Producción de hidrógeno a partir de amoniaco en reactores de paredes catalíticas

Due to the problems associated with the generation and storage of hydrogen in portable applications, the use of ammonia fer the on-site production of hydrogen through its catalytic decomposition has been proposed. This thesis presents an analysis of the existing systems fer the decomposition of ammonia, describing the state of the art of the catalysts used to date and an analysis of the kinetics of the reaction with different catalysts is presented. The structured reactors used are explored, as well as the possibilities offered by catalytic membrana reactors, which allow the simultaneous production and separation of hydrogen. Al2O3, CeO2 and La2O3 have been chosen as catalyst supports, and Ru and Ni as active phases, as well as the Ni-Ru bimetallic phase. The catalysts have been characterized by XRD, TPR, NH3-TPD, HRTEM, SEM, Raman spectroscopy, N2 physisorption, MIP, H2 chemisorption, ICP-OES and XPS. Ceria-based samples are the most active in decomposing ammonia; this has been attributed to a particular metal-support interaction and a lower presence of strong acid sitas. Ru catalysts are more active than Ni-basad samples, but deactivate rapidly. In situ XPS experiments reveal that the active sites fer the catalytic decomposition of ammonia are metallic Ni and Ru. Considering the high cost and limitad availability of Ru, the Ni/CeO2 catalyst appears as a promising system for the decomposition of ammonia dueto its good performance and low cost. Ni-Ru bimetallic catalysts have not surpassed the activity of Ru catalysts, regardless of the order in which the metals are added, however, they show higher activity than Ni/CeO2 and excellent stability. The best catalytic performance has been obtained with catalysts with 2.4-5 % by weight of Ni and 0.4-0.6 % by weight of Ru. Characterization has revealed the existence of an intimate contact between Ni, Ru and CeO2, which is considerad the reason fer the excellent catalytic activity and stability observad. A kinetic model has been developed fer the decomposition of ammonia in a fixed-bed reactor. The dehydrogenation of the ammonia adsorbed on the catalyst surface is probably the limiting step of the reaction and the decomposition of the ammonia is inhibited by the presence of H2. A ceria paste has been preparad without additives and has been used to prepare microchannel ceria structures by 3D printing. The 3D printed caria structures show much higher catalytic activity than conventional cordierite monoliths. The 3D printed ceria structures have been impregnated with different amounts of Ni and Ru, characterized and tested fer the catalytic decomposition of ammonia in a fixed-bed reactor. The best catalytic performance has been achieved with an active phase of 0.5Ni0.1Ru (wt. %). A kinetic expression has been obtained and has been used in a 1D model to simulate the behavior of 3D-printed ceria structures impregnated with Ni-Ru. In order to optimize the catalytic structure, a series of simulations have been carried out to determine the relationship between the geometric parameters of the structures and their catalytic behavior in the decomposition of ammonia. Catalytic tests have been carried out with a membrane reactor to decompose ammonia using the ceria structure with the 0.5Ni0.1Ru bimetallic catalyst deposited on its surface. Three different configurations have been tested: the catalyst as pellets, as a structured reactor and finally an intermediate configuration with the structured catalyst coupled to the same catalyst in the ferm of pellets, analyzing the effect of hydrogen separation from the product stream. The last configuration is the one that has shown the best results.Debido a los problemas asociados con la generación y el almacenamiento de hidrógeno en aplicaciones portátiles, se ha propuesto