction efficiency. [Copyright &y& Elsevier]

Abstract: Photocatalytic synthesis of dioctylsulfide has been performed at room temperature in liquid phase by addition of 1-octanethiol on 1-octene in contact with illuminated TiO2. Under inert atmosphere, dioctylsulfide is selectively obtained whereas in the presence of oxygen high selectivity in n-dioctylsulfide has vanished. This study illustrates the potential of photocatalysis for the production of thio-compounds. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of zirconia textural stabilization by means of basic reflux was studied. In agreement with earlier studies, zirconia was modified by silicon extracted from the glass material in the same manner as if silicon compounds (e.g., TEOS, SiO2) had been added to the reaction mixtures. The reflux in a Teflon bulb without the addition of silicon did not lead to improved textural properties. EXAFS study of both refluxed and nonrefluxed specimens showed their similarity and probably some dehydration of the precipitate. The FTIR, NMR, and XPS spectroscopic characterizations suggested that silicon was strongly segregated on the surface, probably in the form of silicate moieties anchored on zirconia. A reflux stage was necessary to achieve efficient spreading of the silicate over the surface of the precipitate. For the solids calcined at 1173 K, the surface stabilization corresponded to the formation of a “metastable monolayer” coverage, similar to that observed for zirconias doped by other oxoanions, such as molybdate or tungstate. Isooctane hydrocracking and o-xylene hydrogenation were studied in the presence of Pt supported on the oxides as prepared. Hydrodesulfurization of thiophene was carried out in the presence of Mo and NiMo sulphides using the same supports. In all three reactions studied, the digested zirconia support demonstrated properties similar to those of pure silica. [Copyright &y& Elsevier]

(Ni)W/ZrO2 oxide catalysts have been prepared using reactions in molten Na(K)NO3 fluxes at different temperatures ranging from 350 to 500 °C. The solids were characterized using X-ray diffraction (XRD), textural measurements and X-ray photoelectron spectroscopy (XPS). Highly dispersed zirconia with tungstate species grafted on its surface was formed at 450–500 °C. At 350–400 °C tungsten oxide or crystalline intermediate polytungstates of K and Na were observed in the products. Specific surface areas of the solids were high, up to 250 m2/g, due to stabilizing effect of tungstate species. After sulfidation, the catalysts were studied by XPS in situ, and tested in the model reactions of hydrodesulfurisation (HDS) and hydrogenation (HYD). XPS study reveal incomplete sulfidation of tungsten even at 500 °C, suggesting some persistent Zr–O–W bonds. Compared with conventional impregnation NiMo/Al2O3 systems, the (Ni)W/ZrO2 solids showed increased hydrogenating activity. [Copyright &y& Elsevier]

[Display omitted] • Screening of Transition metal sulfides on HY catalysts for SRO of decalin was performed. • Comprehensive GCxGC gives a unique molecular insight of SRO reaction. • A new reaction scheme has been proposed. • New ternary systems efficient at medium temperature are proposed. Bifunctional catalysis combining acidic catalysts and sulfide active phases is usually related to hydrocracking catalysts which balances the hydrogenation function of a NiMo (NiW) alumina supported sulfide catalysts and the acidic function of a zeolite. The discovery of sulfur-resistant catalysts for selective ring opening (SRO) is an important challenge for refiners, considering the future legislation on cetane index of diesel fuels. In the present work, we studied the properties of various transition metal sulfides (TMS) supported on Y zeolite in gas-phase decalin hydroconversion at high hydrogen pressure (5 MPa) in the presence of 0.8 % H 2 S concentration. This screening shows high activities for noble metal based sulfides with a mechanism which proceeds by skeletal isomerization induced by the zeolite. Catalytic activity was improved by the use of ternary sulfides such as Ni 1-x Ru x S 2 or NiRh 2 S 4 on Y zeolites. High decalin conversion levels can be reached below 250 °C with more of 20 % of ring opening products and thanks to the use of comprehensive GC, a detailed mechanism of the SRO of decalin is given. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Pt50-Ir50/ZSM-5 catalyst was more effective for phenol HDO than Pt/ZSM-5 and Ir/ZSM-5 catalysts having the same metal content. • The Pt50-Ir50/ZSM-5 catalyst was more effective for phenol HDO than Pt/ZSM-5 and Ir/ZSM-5 catalysts having the same metal content. • The Pt diffusion into ZSM-5 structure was detrimental for catalyst activity and selectivity toward O-free products. The effect of partial Pt substitution by Ir on the catalytic response of bimetallic Pt-Ir/ZSM-5 (Pt/Ir = 1) catalyst in the liquid-phase hydrodeoxygenation (HDO) of phenol was investigated. To evaluate the catalyst intrinsic activity, the ZSM-5 supported Pt, Ir and Pt + Ir catalysts were prepared with similar total metal loading (ca. 3 wt.%) and acidity. The catalysts were characterized by several physical and chemical techniques and tested in the HDO of phenol reaction carried out in a batch reactor at T = 200 °C under H 2 pressure of 3.0 MPa. For all the catalysts, the phenol transformation mainly proceeds via hydrogenation + dehydration (HYD reaction route) leading to cyclohexane as the main product (selectivity 60–96%). Partial substitution of Pt by Ir in catalyst formulation (Pt50-Ir50/ZSM-5) enhances both activity and selectivity toward O-free products. This was associated to Ir surface enrichment (from HRTEM). The Ir/ZMS-5 and Pt50-It50/ZMS-5 catalysts having well dispersed Ir nanoparticles were more selective toward dehydration than Pt/ZSM-5 having Pt species with a broad size distribution range. The catalyst activity-structure correlation suggests that the dehydration of cyclohexanol (intermediate product) can occur at the interface between the metal and acid sites of the support. [ABSTRACT FROM AUTHOR]

