Добірка наукової літератури з теми "Carbon dioxide methanation"

CO2 methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO2) to synthetic natural gas (CH4). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts and as adsorbent phases upon the combined capture and methanation of CO2. Their promotion effect during methanation of carbon dioxide mainly relies on their ability to generate new basic sites on the surface of metal oxide supports that favour CO2 chemisorption and activation. However, suppression of methanation activity can also occur under certain conditions. Regarding the combined CO2 capture and methanation process, the development of novel dual-function materials (DFMs) that incorporate both adsorption and methanation functions has opened a new pathway towards the utilization of carbon dioxide emitted from point sources. The sorption and catalytically active phases on these types of materials are crucial parameters influencing their performance and stability and thus, great efforts have been undertaken for their optimization. In this review, we present some of the most recent works on the development of alkali and alkaline earth metal promoted CO2 methanation catalysts, as well as DFMs for the combined capture and methanation of CO2.

Catalyst by different carriers prepared of carbon dioxide conversion sequence is: Ni/TiO2> Ni/γ-Al2O3> Ni/MgO > Ni/SiO2. Second metal, Co, Mn, Cu, La and Ce, was significantly enhanced the activity of methanation nickel-based catalysts in the carbon dioxide methanation reaction, but second metal of Cu was bad for the activity of methanation. The 10%Ni/Al2O3 and 2.5%Ce-10%Ni/Al2O3 catalysts were characterized by TG and H2-TPR，it was revealed to Ce which is benefit for reduce NiO reduction temperature and the optimal reduction temperature of the catalysts in between 400°C and 500 °C

The growing emission of carbon dioxide (CO2), combined with its ecotoxicity, is the reason for the intensification of research on the new technology of CO2 management. Currently, it is believed that it is not possible to eliminate whole CO2 emissions. However, a sustainable balance sheet is possible. The solution is technologies that use carbon dioxide as a raw material. Many of these methods are based on CO2 methanation, for example, projects such as Power-to-Gas, production of fuels, or polymers. This article presents the concept of using CO2 as a raw material, the catalytic conversion of carbon dioxide to methane, and consideration on CO2 methanation catalysts and their design.