el uso de amoniaco para la producción in sítu de hidrógeno a través de su descomposición catalítica. En esta tesis se presenta un análisis de los sistemas existentes para la descomposición de amoniaco, describiendo el estado del arte respecto a los catalizadores usados hasta la fecha y se presenta un análisis de la cinética de la reacción con diferentes catalizadores. Se exploran los reactores estructurados utilizados, así como las posibilidades que ofrecen los reactores catalíticos de membrana, que permiten la producción y separación simultánea de hidrógeno. Se han elegido como soportes de los catalizadores Al2O3, CeO2 y La2O3, y como fases activas Ru, Ni, así como la fase bímetálica Ni-Ru. Los catalizadores se han caracterizado por XRD, TPR, NH3-TPD, HRTEM, SEM, espectroscopia Raman, fisisorción de N2, MIP, quimísorción de H2, ICP-OES y XPS. Las muestras a base de ceria son las más activas en la descomposición de amoniaco; esto se ha atribuido a una interacción particular metal-soporte y a una menor presencia de sitios ácidos fuertes. Los catalizadores de Ru son más activos que los basados en Ni, pero se desactivan rápidamente. Los experimentos de XPS in sítu revelan que los sitios activos para la descomposición catalítica del amoniaco son Ni y Ru metálicos. Considerando el alto costo y la disponibilidad limitada de Ru, el catalizador Ni/CeO2 aparece como un sistema prometedor para la descomposición de amoníaco debido a su buen desempeño y bajo costo. Los catalizadores bímetálicos de Ní-Ru no han superado la actividad de los catalizadores de Ru, independientemente del orden en que se añadan los metales, sin embargo, muestran una actividad superior al Ni/CeO2 y una estabilidad excelente. El mejor rendimiento catalítico se ha obtenido con catalizadores con 2.4-5 % en peso de Ni y 0.4-0.6 % en peso de Ru. La caracterización ha revelado la existencia de un contacto íntimo entre Ni, Ru y CeO2, lo que se considera la razón de la excelente actividad catalítica y estabilidad observada. Se ha desarrollado un modelo cinético para la descomposición de amoniaco en un reactor de lecho fijo. La deshidrogenación del amoníaco adsorbido en la superficie del catalizador es probablemente el paso limitante de la reacción y la descomposición del amoniaco se inhibe por la presencia de H2. Se ha una preparado una pasta de cería sin aditivos y se ha utilizado para preparar estructuras de ceria de microcanales mediante impresión 3D. Las estructuras de ceria impresas en 3D muestran una actividad catalítica mucho más alta que la de monolitos de cordierita convencionales. Las estructuras de ceria impresas en 3D han sido impregnadas con diferentes cantidades de Ni y Ru, caracterizadas y probadas para la descomposición catalítica de amoniaco en un reactor de lecho fijo. El mejor rendimiento catalítico se ha logrado con una fase activa de 0.5Ni0.1Ru (wt. %). Se ha obtenido una expresión cinética que se ha empleado en un modelo 1D para simular el comportamiento de las estructuras de ceria impresas en 3D impregnadas con Ni-Ru. Se han realizado una serie de simulaciones para determinar la relación entre los parámetros geométricos de las estructuras y su comportamiento catalítico en la descomposición del amoniaco, con el fin de optimizar la estructura catalítica. Se han realizado ensayos catalíticos con un reactor de membrana para descomponer el amoniaco utilizando la estructura de ceria con el catalizador bímetálico 0.5Ní0.1Ru depositado en su superficie. Se han ensayado tres configuraciones diferentes: el catalizador en forma de pellets, en forma de reactor estructurado y una configuración intermedia con el catalizador estructurado acoplado al mismo catalizador en forma de pellets, analizando el efecto de la separación de hidrógeno de la corriente de productos. La última configuración es la que ha mostrado mejores resultados.Postprint (published version

