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The sorption-enhanced methanation (SEM) process has emerged as a promising technology to produce high quality synthetic natural gas (SNG) from renewable sources under milder conditions than conventional methanation technologies. During the SEM process developed in this paper, an H2O adsorbent is combined with a Rhodium-based catalyst to remove the H2O generated during the CO2 methanation reaction, shifting the equilibrium towards CH4 formation. In this work, several commercial zeolites (3A, 4A, 5A and 13X) were studied as H2O adsorbents under SEM conditions. Based on the study performed, zeolite 4A demonstrated to be the most suitable zeolite which, combined with the proposed catalyst, allowed maximising the production and purity of the obtained CH4. The influence of gas space velocity, H2/CO2 ratio in the feed gas, zeolite/catalyst proportion and cyclic stability were analysed and optimized to maximise CH4 production. When the process was run under SEM conditions using zeolite 4A as sorbent at 275 °C and a gas space velocity of 230 Nml/h·gcat, the CH4 content increased from 10.6 vol% in conventional methanation up to 85 vol% in the SEM conditions. Thus, the enhanced performance of the SEM process was demonstrated

This paper brings the comparison of performances of CO2 conversion by plasma and plasma-assisted catalysis based on the data collected from literature in this field, organised in an open access online database. This tool is open to all users to carry out their own analyses, but also to contributors who wish to add their data to the database in order to improve the relevance of the comparisons made, and ultimately to improve the efficiency of CO2 conversion by plasma-catalysis. The creation of this database and database user interface is motivated by the fact that plasma-catalysis is a fast-growing field for all CO2 conversion processes, be it methanation, dry reforming of methane, methanolisation, or others. As a result of this rapid increase, there is a need for a set of standard procedures to rigorously compare performances of different systems. However, this is currently not possible because the fundamental mechanisms of plasma-catalysis are still too poorly understood to define these standard procedures. Fortunately however, the accumulated data within the CO2 plasma-catalysis community has become large enough to warrant so-called “big data” studies more familiar in the fields of medicine and the social sciences. To enable comparisons between multiple data sets and make future research more effective, this work proposes the first database on CO2 conversion performances by plasma-catalysis open to the whole community. This database has been initiated in the framework of a H2020 European project and is called the “PIONEER DataBase”. The database gathers a large amount of CO2 conversion performance data such as conversion rate, energy efficiency, and selectivity for numerous plasma sources coupled with or without a catalyst. Each data set is associated with metadata describing the gas mixture, the plasma source, the nature of the catalyst, and the form of coupling with the plasma. Beyond the database itself, a data extraction tool with direct visualisation features

Physicochemical properties, kinetic pyrolysis and thermodynamic study of spent green tea, pure spent coffee grounds, spent coffee grounds blended with 50% torrefied barley and coffee husk were experimentally investigated using thermogravimetric analysis under an inert atmosphere to evaluate their thermochemical application. Five isoconversional methods were applied to determine effective activation energy (Ea) of the pyrolysis processes. All methods showed good agreement by determining fluctuating Ea values (150–500 kJ mol−1). Complex Ea profiles with conversion were divided into four stages corresponding to thermal degradation of main biomass constituents (extractives, hemicellulose, cellulose and lignin), indicating that extractives decomposition was the least demanding reaction while lignin decomposition was the most demanding. The kinetic process was verified by reconstruction according to the Friedman parameters. The thermodynamic parameters were evaluated to determine the energy demand and efficiency throughout the process. The values obtained for physicochemical properties such as volatile matter (> 68%) and higher heating value (> 17 MJ kg−1), average Ea (223–319 kJ mol−1) and significant energy efficiency implied that these types of biomass waste have significant reactivity and consequently the highest potential for the production of bioenergy and a range of high-value chemicals and materials.