The transformation of the current energy model towards a more sustainable mix, independent of fossil fuels, requires the exploration of new technologies that are capable of taking advantage of excess electricity derived from renewable energy sources and to use new alternative sources of carbon for the generation of clean fuels. An alternative that combines both is the Power-to-Gas (P2G) technology, whose concept is based on a two-stage process. In the first stage, excess electricity from renewable energies is converted to hydrogen by electrolysis. Then, in a second stage, the H2 produced is transformed to CH4 through methanation with CO2. The CH4 produced is referred to as synthetic natural gas (SNG) and allows large amounts of renewable energy to be distributed from the energy sector to the end-use sectors. The thermo-chemical CO2 methanation process is considered the most efficient route for large-scale SNG production. However, developing a cost-effective CO2 methanation technology is one of the biggest challenges facing the P2G concept. In this context, this thesis focused on the catalyst and reactor design for CO2 methanation. The thesis objectives were addressed in three main aspects, which are: i) design a high-performance catalyst based on metal oxide-promoted Ni/γ-Al2O3 and determine its reaction mechanism; ii) evaluate the stability of the catalyst and the tolerance to sulfur for its implementation in a relevant industrial environment (CoSin project); and finally, iii) develop a CFD model based on experimental kinetic data to understand the role of operating conditions and propose a new reactor configuration. In the first Chapter of this thesis it is presented a general introduction of the SNG production through CO2 methanation process. In the second Chapter, the addition of a promoter (X) on a system composed by Ni and γ-Al2O3 microspheres was studied as the design strategy to develop a micro-sized Ni-X/γ-Al2O3 catalyst. The catalysts based on Ni-CeO2/γ-Al2O3 was proposed as the most feasible due to its high catalytic performance in relation to its economic competitiveness. The optimal composition of each component of the Ni-CeO2/γ-Al2O3 was found through a systematic experimental design. The catalyst composed by 25wt.%Ni, 20wt.%CeO2 and 55wt.%γ-Al2O3 proved to be the most active and stable thanks to its enhanced Ni dispersion and reduction, its high metallic area, and the formation of moderate base sites. In Chapter three, the thermal stability and tolerance to sulfur impurities on the Ni-CeO2/γ-Al2O3 catalyst was further studied using high temperatures and the presence of H2S on the reactants. The strong metal-promoter interaction and the favourable formation of Ce2O2S were revealed as the main causes of its high stability and tolerance to H2S, respectively. Additionally, the implementation of Ni-CeO2/γ-Al2O3 in a two-stage industrial methanation process was performed to evaluate its technical feasibility. The desired gas composition (≥92.5%CH4) was successful obtained using a decreasing temperature profile (T=450-275°C) and P=5bar·g. The high stability recorded during the 2000h of experimentation demonstrated that Ni-CeO2/γ-Al2O3 can be a competitive catalyst for CO2 methanation. Regarding to reactor design, in Chapter four, the design of a fixed-bed multitubular reactor on a Ni-CeO2-Al2O3 catalyst was evaluated for mid-scale SNG production. A CFD mathematical model based on experimental kinetic data was developed. A reactor tube with a diameter of 9.25mm and a length of 250mm was proposed, which should be operated at Tinlet=473K, Twall=373K, GHSV=14,400h-1 and P=5atm to achieve XCO2=99% with Tmax of 673K. On the other hand, a reactor tube (di=4.6mm and L=250mm) with a heat management approach based on free convection was proposed for small-scale SNG production. The optimal conditions were found at GHSV=11,520h-1, Tinlet=503K, P=5atm, and Tair=298K. The feasibility of the simulated reactor proposal was experimentally validated over the micro-sized Ni-CeO2/γ-Al2O3 (XCO2=93% and T=830-495K).
Power-to-Gas (P2G) es una tecnología prometedora para el almacenamiento de combustibles bajos en carbono. El concepto P2G implica la conversión de energía renovable en hidrógeno mediante electrólisis con la posibilidad de combinarlo con CO2 para producir metano (gas natural sintético, SNG). La producción de SNG mediante el proceso termoquímico de metanación de CO2 es particularmente interesante porque ofrece un combustible fácilmente transportable con un amplio mercado probado para aplicaciones de uso final de energía, calor y movilidad. Sin embargo, el desarrollo de una tecnología de metanación de CO2 rentable es uno de los mayores desafíos que enfrenta el concepto P2G. En este contexto, esta tesis se centró en el desarrollo de un catalizador y un reactor para la metanación de CO2. Los objetivos de la tesis se abordaron en tres aspectos principales, que son: i) diseñar un catalizador de alto rendimiento basado en Ni/The transformation of the current energy model towards a more sustainable mix, independent of fossil fuels, requires the exploration of new technologies that are capable of taking advantage of excess electricity derived from renewable energy sources and to use new alternative sources of carbon for the generation of clean fuels. An alternative that combines both is the Power-to-Gas (P2G) technology, whose concept is based on a two-stage process. In the first stage, excess electricity from renewable energies is converted to hydrogen by electrolysis. Then, in a second stage, the H2 produced is transformed to CH4 through methanation with CO2. The CH4 produced is referred to as synthetic natural gas (SNG) and allows large amounts of renewable energy to be distributed from the energy sector to the end-use sectors. The thermo-chemical CO2 methanation process is considered the most efficient route for large-scale SNG production. However, developing a cost-effective CO2 methanation technology is one of the biggest challenges facing the P2G concept. In this context, this thesis focused on the catalyst and reactor design for CO2 methanation. The thesis objectives were addressed in three main aspects, which are: i) design a high-performance catalyst based on metal oxide-promoted Ni/γ-Al2O3 and determine its reaction mechanism; ii) evaluate the stability of the catalyst and the tolerance to sulfur for its implementation in a relevant industrial environment (CoSin project); and finally, iii) develop a CFD model based on experimental kinetic data to understand the role of operating conditions and propose a new reactor configuration. In the first Chapter of this thesis it is presented a general introduction of the SNG production through CO2 methanation process. In the second Chapter, the addition of a promoter (X) on a system composed by Ni and γ-Al2O3 microspheres was studied as the design strategy to develop a micro-sized Ni-X/γ-Al2O3 catalyst. The catalysts based on Ni-CeO2/γ-Al2O3 was proposed as the most feasible due to its high catalytic performance in relation to its economic competitiveness. The optimal composition of each component of the Ni-CeO2/γ-Al2O3 was found through a systematic experimental design. The catalyst composed by 25wt.%Ni, 20wt.%CeO2 and 55wt.%γ-Al2O3 proved to be the most active and stable thanks to its enhanced Ni dispersion and reduction, its high metallic area, and the formation of moderate base sites. In Chapter three, the thermal stability and tolerance to sulfur impurities on the Ni-CeO2/γ-Al2O3 catalyst was further studied using high temperatures and the presence of H2S on the reactants. The strong metal-promoter interaction and the favourable formation of Ce2O2S were revealed as the main causes of its high stability and tolerance to H2S, respectively. Additionally, the implementation of Ni-CeO2/γ-Al2O3 in a two-stage industrial methanation process was performed to evaluate its technical feasibility. The desired gas composition (≥92.5%CH4) was successful obtained using a decreasing temperature profile (T=450-275°C) and P=5bar·g. The high stability recorded during the 2000h of experimentation demonstrated that Ni-CeO2/γ-Al2O3 can be a competitive catalyst for CO2 methanation. Regarding to reactor design, in Chapter four, the design of a fixed-bed multitubular reactor on a Ni-CeO2-Al2O3 catalyst was evaluated for mid-scale SNG production. A CFD mathematical model based on experimental kinetic data was developed. A reactor tube with a diameter of 9.25mm and a length of 250mm was proposed, which should be operated at Tinlet=473K, Twall=373K, GHSV=14,400h-1 and P=5atm to achieve XCO2=99% with Tmax of 673K. On the other hand, a reactor tube (di=4.6mm and L=250mm) with a heat management approach based on free convection was proposed for small-scale SNG production. The optimal conditions were found at GHSV=11,520h-1, Tinlet=503K, P=5atm, and Tair=298K. The feasibility of the simulated reactor proposal was experimentally validated over the micro-sized Ni-CeO2/γ-Al2O3 (XCO2=93% and T=830-495K).-Al2O3 promovido por óxido metálico y determinar su mecanismo, ii) evaluar la estabilidad del catalizador y la tolerancia al azufre para su implementación en un entorno industrial relevante (proyecto CoSin), and iii) desarrollar un modelo CFD basado en datos cinéticos experimentales para comprender el papel de las condiciones de operación y proponer una nueva configuración de reactor. En línea con estos objetivos, un catalizador ternario basado en 25wt.%Ni-20wt.%CeO2-55wt.%The transformation of the current energy model towards a more sustainable mix, independent of fossil fuels, requires the exploration of new technologies that are capable of taking advantage of excess electricity derived from renewable energy sources and to use new alternative sources of carbon for the generation of clean fuels. An alternative that combines both is the Power-to-Gas (P2G) technology, whose concept is based on a two-stage process. In the first stage, excess electricity from renewable energies is converted to hydrogen by electrolysis. Then, in a second stage, the H2 produced is transformed to CH4 through methanation with CO2. The CH4 produced is referred to as synthetic natural gas (SNG) and allows large amounts of renewable energy to be distributed from the energy sector to the end-use sectors. The thermo-chemical CO2 methanation process is considered the most efficient route for large-scale SNG production. However, developing a cost-effective CO2 methanation technology is one of the biggest challenges facing the P2G concept. In this context, this thesis focused on the catalyst and reactor design for CO2 methanation. The thesis objectives were addressed in three main aspects, which are: i) design a high-performance catalyst based on metal oxide-promoted Ni/γ-Al2O3 and determine its reaction mechanism; ii) evaluate the stability of the catalyst and the tolerance to sulfur for its implementation in a relevant industrial environment (CoSin project); and finally, iii) develop a CFD model based on experimental kinetic data to understand the role of operating conditions and propose a new reactor configuration. In the first Chapter of this thesis it is presented a general introduction of the SNG production through CO2 methanation process. In the second Chapter, the addition of a promoter (X) on a system composed by Ni and γ-Al2O3 microspheres was studied as the design strategy to develop a micro-sized Ni-X/γ-Al2O3 catalyst. The catalysts based on Ni-CeO2/γ-Al2O3 was proposed as the most feasible due to its high catalytic performance in relation to its economic competitiveness. The optimal composition of each component of the Ni-CeO2/γ-Al2O3 was found through a systematic experimental design. The catalyst composed by 25wt.%Ni, 20wt.%CeO2 and 55wt.%γ-Al2O3 proved to be the most active and stable thanks to its enhanced Ni dispersion and reduction, its high metallic area, and the formation of moderate base sites. In Chapter three, the thermal stability and tolerance to sulfur impurities on the Ni-CeO2/γ-Al2O3 catalyst was further studied using high temperatures and the presence of H2S on the reactants. The strong metal-promoter interaction and the favourable formation of Ce2O2S were revealed as the main causes of its high stability and tolerance to H2S, respectively. Additionally, the implementation of Ni-CeO2/γ-Al2O3 in a two-stage industrial methanation process was performed to evaluate its technical feasibility. The desired gas composition (≥92.5%CH4) was successful obtained using a decreasing temperature profile (T=450-275°C) and P=5bar·g. The high stability recorded during the 2000h of experimentation demonstrated that Ni-CeO2/γ-Al2O3 can be a competitive catalyst for CO2 methanation. Regarding to reactor design, in Chapter four, the design of a fixed-bed multitubular reactor on a Ni-CeO2-Al2O3 catalyst was evaluated for mid-scale SNG production. A CFD mathematical model based on experimental kinetic data was developed. A reactor tube with a diameter of 9.25mm and a length of 250mm was proposed, which should be operated at Tinlet=473K, Twall=373K, GHSV=14,400h-1 and P=5atm to achieve XCO2=99% with Tmax of 673K. On the other hand, a reactor tube (di=4.6mm and L=250mm) with a heat management approach based on free convection was proposed for small-scale SNG production. The optimal conditions were found at GHSV=11,520h-1, Tinlet=503K, P=5atm, and Tair=298K. The feasibility of the simulated reactor proposal was experimentally validated over the micro-sized Ni-CeO2/γ-Al2O3 (XCO2=93% and T=830-495K).-Al2O3 se propone como el más factible debido a su alto rendimiento catalítico en relación a su competitividad económica. La fuerte interacción metal-promotor y la formación favorable de Ce2O2S se revelaron como las principales causas de su alta estabilidad y tolerancia al H2S, respectivamente. Adicionalmente, su exitosa implementación en un proceso de metanación industrial de dos etapas demostró su viabilidad técnica. Finalmente, se propone un reactor multitubular para la producción de SNG a mediana escala. Por otro lado, para la producción de SNG a pequeña escala, se propone un nuevo diseño de reactor con un enfoque de gestión del calor basado en la libre convención.