Catalytic ammonia decomposition for hydrogen production on Ni, Ru and Ni–Ru supported on CeO2

Ceria-supported Ni, Ru and NiRu catalysts have been tested in the catalytic decomposition of ammonia to yield hydrogen and their performance in long-term tests has been compared to alumina-supported Ni and Ru samples. The catalysts have been characterized by XRD, TPR, NH3-TPD, HAADF-STEM, SEM, BET and XPS. Ceria-based samples are more active in ammonia decomposition with respect to their alumina-based counterparts, which has been ascribed to a particular metal-support interaction, while acidity does not seem to play an important role. Ru-based catalysts are more active than Ni-based samples, but they deactivate rapidly, in particular the Ru/Al2O3 sample. This is ascribed to loss of exposed Ru, as demonstrated by XPS and HAADF-STEM. Considering the high cost and limited availability of Ru, the Ni/CeO2 catalyst appears as a promising system for ammonia decomposition due to its good performance and low cost. In situ XPS experiments reveal that the active sites for the catalytic decomposition of ammonia are metallic Ni and Ru. Bimetallic NiRu catalysts do not outperform their monometallic counterparts, irrespective of the order in which the metals are added.Postprint (author's final draft

Review of the Decomposition of Ammonia to Generate Hydrogen

Because of the problems associated with the generation and storage of hydrogen in portable applications, the use of ammonia has been proposed for on-site production of hydrogen through ammonia decomposition. First, an analysis of the existing systems for ammonia decomposition and the challenges for this technology are presented. Then, the state of the art of the catalysts used to date for ammonia decomposition is described considering the catalysts composed of noble and non-noble metals and their combinations, as well as novel materials such as alkali metal amides and imides. The effect of the supports and promoters used is analyzed in detail, and the catalytic activity obtained is compared. An analysis of the kinetics of the reaction obtained with different catalysts is also presented and discussed, including the reaction mechanism, the determining step of the reaction, and the apparent activation energy. Finally, the structured reactors used to date for the decomposition reaction of ammonia are explored, as well as the possibilities offered by catalytic membrane reactors, which allow the on-site simultaneous production and separation of hydrogen.Peer ReviewedPostprint (author's final draft

Investigation of the evolution of Pd-Pt supported on ceria for dry and wet methane oxidation

Efficiently treating methane emissions in transportation remains a challenge. Here, we investigate palladium and platinum mono- and bimetallic ceria-supported catalysts synthesized by mechanical milling and by traditional impregnation for methane total oxidation under dry and wet conditions, reproducing those present in the exhaust of natural gas vehicles. By applying a toolkit of in situ synchrotron techniques (X-ray diffraction, X-ray absorption and ambient pressure photoelectron spectroscopies), together with transmission electron microscopy, we show that the synthesis method greatly influences the interaction and structure at the nanoscale. Our results reveal that the components of milled catalysts have a higher ability to transform metallic Pd into Pd oxide species strongly interacting with the support, and achieve a modulated PdO/Pd ratio than traditionally-synthesized catalysts. We demonstrate that the unique structures attained by milling are key for the catalytic activity and correlate with higher methane conversion and longer stability in the wet feed.Peer ReviewedPostprint (published version

Catalytic honeycombs for producing methane from CO2 and H2

In the experimental part of the work several catalysts are tested, in order to determine the best candidate among them to produce methane from the reaction between carbon dioxide and hydrogen. These catalysts are 10%Ni/Al2O3, (1%Ru-7%Mn-12%Cu)/Al2O3 and 10%Ni/CeO2. Alumina and ceria supports are prepared using different methods. Generally, CO2 conversion, CH4 selectivity and the yield have shown to be higher at higher temperature and pressure. Considering the supports, ceria has shown better results compared to alumina. Among the alumina supports, the one produced through direct calcination of Al(OH)3 presented better results. Regarding the catalytic properties of ceria supports they follow the trend: NICEO2-np > NICEO2-nr > NICEO2-nc ≈ NICEO2-H ≈ NICEO2-A, where the first 3 supports are prepared using an ultrasonic atomizer and a hydrothermal rector under conditions that give polycrystals, rods and cubes respectively. NICEO2-H and NICEO2-A are prepared by direct precipitation of Ce(NO3)3.6H2O with NaOH and ammonia solution, respectively. Polycrystalline ceria prepared using a hydrothermal reactor was found to be the best catalyst support among those tested, showing maximum methane production at 250°C under a pressure of 3 bar. In addition, ceria supported catalysts have demonstrated to be more selective to methane than alumina supported catalysts. Regarding the active metal, nickel offers better results. A monolithic honeycomb support is prepared by impregnating it with NICEO2-np catalyst and tested. The final yield is 73.4%, obtained using reactant flow rates of 25 mL/min of CO2 and 100 mL/min of H2 (GHSV = 1,500 h -1 ), at 350°C and under a pressure of 3 bar. After the catalytic tests, the catalysts are characterized using Scanning Electron Microscope and X-Ray Photoelectron Spectroscopy to verify composition, shape and particle size. There is evidence that the active metal impregnation didn’t influence the particles shape. The analysis of the used catalysts has demonstrated that the particles have suffered sintering effect and they are covered with carbon produced in the reaction. The results of XPS analysis show that if Ni/Ce ratio is high the methane production is lower. The second part of the work starts with the design of the ideal industrial system. After that it is scaled to two different applications of cement industry emissions, in Spain (Pamplona) and Germany (Mainz). A life cycle assessment through the SimaPro 8 software is performed. Three scenarios are compared: the system implemented in the Spanish and German factories and the natural gas extraction summed to CO2 emission impacts, which represent the non application of the system. The results show that to not apply the CO2 methanation system leads to a higher negative environmental impact with respect to its application. The methanation application phase which has the higher environmental impact is the construction phase of the wind energy plant. The manufacturing phase of the methanation system itself doesn’t cause high impacts. The Endpoint method indicates that the German system has a slightly higher environmental impact than the Spanish system. A sustainability analysis of the ideal industrial installation is carried out using MIVES software. The options are compared on economic, environmental and social plans. According to the assigned weight of the indicators, the application of a CO2 methanation system is a sustainable option. In particular, the German system application resulted in being the best option out of the three. In the chosen cement factory it can be an effective solution and the best compromise among the economic cost, the environmental benefit and the social effects

