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The main compounds present in the HTL micro-algal bio-oil were C16 and C18 carboxylic acids from triglycerides hydrolysis. Fatty amides, and cyclic aromatics nitrogen and oxygen compounds formed from the decomposition of carbohydrates and proteins were also found. The N and O content were, respectively 2.6 wt. % and 11.7 wt. %.The experiment performed with nickel phosphide showed the same conversion as an experiment without catalyst, indicating that, even though phosphides have been reported in the literature as a potential candidate to replace sulfide catalysts, more advances should be done to increase the activity of this active phase.However, the sulfide and nitride catalysts permitted to reduce the number of contaminants and improved the quality of bio-oil. The main compounds formed after the upgrading step were C15, C16, C17, and C18 from carboxylic acids hydrogenation (HDO) or decarboxylation/decarbonylation (DCO). More than 60% of upgraded bio-oil eluted on the diesel range, which corroborates the potential of microalgae as a feedstock for biofuel production. The degree of deoxygenation and denitrogenation were, respectively, 91% and 67% for sulfide catalyst, 93% and 46% for nitride catalyst, and 84% and 6% for phosphide. Therefore, NiWS/Al2O3 had a higher hydrodenitrogenation (HDN) ability than NiMoN and Ni2P/Al2O3 catalysts. GCxGC-MS/FID analysis revealed that fatty amides were first converted into nitriles and then in alkanes. The experiments performed over Ni2P/Al2O3 and without catalyst showed a family of nitriles that are completely converted with nitride and sulfide systems. Besides, it was also observed that NiWS/Al2O3 converted more cyclic nitrogen compounds, such as, pyrroles, indoles, and carbazoles than NiMoN which is associated with a higher hydrogenation ability of this catalyst, since these nitrogen molecules should be hydrogenated before the HDN reaction. These results were also corroborated by GPC-DAD analyses which indicate a lower absorbance for the upgraded bio-oil over sulfide catalyst which is associated with a lower degree of aromaticity of this sample.The HHV increased from 36 MJ/kg in the HTL micro–algal bio-oil to 47 MJ/kg in the upgraded bio-oil over sulfide catalyst, and the average molar mass reduced from 363 to 265 g/mol indicating that heavy molecules were converted during the upgrading step.

In recent years, catalytic depolymerization of lignin has been widely performed to obtain aromatic monomers under reductive or oxidative operating conditions [1]. However, starting with a recalcitrant technical lignin, co-produced in pulp industry or cellulosic biorefinery, the depolymerization only lead to poor monomers yield that prevent a valuable process. Another option to valorize technical lignin is to use it as a macromer in polymer applications. For instance, lignin can be used to replace polyol in polyurethane synthesis [2]. Other approaches were proposed using either lignin or lignin-derivatives to be incorporated into polymer synthesis [3]. Lignin derivatives might be more interesting than lignin if they are well-defined and possess higher amount of OH groups that can be further functionalized. Thus, one approach would consist in depolymerizing softly the lignin to create OH- groups that are phenolics or aliphatics. This can be done by cleavage of the ether inter-units linkages in lignin (-O-4, -O-4 or 4-O-5) and also by demethylation of the methoxy groups in the syringyl and guaiacyl units of the macromolecule. In literature, catalysts with lewis acidity were prone to be efficient to cleave these ether functions. However, until now, the most efficient demethylation method proposed is using HI acid formed in situ by using Iodocyclohexane in DMF [4]. This suggests that lewis acids are not the only candidates of choice for this process. We thus undertook a study to develop heterogeneous catalysts able to cleave selectively ether bonds of a technical lignin. In order to make a large screening of catalysts, we have chosen Pd/C already successfully used in lignin depolymerization, CoMo catalysts in oxide and sulfide forms active under reductive conditions, tungstated alumina (AlW) prepared to have only lewis acid sites [6], a silica-supported phosphotungstic acid and a well-known H-ZSM5 zeolite.