This Dissertation investigates the kinetics of CO2 methanation over nickel and cobalt catalysts. Methanation was studied for both Ni/γ-Al2O3 and Co/ZrO2 catalysts, which were synthesised using an incipient wetness impregnation technique and subsequently characterised using analyses based on gas adsorption, XRD, TPR and thermogravimetry. Separately a CO hydrogenation reaction, the Fischer-Tropsch process, was modelled numerically to examine the influence of mass transfer in practical, commercial pellets of catalyst. The kinetics of methanation was investigated for Ni/γ-Al2O3 over a wide range of reactant partial pressures using a gradientless, spinning-basket reactor operated in batch mode and in a laboratory-scale, continuous fixed-bed reactor. Langmuir-Hinshelwood kinetic models were developed to represent the observed kinetics in each reactor: these models were then compared. For the batch reactor, a rate expression based the dissociation of a chemisorbed CO intermediate being the rate-limiting step was found to be consistent with the experimental results. However, results from the fixed-bed suggested that the hydrogenation of an adsorbed C atom determined the rate of reaction. These differences in the kinetics on Ni/γ-Al2O3 between the fixed-bed and batch reactors suggest that a Langmuir approach using a single, rate-determining step may not be representative across all conversions. The rate over the Co/ZrO2 catalyst was characterised in the fixed-bed reactor over a range of reactant partial pressures at temperatures between 433 K and 503 K. The rate was observed to be dependent on hydrogen partial pressure and temperature, with the rate increasing with both. Previous research has reported a wide range of values of the apparent activation energy, with a study suggesting it was sensitive to pressure. Accordingly, the apparent activation energy was investigated for pressure sensitivity over a range of pressures between 5 and 15 barg: it was found to be constant. The values determined (~88-91±8 kJ/mol) were notably consistent with those reported for CO hydrogenation on cobalt. Kinetic schemes based on Langmuir-Hinshelwood and power law equations were evaluated, with the results best described by a reaction scheme based on the carbide pathway, with a rate-determining step of CH hydrogenation. A reaction-diffusion model of the Fischer-Tropsch process in a 2-D hollow cylinder was developed and analysed across a range of Thiele moduli and the extents of error in both effectiveness factor and selectivity were quantified relative to one-dimensional sphere and slab analogues. The errors between 2-D and 1-D analogues were found to be most significant between Thiele moduli of ~0.25 and ~3. Hollow cylinder effectiveness factors were bounded by those of sphere and slab above and below Thiele moduli of ~0.75 and ~1.15 respectively for the conditions examined, with the effectiveness factors exceeding those of both sphere and slab models between these moduli. A comparison of the hollow cylindrical pellets against spheres of equivalent volume demonstrated that hollow cylinders provided improved fixed-bed performance, with improved effectiveness factors and selectivities due to the lowered diffusion lengths of the hollow cylindrical geometry.