1. Synthesis of the CeO2 supports. 2. Physicochemical characterization techniques and devices. 3. Plasma-catalytic and thermo-catalytic setups & experimental procedures. 4. SEM and TEM characterization: 4.1. CeO2 supports. 4.2. Reduced Ni-catalysts. 4.3. Spent Ni-catalysts (used in plasma-catalytic methanation). 5. X-ray diffraction. 6. N2-adsorption isotherms. 7. X-ray photoelectron spectrometry. 8. Raman spectroscopy. 9. 10 h time-on-stream methanation experiments

La Unión Europea tiene como objetivo alcanzar un escenario de emisiones neutras de gases de efecto invernadero en 2050 (denominado Pacto Verde o "Green deal"), para lo cual el uso tanto de energías renovables, así como de tecnologías de almacenamiento de carbono resultarán clave. Una solución prometedora en dicho escenario será la producción de gas natural sintético, GNS (metano), a partir de hidrógeno renovable y de CO2 proveniente de procesos industriales en los que se ha implantado una tecnología de captura o separación de CO2. Dentro de las tecnologías de producción de GENS de alta calidad se encuentra la metanación asistida con adsorción de H2O (Sorption-Enhanced Methanation - SEM). En este proceso se combinan un catalizador y un material adsorbente que retira el vapor de H2O producido durante la reacción de metanación de CO2 con H2, favoreciendo así la producción de CH4. El objetivo de este trabajo ha sido demostrar el potencial de este proceso SEM utilizando un catalizador comercial de metanación junto con adsorbentes de agua tradicionales, como son las zeolitas. Se han estudiado diferentes combinaciones catalizador-zeolita con el fin de maximizar tanto la producción como la pureza del CH4 obtenido.

Sorption-enhanced methanation (SEM) is one of the solutions proposed for the production of high quality synthetic natural gas (SNG) under mild conditions of temperature and pressure. In this novel process, the methanation reaction is performed in the presence of an adsorbent that retains the water produced as by-product. The SEM potential of a Rh-based catalyst and a zeolite 5A adsorbent has been demonstrated for both CO and CO2 hydrogenation. Pure CH4 production was possible operating at 275 °C and atmospheric pressure under sorption-enhanced CO2 methanation conditions for space velocities of up to 514 mlCO2/gcat/h. For sorption-enhanced CO methanation, CH4 purities of 86 vol% were achieved under the same operating conditions but at lower space velocity (440 mlCO/gcat/h). Finally, SEM/regeneration cycles were performed for a feed gas containing CO and CO2, achieving stable performance throughout the cycles and a constant CH4 purity of about 60 vol% for the operating conditions chosen.

A sequential two-step thermochemical process was studied for spent green tea waste (SGTW), involving an initial pyrolysis step followed by thermal or catalytic cracking. This process was carried out in two bench-scale reactors (fixed bed reactor and tubular reactor) serially coupled. At a fixed pyrolysis temperature of SGTW (550 °C), the application of high cracking temperatures (700 and 800 °C) positively affected both the yield and composition of the gas product. Consequently, it has the potential to be used for the production of diverse biofuels and chemicals, or to be partially recycled to optimize the process efficiency. Moreover, the use of inexpensive catalysts, particularly dolomite, was considered advantageous, since the syngas yield (56.5 wt%) and its potential were greatly enhanced, reaching a H2/CO ratio of 1.5. The homogenous biochar obtained, with a calorific value of 26.84 MJ/kg, could be harnessed as good-quality fuel for briquette applications and as a biofuel source for generating stationary power. Furthermore, catalytic cracking pyrolysis was examined for different types of coffee waste, revealing that this process is a simple and clean solution to valorize oxygen-rich lignocellulosic biomass and generate valuable gaseous by-products.