Fossil fuel demand is continuously increasing, particularly in the field of transport, where light petroleum products and middle distillate products are used. The transformation of the heavy oil cuts into middle distillate fuel is essential to meet current and future demand for fuels. The most widely consumed products, such as diesel, can be produced by hydrocracking reactions [1]. On the other hand, the development of new generations of non-fossil fuels, such as biomass derivatives, is of great interest [2]. Co-processing VGO (Vacuum Gas Oil) with bio-oil has been investigated in a few studies [3]. The aim of this work is to shed light on the impact of bio-liquids on the hydrocracking reactions with mineral feed into middle distillates. We studied various bioliquids coming from wood biomass having undergone different treatments like stabilized pyrolysis oil (SPO) or hydrothermal liquefaction (HTL). The study evaluates, in a semi-batch reactor under hydrogen pressure, the performance of sulfide catalysts in the presence of a bio-liquid-VGO (Vacuum Gas Oil) mixture.

Microalgae seem to be a potential raw material for third-generation fuel production due to their high growth rate, the potential for CO2 fixation, and high lipids content which can provide a high biofuel yield. Hydrothermal liquefaction (HTL) is a thermochemical process that has been used for the conversion of microalgae in bio-oil. However, the HTL micro-algal bio-oil contains a high amount of heteroatoms such as N, O, and sometimes S which causes harmful emissions upon combustion and also reduced the quality of the fuel. Therefore, an upgrading step is required before the commercialization of this kind of biofuel to reach transportation fuel specifications. Being part of the Rafbioalg project (ANR-18-CE43-0009) that explores the production of biofuel from algae growth until fuel combustion with a LCA analysis of the all value chain, we investigated the catalytic upgrading step of the HTL algal oils. The whole algae, Chlorella Sorokiniana grew at CEA Cadarache, was converted to a bio-oil using a continuous reactor at 300 °C, under 10 MPa for 15 min at Liten laboratory in CEA Grenoble. The bio-oil was upgraded using a batch reactor at 375 °C under 10 MPa (H2), over NiWS/Al2O3, NiMoN, and Ni2P/Al2O3. The nitride and phosphide catalysts were prepared using a methodology described in the literature. The produced HTL and HDT oils were characterized by CHONS, XRF, ICP-OES, GPC–RID/DAD, 13C-NMR, SIMDIS, and GCxGC-MS/FID. The hydroconversion experiments performed with nickel phosphide showed the same conversion as an experiment without catalyst, indicating that, even though Ni phosphides have been reported in the literature as good candidate to replace sulfide catalysts, this active phase is not efficient for algal oil. However, the W sulfide and Mo nitride catalysts permitted to reduce O, N and S content and thus improved the quality of bio-oil. The main compounds formed after the upgrading step were C15, C16, C17, and C18 from carboxylic acids hydrogenation (HDO) or decarboxylation/decarbonylation (DCO). More than 60 wt% of upgraded bio-oil eluted on the diesel range, which corroborates fully the potential of microalgae as a feedstock for biofuel production. The degree of deoxygenation and denitrogenation were, respectively, 91% and 67% for sulfide catalyst, 93% and 46% for nitride catalyst, and 84% and 6% for phosphide. Therefore, NiWS/Al2O3 had a higher hydrodenitrogenation (HDN) ability than NiMoN and Ni2P/Al2O3 catalysts. GCxGC-MS/FID analysis revealed that fatty amides were first converted into nitriles and then in alkanes. The experiments performed over Ni2P/Al2O3 and without catalyst showed a family of nitriles that are completely converted with nitride and sulfide systems. Besides, it was also observed that NiWS/Al2O3 converted more cyclic nitrogen compounds, such as, pyrroles, indoles, and carbazoles than NiMoN which is associated with a higher hydrogenation ability of this catalyst, since these nitrogen molecules should be hydrogenated before the HDN reaction. The HHV increased from 36 MJ/kg in the HTL micro–algal bio-oil to 47 MJ/kg in the upgraded bio-oil over sulfide catalyst, and the average molar mass reduced from 363 to 265 g/mol indicating that heavy molecules were converted during the upgrading step.

