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PhD thesis (M/F). New systems for hydrogen chemical storage without molecular hydrogen

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Date Limite Candidature : jeudi 24 juin 2021

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General information

Reference : UMR5256-VALMEI-004
Date of publication : Thursday, June 3, 2021
Scientific Responsible name : Valérie MEILLE
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 September 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The process of hydrogen storage/destocking in organic liquids is promising in terms of safety and hydrogen storage density. However, the endothermicity of dehydrogenation (hydrogen restitution) induces low energy efficiency compared to direct storage of gaseous hydrogen. The LOHC-DIPAFC (Liquid Organic Hydrogen Carriers / Direct IsoPropAnol Fuel Cell) coupling, consisting of a hydrogen transfer reactor between cycloalkanes and acetone coupled to an isopropanol Fuel Cell, seems to overcome this drawback but remains very exploratory. We propose to optimize the H2 transfer reaction by studying both the chemistry of the reaction (catalyst synthesis, selectivity of the reaction) and the process (thermodynamics, reactor sizing, system dynamics). Simulations and experiments (in batch and continuous reactors) will be carried out jointly in order to arrive more efficiently at an optimal process.

While the catalytic hydrogenation/dehydrogenation reactions of hydrocarbons have been extensively studied, the catalytic hydrogen transfer reaction has been less studied. A performance mapping of the hydrogen transfer reactors will be a prerequisite for the design of the overall process. It will have to take into account the different possible operating variables which are the pairs of ketone/cycloalkane and alcohol/aromatic molecules, the temperature, the pressure, the state of the compounds (liquid or gaseous) and the thermodynamic properties (solubility, saturating vapour pressure,...), the type of reactor used (batch, bubble column, structured reactors,...).

a- Bibliographic synthesis on hydrogen transfer from ketones by LOHCs (part carried out at IRCELYON).
Apart from the publication of reference to this project [1], there is no publication treating this reaction for the objective we are targeting. However, based on hydrogen transfer reactions between cycloalkane/aromatic and alcohol/ketone pairs, where transfer is often used from alcohol as a source of hydrogen, the most suitable catalysts for selective transfer will be identified. Catalysts not using noble metals will be particularly targeted.

b- Thermodynamics of reactions and liquid-vapour equilibria, on different pairs of LOHCs (part carried out at LAGEPP).
As the global system depends on the thermodynamic properties of the chosen LOHCs pairs, thermodynamic property calculations will be carried out using the Prosim software to estimate the compositions of the liquid and gas phases for different Cycloalkane/acetone ratios at the reactor inlet and Aromatic/Alcohol ratios at the end of the reaction, temperatures and pressures of the mixtures. In the case of the LOHC DBT/Perhydro-DBT couple, the different products will be mainly in liquid form whereas the components of the isopropanol/acetone couple may be partly gaseous, depending on the temperature and pressure conditions. Knowledge of the liquid/vapour equilibrium is therefore essential.
Experiments will also be carried out to check the composition of the gas and liquid phases under different pressure and temperature conditions.
It will also be calculated the conversions to thermodynamic equilibrium that it is possible to achieve under these same conditions. This will make it possible to define operating conditions that are most in line with those of the direct isopropanol fuel cell.

c- Implementation of the reaction / kinetic measurements and limitations by transfer (part carried out at IRCELYON).
The hydrogen transfer tests will be carried out initially in a closed reactor (in a two or three-phase stirred vessel), by screening different catalysts synthesized or commercially available. NB: Pending the delivery of a reactor at IRCELYON, a larger volume reactor will be used for the preliminary tests at LAGEPP. The test reaction will be hydrogenation by transfer of acetone by perhydro-DBT. Special attention will be paid to the selectivity of the reaction. Since the reactions must be reversible for the system to work, no C-C or C-O hydrolysis will be tolerated.
After selecting at least 1 catalyst, the reactor will be modified to operate continuously. The catalyst will be coated on foam. The purpose of these experiments is to complete the mapping of possible operating conditions, to evaluate hydrogen transfer kinetics, to highlight potential limitations by mass transfer between phases and to verify the data obtained by Prosim on the liquid-vapour and thermodynamic equilibria of the reactions.

[1] : G. Sievi, D. Geburtig, T. Skeledzic, A. Bosmann, P. Preuster et al., Energy Environ. Sci., 2019, 12, 2305-2314.

Work Context

This research requires skills in both catalysis/catalyst shaping/kinetic and analytical monitoring of catalytic reactions and process/thermodynamics/systems. The association of the Lyon-based laboratories IRCELYON and LAGEPP is therefore perfectly adapted to the needs of the project. V. Meille, CR in catalysis, develops methods for coating catalysts on structured reactors and is involved in the construction of pilot reactors and their operation (kinetics). I. Pitault, CR in Process Engineering, is specialized in the study and design of reactive processes and in particular their dynamic modeling. The 2 researchers will be respectively director and co-director of the thesis.
The collaboration will be reinforced by the intervention of other members of their teams.

Additional Information

CNRS PhD thesis in the framework of the NOSY-H2 project, laureate of 80|PRIME call.

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