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Kinetic study and deactivation phenomena for the methanation of CO2 and CO mixed syngas on a Ni/Al2O3 catalyst
No full textInternational audienceThis study presents a detailed kinetic and deactivation analysis of a 24 wt% Ni/Al2O3 catalyst for the hydrogenation of CO2 and CO to CH4, focusing the attention on the CO2 and CO co-methanation. More than 300 reaction conditions were tested on a fixed-bed reactor obtaining 907 observations. Among them, 852 measurements were used to derive the kinetic parameters in an isothermal reactor model. Power-law models accurately describe CO2 or CO methanation, but fail to predict co-methanation due to preferential adsorption of CO. On the contrary, a three-reactions Langmuir-Hinshelwood-Hougen-Watson model (model M4) successfully described it together with the different hydrogenation pathways. Experimental and literature insights suggest that CO2 adsorption occurs via either dissociative or H-assisted associative mechanism, and then, the high H* coverage favors its conversion into CH4 via the so-called dissociative formyl (CHO*) route. On the contrary, the exergonic CO adsorption increases the CO* coverage promoting the dissociative carbon (C*) route. In addition, C* species are responsible for the higher deactivation rates in CO methanation due to the formation of nickel carbides and coking. Long-term stability tests revealed several deactivation phenomena. CO2 methanation induced mild sintering, while CO methanation led to a significant decrease in stability. Notably, co-methanation improved stability at low temperature by suppressing nickel carbide formation. Contaminants like O2 and C2H4 decreased the stability due to re-oxidation and coking, respectively, while poisons like H2S deactivated the catalyst irreversibly. Power-law deactivation models were developed to predict the activity loss, supporting the potential scale-up of CO2 and CO methanation processes
Transition éthique dans le milieu équestre: tensions, régulations et recompositions de l’action collective
No full textInternational audienceLes pratiques équestres actuelles sont remises en cause par des mobilisations citoyennes et militantes qui exigent une prise en compte du bien-être animal, sur différentes arènes, qu’elles soient numériques ou non. Nous étudions les rhétoriques et les mises en scène mobilisées ainsi que les éventuelles ouvertures au dialogue entre les camps, aménagées pour accompagner la transition vers des pratiques plus éthiques. En!n, nous identifions les recompositions de l’action collective et leurs effets sur les pratiques et sur l’évolution des discours organisationnels
Dissolved carbonate exports in the Chevaline river (Choranche, Vercors). Period 2008–2018
No full textInternational audienceHere we present some preliminary results on the export of dissolved carbonates in a mid-mountain underground river: Chevaline (Vercors, France). A hydrometric station (2008–2018) records water levels, temperatures, and conductivities (every 30 minutes). Water levels are converted into flow rates and conductivity is converted into dissolved carbonate concentrations. This allows us to calculate dissolved carbonate flow rates. The underground river is subject to significant encrustation. Some of the calcite is deposited upstream of the measuring station and some far downstream. The measurements we propose do not account for all the dynamics of karst dissolution. However, they do allow us to analyze the dissolved export downstream of this mid-mountain karst system. The flow distribution shows a strong asymmetry with flows varying from 0 to 3.6 m3/s. The median is 37.7 l/s. The same distribution of dissolved carbonate exports is observed with carbonate flows ranging from 0 to 880 g/s. The amplitude of carbonate concentrations is limited to between 186 and 296 mg/l. It is the quantity of water that controls carbonate flows, not the carbonate content. We then analyze the evolution of dissolved exports over 10 years. Dissolved carbonate exports show variations ranging from single to double during this period (min: 415 t, max: 923 t). We then recalculate these dissolved exports according to the four hydrological situations of equal duration: low water, low flow, high flow, and floods. Floods represent an average of 25% of the hydrological time over 10 years. They account for 63% to 78% of chemical erosion
Chitosan hydrogels as passive samplers for the analysis of norovirus in various types of water
No full textInternational audienc
Safe, sustainable and recyclable by design (SSRbD): A qualitative integrated approach applied to polymeric materials early in the innovation process
