Etude catalytique et cinétique de la méthanation du CO₂ en lit fixe et sous plasma micro-ondes

The aim of this thesis is the development of a CO₂ methanation process, within the power to gas framework, in order to be able to store the excess of electrical energy produced from renewable sources. For this purpose, high-performance Ni and Co catalysts have been developed and characterized by several techniques. The effect of nickel content, calcination temperature and cobalt addition was examined. The characterizations carried out have shown that nickel content and calcination temperature affect the nature of metal species present on the catalyst surface, as well as the reducibility of these species. A contrasting effect on reducibility and dispersion was found after cobalt addition. A 200 hours deactivation test was conducted with the most relevant catalysts. Then, a kinetic model taking into account thermal phenomena in the catalytic bed was processed. Finally, a process for CO₂ hydrogenation under microwave plasma has been developed and the synergistic effect between plasma and catalyst has been studied. This thesis is a multidisciplinary study of CO₂ methanation, starting with the catalyst, going through the process and modelling, and ending with the design of a plasma process.L’objet de cette thèse est la conception d’un procédé de méthanation du CO₂, s’inscrivant dans le cadre du concept Power-to-Gas (PtG), pour pouvoir stocker l’excès d’électricité produite à partir des sources renouvelables. Pour ceci, des catalyseurs performants à base de Ni et de Co ont été développés et caractérisés par plusieurs techniques. L’effet de la teneur en nickel, de la température de calcination et de l’ajout du cobalt a été examiné. Les caractérisations effectuées ont montré que la teneur en nickel et la température de calcination affecte la nature des espèces métalliques présentes à la surface du catalyseur, ainsi que la réductibilité de ces espèces. Il a été constaté que l’addition du cobalt résulte en un effet opposé sur la réductibilité et sur la dispersion du métal. Plusieurs tests catalytiques dans différentes conditions ont été conduits avec les catalyseurs préparés pour estimer leur activité et sélectivité en méthane. Un test de stabilité sur 200 h a été conduit avec les catalyseurs les plus pertinents. Ensuite, un modèle cinétique tenant compte des phénomènes thermiques dans le lit catalytique a été proposé et les paramètres ont été estimés. Enfin, un procédé d'hydrogénation du CO₂ sous plasma micro-ondes a été développé et l'effet synergique entre plasma et catalyseur a été étudié. Cette thèse constitue une étude multidisciplinaire de la méthanation du CO₂, démarrant avec le catalyseur, passant par le procédé et la modélisation, et finissant par la conception d’un procédé sous plasma micro-ondes

Catalytic and kinetic study of CO₂ methanation in a fixed bed and a plasma microwave reactor

L’objet de cette thèse est la conception d’un procédé de méthanation du CO₂, s’inscrivant dans le cadre du concept Power-to-Gas (PtG), pour pouvoir stocker l’excès d’électricité produite à partir des sources renouvelables. Pour ceci, des catalyseurs performants à base de Ni et de Co ont été développés et caractérisés par plusieurs techniques. L’effet de la teneur en nickel, de la température de calcination et de l’ajout du cobalt a été examiné. Les caractérisations effectuées ont montré que la teneur en nickel et la température de calcination affecte la nature des espèces métalliques présentes à la surface du catalyseur, ainsi que la réductibilité de ces espèces. Il a été constaté que l’addition du cobalt résulte en un effet opposé sur la réductibilité et sur la dispersion du métal. Plusieurs tests catalytiques dans différentes conditions ont été conduits avec les catalyseurs préparés pour estimer leur activité et sélectivité en méthane. Un test de stabilité sur 200 h a été conduit avec les catalyseurs les plus pertinents. Ensuite, un modèle cinétique tenant compte des phénomènes thermiques dans le lit catalytique a été proposé et les paramètres ont été estimés. Enfin, un procédé d'hydrogénation du CO₂ sous plasma micro-ondes a été développé et l'effet synergique entre plasma et catalyseur a été étudié. Cette thèse constitue une étude multidisciplinaire de la méthanation du CO₂, démarrant avec le catalyseur, passant par le procédé et la modélisation, et finissant par la conception d’un procédé sous plasma micro-ondes.The aim of this thesis is the development of a CO₂ methanation process, within the power to gas framework, in order to be able to store the excess of electrical energy produced from renewable sources. For this purpose, high-performance Ni and Co catalysts have been developed and characterized by several techniques. The effect of nickel content, calcination temperature and cobalt addition was examined. The characterizations carried out have shown that nickel content and calcination temperature affect the nature of metal species present on the catalyst surface, as well as the reducibility of these species. A contrasting effect on reducibility and dispersion was found after cobalt addition. A 200 hours deactivation test was conducted with the most relevant catalysts. Then, a kinetic model taking into account thermal phenomena in the catalytic bed was processed. Finally, a process for CO₂ hydrogenation under microwave plasma has been developed and the synergistic effect between plasma and catalyst has been studied. This thesis is a multidisciplinary study of CO₂ methanation, starting with the catalyst, going through the process and modelling, and ending with the design of a plasma process