This paper investigates the boosting effect on friction reduction performance of a fatty triamine (AM) when used as a third organic additive to base oil containing molybdenum-based additives and ZDDP for different tribopairs. The addition of the AM gives an unreached friction level under boundary lubrication with organic molybdate and ZDDP for steel. The structure of the tribofilm obtained with ternary mixture composed of stoichiometric MoS 2 long sheets located on top surface and aligned in the sliding direction could be at the origin of this remarkable behavior. Finally, a tribochemical action mechanism is proposed to describe the functionality of AM in boosting the formation of long MoS 2 lamellar sheets. [ABSTRACT FROM AUTHOR]

Fast pyrolysis followed by catalytic hydroconversion is a value chain aimed to transform lignocellulosic biomass into biofuel or chemicals. During hydroconversion, desired catalytic deoxygenation reactions are in competition with thermal side reactions like condensation or oligomerization. These undesired pathways lead to high molecular weight compounds (i.e. macromolecules) that are responsible for catalyst deactivation and severe plugging of the reactor. We investigate here the impact of a phenolic compound on the formation of these macromolecules. Catalytic hydroconversion of a fast pyrolysis bio-oil and a bio-oil/guaiacol (50/50 wt%) mixture were carried out in a batch reactor using a NiMo/alumina catalyst. An extended analytical strategy has been developed involving size-exclusion chromatography (SEC) and liquid state 13 C NMR dedicated to the in depth characterization of effluents as well as physicochemical analysis of the fresh and used catalyst (XRD, Hg porosimetry, N 2 physisorption, STEM). This strategy allowed bringing new insights on aromatic structures larger than 1000 g.mol −1 and their formation mechanism. This formation can be chemically inhibited by the introduction of organic component such as guaiacol. This stabilization was mainly observed and explained at low temperature and short reaction time. [ABSTRACT FROM AUTHOR]

In the present work, the catalytic activity and selectivity for the conversion of 2-methoxyphenol over ReOx catalysts supported on SiO 2 , Al 2 O 3 and SiO 2 -Al 2 O 3 in a batch reactor at 300 °C and 5 MPa of hydrogen pressure were studied. Additionally, several SiO 2 -supported ReOx catalysts were synthesized with different metal loadings. These catalysts were characterized by N 2 adsorption, X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR), temperature-programmed desorption of ammonia (TPD-NH 3 ), Raman spectroscopy and ultraviolet visible (UV–vis-DR) spectroscopy. ReOx catalyst supported over SiO 2 revealed the highest catalytic activity and selectivity towards deoxygenated products. This was attributed to a higher formation of oxygen vacancies (active sites) on SiO 2 , due to a weaker metal-support interaction. The increase of Re content on SiO 2 resulted in an increase of guaiacol conversion, reaching a maximum at about 1.8 atoms of Re per nm 2 of support. The decrease of activity over 1.8 atoms of Re per nm 2 of support was correlated to loss of active site due to the formation of aggregates of ReOx. [ABSTRACT FROM AUTHOR]