Molybdenum disulfide is a widely used catalyst for hydrodesulfurization (HDS) of petroleum fractions. The current view attributes HDS catalytic activity to the edges of nanoscopic MoS2 slabs. However, some experimental results indicate that the description of these systems should be improved, namely with the help of recently emerged concept of ultradispersed metal-based catalysts. Along with MoS2 slabs, small subnanometric species are present in the systems which can act as catalytic sites for HDS [D. Ryaboshapka et al., Appl. Catal. B 302 (2022) 120831]. In this work we studied HDS catalytic performance and active species of ultradispersed catalysts with 1 wt.% Mo, prepared on different supports: TiO2, SiO2 (KIT-6), Al2O3 and activated carbon. It might be expected that Mo species on oxides would bond strongly with surface oxygen and remain single-atomic, whereas Mo species would bond weakly with carbon surfaces and form larger clusters. Conventional characterization techniques (TEM, Raman, XRD, UV-vis, DRS) confirmed that no MoS2 nanoparticles were present in the samples. On the HAADF-STEM images, small Mo clusters along with single atoms were observed. The species formed during sulfidation and HDS reaction were monitored by means of operando XAS at the ROCK beamline of SOLEIL synchrotron. The differences in sulfidation trends between the samples were compared. All the catalysts demonstrated high specific activity in HDS of thiophene (Fig. 1b). The differences in HDS rates and in selectivity were confronted to the evolution of Mo species depending on the used support. For the first time, it was shown that sulfided ultradispersed Mo species supported both on oxides and carbon are active in HDS. Depending on the nature of the support, the strength of metal-support interaction changed, impacting the nature of species formed on the support surface.

journée dédiée à la multidimensionnalité en chromatographie :présentation sur :la chromatographie bidimensionnelle en phase gazeuse appliquée aux procédés de conversion des carburants

HTL operating conditions have been optimized for the production of an HTL oil from µalgae (C. Sorokiniana)

SSCI-VIDE+ECI2D+DLA:CGE; International audience; Le projet RafbioAlg financé par l'ANR propose d'évaluer le développement d'une filière de production de biocarburants à partir de micro-algues. Les 5 partenaires du projet ont chacun un rôle bien défini: CEA Cadarache pour la production et sélection des micro-algues, le CEA Liten à Grenoble pour la conversion des micro-algues par HTL, l'IRCELYON pour la coordination du projet et la conversion catalytique des bio-huiles algales, le CORIA de Rouen pour l'étude de la combustion des biocarburants et le LBE INRA Narbonne pour une analyse de cycle de vie (LCA).

RMN+ECI2D+DLA:CLO:CGE; International audience; The use of co-produced lignin from pulp industry or biorefinery gains nowadays a strong interest to produce aromatic compounds in a sustainable way. The valorization of those technical lignins faces their complex structure and the study of lignin conversion requires huge analytic development and careful mass and carbon balance effort during the conversion. Heterogeneous catalysts have proved to increase the liquefaction of lignin by solvolysis especially under hydrogen pressure. We report here the last results obtained for lignin valorization by catalytic hydroconversion, with a CoMo based sulfide catalyst, as a mean to depolymerize lignin and produce aromatic compounds. The originality is the use of a batch reactor opened on the gas-phase, with a continuous feeding of H2, a reflux/condensing system to remove continuously light products and water from the reacting mixture and recycle the solvent. The advanced reaction system has been demonstrated to be powerful compared to a traditional batch system previously used and allows to separate the deoxygenated monomers easily from the reaction mixture. The water formed was also successfully recovered in cold trap and quantified, and, we followed the gases formed online, which is important to get kinetic insights.