[EN] Among the different processes for carbon capture and utilisation, CO2 methanation is experiencing a renaissance as a promising technology for the development of Power-to-gas as an energy storage solution and carbon circular economy. The field of plasma catalysis, which considers the association of a catalyst with non-thermal plasma, has been recently developed for boosting CO2 methanation. The challenges of plasma catalysis focus on taking advantage of the activated species and electrons created by the plasma to achieve more favourable reaction pathways and interaction with the active sites of the catalyst and on plasma-catalyst synergy, meaning the enhancement of the catalyst properties by contact with plasma and vice versa. The goal of this work is to explore the effect of morphology and physicochemical properties of nanostructured Ni/CeO2 catalysts on plasma-catalyst synergy and to highlight the key characteristics of the catalysis that control an efficient plasma-assisted CO2 methanation in order to advance in the rational design of materials tailored for applications in plasma catalysis. For the plasma-assisted CO2 methanation tests, a suitable non-thermal plasma type is the dielectric barrier discharge due to mild temperature conditions, which allow the catalyst to be in direct contact with the plasma in a packed bed configuration, and operation at atmospheric pressure, promising for industrial applications. Nickel catalysts supported on Ce-based metal oxides have been proposed in recent publications for plasma-assisted CO2 methanation. Ni is a reliable solution as it is active for CO2 methanation as well as cost-effective. Cerium oxide (CeO2) is an interesting material to be used as support thanks to its redox properties related to the tendency to form oxygen vacancies. Such property can be tuned by enhancing the non-stoichiometric nature of the CeO2 surface, either by doping or, as in this case, by morphology modification, which has been reported for ce, [ES] Entre los diferentes procesos de captura y utilización del carbono, la metanización del CO2 experimenta últimamente un renacimiento como tecnología prometedora para el desarrollo de la conversión de electricidad en gas, del almacenamiento de energía y de la economía circular del carbono. El campo de la catálisis asistida por plasma, que considera la asociación de un catalizador con plasma no térmico, se ha desarrollado recientemente para impulsar la metanización de CO2. Los retos de esta tecnología se centran en aprovechar las especies activadas y los electrones para conseguir vías de reacción e interacción más favorables con los sitios activos del catalizador y en la sinergia plasma-catalizador, es decir, la mejora de las propiedades del catalizador por contacto con el plasma y viceversa. El objetivo de este trabajo es explorar el efecto de la morfología y las propiedades físicoquímicas de los catalizadores de Ni/CeO2 nanoestructurados en la sinergia plasma-catalizador y resaltar las características clave del catalizador que controlan una eficiente metanación de CO2 asistida por plasma con el fin de avanzar en el diseño de materiales para aplicaciones en plasma catálisis. Para los experimentos de metanación de CO2 asistida por plasma, un tipo de plasma no térmico adecuado es la descarga de barrera dieléctrica debido a las condiciones de temperatura suaves, que permiten que el catalizador esté en contacto directo con el plasma en una configuración de lecho fijo, y el funcionamiento a presión atmosférica, prometedor para aplicaciones industriales. En publicaciones recientes se han propuesto catalizadores de níquel soportados sobre óxidos metálicos basados en Ce para la metanación de CO2 asistida por plasma. El niquel es un metal adecuado ya que es activo para la metanación de CO2, además relativamente de bajo costo. El óxido de cerio (CeO2) es un material interesante para ser utilizado como soporte gracias a sus propiedades de redox relacionadas con la tendencia, [FR] Parmi les différents procédés de capture et d'utilisation du carbone, la méthanisation du CO2 connaît une renaissance comme une technologie prometteuse pour le développement du Power-to-gas et en tant que solution de stockage de l'énergie et de l'économie circulaire du carbone. Le domaine de la catalyse plasma, qui considère l'association d'un catalyseur avec un plasma non thermique, a été récemment développé pour stimuler la méthanation du CO2. Les défis de la catalyse assistée par plasma consistent à tirer profit des espèces activées et des électrons créés par le plasma pour obtenir des voies de réaction et des interactions plus favorables avec les sites actifs du catalyseur, ainsi que de la synergie plasma-catalyseur, c'est-à-dire de la modification des propriétés du catalyseur par contact avec le plasma et vice-versa. L'objectif de cette thèse est d'explorer l'effet de la morphologie et des propriétés physicochimiques des catalyseurs Ni/CeO2 nanostructurés sur la synergie plasma-catalyseur et de mettre en évidence les caractéristiques clés du catalyseur qui permettent une méthanisation efficace du CO2 assistée par plasma, afin de progresser dans la conception rationnelle de matériaux adaptés aux applications de la plasma-catalyse. Pour les essais de méthanation du CO2 assistée par plasma, les plasmas froids à décharge de barrière diélectrique (DBD) permettent des températures douces, ainsi qu’un contact direct entre le plasma et le catalyseur dans une configuration de lit fixe. Au même temps ils permettent l’opération sous pression atmosphérique, conditions idéales pour des applications industrielles. Des catalyseurs à base de nickel supportés par des oxydes métalliques à base de Ce ont été proposés dans des publications récentes pour la méthanisation du CO2 assistée par plasma. Le nickel est une solution fiable, car il est actif dans la méthanisation du CO2 et au même temps économiquement rentable. L'oxyde de cérium (CeO2) est un matériau intéressant à uti