There is a real interest in developing biofuels from microalgae. Their high productivity, lipid content and their capacity to capture CO 2 make microalgae a competitive biomass for energy purposes and environmental concerns. Among various valorisation pathways of such biomass, hydrothermal liquefaction (HTL) process attracts interest. This process converts microalgae between 270 and 350 °C, in hot compressed water to produce a biocrude oil, which is then upgraded to produce biofuel. Biocrude oil is mainly composed of carboxylic acids and oxygenated compounds but also contains some cyclic nitrogen molecules or amides which are hard to upgrade and thus detrimental for biofuel quality. Therefore, in addition to the usual problem of oxygenated compounds in biocrude oils, the use of algae introduces another difficulty with the nitrogen compounds. The present review attempts to summarize the nature of the nitrogen compounds in algae, and their transformation during HTL conversion. [Display omitted] • Overview of amino acids degradation pathways during hydrothermal liquefaction. • There is a link between biomass and hydrothermal liquefaction products. • Nitrogen compounds in biocrude oil comes mainly from proteins degradation. • Each amino acid has a specific reactivity in hydrothermal liquefaction conditions. • Some pigments and lipid classes lead to nitrogen compounds in biocrude oil. [ABSTRACT FROM AUTHOR]

Although catalytic hydroconversion of pyrolysis bio-oils has been studied for many years, side reactions such as condensation or oligomerization leading to high molecular weight compounds still need comprehensive studies. In this work, the catalytic hydroconversion of D-glucose, furfural, acetic acid and guaiacol representative of pyrolysis bio-oils was investigated separately before testing a 5-component mixture. Thanks to a detailed analytical strategy (i.e. SEC, 13 C NMR, GC, HPLC), this paper focuses on the effect of guaiacol conversion on sugar-like macromolecules. The study of single D-glucose and furfural revealed the fast production of high molecular weight compounds (up to 700 g mol −1 ) that were proven to further precipitate (from D-glucose). Guaiacol addition led to a decrease of the solid production through solubilizing and/or reacting with macromolecules. This phenomenon produced larger soluble macromolecules (up to 5000 g mol −1 ). Results show that guaiacol and its hydroconversion products formed soluble macromolecules at short reaction times and low temperatures. [ABSTRACT FROM AUTHOR]

Catalytic hydroconversion of pyrolysis bio-oils is a promising process that can greatly contributes to their deoxygenation. Other simultaneous reactions such as condensation or oligomerization leading to heavy molecular weight compounds are detrimental to the process and still not well understood. This study deals with the hydroconversion of D -glucose and furfural in a batch reactor with a NiMo/alumina catalyst. Considering the carbon balances and SEC-RI analysis of hydroconversion products, we describe fast reaction pathways leading to soluble macromolecules (up to 700 g mol −1 ) that are further precipitated into the solid phase. From the D -glucose conversion, 13 C NMR analysis of residues revealed significant amounts of aromatic carbons. Also detected by FTICR-MS analysis of a liquid effluent, those structures were likely formed through dehydration reactions. Finally, a high water content in the feed demonstrated that D -glucose was preserved from dehydration reactions contrary to furfural which is prone to be hydrolyzed into soluble macromolecules precursors. [ABSTRACT FROM AUTHOR]

The hydroconversion of a wheat straw soda lignin was studied in a batch reactor, in tetralin solvent, with a NiMoS/Al 2 O 3 catalyst under H 2 pressure at 350 °C. Gaseous, solid and liquid products were separated, quantified and detailed analyses were performed in order to describe and to understand the various reactions occurring versus residence time. In those operating conditions, the weakest β-O-4 and α-O-4 ether linkages of the lignin were first cleaved. The lignin was thus progressively converted into smaller hydrogenated and deoxygenated fragments called lignin residues which were extensively characterized by GPC and NMR. In the liquid phase, smaller monomers and dimers were identified by GC × GC/MS and quantified by GC × GC/FID. The evolution of these molecules was investigated as a function of residence time in order to investigate the catalytic transformation scheme of lignin. [ABSTRACT FROM AUTHOR]