New Ni-based catalysts have been developed and applied for the steam dry reforming (SDR) and the methanation reaction of clean biogas, exploring the possibility of converting its CO2 fraction into a useful product (syngas or biomethane) instead of separating and discharging it. The catalysts were prepared from hydrotalcite-type precursors through co-precipitation, with the addition of promoters (Ru, Rh, La) or basic sorbents (CaO). Then, they were deeply characterised before and after reaction by BET, XRD, H2-TPR, CO2-TPD analyses, and Raman spectroscopy. The results obtained for SDR at low temperature (700°C) showed that, although the catalysts synthetised were active and stable in terms of CH4 conversion, the conversion values reached were not yet compatible with the industrial requirements. On the other hand, a promising Ni-Ru bimetallic catalyst was developed for high temperature SDR (900°C), presenting a convenient alternative to the already studied Ni-Rh and Ni-Ir formulations. The synergic effect of the two metals significantly enhanced the catalyst stability and resistance toward coke formation, while achieving high methane and carbon dioxide conversions and producing syngas with a H2/CO ratio compatible with downstream applications such as Fischer-Tropsch or methanol synthesis. Finally, the feasibility of the direct methanation of clean biogas was assessed, using a Ni-La catalyst. Its activity was studied simulating the industrial conditions for the reaction, achieving CO2 conversions up to 90% with a total selectivity for methane production.