No full textInternational audienceThe safe and sustainable by design (SSbD) concept integrates functionality with safety and sustainability aspects at an early phase of the innovation and product development process. A qualitative integrated safe, sustainable-and-recyclable-by-design (SSRbD) approach was developed in a series of co-creation workshops involving risk assessors, toxicologists, eco-design and sustainable development experts. The SSRbD approach consists of: 1) the identification of functionality, criticality, toxicity, environmental, social, circularity/recyclability, and economic impacts in a life cycle thinking perspective; 2) the development ofSSRbD strategies; and 3) verification of SSRbD strategies. This first 2 steps were applied to three case studies (Building sector: New recyclable-by-design bio-sourced polyurethane (PU) to replace PVC (Polyvinyl Chloride) as insulating material for window frames; Transport sector: Fire resistant, intrinsically recyclable epoxy-vitrimer materials for sustainable composites to replace metal for train body; and Packaging sector: Recyclable MultiNanoLayered (MNL) films to replace multi-layer films for packagingwith drastically reduced concentrations of compatibilizers). A guidance for identifying polymer material relevant information needs was developed. In terms of internal organization, an interdisciplinary group for case study assessment was developed. Each case study comes with challenges and needs, which is why a tailor-made approach is required for application of SSRbD of polymeric materials and products
Use of Carbon Nanotubes for the Functionalization of Concrete for Sensing Applications
No full textInternational audienceThis study advances the development of self-sensing concrete through functionalization with carbon nanotubes (CNTs) for structural health monitoring. Through experimental analyses, it relies on its dual responsiveness to mechanical and thermal stimuli. Three-point bending and thermal tests were systematically conducted on concrete samples with CNT concentrations ranging from 0 to 0.05 wt.% of cement, evaluated at 7- and 28-day curing periods. Mechanical testing demonstrated curing-dependent behavior: At 7 days, mechanical strength and electrical current response exhibited pronounced variability across CNTs loadings, with optimal balance achieved at 0.01% CNTs. At 28 days, the tests show that the mechanical properties are relatively stabilized, reaching the highest value at 0.006 wt.% CNTs and achieving the best electrical sensitivity at 0.01 wt.% CNTs. The thermal experiments revealed faster current modulation in the 7-day samples than in the 28-day counterparts, with intermediate CNT concentrations (e.g., 0.01 wt.%) showing a more sensitive response. The sensitivity was analyzed for both mechanical and thermal changes to further evaluate the feasibility of using CNT-reinforced concrete as a sensor material. Conductivity measurements on fully cured samples indicated that all samples exhibited electrical conductivities in the 10−4 S/m range, suggesting semiconductive behavior, while 0.006 wt.% CNTs yielded the highest conductivity. Higher CNT content did not further improve conductivity, likely due to agglomeration disrupting the network. These findings confirm CNT-modified concrete’s dual electromechanical and thermal responsiveness and support its potential as a multifunctional sensing material
La moisson du Soleil. L'hélio-odyssée d'Augustin Mouchot racontée par lui-même
No full textInternational audienceConstruit sur un procédé narratif original, cet ouvrage restitue à la première personne le parcours de recherche et d'expérimentations solaires du précurseur français Augustin Mouchot (1825-1912). L'ouvrage comporte de nombreux extraits de la presse de l'époque et d'archives inédites. Il complète, dans une perspective de médiation scientifique et d'ouverture à un plus large public, la biographie historique L'invention de l'énergie solaire que nous avons fait paraître en 2023. A la différence de ce dernier le présent ouvrage ne concerne que la période de recherches sur l'énergie solaire de la vie d'augustin Mouchot
Mathematical modeling of a force–velocity-position relationship in vertical jump
No full textInternational audienc
Rapidity and multiplicity dependence of charged-particle flow in Pb collisions at TeV
No full textInternational audienceThe elliptic and triangular flow of charged particles are measured using two-particle angular correlations in Pb collisions in the pseudorapidity range \cal{2.0 4.8}. The data sample was collected by the LHCb experiment in 2016 at a centre-of-mass energy per nucleon pair of TeV, containing in total approximately 1.5 billion collision events. Non-flow contributions are obtained in low-multiplicity collisions and subtracted to extract the flow harmonics. The results are presented as a function of event multiplicity and hadron transverse momentum. Comparisons with a full (3+1)D dynamic model indicate that it overestimates the measured elliptic flow. A comparison between the forward and backward regions reveals no significant differences in flow parameters, suggesting that final-state effects may dominate over initial-state effects in the origin of flow in small systems
Physics-Informed Gaussian Processes model for heat source identification
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