MICROSCOPIE:RX+ATARI:CARE:ECI2D+MAO:FBS:FCA:CGE:SLO:PVE; International audience; Nowadays, design of new catalysts has to take into account scarcity of sensitive elements especially noble metals. When decreasing metal loading over a support to address this scarcity, new types of catalytic sites (single atoms, subnanometric clusters) can be stabilized [1]. Such highly dispersed sites have to be more efficient as their number is limited at low loading. Furthermore, the interface between such highly dispersed sites and the support plays a key role since it determines their thermodynamic stability for a given atmosphere as well as their electronic and catalytic properties. We have recently demonstrated the dynamic nature of Pt NPs supported on ceria under reducing/oxidizing sequences at temperatures below 500 °C [2]. This concept of dynamic catalysts can be used to tailor and stabilize more efficient catalytic sites by applying appropriate treatments.This work aims to get new insights into the impact of redox sequences on the Pt/CeO2 interactions for tailoring DOC catalysts. A Pt/CeO2 catalyst containing single-atom Pt was prepared and exposed to model redox sequences in H2/O2 at mild temperatures. The catalyst was reduced either at 250 °C or 500 °C to get different kinetics of the dynamic Pt NPs construction. Then, it has been re-oxidized at three different temperatures (RT, 250 °C, 500 °C) to modulate the redispersion rate. Combined characterization techniques were implemented such as HAADF STEM microscopy, in-situ Raman spectroscopy, in-situ XRD, XPS, CO-FTIR and H2-TPR to deeply characterize the catalyst after redox sequences, in connection with its catalytic activity for CO, NO and propene oxidation in a simulated lean exhaust containing water.Stabilization of raft-like Pt clusters of ca 1 nm diameter in strong interaction with CeO2 was evidenced after redox sequences at 250 °C without Pt incorporation into the CeO2 bulk. These particular sites appeared an intermediate state between single atoms and 3D particles with suitable properties for CO adsorption. They were essentially observed after the 250 °C/RT sequence for which CO was converted at low temperature. Furthermore, the 250 °C/RT sequence was shown to strongly improve CeO2 reducibility and to stabilize new sites containing Pt2+, Ce4+ cations and peroxo species that could be located at the Pt raft/CeO2 and involved in the reaction mechanism. Finally, a new methodology using in situ Raman mapping showed that dynamics between Pt single atoms and 3D particles take place at the microscale, i.e. at the powder grain scale. [1] J. Jones, H. Xiong, A.T. DeLaRiva, E.J. Peterson, H. Pham, S.R. Challa, G. Qi, S. Oh, M.H. Wiebenga, X.I. Pereira Hernández, Y. Wang, A.K. Datye, Science, 2016, 353, 6295.[2] A.M. Gänzler, M., Casapu, P. Vernoux, S. Loridant, F.J.C.S. Aires, T. Epicier, B. Betz, R. Hoyer, J.-D. Grunwaldt, Angew. Chem. 56 (2017) 13078-13082.