[ES] La presente tesis doctoral se centra en el desarrollo de nuevas membranas de separación de gases, así como su empleo in-situ en reactores catalíticos de membrana para la intensificación de procesos. Para este propósito, se han sintetizado varios materiales, como polímeros para la fabricación de membranas, catalizadores tanto para la metanación del CO2 como para la reacción de síntesis de Fischer-Tropsch, y diversas partículas inorgánicas nanométricas para su uso en membranas de matriz mixta. En lo referente a la fabricación de las membranas, la tesis aborda principalmente dos tipos: orgánicas e inorgánicas. Con respecto a las membranas orgánicas, se han considerado diferentes materiales poliméricos, tanto para la capa selectiva de la membrana, así como soporte de la misma. Se ha trabajado con poliimidas, puesto que son materiales con temperaturas de transición vítrea muy alta, para su posterior uso en reacciones industriales que tienen lugar entre 250-300 ºC. Para conseguir membranas muy permeables, manteniendo una buena selectividad, es necesario obtener capas selectivas de menos de una micra. Usando como material de soporte otro tipo de polímero, no es necesario estudiar la compatibilidad entre ellos, siendo menos compleja la obtención de capas finas. En cambio, si el soporte es de tipo inorgánico, un exhaustivo estudio de la relación entre la concentración y la viscosidad de la solución polimérica es altamente necesario. Diversas partículas inorgánicas nanométricas se estudiaron para favorecer la permeación de agua a través de los materiales poliméricos. En segundo lugar, en cuanto a membranas inorgánicas, se realizó la funcionalización de una membrana de paladio para favorecer la permeación de hidrógeno y evitar así la contaminación por monóxido de carbono. El motivo por el cual se dopó con otro metal la capa selectiva de la membrana metálica fue para poder emplearla en un reactor de Fischer-Tropsch. Con relación al diseño y fabricación de los reactores, durante esta tesis, se desarrolló el prototipo de un microreactor para la metanación de CO2, donde una membrana polimérica de capa fina selectiva al agua se integró para evitar la desactivación del catalizador, y a su vez desplazar el equilibrio y aumentar la conversión de CO2. Por otro lado, se rediseñó un reactor de Fischer-Tropsch para poder introducir una membrana metálica selectiva a hidrogeno y poder inyectarlo de manera controlada. De esta manera, y siguiendo estudios previos, el objetivo fue mejorar la selectividad a los productos deseados mediante el hidrocraqueo y la hidroisomerización de olefinas y parafinas con la ayuda de la alta presión parcial de hidrógeno.
[CAT] La present tesi doctoral es centra en el desenvolupament de noves membranes de separació de gasos, així com el seu ús in-situ en reactors catalítics de membrana per a la intensificació de processos. Per a aquest propòsit, s'han sintetitzat diversos materials, com a polímers per a la fabricació de membranes, catalitzadors tant per a la metanació del CO2 com per a la reacció de síntesi de Fischer-Tropsch, i diverses partícules inorgàniques nanomètriques per al seu ús en membranes de matriu mixta. Referent a la fabricació de les membranes, la tesi aborda principalment dos tipus: orgàniques i inorgàniques. Respecte a les membranes orgàniques, diferents materials polimèrics s'ha considerat com a candidats prometedors, tant per a la capa selectiva de la membrana, així com com a suport d'aquesta. S'ha treballat amb poliimides, ja que són materials amb temperatures de transició vítria molt alta, per al seu posterior ús en reaccions industrials que tenen lloc entre 250-300 °C. Per a aconseguir membranes molt permeables, mantenint una bona selectivitat, és necessari obtindre capes selectives de menys d'una micra. Emprant com a material de suport altre tipus de polímer, no és necessari estudiar la compatibilitat entre ells, sent menys complexa l'obtenció de capes fines. En canvi, si el suport és de tipus inorgànic, un exhaustiu estudi de la relació entre la concentració i la viscositat de la solució polimèrica és altament necessari. Diverses partícules inorgàniques nanomètriques es van estudiar per a afavorir la permeació d'aigua a través dels materials polimèrics. En segon lloc, quant a membranes inorgàniques, es va realitzar la funcionalització d'una membrana de pal¿ladi per a afavorir la permeació d'hidrogen i evitar la contaminació per monòxid de carboni. El motiu pel qual es va dopar amb un altre metall la capa selectiva de la membrana metàl¿lica va ser per a poder emprar-la en un reactor de Fischer-Tropsch. En relació amb el disseny i fabricació dels reactors, durant aquesta tesi, es va desenvolupar el prototip d'un microreactor per a la metanació de CO2, on una membrana polimèrica de capa fina selectiva a l'aigua es va integrar per a així evitar la desactivació del catalitzador i al seu torn desplaçar l'equilibri i augmentar la conversió de CO2. D'altra banda, un reactor de Fischer-Tropsch va ser redissenyat per a poder introduir una membrana metàl¿lica selectiva a l'hidrogen i poder injectar-lo de manera controlada. D'aquesta manera, i seguint estudis previs, el objectiu va ser millorar la selectivitat als productes desitjats mitjançant el hidrocraqueix i la hidroisomerització d'olefines i parafines amb l'ajuda de l'alta pressió parcial d'hidrogen.
[EN] The present thesis is focused on the development of new gas-separation membranes, as well as their in-situ integration on catalytic membrane reactors for process intensification. For this purpose, several materials have been synthesized such as polymers for membrane manufacture, catalysts for CO2 methanation and Fischer-Tropsch synthesis reaction, and inorganic materials in form of nanometer-sized particles for their use in mixed matrix membranes. Regarding membranes manufacture, this thesis deals mainly with two types: organic and inorganic. With regards to the organic membranes, different polymeric materials have been considered as promising candidates, both for the selective layer of the membrane, as well as a support thereof. Polyimides have been selected since they are materials with very high glass transition temperatures, in order to be used in industrial reactions which take place at temperatures around 250-300 ºC. To obtain highly permeable membranes, while maintaining a good selectivity, it is necessary to develop selective layers of less than one micron. Using another type of polymer as support material, it is not necessary to study the compatibility between membrane and support. On the other hand, if the support is inorganic, an exhaustive study of the relation between the concentration and the viscosity of the polymer solution is highly necessary. In addition, various inorganic particles were studied to favor the permeation of water through polymeric materials. Secondly, as regards to inorganic membranes, the functionalization of a palladium membrane to favor the permeation of hydrogen and avoid carbon monoxide contamination was carried out. The membrane selective layer was doped with another metal in order to be used in a Fischer-Tropsch reactor. Regarding the design and manufacture of the reactors used during this thesis, a prototype of a microreactor for CO2 methanation was carried out, where a thin-film polymer membrane selective to water was integrated to avoid the deactivation of the catalyst and to displace the equilibrium and increase the CO2 conversion. On the other hand, a Fischer-Tropsch reactor was redesigned to introduce a hydrogen-selective metal membrane and to be able to inject it in a controlled manner. In this way, and following previous studies, the aim is to enhance the selectivity to the target products by hydrocracking and hydroisomerization the olefins and paraffins assisted by the presence of an elevated partial pressure of hydrogen.
I would like to acknowledge the Spanish Government, for funding my research with the Severo Ochoa scholarship.
Escorihuela Roca, S. (2019). Novel gas-separation membranes for intensified catalytic reactors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/121139
TESIS