Uno de los principales inconvenientes del uso de combustibles fósiles para la obtención de energía es la emisión de CO2 a la atmósfera. Para combatir los efectos negativos de dichas emisiones, se están desarrollando nuevas tecnologías de producción de biocombustibles a partir de residuos o biomasa que ayudarían a descarbonizar el sistema energético actual. La producción de CH4 presenta grandes ventajas en lo que respecta a su uso y almacenamiento ya que puede sustituir directamente al gas natural, mientras que puede ser almacenado sin ninguna restricción en la red de transporte de gas. Una alternativa poco explorada para aumentar la eficiencia del proceso de metanación convencional (CO2+ 4H2↔CH4+2H2O) es el proceso de metanación asistida o mejorada (SEM), en el que se propone llevar a cabo la metanación en presencia de un material adsorbente que retira el H2O generada en la reacción desplazando el equilibrio hacia la formación de CH4. De esta forma, se conseguirían mayores conversiones a CH4 operando en condiciones menos exigentes de presión y temperatura. El objetivo de este trabajo fue demostrar el potencial del proceso SEM para una mezcla H2/CO2 utilizando un catalizador comercial de Rodio y una zeolita 5A como adsorbente de H2O.

The catalytic co-pyrolysis of grape seeds and polystyrene was successfully scaled-up from thermogravimetric analysis to an auger reactor pilot plant. Agricultural residues were co-pyrolyzed with waste polystyrene plastics (up to 20 wt%) using calcium oxide as the catalyst. Particularly, an upgraded organic fraction was produced where synergetic positive effects were observed due to both the presence of plastics and of the CaO catalyst. These effects were mainly reflected in the production of a more deoxygenated and practically dehydrated organic fraction, rich in aromatic compounds and with a remarkable heating value. The synergetic positive effect of these materials is mainly attached to the promotion of the H2 transfer reactions resulting from the scission of polystyrene radicals, and from the decarboxylation and dehydration effects associated with CaO. Moreover, a non-condensable H2-rich gas stream with remarkably low CO2 concentration, proved potentially valuable not only for use in further energetic applications but also as a potential source of synthetic fuels. The great potential of this process in the production of bio-products was, thus, demonstrated in a representative scale.

This work studies the gasification of char derived from waste tire pyrolysis (pCB) by using a thermogravimetric analyzer under CO2/N2 atmospheres (20/80, 25/85 and 30/70 vol%) at different temperatures (825 °C, 850 °C, 875 °C, 900 °C and 925 °C). The main goal is the assessment of three different kinetic models for predicting not only the conversion (X) versus time (t) curve, but also the reaction rate (dX/dt) versus conversion (X) one, with high accuracy. At this respect, the Changing Grain Size Model (CGSM), the Random Pore Model (RPM) and a new model based on the RPM named the Hybrid Modified Random Pore Model (HMRPM) were used. The three models were fitted and the kinetic parameters such as the apparent kinetic constant (Ki(T,pj)), the reaction order (n), the activation energy (Ea) and the pre-exponential factor (A) were determined. The results suggest that the HMRPM is the model with better fitting because its ability to reproduce both conversion (X) and reaction rate (dX/dt); and hence, it is reliable to be integrated in both particle and reactor models, i.e. when the process is being designed and scaled-up. A drastically decrease in the reaction rate at the first stage of conversion (<20%) suggests a possible effect of volatile matter and inorganic compounds contained into the pCB. The n, Ea and A were found to be 0.543, 147.27 kJ/mol and 4.547 × 105 s−1, respectively.

