The thermochemical process converts almost any kind of biomass to a desired final product, i.e. gaseous or liquid transportation fuels and chemicals. The transportation fuels obtained in this way are renewable biofuels, which are alternatives to fossil fuels. During the last few years, thermochemical plants for the production of bioethanol have been launched and another is under construction. A total of about 290 million liters of ethanol are expected to be processed per year, mostly using municipal solid waste. Considerable efforts have been made in order to find a more selective catalyst for the conversion of biomass-derived syngas to ethanol. The thesis is the summary of five publications. The first two publications (Papers I and II) review the state of the art of ethanol and higher alcohols production from biomass, as well as the current status of synthetic fuels production by other processes such as the Fischer-Tropsch synthesis. Paper III analyses the catalytic performance of a mesoporous Rh/MCM-41 (MCM-41 is a hexagonal mesoporous silica) in the synthesis of ethanol which is compared to a typical Rh/SiO2 catalyst. Exhaustive catalytic testing including the addition of water vapor and modifying the hydrogen partial pressure in the syngas feed-stream which, in addition to the catalyst characterization (XRD, BET, XPS, chemisorption, TEM and TPR) before and after the catalytic testing, have allowed concluding that some water vapor can be concentrated in the pores of the Rh/MCM-41 catalyst. The concentration of water-vapor promotes the occurrence of the water gas shift reaction, which in turn induces some secondary reactions that change the product distribution, as compared to results obtained from the typical Rh/SiO2 catalyst. These results have been verified in a wide range of syngas conversion levels (1-68 %) and for different catalyst activation procedures (catalyst reduction at 200 °C, 500 °C and no-reduction) as shown in Paper IV. Finally, similar insights about the use of mesoporous catalyst have been found over a Cu/MCM-41 catalyst, shown in Paper V. Also in Paper V, the effect of metal promoters (Fe and K) has been studied; a noticeable increase of ethanol reaction rate was found over Cu-Fe-K/MCM-41 catalyst as compared to Cu/MCM-41. / <p>QC 20161125</p>

This thesis comprises an assessment of a novel concept to produce high purity hydrogen using mixed oxide ion/electronic conductor (MIEC) membranes and energy provided by solar concentrators (i.e. parabolic troughs or parabolic dishes). The vision of this concept is that it will be used to produce tons of high purity hydrogen for fuel cells, which is a scarce commodity with an increasing demand from residential and transportation power generation applications. The MIEC membrane activates a steam reforming reaction between water and methane to produce hydrogen of high purity on the water side and syngas on the fuel side. Expectations are that this concept has cost advantages over other thermo-chemical water-dissociation methods, using a lower temperature and no electricity for the reaction process. The thesis’ focus is on techno-economic aspects of the concept, as part of an application process for project financing by the European Commission of Research and Innovation. The assessment in the thesis shows that the overall efficiency of the concept is expected to be very low. It also identifies the difficulties of providing stable working conditions for the concept. Suggestions to improve the concept are proposed to address the most urgent problems of the concept. These suggestions illuminate the opportunities that actually do exist to combine MIEC membranes, solar energy and thermo-chemical water splitting into a working concept. These improvements include using parabolic dishes instead of parabolic troughs, using furnaces with control systems and using a viable flow rate. The production capacity of high purity hydrogen is expected to be approximately 89 mg per minute in a membrane bundle (i.e. 150 thin membrane fibers with an oxygen permeation flux of 1 ml cm-2 min-1) if these improvements were implemented. This would imply that the studied concept needs further development to produce high purity hydrogen in quantities that could meet the shortage on the commercial fuel cell markets.

Maitriser la logistique de la chaine du froid à des températures de -20°C/-30°C reste un enjeu majeur de sécurité sanitaire. Des solutions auto-réfrigérées basées sur des systèmes thermochimiques sont très adaptées à la mise en température rapide de caissons isothermes et de leur maintien pendant plusieurs heures. Différents concepts et configurations de procédés répondant à cette problématique sont proposés. Leur modélisation dynamique de type nodale, impliquant une gestion thermodynamique d'un ou plusieurs réacteurs, a permis d'analyser leur comportement et d'évaluer leur pertinence. Les configurations les plus performantes sont sélectionnées et analysées afin d'établir un pré-dimensionnement industriel du procédé. D'autre part, la fiabilité de ces systèmes thermochimiques repose sur la qualité des transferts de masse et de chaleur au sein des réacteurs. A cette fin, une approche de diagnostic de dysfonctionnements possibles de réacteurs est développée. La méthodologie proposée s'appuie sur la comparaison de la réponse expérimentale du réacteur testé à celle modélisée d'un réacteur opérant dans les mêmes conditions opératoires présentant ou non des défauts. Une base de données de comportements de réacteurs défaillants, établie par simulation de défauts de typologie et d'intensité connues, permet ainsi la détection et l'identification rapide de possibles dysfonctionnements de réacteurs issus de la chaine de fabrication. / A better cold chain logistics understanding and control is a major safety issue in deep freezing processes within -20°C/-30°C. Self-cooling solutions based on thermochemical systems appear very suitable for rapid cooling of isothermal containers and its temperature regulation for several hours. Different process concepts and configurations are presented to tackle this problem. Through their dynamic nodal modeling, involving thermodynamic management of one or various reactors, an analysis of their behaviors is performed to evaluate their relevance. A selection of the best performing configurations leads us to an industrial pre-design.To undertake quality measures, a diagnosis approach for possible reactors malfunctions is developed. The methodology is based on a comparison of experimental responses between tested reactor and reference one under the same operating conditions. A database of simulated faulty behaviors will allow the detection and identification of possible malfunctions of reactors coming from the production line.