Découverte en 1902, la méthanation du C02 reçoit un intérêt grandissant pour son application aux procédés de stockage d'énergie électrique nécessaires au développement des énergies renouvelables. Sa mise en œuvre requiert le développement de réacteurs catalytiques innovants répondant au cahier des charges de cette application. Ces travaux sont dédiés à l'étude et l'optimisation de trois types de réacteurs-échangeurs conçus au cours de cette thèse :-un réacteur à lit fixe annulaire, -un réacteur à lit fixe milli-structuré et un réacteur à mousses métalliques supports de catalyseur. Leurs performances globales sont déterminées expérimentalement. La désactivation du catalyseur est étudiée et ses causes identifiées. Une modélisation des trois réacteurs permet la simulation de leur fonctionnement. Les propriétés hydrodynamiques et thermiques de leurs structures internes et les vitesses de réaction sont caractérisées expérimentalement. Les résultats numériques des simulations sont comparés aux expériences et complètent l'étude du comportement des réacteurs. Les modèles identifiés permettent finalement d'étudier les limites et les potentiels de ces réacteurs
Discovered in 1902, the C02 methanation is getting a growing interest for its application to electricity storage processes needed for the development of renewable anergies. lts implementation requires the development of innovative catalytic reactors compatible with the specifications of this application. The present work focuses on the study of three reactor-exchangers designed during this thesis: - an annular fixed bed reactor, a milli-structured fixed bed reactor and a reactor which uses metallic foams as catalyst carriers. Their global performances are experimentally evaluated. The catalyst deactivation is studied and its causes identified. A modeling of these three reactors allows the simulation of their behavior. The hydrodynamic and thermal properties of their internai structure and the reaction kinetics are experimentally characterized . The numerical results of the simulations are compared to the experimental data and complete the analysis of the reactors behavior.The identified models are finally used to study the limits and the potentialities of the reactors