[EN] Polycyclic aromatic hydrocarbons are persistent pollutants with a great carcinogenic capacity. They are generated in combustion and pyrolysis processes of organic materials and their control in hot gases is very important. Previous experimental studies have shown that their adsorption in hydrophobous materials as activated carbons has demonstrated to be a valuable control technology, due to the non-polar character of these molecules. In this study, molecular simulation tools have been utilized to further study the adsorption of these polycyclic aromatic hydrocarbons in activated carbons. Phenanthrene and carbon slit pores of different sizes have been chosen as models of adsorbate molecule and activated carbon. In the conditions of release of these emissions at 150 ºC and partial pressure around 2 Pa, the results have indicated that a pore size of 17 Å would maximize the pollutants retention., [ES] Los hidrocarburos aromáticos policíclicos son contaminantes persistentes con alta capacidad cancerígena. Se generan en procesos de combustión y pirólisis de materiales orgánicos por lo que controlar su emisión en gases calientes es de gran importancia. Estudios experimentales previos han demostrado que, debido a su carácter no polar, su adsorción en materiales hidrófobos como carbones activados es una tecnología de control prometedora. En este estudio se utilizan herramientas de simulación molecular para profundizar en el estudio de la adsorción de hidrocarburos aromáticos policíclicos en carbones activados. Se han elegido como modelos la molécula de fenantreno y el poro de carbono de rendija de distintos tamaños. En las condiciones de emisión de estos compuestos a 150 ºC y una presión parcial próxima a 2 Pa, los resultados indican que un tamaño de poro de 17 Å maximizaría la retención de estos contaminantes.

Co-pyrolysis of grape seeds and polystyrene was conducted in a fixed-bed reactor, followed by an analysis of the organic phase for possible further application as a drop-in fuel. Significant positive synergistic effects were found with the addition of polystyrene (5–40 wt%) to the conventional pyrolysis of grape seeds. There was a considerable improvement in the organic phase yield, in particular, reaching values over 80 wt%, markedly higher than those obtained from conventional pyrolysis (61 wt%). Fuel properties of the bio-oil were also upgraded, with a decrease in oxygen content and an increase in the heating value. An organic bio-oil fraction with pH values ranging from 5.4 to 6.2 was obtained, reducing the issues associated with handling bio-oils obtained from common pyrolysis of lignocellulosic biomass, usually ranging pH between 2 and 3. Finally, an increment in the desired compounds, mainly aromatics, was also attained, while at the same time achieving a low content of undesired compounds, such as phenols. It was demonstrated that polystyrene can act as a H2-donor, favoring oligomerization, cyclation and hydrodeoxygenation reactions into aromatic compounds.

The paper presents a detailed analysis of the effect of a high number of oxidation-reduction cycles on the steam-methane reforming process over a commercial Ni-based catalyst under conditions of intrinsic kinetics. These cycles take place within the sorption-enhanced steam-methane reforming process for hydrogen production including sorbent regeneration step. Experiments of steam-methane reforming and reverse water-gas shift reactions were carried out to obtain a complete characterisation of the system kinetics. After 80 cycles, methane conversion increased, while carbon dioxide conversion remained fairly constant. After 125 cycles, methane showed no significant changes in conversion compared to the increase exhibited by carbon dioxide. The kinetic model of Xu and Froment fitted the experimental results to provide the activation energies of the main reactions, which presented an evolution with redox cycles in line with the trends observed for conversion. The reactions with methane initially reduced their activation energy, facilitating conversion, while the reactions with carbon dioxide initially kept the activation energy constant, subsequently reducing it.

In this work, a thermogravimetric analyser was used to assess the pyrolysis kinetics of pineapple, orange and mango peel wastes and agro-industrial by-products, rice husk and pine wood. Five isoconversional methods (KAS, FWO, Starink, Vyazovkin and Friedman) and one model-fitting method (DAEM) accurately fitted the experimental data at three heating rates (5, 10 and 20 °C/min) between 10% and 90% conversion. These methods agree with the trends shown by the activation energy (Ea) distribution calculated, with fluctuations between 150 and 550 kJ/mol. The fluctuations of Ea in the whole range of conversion, in addition to a higher number of relevant reactions obtained by DAEM for fruit peel samples compared to agro-industrial samples, are associated with a higher extractive content in the peels. Kinetic parameters fitted by DAEM were successfully verified at the highest heating rate studied.