Synergetic effect of microwave plasma and catalysts in CO2 methanation

[EN] The reduction of CO2 concentration in our atmosphere consists in a big challenge for researchers, who are trying to explore novel technologies in order to transform CO2 into high added-value products. CO2 conversion into methane using microwave plasma (MWP) manifests as a very promising solution due to the ease of transport of methane and its storage. Microwave plasma represents a source of high-energy electrons, active ions and radicals that enhance or enable chemical reaction. It can be supplied by electricity generated from renewable resources. Then, MWP does not require any electrode to be generated and thus, the cost of those electrodes and of maintenance is reduced compared to glow discharge or DBD plasmas. MWP also can be generated over wide range of pressure (between 10 mbar-1bar). In addition, in the case of MWP, more electrons and active species are produced in comparison with other type of plasma[1–4]. MWP is a very suitable medium for this chemical reaction and leads to an efficient dissociation of CO2. The catalytic reduction of CO2 with H2 using MWP has been investigated in this work and the synergetic effects between the plasma and several catalysts were studied. First, the reaction was carried out without any catalysts and the effect of CO2/H2 ratio, total flow rate and input energy were evaluated. Then, a microwave generated plasma process was coupled with several Nickel catalysts that we prepared and characterized [5] in order to lead the reaction into methane formation. Multiple configurations were studied by changing the position of the catalyst bed. Obtained results were compared with conventional catalytic tests made with the same catalysts. It was found that the conversion of CO2 and energy efficiency increased using plasma assisted catalytic methanation of CO2 in comparison with conventional process. Operating conditions were studied in order to optimize methane production and energy efficiency of Plasma-catalytic process.Alrafei, B.; Delgado-Liriano, J.; Ledoux, A.; Polaert, I. (2019). Synergetic effect of microwave plasma and catalysts in CO2 methanation. En AMPERE 2019. 17th International Conference on Microwave and High Frequency Heating. Editorial Universitat Politècnica de València. 51-58. https://doi.org/10.4995/AMPERE2019.2019.9806OCS515

Remarkably stable and efficient Ni and Ni-Co catalysts for CO2 methanation

International audienceCO2 methanation is one of the most promising ways to store energy based on the power-togas concept. In this study, efficient nickel (Ni) and nickel-cobalt (Ni-Co), supported on alumina catalysts with different amounts of Ni and Co were prepared, characterized and used for CO2 methanation under the atmospheric pressure. The catalysts were prepared in the form of extrudates for catalytic tests. The effect of Ni content and the influence of Co on Ni catalysts were studied in a packed bed methanation reactor at laboratory scale. An optimal Ni-Co content was identified based on CO2 and H2 conversion and CH4 selectivity and yield. The addition of Co improved the reducibility of Ni species and Ni particles' dispersion over the support. Therefore, the presence of Co enhanced the catalyst activity and selectivity towards CH4. Moreover, it was observed that low reaction temperatures (lower than 350 °C) can be used when lowering the Ni content (i.e. 10% wt.). This major fact is favourable to the reduction of the overall process energy consumption and to the decrease of the catalysts' deactivation at high temperature (>400 °C), such as the active phase sintering. Finally, the Ni and Ni-Co catalysts prepared in this work for CO2 methanation presented a remarkably high stability over 200 h of continuous reaction

Synthetic natural gas production from the three stage (i) pyrolysis (ii) catalytic steam reforming (iii) catalytic hydrogenation of waste biomass

Synthetic natural gas (methane) production was systematically investigated by optimizing various operating parameters using a three stage (i) biomass pyrolysis (ii) catalytic steam reforming (iii) catalytic hydrogenation reactor system. Several operating parameters were optimized including catalytic steam reforming temperature, steam weight hourly space velocity (WHSV), catalytic hydrogenation temperature and hydrogen gas space velocity. In addition, the influence of different metal catalysts (Ni/Al2O3, Fe/Al2O3, Co/Al2O3, and Mo/Al2O3), catalyst calcination temperature, catalyst metal loadings, and different catalyst support materials (Al2O3, SiO2, and MCM-41) was carried out specifically to optimize catalytic hydrogenation in the third stage reactor. The highest methane yield of 13.73 mmoles g−1biomass (22.02 g CH4 100 g−1biomass) was obtained with a second stage catalytic steam reforming temperature of 800 °C over a 10 wt% Ni/Al2O3 catalyst and with a steam WHSV of 5 mL h−1 g−1catalyst together with a third stage catalytic hydrogenation temperature of 350 °C over a 10 wt% Ni/Al2O3 catalyst with added hydrogen gas space velocity of 2400 mL h−1 g−1catalyst