Dans cette étude de doctorat, la technique de dépôt tridimensionnel de fibres (3DFD) a été appliquée pour développer et fabriquer des structures de support catalytique multi-canaux avancées. En utilisant cette technique, le matériau, la porosité, la forme et la taille des canaux et l'épaisseur des fibres peuvent être contrôlées. L'objectif de cette recherche est d'étudier les performances des supports structurés 3D conçus pour la méthanation du CO2 en termes d'activité, de sélectivité de stabilité et d’étudier l'impact des propriétés spécifiques introduites dans la conception structurale des supports
In this doctoral study, the three dimensional fibre deposition (3DFD) technique has been applied to develop and manufacture advanced multi-channelled catalytic support structures. By using this technique, the material, the porosity, the shape and size of the channels and the thickness of the fibres can be controlled. The aim of this research is to investigate the possible benefits of 3D-designed structured supports for CO2 methanation in terms of activity, selectivity and stability and the impact of specific properties introduced in the structural design of the supports

The development of methanation technology is supported by detailed modeling and process simulation to optimize the design and study of its reaction dynamic properties. The chapter presents a discussion of selected catalysts and its kinetic models in the methanation reaction. The development models of fixed-bed reactors in the methane synthesis were also presented. Chemical and physical modeling of methanation reactions with optimization, exploitation, and the analysis of critical processes in time is an important contribution to the technology modernization.

Conversion technologies able to transform renewable energy sources (RES) based electricity in gaseous fuels, which can be stored over long timeframes, represent a key focus point considering the low carbon society development. Thus, Power-to-Gas technologies emerge as a viable solution to mitigate the variability of RES power generation, enabling spatial and temporal balancing of production vs. demand mismatches. An additional benefit in this context is brought by the decarbonization facilities, employing polluting carbon dioxide (CO2) emissions and RES-based electricity to produce synthetic natural gas with high methane (CH4) concentration. The fuel obtained can be stored or injected in the gas distribution infrastructure, becoming a clean energy vector. This paper investigates the functional parameters of such technologies, aiming to comparatively analyze their suitability for further integration in hybrid and ecofriendly energy systems. Given the stability of CO2 molecule, a catalyst must be used to overcome the methanation reaction kinetics limitations. Therefore, the required conditions (in terms of pressure and temperature) for CO2 methanation reaction unfolding are analyzed first. Further, CO2 conversion rate and CH4 selectivity are investigated in order to provide a detailed comparison of available technologies in the field, addressing moreover the particularities of catalyst preparation processes. It is found that Nickel (Ni) based catalysts are performing well, achieving good performances even at atmospheric pressure and low temperatures. It is remarkable that, within a [300,500]℃ temperature range, Ni-based catalysts enable a CO2 conversion rate over 78% with a CH4 selectivity of up to 100%. Last, integration perspectives and benefits are discussed, highlighting the crucial importance of the results presented in this paper.

The natural gas distribution infrastructure is well developed in many countries, enabling the fuel to be transported long distances via pipelines and easily delivered throughout cities. Using the existing pipeline to transport renewably generated synthetic natural gas (SNG) can leverage the value of the product. While the price of natural gas is near record lows in the United States, many other countries are working to develop SNG as an alternative fuel for transportation markets, especially in Europe and for island nations. This study presents an SNG plant design and evaluates its performance for producing SNG by reacting renewably generated hydrogen with carbon dioxide. The carbon dioxide feedstock is assumed to be captured and scrubbed from an existing coal fired power plant at the city-gate, where the SNG plant is co-located. Historically, methanation has been a common practice for eliminating carbon monoxide and carbon dioxide in various chemical processes such as ammonia production and natural gas purification; for these processes, only small amounts (1–3% molar basis) of carbon oxides need to be converted to methane. A “bulk” methanation process is unique due to the high concentration of carbon oxides and hydrogen. In addition, the carbon dioxide is the only carbon source, and the reaction characteristics of carbon dioxide are much different than carbon monoxide. Thermodynamic and kinetic considerations of the methanation reaction are explored to model and simulate a system of reactors for the conversion of hydrogen and carbon dioxide to SNG. Multiple reactor stages are used to increase temperature control of the reactor and drain water to promote the forward direction of the methanation reaction. Heat recuperation and recovery using organic Rankine cycle units for electricity generation utilizes the heat produced from the methanation reaction. Bulk recycle is used to increase the overall reactant conversion while allowing a satisfactorily high methane content SNG product. A hydrogen membrane separates hydrogen for recycle to increase the Wobbe index of the product SNG by increasing the methane content to nearly 93% by volume. The product SNG has a Wobbe index of 47.5 MJ/m3 which is acceptable for natural gas pipeline transport and end-use appliances in the existing infrastructure. The overall plant efficiency is shown to be 78.1% HHV and 83.2% LHV. The 2nd Law efficiency for the SNG production plant is 84.1%.