La producción de CH4 a partir de residuos o biomasa es una alternativa prometedora para la descarbonización del sistema energético actual, ya que puede ser un sustituto directo del gas natural. Una alternativa poco explorada para incrementar la eficiencia del proceso de metanación convencional (CO2 + 4H2 ↔ CH4+2H2O) es el proceso de metanación asistida o mejorada (SEM) [1,2], en el que se lleva a cabo la metanación en presencia de un material adsorbente que retira el H2O producida en la reacción, desplazando el equilibrio hacia la formación de CH4. El objetivo de este trabajo fue demostrar el potencial del proceso SEM para una mezcla H2/CO2 utilizando un catalizador comercial de Rodio y una zeolita 5A como adsorbente del H2O. El estudio se llevó a cabo en un reactor de lecho fijo a escala laboratorio acoplado a un espectrómetro de masas. La Tabla 1 resume los principales resultados obtenidos en los experimentos de metanación convencional y SEM. Las condiciones de operación se optimizaron para que ambos materiales funcionasen adecuadamente durante el SEM. A 275 ºC y 0.58 kgCO2/h.kgcat se consiguió incrementar la conversión del CO2 de un 78.7 % hasta un 100 %, obteniéndose una corriente pura en CH4 (Figura 1). Una vez la zeolita se saturó de H2O, la pureza del CH4 empezó a disminuir (breakthrough), alcanzándose la composición del proceso convencional de metanación (post-breakthrough). De esta manera se demuestra el potencial del proceso SEM utilizando un catalizador y una zeolita comerciales para obtener una corriente pura de CH4.

The effective use of renewable sources to produce energy is an important objective to reduce the environmental impact caused by the exploitation of fossil fuels. The use of lignocellulosic biomass becomes one of the most promising alternatives, as it is the only renewable source of carbon that can produce products similar to fossil fuels through the pyrolysis process and does not compete with the food market. Unfortunately, the properties of pyrolytic bio oils as fuels are very poor and different improvement strategies need to be implemented. Among all the strategies, co pyrolysis of biomass and plastic waste such as polystyrene ( emerges as a promising way to achieve this goal). For synergistic reasons these raw materials are processed by co pyrolysis giving the process the possibility to achieve this objective economically. The present work develops a new and low cost strategy based on the in situ co pyrolysis of biomass and plastic wastes that allows the user to obtain an advanced bio oil to be used directly or to be processed in bio refineries. The implementation of new, simple and low cost strategy through co pyrolysis of grape seeds and PS in a specifically designed fixed bed reactor, that allows the user to directly obtain high quality bio oils to be used as renewable energetic vector.

The characteristics of bio-oil produced from biomass pyrolysis can be improved by co-feeding waste materials. In this work, co-pyrolysis of lignocellulosic biomass with six different waste plastics (waste tyre (WT), polylactic acid (PLA), polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP) and high density polyethylene (HDPE)) were conducted in a thermogravimetric analyser to study thermal decomposition of the mixtures. The distributed activation energy model (DAEM) was applied to pure feedstocks at 5 and 10 °C/min heating rates to fit the kinetic parameters. The model was used to simulate the co-pyrolysis of biomass/plastic mixtures assuming additive effect of components at different weight proportions and heating rates. Profiles of the fraction of mass remaining for mixtures at 100 °C/min were reproduced with a remarkable agreement. Discrepancies between the experimental and calculated profiles were considered as a measure of the extent of interactions occurring in the co-pyrolysis. Projections of the behaviour of mixtures under flash pyrolysis conditions were performed to study important aspects of the process, such as radical interactions and optimum working temperature

Catalytic co-pyrolysis of grape seeds and waste tyres was performed in a fixed-bed reactor using calcined calcite as a catalyst. The organic phase obtained was analysed for its further application as a potential and stable drop-in fuel. Remarkable positive effects were achieved after the joint incorporation of both waste tyres and calcined calcite to grape seeds in the process. More specifically, the addition of considerable amounts of waste tyres (between 20 and 40 wt%) with a constant ratio of feedstock to calcined calcite of 1 were considered the optimal experimental conditions to promote positive synergistic effects on bio-oil yields and its characteristics as a fuel. Thus, when the proportion of waste tyres in the feed reached 40 wt%, the organic phase yield was considerable improved, reaching up values higher than 73 wt%, significantly greater than those obtained from conventional pyrolysis (61 wt%). Moreover, oxygen content was reduced to 4.2 wt%, minimizing any problems related to corrosivity and instability. HHV was enlarged from 15.3 up to 27.3 MJ/kg, significantly increasing the value of the resulting bio-oil. pH values and specially total acid number were also improved reaching values down to 1 mg KOH/gbio-oil in all cases. Additionally, a more valuable chemical composition was achieved since the production of aromatic and cyclic hydrocarbons was maximized, while a significant reduction in phenolic compounds was achieved. Moreover, bio-oil sulphur content was drastically reduced in comparison with the pyrolysis of waste tyres by itself from 0.6 down to 0.2 wt%. The role of calcined calcite was, directly related to the promotion of dehydration reactions of acids and phenols in order to generate hydrocarbons. On the other hand, radical interactions between the biomass and waste tyres pyrolysis products played a fundamental role in the production of more valuable compounds. Finally, the CO2 capture effect produced a more environmentally friendly gas while maintaining its calorific value.