This work showed that the use of AlO-TiO as carriers has a positive effect on the activity of supported NiW catalysts in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene carried out in a batch reactor at 320 °C and total H pressure of 5.5 MPa. Two AlO-TiO mixed oxides with Al/Ti atomic ratios of 10 and 2 were synthesized by sol-gel method together with the pure AlO synthesized as reference support. For NiW/AlO-TiO and NiW/AlO catalysts, a metal load of 17 and 5.5 wt% of W and Ni were considered respectively. It was found that both AlO-TiO-supported catalysts exhibited higher activity than alumina-supported one. The catalyst with a largest TiO content (NiW/AT2) demonstrated to be 23 % more active with respect to NiW/AlO. Solids were characterized by temperature-programmed reduction (TPR), high resolution transmission electronic microscopy and X-ray photoelectronic spectroscopy (XPS) techniques. A decrease in support-metal interaction (from TPR) was observed when Ti content increased, which could lead to a higher amount of NiWS phase (from XPS). Besides, a slight increase in the slabs length in WS was observed for titania-containing catalyst with respect to NiW/AlO, indicating that the dispersion can still be optimized. The atomic ratio Al/Ti = 2 of the NiW/AlO-TiO catalyst proved to be a potential substitute for current catalysts for sulfur reduction in ultra-clean diesel. [ABSTRACT FROM AUTHOR]

The kinetics of guaiacol conversion over ReS 2 /SiO 2 and ReOx/SiO 2 catalysts in a batch reactor at 300 °C and 5 MPa hydrogen pressure was studied. The ReOx/SiO 2 catalyst was more active and selective towards deoxygenated products (mainly cyclohexane), while the ReS 2 /SiO 2 catalyst was more selective towards the formation of phenol. Langmuir–Hinshelwood kinetic models were developed in order to identify changes in the reaction mechanism with the ReOx/SiO 2 and ReS 2 /SiO 2 catalysts. The results for the guaiacol conversion over ReS 2 /SiO 2 catalyst were fitted to a model that assumes the presence of two different kinds of active sites and that hydrogen adsorption is generated through heterolytic dissociation. The conversion of guaiacol over the ReOx/SiO 2 catalyst was fitted to a model that assumes hydrogen adsorption via homolytic dissociation and a single catalytic site. [ABSTRACT FROM AUTHOR]

The impregnation parameters setting is an essential strategy to find efficient active phase precursors in heterogeneous catalysts due to the close connection between the chemistry of impregnated aqueous solution and the nature of metal-support interactions. In this work, the effect of impregnation solution pH on active NiWS phase formation was studied. Ni/W/Al 2 O 3 catalysts were prepared by impregnation of a W/Al 2 O 3 -based catalyst using aqueous nickel-citric acid (CA) solutions (CA/Ni = 2) at different pH values (0.3, 3.4, 5.1 and 8.7). The citric acid presence and the impregnation pH influenced the NiWS phase formation. Citric acid provided isolation to supported metal species avoiding strong metal-support interactions, delaying nickel reduction at higher temperatures and decreasing WS 2 sintering when compared with a free-citric acid catalyst. An increase of 2.2 times in NiWS fraction was related to these citric acid features. Furthermore, the solution pH influenced the aqueous and supported nickel speciation. Dispersed nickel species were associated with AlO-Ni-Cit surface complexes generated by the adsorption of [Ni(HCit)(Cit)(H 2 O) 4 ] 3− or [Ni(Cit) 2 (H 2 O) 4 ] 4− over alumina surface. In turn, these surface complexes were associated with a higher W sulfidation. 3-fold increases in Ni/W/Al 2 O 3 catalytic activity for hydrodesulfurization of 4,6-dimethyldibenzothiophene were reached by the presence of citric acid and a pH of nickel-citric acid solution around 5. Therefore, the active NiWS species formation in Ni/W/Al 2 O 3 catalysts was improved with citric acid addition and furthermore, it was notably optimized by the control of the nickel species via tuned impregnation pH. [ABSTRACT FROM AUTHOR]