Abstract Underground bio-methanation is a promising technology for large-scale renewable energy storage. Additionally, it enables the recycling of CO2 via the generation of "renewable methane" in porous reservoirs using in-situ microbes as bio-catalysts. Potential candidate reservoirs are depleted gas fields or even abandoned gas storages, providing enormous storage capacity to balance seasonal energy supply and demand fluctuations. This paper discusses the underlying bio-methanation process as part of the ongoing research project "Bio-UGS – Biological conversion of carbon dioxide and hydrogen to methane," funded by the German Federal Ministry of Education and Research (BMBF). First, the hydrodynamic processes are assessed, and a review of the related microbial processes is provided. Then, based on exemplary field-scale simulations, the bio-reactive transport process and its consequences for operation are evaluated. The hydrogen conversion process was investigated by numerical simulations on field scale. For this, a two-phase multi-component bio-reactive transport model was implemented by (Hagemann 2018) in the open-source DuMux (Flemisch et al. 2011) simulation toolkit for porous media flow. The underlying processes include the transport of reactants and products, consumption of specific components, and the related growth and decay of the microbial population, resulting in a bio-reactive transport model. The microbial kinetic parameters of methanogenic reactions are taken from the available literature. The simulation study covers different scenarios on conceptional field-scale models, studying the impact of well placement, injection rates, and gas compositions. Due to a significant sensitivity of the simulation results to the bio-conversion kinetics, the field-specific conversion rates must be obtained. Thus, the Bio-UGS project is accompanied by laboratory experiments out of the frame of this paper. Other parameters are rather a matter of design; in the present case of depleted gas fields, those parameters are coupled and can be chosen to convert fully hydrogen and carbon dioxide to methane. Especially the well spacing can be considered the main design parameter in the likely case of a given injection rate and gas composition. This study extends the application of the previously developed code from a homogeneous-2D to the heterogeneous-3D case. The simulations mimic the co-injection of carbon dioxide and hydrogen from a 40 MW electrolysis.

Extrapolation of primary energy consumption of the world between 1990 and 2005 to the future revealed the complete exhaustion of oil, uranium, natural gas and coal reserves on the Earth in 2034, 2040, 2040 and 2054, respectively. We have been proposing global carbon dioxide recycling to use renewable energy for all people in the whole world. The electricity converted from renewable energy will be used for production of hydrogen by seawater electrolysis. Hydrogen, for which no infrastructures of transportation and combustion exist, will be converted to methane by the reaction with carbon dioxide captured by energy consumers. Among systems in global carbon dioxide recycling, seawater electrolysis and carbon dioxide methanation have not been performed industrially. We created energy-saving cathodes for hydrogen production and anodes for oxygen evolution without chlorine formation in seawater electrolysis, and ideal catalysts for methane formation by the reaction of carbon dioxide with hydrogen. This paper reviews the characteristics and performance of these materials in the systems.

Object of this paper is the modelling, process design and simulation of a waste incineration plant integrated with a novel CO2 chemical sequestration system for CH4 production. The main components of the proposed system are: the incineration plant (whose operational data are considered known here), a Sabatier reactor for CH4 production, a post-combustion monoethanolamine (MEA) chemical absorption unit and a H2O electrolyser. Carbon dioxide captured from the waste plant stack gases and hydrogen from water electrolysis feed the Sabatier chemical reactor in a temperature range of 250–450°C. Through the exothermic methanation reaction (CO2 + 4H2 = CH4 + 2H2O + Heat), methane is produced with a conversion yield of 90–95%. Through a perm-selective membrane, hot steam can be extracted from the reactor and recycled to cover about 40% of the MEA regenerating re-boiler duty. The methanation of CO2 is an established carbon capture technique, profitably suitable for waste plants. When the produced methane is burned, the CO2 absorbed in the process returns to the environment, enacting in a global sense a quasi-zero-emissions cycle. The possible integration of the electrolyser with renewable-generated electricity has been investigated to evaluate the storage capacity of electrical energy as “renewable methane”, which from a technical point of view is more suitable than hydrogen to be stored, burned or sent into natural gas pipelines. A thermo-economic analysis is presented to evaluate the exergetic performance of the proposed system and the final cost of products.