SSCI-VIDE+ECI2D+DLA:CGE; International audience; None

+ECI2D+CMT:EPU:PAF:LCS:CGE; National audience; Photocatalytic alcohol dehydrogenation is of great interest to produce green and sustainable H2. Many parameters are involved in this process making it hard to design an efficient, cheap and stable photocatalyst.We proposed to study transition metal sulfides (MSx) supported on titanium dioxide (MSx/TiO2). This system can give an insight into the photocatalytic mechanism. Sulfides have highly tunable properties: electrochemical behavior, ability to activate H2, electronic structure.Four MSx/TiO2 (MSx = MoSx, HgS, NiS2 and RuS2) were prepared and fully characterized with microscopy and XPS, for instance. Their overall efficiency was measured for the dehydrogenation of various alcohol-water mixtures. It allows investigating the oxidation half-reaction. The isopropanol-water mixture was kept as an ideal reactive mixture.In addition to the photonic efficiency (PE), a pre-exponential factor (Aapp) and an apparent activation energy (Ea,app) were measured (See Figure). Those parameters were correlated with the intrinsic parameters of the photocatalyst.The various steps of the photocatalytic process were investigated. Action spectra evidence that the photons absorbed by the MSx do not contribute to the H2 production. Electrocatalytic hydrogen production models the H+ reduction step of the photocatalytic process. Hydrodesulfurization estimates the ability of the MSx to activate H2. It models the H-H coupling step of the photocatalytic process.The RuS2/TiO2 photocatalyst was extensively studied. Various mass of photocatalyst, co-catalyst loading and incident flux of photons were employed. Their influence on PE, Aapp and Ea,app was determined.Finally, the methodology developed in [1] - combining UPS and UV-Vis absorption spectroscopies - determines the electronic structure of the MSx/TiO2. It concludes on its influence on the overall efficiency. [1] C. Maheu, L. Cardenas, E. Puzenat, P. Afanasiev, C. Geantet, Phys. Chem. Chem. Phys., 20, 25629, 2018.

International audience

SSCI-VIDE+ECI2D+DLA:CGE; International audience; Lignin which represents almost 30 wt% of lignocellulosic biomass is the most relevant and abundant bio-resource to produce aromatic compounds thanks to its original polymeric structure composed by methoxy- and hydroxy-phenylpropane units with ether inter-unit linkages [1,2]. The full valorization of lignin co-produced in pulp industry or ethanol biorefinery would be highly beneficial for carbon economy as well as environmental reasons. However the conversion of lignin is not an easy step due to the complex analysis of the starting material and the numerous products formed. Among the various thermochemical processes already proposed in literature, catalytic hydroconversion appeared very attractive to lead to high liquid yield. We propose here the catalytic hydroconversion, with a CoMo based sulfide catalyst, as a mean to depolymerize lignin and produce aromatic compounds. The originality of this work is the use of a batch reactor opened on the gas-phase, with a continuous feeding of H2, a reflux system to remove continuously light products and water from the reacting mixture and recycle the solvent. This advanced reaction system has been demonstrated to be powerful compared to a traditional batch system previously used [4, 5].

+ECI2D+CMT:LCS:EPU:PAF:CGE; International audience; The electronic structure of a semiconductor rules its optoelectronic properties. In photocatalysis, the size of the band gap determines the photons that can be absorbed. The position of the valence band maximum (EVB) and of the conduction band minimum (ECB) fix the potential of the photogenerated holes and electrons, respectively. But each powder has its own electronic structure. It is like the fingerprint of a semiconductor. It depends for instance on: the elements composing the semiconductor, the presence of defects and on the size of the particles.For those reasons, it was mandatory to have a methodology determining the absolute electronic structure of any powder. We proposed such a methodology combining UPS and UV-Vis absorption spectroscopies [1].Two methods are proposed to get layers on a conductive substrate. They both allow getting UPS spectra. The first consists in electrodepositing a charging solution on the substrate and the second consists in drop-casting a powder suspended in alkanes on the substrate.As proof of concept, the absolute EVB was measured at 7.1 eV and 6.7 eV below the vacuum level for commercial anatase and rutile powders, respectively. UV-Vis absorption spectroscopy gives the size of the band gap for the two powders. UPS and UV-Vis spectroscopies combined, give their all band structure which is shown on the Figure.We also analyzed the low energy range of the UPS spectra. It informs on the valence band states of the powders. Four states were identified for the rutile and the anatase. It evidences that the only state contributing to the photocatalytic processes are the non-bonding O 2p orbitals. Commonly the incident energy is not enough to excite below the threshold of the Figure (Ethr.).Adding a co-catalyst to TiO2 increases its photocatalytic efficiency. It is mostly due to a better charge carrier separation. We focused our work on transition metal sulfides supported on TiO2 for the photocatalytic hydrogen production. UPS on TiO2 decorated with RuS2 shows the states of the two semiconductors. Understanding and tuning the sulfides states may help to increase the photocatalytic activity of the material. Bibliography[1] C. Maheu, L. Cardenas, E. Puzenat, P. Afanasiev and C. Geantet, Phys. Chem. Chem. Phys., 2018, 20, 25629