Wood catalytic pyrolysis using calcium-based materials was studied in an auger reactor at 450 °C. Two different catalysts, CaO and CaO·MgO were evaluated and upgraded bio-oils were obtained in both cases. Whilst acidity and oxygen content remarkable decrease, both pH and calorific value increase with respect to the non-catalytic test. Upgrading process was linked to the fact that calcium-based materials could not only fix the CO2-like compounds but also promoted the dehydration reactions. In addition, process simulation demonstrated that the addition of these catalysts, especially CaO, could favour the energetic integration since a lowest circulation of heat carrier between combustor and auger reactor should be needed. An energy self-sustained system was obtained where thermal energy required for biomass drying and for pyrolysis reaction was supplied by non-condensable gas and char combustion, respectively.

Sorption Enhanced Reforming (SER) is a very promising option that allows H2 production coupled with capturing CO2 by sorption. The present research work focus in the sorbent point of view and several synthetic materials with a high CO2 absorption capacity and chemically and mechanically stable during multi-cyclic operation (at least 40 calcination-carbonation cycles and 100 cycles in some cases) under the typical SER process conditions have been developed. Two different synthesis routes (co-precipitation and mechanical mixing) have been followed trying to evaluate the effect of two different inert supports (magnesium oxide and mayenite) on the evolution of the CO2 carrying capacity of the materials. Also, sorbents have been synthesized with different morphologies (powder and particles) and sizes (from 100 microns up to 2 mm) in order to test their reactivity and mechanical suitability for large scale reactor system operation. Synthetic dolomite with a molar CaO/MgO ratio of 2:1 synthesized by co-precipitation method exhibited very stable performance for 100 consecutive carbonation/calcination cycles and a residual CO2 carrying capacity of 0.29 grCO2/grcalcined sorbent. Also a very promising result has been obtained for this sorbent mixed with a commercial catalyst in a preliminary SER experiment that yield a H2 production of 92 % vol. (d.b.).

The operational limits of a commercial nickel-based catalyst under the conditions of a sorption-enhanced steam-methane reforming process coupled to a Ca/Cu chemical loop are investigated for high-purity H2 production in a cyclic operation. The performance of the reforming catalyst is tested by means of a high number of oxidation-reduction-reforming cycles. After 100 oxidation-reduction cycles, this catalyst retains its exceptional reforming activity. The methane conversion values are close to the thermodynamic equilibrium under very demanding conditions: temperature between 500 ºC - 700 ºC and mass hourly space velocity of 8.8 kgCH4 h-1 kgcat-1. After 200 cycles, the sample shows reduction in its reforming activity in line with a lower dispersion of the Ni species. Sintering of Ni nanocrystals is evidenced during the oxidation-reduction multi-cycles. The performance of the catalyst after 200 oxidation-reduction cycles mixed with a CaO-based CO2 sorbent is studied under optimal conditions calculated for the sorption-enhanced reforming process coupled to a Ca/Cu cycle (temperature of 650 ºC, steam/methane ratio of 4, sorbent/catalyst ratio of 4 and space velocity of 0.75 kgCH4 h-1 kgcat-1). Remarkably, an equilibrium value over 92 vol.% H2 concentration is achieved, highlighting this catalyst as a promising candidate for the next steps of the process development.