The conversion of guaiacol, a lignin model compound, over SiO 2 -supported Re metal, oxide and sulfide catalysts in a batch reactor at 300 °C and 5 MPa of hydrogen pressure were studied. The oxide catalyst was prepared by wet impregnation with a loading of 2.5 atom of Re per nm 2 of support. The sulfide and metal catalysts were prepared by sulfidation and reduction, respectively, of the Re oxide catalyst. The catalysts were characterized by N 2 adsorption, X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) and transmission electron microscopy (TEM). Catalytic activity was correlated with XPS analysis of the post-reaction catalysts. The ReOx/SiO 2 catalyst was the most active and selective towards deoxygenated products, and this was attributed to increase in the concentration of metal oxide defect sites (due to in situ partial reduction of the oxide catalyst during the reaction). This result reveals the high potential of ReOx/SiO 2 catalyst for bio-oil upgrading because it shows, among other things, that it is unnecessary to add undesirable sulfiding agent to maintain catalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: A wheat straw soda lignin was characterized and converted into gases and liquids under H2 pressure, at 350°C over a supported NiMo sulfide catalyst, using tetralin as a hydrogen-donor solvent in a batch autoclave. The aim of this work was to evaluate the transformations occurring during the temperature increasing step to reach a pseudo-t 0 and the impact of the catalyst presence in the mixture. A well-developed products separation protocol made possible to isolate and to characterize gases, organic liquid, lignin residue and solids (catalyst and char). A limited quantity of solids (or char) was produced however. As the lignin residue is one of the main intermediates of the lignin conversion pattern, the nature of this material has to be carefully determined. Thanks to several appropriate characterization techniques (GPC, NMR, FTIR), the conversion was followed and the lignin residue was compared to the initial lignin in order to understand the transformations occurring during the process. [Copyright &y& Elsevier]

Abstract: Coal liquids from Direct Coal Liquefaction (DCL) are one of the possible substitutes of conventional hydrocarbons resources. However the primary liquids obtained from DCL (i.e. outflow liquids of the first reactor in a two stages liquefaction process) do not meet the product specifications and need to be upgraded via downstream catalytic hydrotreatment processes. The in depth knowledge of the feed of this upgrading step is of key importance to design better catalysts. In this study, we applied new cutting-edge techniques to improve the characterization of a coal derived liquid obtained from a liquefaction step starting from Scottish bituminous coal. For this purpose, bidimensional chromatography (GC×GC), and 13C nuclear magnetic resonance (NMR) were used to analyze four cuts of the coal liquid with the following boiling points intervals: heavy naphtha (initial boiling point: IBP-215°C), gas oil (215–343°C), vacuum gas oil (343–524°C) and vacuum residue (524+ °C). The analyses showed high aromaticity of all four cuts. The weight content of aromatics in the gas oil fraction, was 75%, with a majority of two rings aromatics and the remainder consisting mostly of normal paraffins. In the vacuum gas oil cut, which contains mostly four aromatic rings, we found 11wt% of asphaltenes (compounds in n-heptane), an unexpected high amount comparing to petroleum VGO fractions. The amount of heptane-insoluble (asphaltenes, preasphaltenes and sediments) is as high as 80% in the vacuum residue fraction (524+ °C). Aromaticity given by 13C NMR in this cut is as high as the level observed in petroleum asphaltenes (Caro =53wt%). High content of heteroelements, which highly increase the polarity of the molecules, in the coal liquid and especially in the vacuum residue can explain the enhanced amount of n-heptane-insoluble compounds. [Copyright &y& Elsevier]

Abstract: Through a combined experimental and density functional study, we investigate the deoxygenation of ethyl heptanoate catalyzed by three relevant unsupported (bulk) transition metal sulfide catalysts: MoS2, Ni3S2 and Ni-promoted MoS2 (with various Ni/Mo ratio). Two pathways compete for this reaction: hydrodeoxygenation (HDO) and decarboxylation/decarbonylation (DCO). It is shown experimentally that the presence of Ni either in the NiMoS mixed phase or in the Ni monosulfide phase may change the selectivity between the HDO and DCO pathway. To understand the origin of this selectivity, we study the deoxygenation pathways of two relevant intermediates: carboxylic acid and aldehyde. In particular, DFT calculations highlight that the aldehyde decarbonylation occurs via its dehydrogenation into the alkanoyl and/or ketene intermediates on the Ni3S2 (111) surface. These pathways are found to be more favorable on Ni3S2 than on MoS2-based catalysts. This trend is explained by the presence of Ni3 triangular facets on Ni3S2 (111) enhancing the formation of the unsaturated alkanoyl and/or ketene intermediates as well as the CO product. We finally propose a detailed analysis of the promoting effect of Ni on MoS2, when present in the NiMoS structure. [Copyright &y& Elsevier]

