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Photoreduction of CO2 to CH4 over Efficient Z-Scheme γ -Fe2O3/g-C3N4 Composites
No full textInternational audienceA series of composite γ-Fe2O3/g-C3N4 (denoted as xFeCN with x equal 5, 10, 15, and 20 of γ-Fe2O3 percentage in weight) was prepared by calcination and precipitation-impregnation methods. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectrometry (XPS) characterizations indicated the successful synthesis of Z-scheme FeCN composites. A red shift of the light absorption region was revealed by UV-vis diffuse reflectance spectroscopy (UV-DRS). In addition, photoluminescence spectroscopy (PL) spectra showed an interface interaction of two phases Fe2O3 and g-C3N4 in the synthesized composites that improved the charge transfer capacity. The photocatalytic activity of these materials was studied in the photoreduction of CO2 with H2O as the reductant in the gaseous phase. The composites exhibited excellent photoactivity compared to undoped g-C3N4. The CH4 production rate over 10FeCN and 15FeCN composites (2.8 × 10−2 and 2.9 × 10−2 μmol h−1 g−1, respectively) was ca. 7 times higher than that over pristine g-C3N4 (0.4 × 10−2 μmol h−1 g−1). This outstanding photocatalytic property of these composites was explained by the light absorption expansion and the prevention of photogenerated electron-hole pairs recombination due to its Z-scheme structure
Efficient polymerization and crystallization kinetics coupling of polyamide 6 synthesis for liquid composite molding process modeling
No full textInternational audienceVariabilities in polyamide 6 (PA6) composite manufacturing by liquid processes can occur due to polymerization, crystallization, and flow through a fibrous preform. Numerical simulations of the process predicting the kinetics can facilitate manufacturing optimization. This study proposes an efficient modeling approach that can be integrated in current simulation discretization methods such as the finite volume method (FVM) while considering the interaction between PA6 polymerization and crystallization. Using polymerization and crystallization models issued from the literature, a previous study determined Hillier coupling method to be able to predict PA6 kinetics. A simpler and more efficient coupling will be introduced and adapted to account for process variability. It was integrated into an FVM framework for process simulation of injection showcasing the capabilities of the model to predict potential crystallization discrepancies
Characteristics and evolution of heavy components in bio-oil from the pyrolysis of cellulose, hemicellulose and lignin
No full textInternational audienceThree main components of biomass were pyrolyzed individually in a closed reaction system at 500–700 °C for 60s and 90s. Then bio-oil heavy compounds were further analyzed with Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) and Kendrick mass defect (KMD) analysis. The evolution paths of heavy compounds for the different pyrolysis stages were proposed. It was found that the sugars and phenolic-like species in heavy compounds were the most active substances during secondary reactions. Moreover, the rising temperature promoted this secondary reaction of phenolic-like species as the decrease in their abundances growing from 13% to 54%, while contrarily inhibited it for hemicellulose as the decrease in their abundances changing from 44% to −2%. The lignin-derived lipids and unsaturated hydrocarbons that generated in the secondary reactions increased with rising temperature. KMD analysis showed that the heavy compounds of cellulose and hemicellulose prefer homologous evolution during pyrolysis, while those of lignin had more complex evolution paths like cracking and recombination
Excipients lipidiques et technologie d’enrobage sans solvant impact fonctionnel et biopharmaceutique
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Amélioration de la cinétique de dissolution de la nifédipine cristallisée par procédé anti-solvant de CO2 supercritique
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Catalytic conversion of bioresource to graphene-based materials
No full textInternational audienceGraphene is a bidimensional material with one atomic layer as thickness. Graphene sheets are highly organized in graphitic structure or randomly oriented in turbostratic structure, leading to the formation of carbon nanotubes, carbon fibers, carbon black. Depending on the characteristics such as the length and the orientation of the graphene sheets, various properties could be developed: electrical conductivity, mechanical or thermal resistance. Therefore, graphene is considered as a highperformance material, in applications such as batteries, energy storage, electronics, and biology. Currently, materials are produced from petroleum-based industries (exfoliation or chemical vapor deposition) leading to a high negative environmental impact. Graphene production from carbon resources requires the progressive organization of carbon atoms into fused benzene rings (namely basic structural units), then the coalescence for larger graphene sheets over 2000°C. Their organization (graphitic, turbostratic) will impact the final properties of the designed material. Aromatization and coalescence phenomena are strongly related to the original feedstock, and resources are sorted into graphitizable and non-graphitizable materials. The aim is to use bioresources (biomass polymers), non-graphitizable carbons, to enhance the quantity and the quality of graphenic domains during catalytic pyrolysis up to 1800°C. For this purpose, the catalysts are more likely selected among inherent biomass minerals providing a green approach for graphene synthesis. This study investigates the impact of catalyst on the evolution of the graphenic structure, texture and nanotexture in biochars. Graphitization experiments have been carried out in a high-temperature furnace (1800°C) with raw materials (lignin or cellulose) either impregnated or not with Ca or P catalysts. The remaining biochar was characterized to evaluate the quality of graphitization using combined techniques: HRTEM, Raman Spectroscopy and XRD. The impregnation of raw materials significantly improved the graphitization parameters such as length of basal sheets, stacking and significantly reduced the amount of amorphous carbon.</div
Experimental Evaluation of a Pilot-Scale Thermocline Thermal Energy Storage Combining Latent and Sensible Materials
No full textInternational audienceThis work presents the experimental evaluation of pilot-scale thermocline that integrates a layer of phase change material (PCM) at the top of a sensible heat storage material in a thermocline thermal energy storage (TES) tank. The TES is integrated to the MicroSol-R parabolic trough pilot plant at the PROMES research facility in Odeillo, France. The tank is filled with alumina spheres as sensible heat storage. The PCM is NaNO3 encapsulated in stainless steel horizontal tubes that fill about 5.5% of the tank volume. The charge is evaluated at three mass flow rates 2600, 3000, and 3900 kg/h at two different operating temperature ranges 285-315 ºC and 295-330 ºC. The discharge is studied at three mass flow rates 1600, 2000, and 3000 kg/h from 315 to 220 ºC and 330 to 225 ºC. The performance of the TES is analyzed with two main indicators: the thermocline thickness and the efficiency during the charge and discharge. The results indicate that lower mass flow rates during the charging process result in smaller thermocline thickness. Similarly, during discharge, the thermocline thickness reduces with lower discharge rates. Efficiency evaluation during discharge suggests that an optimal flow rate could be achieved