Catalytic honeycombs for producing methane from CO2 and H2

In the experimental part of the work several catalysts are tested, in order to determine the best candidate among them to produce methane from the reaction between carbon dioxide and hydrogen. These catalysts are 10%Ni/Al2O3, (1%Ru-7%Mn-12%Cu)/Al2O3 and 10%Ni/CeO2. Alumina and ceria supports are prepared using different methods. Generally, CO2 conversion, CH4 selectivity and the yield have shown to be higher at higher temperature and pressure. Considering the supports, ceria has shown better results compared to alumina. Among the alumina supports, the one produced through direct calcination of Al(OH)3 presented better results. Regarding the catalytic properties of ceria supports they follow the trend: NICEO2-np > NICEO2-nr > NICEO2-nc ≈ NICEO2-H ≈ NICEO2-A, where the first 3 supports are prepared using an ultrasonic atomizer and a hydrothermal rector under conditions that give polycrystals, rods and cubes respectively. NICEO2-H and NICEO2-A are prepared by direct precipitation of Ce(NO3)3.6H2O with NaOH and ammonia solution, respectively. Polycrystalline ceria prepared using a hydrothermal reactor was found to be the best catalyst support among those tested, showing maximum methane production at 250°C under a pressure of 3 bar. In addition, ceria supported catalysts have demonstrated to be more selective to methane than alumina supported catalysts. Regarding the active metal, nickel offers better results. A monolithic honeycomb support is prepared by impregnating it with NICEO2-np catalyst and tested. The final yield is 73.4%, obtained using reactant flow rates of 25 mL/min of CO2 and 100 mL/min of H2 (GHSV = 1,500 h -1 ), at 350°C and under a pressure of 3 bar. After the catalytic tests, the catalysts are characterized using Scanning Electron Microscope and X-Ray Photoelectron Spectroscopy to verify composition, shape and particle size. There is evidence that the active metal impregnation didn’t influence the particles shape. The analysis of the used catalysts has demonstrated that the particles have suffered sintering effect and they are covered with carbon produced in the reaction. The results of XPS analysis show that if Ni/Ce ratio is high the methane production is lower. The second part of the work starts with the design of the ideal industrial system. After that it is scaled to two different applications of cement industry emissions, in Spain (Pamplona) and Germany (Mainz). A life cycle assessment through the SimaPro 8 software is performed. Three scenarios are compared: the system implemented in the Spanish and German factories and the natural gas extraction summed to CO2 emission impacts, which represent the non application of the system. The results show that to not apply the CO2 methanation system leads to a higher negative environmental impact with respect to its application. The methanation application phase which has the higher environmental impact is the construction phase of the wind energy plant. The manufacturing phase of the methanation system itself doesn’t cause high impacts. The Endpoint method indicates that the German system has a slightly higher environmental impact than the Spanish system. A sustainability analysis of the ideal industrial installation is carried out using MIVES software. The options are compared on economic, environmental and social plans. According to the assigned weight of the indicators, the application of a CO2 methanation system is a sustainable option. In particular, the German system application resulted in being the best option out of the three. In the chosen cement factory it can be an effective solution and the best compromise among the economic cost, the environmental benefit and the social effects

Catalytic ammonia decomposition for hydrogen production on Ni, Ru and Ni–Ru supported on CeO2

Ceria-supported Ni, Ru and NiRu catalysts have been tested in the catalytic decomposition of ammonia to yield hydrogen and their performance in long-term tests has been compared to alumina-supported Ni and Ru samples. The catalysts have been characterized by XRD, TPR, NH3-TPD, HAADF-STEM, SEM, BET and XPS. Ceria-based samples are more active in ammonia decomposition with respect to their alumina-based counterparts, which has been ascribed to a particular metal-support interaction, while acidity does not seem to play an important role. Ru-based catalysts are more active than Ni-based samples, but they deactivate rapidly, in particular the Ru/Al2O3 sample. This is ascribed to loss of exposed Ru, as demonstrated by XPS and HAADF-STEM. Considering the high cost and limited availability of Ru, the Ni/CeO2 catalyst appears as a promising system for ammonia decomposition due to its good performance and low cost. In situ XPS experiments reveal that the active sites for the catalytic decomposition of ammonia are metallic Ni and Ru. Bimetallic NiRu catalysts do not outperform their monometallic counterparts, irrespective of the order in which the metals are added