Abstract: Three different zeolites, γ-alumina and silica supports were used to prepare ReS2 catalysts by incipient wetness impregnation of ammonium perrhenate (NH4ReO4). The catalysts were characterized and tested in the hydrodesulfurization (HDS) of thiophene in an atmospheric fixed bed reactor, and of the 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS in a high pressure stirred tank reactor. The results showed that the acidity of the zeolites has a detrimental influence over hydrodesulfurization activity of the Re sulfide, contrarily to the enhancement observed previously with zeolite-supported Mo sulfide catalysts. The catalyst prepared over a non-acidic zeolite (HSZ-390) was found very efficient in thiophene HDS and comparable to silica for 4,6-DMDBT. [ABSTRACT FROM AUTHOR]

Abstract: We use a multitechnique approach to reveal how the nature and concentration of surface acid–basic OH groups present on anatase-TiO2 nanocrystallites depend on their morphologies. Coupling recent density functional theory (DFT) calculations with three physical characterization techniques (X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy), the different infrared (IR) spectroscopic properties of two anatase samples are explained by morphology effects resulting from the synthesis pathways. Whereas a conventional route leads to anisotropic shapes, the multigelation method leads to more “spherical” shapes. As shown by the DFT calculations, the assignment of the OH stretching bands depends on the surfaces exposed by the anatase-TiO2 nanocrystallites. The signature of the nanocrystallites morphology can thus be captured by IR spectroscopy. [Copyright &y& Elsevier]

Mesoporous titanium oxide with a high specific surface area of 120 m2/g prepared by a novel method developed by Chiyoda was used for supporting molybdenum sulfide. In order to examine the influence of the surface area on the properties of the molybdenum sulfide phase, two different samples of titanium oxide were studied, a commercial one with a surface area of 72 m2/g and that prepared by Chiyoda. Molybdenum was deposited on the TiO2 supports by incipient wetness impregnation with ammonium heptamolybdate in one or two steps depending on the Mo loading. Some samples were also prepared by impregnation of ammonium heptamolybdate basified by ammonia. Raman spectroscopy and XPS were used to examine the nature of the molybdate phase and its dispersion in the oxidic state. HREM and XPS were used for studying the sulfided state. As expected, the maximum amount of well-dispersed molybdenum is higher on the Chiyoda support than on the reference support with a lower surface area. The catalytic properties of the catalysts were studied in dibenzothiophene conversion. For the Chiyoda support, the catalytic activity varied linearly with the Mo loading up to 6–7 Mo/nm2 then became nearly constant for the higher loadings. Much higher activities (six times, expressed per gram of catalyst) were obtained compared to molybdenum sulfide supported on alumina. [Copyright &y& Elsevier]

Niobium-molybdenum disulfide solid solution (NbxMo1−xS2) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the NbxMo1−xS2 solid solution (HDS of DBT, Ptot=33 bar) is not decreased in the presence of H2S up to p(H2S)=200 Torr, at least up to x=0.4. [Copyright &y& Elsevier]

• Mo-Re catalyst with equal composition produce the highest phenol conversion. • Synergistic effect between both Re and Mo oxide species has been reported. • Mo-Re catalysts are active due to the formation of oxygen vacancy on the ReO x species. Liquid-phase hydrodeoxygenation of phenol over silica-supported MoOx-ReOx catalysts was investigated at 300 °C and 5 MPa of H 2. Mixed-oxides catalysts with similar surface metal density (2.3 atoms of metal per nm2 of SiO 2) but different relative Mo and Re loadings were prepared by incipient wetness impregnation. The catalysts were characterized by N 2 adsorption, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), ultraviolet visible diffuse reflectance (UV–vis-DR) spectroscopy, X-ray diffraction (XRD) and temperature programmed desorption of NH 3 (TPD-NH 3). All the catalysts were highly active and selective towards deoxygenated products. However, MoOx/SiO 2 was the most selective towards cyclohexane formation. Higher amount of benzene was produced with the Re-containing catalysts than it was over the MoOx/SiO 2 catalyst, indicating that ReOx favored direct deoxygenation over hydrogenation of the aromatic ring. The catalyst containing equimolar amounts of MoOx and ReOx exhibited the highest yield of benzene. This result can be attributed to a synergistic effect that arises from electronic interaction between rhenium and molybdenum oxides which favors the formation of new oxygen vacancy sites. The study reveals that benzene selectivity is mainly influenced by ReOx sites and the activity can be tuned by a balance of MoOx and ReOx sites. [ABSTRACT FROM AUTHOR]