SSCI-VIDE+ECI2D+DLA:CGE; International audience; Lignin, which represents almost 30 wt% of lignocellulosic biomass, is an abundant bioresource which can produce aromatic compounds due to its natural structure. Among various conversion methods, catalytic hydroconversion can depolymerize lignin and produce such aromatic compounds. In the present work, we illustrate the potential of this route by using sulfide catalysts in a batch reactor open for gas phase with a continuous feeding of H2, and equipped with a condensing reflux followed by cooled traps to remove continuously light products and water from the reacting mixture and recycle the H-donor solvent.

+ECI2D+CMT:EPU:PAF:LCS:CGE; International audience; Photocatalytic alcohol dehydrogenation is of great interest to produce green and sustainable H2. Our aim is to identify which parameters play a key role in the photocatalytic mechanism. To do so, we supported four transition metal sulfides (HgS, MoSx, NiS2 and RuS2) on commercial anatase (MSx/TiO2) through a method previously reported. [1] Photocatalytic tests were performed with the MSx/TiO2 in a mix of isopropanol and water (50%vol). The semi-batch reactor was illuminated either with a 370 nm LED or with a 300W Xe lamp equipped with filters. Photon Yield (PY) is calculated as the ratio between the rate of H2 production and the incident flux of photons between 290 and 390 nm. Values are reported on Figure 1. Each of the MSx/TiO2 is active for the conversion of isopropanol in H2 and more active than bare TiO2. Water circulation regulates the temperature of the photoreactor. The PY was therefore measured at various temperature. All the MSx/TiO2 followed an Arrhenius law at least between 5°C and 45°C. Two additional parameters are extracted: a pre-exponential factor (Aapp) and an apparent activation energy (Ea,app). To measured PY at four temperatures, the test lasts at least 20 hours. We confirmed, partly through XPS, that after photocatalytic tests MSx phases were kept. Additionally, we measured the PY at different wavelength, the so-called action spectrum. It evidence that photons only absorbed by the MSx do not participate significantly to the H2 production. As the TiO2, the mass of photocatalyst and the reactor geometry are unchanged, we assumed that the amount of photons absorbed is also unchanged. Variation of PY observed on Figure 1 must be due to intrinsic properties of the MSx.Indeed, the lowest Ea,app were obtained for MoSx and RuS2 (Ea,app = 19 kJ/mol). We made a screening of the bulk sulfides for the electrocatalytic H2 production and a screening of the supported sulfides for thiophene hydrodesulfurization (HDS). Such model reaction shows the ability of a sulfide to catalyze H-H recombination. It showed that MoSx and RuS2 are the two best electrocatalysts with similar activity. On the contrary, the rate of HDS for the MoSx is six times higher than for the RuS2 whereas Ea,app are equal. As a result, the reduction of proton in hydrogen radical is the rate-determining step and recombination of two hydrogen radicals in H2 is faster. Note also that depending on the MSx the driving force of the PY is either the Aapp or Ea,app (See Figure 1). It will be discussed regarding the intrinsic properties of the MSx/TiO2. The slow kinetic for proton reduction is either due to a limited amount of electrons available (electronic structure is the key parameter) or due to low electrocatalytic activity (electrochemical behavior is the key parameter). Those results agree with a microkinetic model established for the photocatalytic dehydrogenation of isopropanol. To distinguish which parameter is the key one, we determined the electronic structure of the MSx/TiO2 with a methodology reported in Maheu et al. [2] UPS evidences that the contribution of the MSx in the valence band states is crucial.