Ammonia decomposition over 3D-printed CeO2 structures loaded with Ni

Binder-free ceria pastes have been formulated and used to prepare ceria structures with a woodpile arrangement of microchannels through 3D printing. After loading them with nickel, these catalytic structures have been tested for ammonia decomposition to obtain hydrogen, and their performance has been compared with those of conventional Ni/CeO2 powder catalysts and with that of a conventional cordierite honeycomb washcoated with Ni/CeO2. Samples have been characterized by N2 physisorption, inductively coupled plasma optical emission spectrometry (ICP-OES), X-Ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. At the same reaction temperature and flow rate to catalyst weight ratio (F/W), the 3D-printed ceria structures show a catalytic activity much higher than that of the cordierite honeycomb on a reactor volume basis. Additive manufacturing represents a valuable tool to prepare customized ceria-based catalytic structures for practical application with a variety of geometries not attainable with conventional methods.Postprint (author's final draft

Catalytic ammonia decomposition over Ni-Ru supported on CeO2 for hydrogen production: Effect of metal loading and kinetic analysis

Ceria-supported Ni-Ru bimetallic catalysts with different metal loadings have been prepared by co-impregnation, characterized and tested in the production of hydrogen from the catalytic decomposition of ammonia. The bimetallic catalysts showed an excellent catalytic performance in long-term stability tests with respect to monometallic Ru/CeO2 and Ni/CeO2 and in multicycle tests under pure ammonia. The best catalytic performance has been obtained over catalysts with 2.4−5 wt.% Ni, 0.4−0.6 wt.% Ru, and a Ni/Ru wt.% ratio of ca. 7. TOFH2 values exceeding 2 s−1 have been obtained, which are among the highest reported for ammonia decomposition at 400 °C. Raman spectroscopy, XRD, HRTEM, XPS, TPR and H2 chemisorption have revealed the existence of an intimate contact between Ni and Ru and CeO2, which is considered the reason of the excellent catalytic activity and stability observed. A kinetic model has been developed using the Langmuir-Hinshelwood-Hougen-Watson approach for the decomposition of ammonia in a fixed bed reactor. The reaction rate expression of the ammonia decomposition on Ni-Ru bimetallics supported on ceria suggests that the dehydrogenation of the ammonia adsorbed on the surface of the catalyst is the limiting step of the reaction and that ammonia decomposition is inhibited by the presence of H2.Fil: Lucentini, Ilaria. Universidad Politécnica de Catalunya; EspañaFil: García Colli, Germán. Universidad Nacional de La Plata; ArgentinaFil: Luzi, Carlos Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Serrano, Isabel. Universidad Nacional de La Plata; ArgentinaFil: Martinez, Osvaldo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Llorca Piqué, Jordi. Universidad Politécnica de Catalunya; Españ

Modelling and simulation of catalytic ammonia decomposition over Ni-Ru deposited on 3D-printed CeO2

3D-printed ceria structures have been prepared by robocasting, without using any additive, and impregnated with different amounts of Ni and Ru, characterized and tested for the catalytic decomposition of ammonia in a fixed bed reactor. The best catalytic performance has been achieved with an active phase of 0.5Ni0.1Ru (w/w%). A kinetic expression has been obtained using a crushed catalytic structure, which has been employed in a 1D model to simulate the behaviour of the Ni-Ru impregnated 3D-printed ceria structures. The results have been compared with the experimental data to validate the proposed model. A series of simulations have been performed to determine the relationship between the geometric parameters of the 3D-printed structures and their catalytic performance in the ammonia decomposition, in order to optimize the catalytic structure with the aim of supplying the hydrogen produced to a PEM-type fuel cell.Fil: Lucentini, Ilaria. Universidad Politécnica de Catalunya; EspañaFil: Garcia Colli, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Luzi, Carlos Daniel. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Serrano, Isabel. Universidad Politécnica de Catalunya; EspañaFil: Soler, Lluís. Universidad Politécnica de Catalunya; EspañaFil: Divins, Núria J.. Universidad Politécnica de Catalunya; EspañaFil: Martinez, Osvaldo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Llorca Piqué, Jordi. Universidad Politécnica de Catalunya; Españ