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SSCI-VIDE+ING+DFA:CDA; International audience; Metal-Organic Frameworks have been investigated as adsorbents for Heat-Pump applications, especially for chilling applications using water as working fluid. Today, Silica Gel bead is the current adsorbent technology which is used in adsorption chillers. While its water adsorption capacity is relatively limited, its very low manufacture cost made Silica Gel beads very competitive. Nevertheless, the performances of silica gel are still limited to address important application challenges. Technico-economical studies show that new very performing adsorbents shall be investigated for the conversion of low temperature heat produced by data center.Thanks to their very high adsorption capacity, type V isotherm and ease for regeneration thanks to their low heat of adsorption, MOFs are in principle ideal candidates for cycling adsorption and desorption of water. As consequence MOF could outperform silica gel based on technical criteria. Especially, Al-fumarate is regarded with promises as it is stable in hydrothermal conditions and can be produced without organic solvents. In addition, due to its framework flexibility upon adsorption Al-fumarate shows adsorption isotherm displacement as function of the temperature which shall enable a facilitated regeneration .However to date, technico-economical studies of Al-fumarate as adsorbent for adsorption chillers have not been published yet. To date, the promises rely mostly on water uptake at equilibrium conditions. In the frame of PRODIA, an European program, Al-fumarate beads have been developed to meet ambitious technical targets while being cost compatible.While the paper will not discuss the development of manufacture process, it is worth mentioning that the synthesis processes and shaping technics which have been developed meet industrialization criteria. The continuous mechano-chemical synthesis on Al-fumarate without solvent enables upscaling at high production rates whilst achieving high yields, adsorbent quality and higher operational safety. In addition, an original scalable shaping process was developed enabling continuous production of robust and size-controlled spheres from 0.3 to 2mm made of Al-fumarate.In the course of the development, we found that the cycling capacity on Al-fumarate beads were lower than the pristine powder at thermodynamic equilibrium. Three phenomena which could penalized adsorption capacities in were identified and investigated.1/ does the guest induced transformation of Al-fumarate occur in the time frame of the adsorption-desorption processes ?2/ are the uptake kinetics limited by a diffusion regime in the Al-fumarate porous beads ? due to the binders ? or due to the bead size ?3/ are the uptake kinetics limited by mass transport limitation in or between Al-fumarate beads ?In order to unravel the origin of kinetic limitations on Al-fumarate beads, series of beads of different diameter (0.4, 1.2, 1.6mm) and binder contents were synthesized. Mass ad heat transport were measured in a special device in adsorption and desorption modes. Kinetic results are compared with silica-gel beads. We will show that beads of 0,4 mm of diameter show fast uptake kinetics.Small spheres of 0.4 mm of Al- and Zr-MOF were produced at multi-kg scale. The performances of MOFs were evaluated in 3 liter adsorber demonstrator. We will show that MOFs outperform commercial Silica Gel under standard cycling conditions. Results in extremely low regeneration temperature will be presented and discussed in the frame application market requirements.

Dimethylcarbonate (DMC) is used in polymer synthesis as well as a fuel additive and solvent. The current industrial DMC production is a polluting and hazardous process. On the other hand, the direct carboxylation of methanol with CO2 is a green route to DMC. However, this reaction is highly limited by thermodynamics, limiting the conversion to less than 1%. The integration of a catalyst in a catalytic membrane reactor for water and DMC removal, would shift the equilibrium conversion thereby improving the DMC yield. The aim of this thesis is to develop and study highly active catalysts for DMC synthesis. This manuscript covers: (i) catalyst screening (ii) a structure-activity relationship study (iii) a mechanistic approach and (iv) a kinetic study. A protocol to measure the activity at low conversion has been developed. Catalyst screening evidenced solid solutions of ceria/zirconia (CZ) as the most active and selective. Flame sprayed pyrolysis ceria/zirconia are one order of magnitude more active than coprecipitated CZ. Interestingly, structural and textural features like crystalline and porous structure were similar regardless of the activity. Nevertheless, the activity could be correlated to the nature and the density of the methoxides and carbonates surface species. The mechanism was refined by isotopic exchange and DRIFT experiments. A kinetic study was performed in a batch reactor that integrated the physical equilibria of the gas-expanded reacting mixture., Le carbonate de diméthyle (DMC) est utilisé comme intermédiaire en chimie des polymères. Actuellement, la production industrielle du DMC met en jeu un procédé polluant et dangereux. En revanche, la synthèse du DMC à partir de méthanol et de CO2 est un procédé « vert ». Cependant, la thermodynamique de la réaction est très défavorable, se traduisant par une conversion inférieure à 1%. L’objectif de cette thèse est de développer et d’étudier des catalyseurs très actifs qui, couplés à un réacteur membranaire, permettraient d’augmenter le rendement et l’activité. Ce manuscrit couvre plusieurs aspects : i) une étude de criblage de catalyseurs, ii) une étude de type structure-activité sur des séries de catalyseurs, basée sur des caractérisations structurales, texturales et de surface, iii) une étude mécanistique et iv) une étude cinétique. Un protocole de mesure d’activité adapté aux faibles conversions est développé. Le criblage catalytique met en évidence l’activité des solutions solides de cérine-zircone (CZ). Les CZ préparées par pyrolyse de flamme sont un ordre de grandeur plus actives que les CZ préparées par coprécipitation. De façon surprenante, il n’est pas possible a priori de distinguer des catalyseurs très actifs et peu actifs à partir de leurs caractéristiques structurales et texturales. Cependant, on observe que l’activité est corrélée à la densité et à la nature des espèces de surfaces méthoxides et carbonates. Le mécanisme réactionnel de l’état de l’art est affiné grâce à des mesures d’échanges isotopiques et de DRIFT. L’étude cinétique intègre des corrections thermodynamiques de l’équilibre de phases du binaire MeOH-CO2 qui constitue un liquide expansé

International audience; Number of methods have been reported in the literature for the preparation of dimethyl carbonate (DMC) as an important chemical compounds typically applied in methylation and carbonylation reactions. Recently a particular attention has been paid to the reaction of methanol with carbon dioxide as an alternative to other syntheses involving hazardous and toxic components [1]. In such a reaction system a highly active catalyst is required to make this method competitive in comparison with other types of synthesis routes.In this work we report on the preparation of ceria-zirconia mixed-oxides, which are considered as particularly promising for meeting the requirements leading to performable DMC synthesis. The synthesis strategy is based on the preparation of a supported catalyst starting from polymeric sols/gels (prepared by the Pechini method) which are subsequently deposited/infiltrated uniformly on/in inert porous ceramic support. Before performing the catalyst deposition step unsupported CeO2-ZrO2 powders have prepared and characterized in order to confirm the formation of the required uniform mixed-oxide with both defined composition and textural characteristics. The optimized sol formulations were subsequently used for the impregnation of the porous ceramic supports. During deposition, the sol viscosity was also controlled in order to limit the formation of a surface coating which was shown to suffer from attrition. The as-prepared catalyst has been tested for DMC synthesis in a continuous stirred tank reactor evaluating its catalytic activity as a function of the quantity and specific surface area of the active phase deposited on/in the porous ceramic support. [1] S. T. Hong et al., Synthesis of dimethyl carbonate from methanol and supercritical carbon dioxide, Research on Chemical Intermediates 32 (2006) 737-747.

International audience; Nano-zeolites and hierarchical zeolites have shown enhanced transport properties that are generally attributed to a shorter diffusion path length (L). However, the concomitant increase in the external surface of these types of zeolites may also affect overall transport as the interfaces may act as diffusion barriers. Recently, hollow zeolite crystals have been presented as an alternative zeolite morphology. They possess a large inner cavity and an overall size and shape similar to those of plain microporous zeolite. In contrast to classic hierarchical zeolite materials, the inner cavity of the hollow zeolite induces a shortened diffusion path length with no effect on external surface area. In this work, we have studied the impact of diffusion path length on transport properties by comparing the characteristic time of transport of hydrocarbons in plain zeolite crystals and their hollow counterparts, using zero-length column (ZLC) measurements. Our results show that hollow morphology doubles or quadruples the transport speed for Silicalite-1 and Beta zeolites, respectively. Compared to other reports focusing on nanosized or hierarchical zeolites, this study is free of any bias due to major modifications in external surface area, because hollow and plain zeolites have very similar crystal dimensions.

SSCI-VIDE+ING+DFA:CDA; International audience; We present here the results of a 3-year project aiming at the development of pilot scale production and shaping of MOFs and at their demonstration in Heat-Pump application at kilogram scale in relevant process conditions.Although MOFs outperform commercial adsorbents for heat-pump application in terms of higher water uptake and cyclability, their commercialisation was until now strongly penalized by their price due to high production process costs. The objective of this program was to develop low cost manufacture processes allowing the production of advanced and cost-competitive adsorbents. We have developed innovative and scalable MOF production processes including synthesis and shaping, for which (i) manufacturing equipment’s are readily available at industrial scale, and (ii) enable upscaling at high production rates whilst achieving high yields, product (sorbent) quality and higher operational safety. We will present three main technological innovations: (i) aqueous synthesis of UiO-66 without the use of corrosive acid modulator (ii) continuous mechano-chemical synthesis on Al-fumarate without solvent and (iii) original scalable shaping process enabling continuous production of robust and size-controlled spheres (beads). In contrast to other adsorbents, we discovered that performances of MOF were jeopardized due to severe mass transport limitations likely due to the organic binder. In order to overcome this limitation small spheres of 0.4 mm (0.3 mm – 0.7 mm) of Al- and Zr-MOF were produced at multi-kg scale. The performances of MOFs were evaluated in 3 liter adsorber demonstrator. We will show that MOFs outperform commercial Silica Gel under standard cycling conditions with stability over 10.000 cycles. Results in extremely low regeneration temperature will be presented and discussed in the frame application market requirements.This work has received funding from the EU under grant agreement No 685727.