The joint performance of a CaO-based sorbent and a Ni-based commercial catalyst has been assessed under relevant conditions for the SER stage in the Ca/Cu H 2 production process. These conditions comprise processing CH 4 space velocities suitable for the scaling up of the process, operation of the sys- tem at pressure, and testing materials that had experienced up to 200 oxidation/reduction cycles. The system, catalyst and CaO-based sorbent, was able to fulfil the SER equilibrium composition up to 2.5 kg CH 4 h 1 kg cat 1 ,CH 4 space velocity that would allow the scaling up of the process. In this way, a gas stream containing up to 95% vol. H 2 was obtained at 923 K, steam to carbon ratios of 3.2 and 4, sor- bent to catalyst weight ratios from 4 to 15 and for operation pressures between 1 and 9 bar. The effect of oxidation/reduction cycles on catalyst performance was assessed, and the mixture sorbent and aged cat- alyst was able to process up to 2.5 kg CH 4 h 1 kg cat 1 , corroborating the operational limit determined for the fresh materials. The total operation pressure (from 1 to 9 bar) did not have an important influence on H 2 yield, and/or materials performance. Sorbent carbonation reaction rates up to 4.42 * 10 2 kmol h 1 kg sorb 1 were determined in the experiments, being this parameter responsible of the limit in CH 4 space velocity that can be successfully converted through this sorbent/catalyst system. The experimental results have been successfully described by a pseudo-homogeneous reactor model that incorporates the main kinetic expressions of the reactions involved in the SER stage.

A highly effective hydrocarbon (HC) trap for the abatement of cold start HC emissions with specific adsorption sites for the different molecules present in the exhaust gases has been designed by means of molecular simulation tools, and later synthesized.

The modelling of breakthrough curves obtained in the adsorption of propene as a model compound onto different inorganic solids is described. All the runs were performed in a fixed bed at atmospheric pressure, employing a process temperature of 30 °C and propene concentrations in the range 0.0022–0.0222 mol/Nm3. The experimental conditions were therefore similar to those observed in the initial flue gases of cold start engines. The work described was mainly focused on the study of the influence of the adsorbent characteristics (composition, porous structure and surface area) on the kinetics of the adsorption process. The equilibrium adsorption values were initially determined from the breakthrough curves and satisfactorily fitted by the Langmuir isotherm model. These values were then used together with experimental breakthrough curves to analyse the kinetic expressions obtained applying the Linear Driving Force (LDF) model to the dynamic adsorption process. Values of the mass-transfer coefficient, surface and effective diffusion coefficients of propene have been calculated and are reported.

Propene adsorption isotherms, breakthrough curves and temperature programme desorption profiles have been obtained for six different crystalline materials with distinctive framework structures (3D and 1D) and a variety of Si/Al ratios and cations (four zeolites: Silicalite-1, BETA, ZSM-5, Mordenite; and two silicoaluminophosphate molecular sieves: SAPO-41 and SAPO-5). Moreover, for a proper evaluation of the solids in a propene trap under cold start conditions, cold start tests have been performed, carrying out four cycles (adsorption/desorption) to analyze the ageing process of the materials. A detailed analysis of the experimental results points out that materials with high equilibrium propene adsorption capacity at 30 °C, where propene is mainly chemisorbed and, which presents some kinetics restrictions, seem to be the best for a propene trap under cold start conditions. BETA and ZSM-5 zeolites and SAPO-5 silicoaluminophosphate molecular sieve are promising materials as propene traps.

Nowadays, waste tires disposal has become a relevant environmental problem. Although pyrolysis processes seem to be a feasible alternative treatment, a proper application for generated residues is a task to be solved. In this context, the aim of this work is to valorize pyrolytic tire char by means of the production of a useful adsorbent for air purification. An activation process with CO2 was chosen to control the process of microporosity generation. The activation reaction and the textural properties were followed to achieve the understanding of porosity evolution. A change in the reaction rate in the first steps of the process was observed, followed by a linear relationship between activation time and burnoff. Microporosity is generated in two main processes. At the beginning, narrow microporosity is formed, and later, a widening of the micropores is taking place. The performance of the new obtained samples for hot gas cleaning was tested by a process of Phenanthrene (Phe) adsorption in a fixed bed reactor with a process temperature of 150 °C at low inlet concentrations. It was concluded that the porosity development, both micro- and nonmicroporosity, increases the Phe adsorption capacity of activated carbons, likely due to a multilayer adsorption process.

An assessment of the air quality of Zaragoza (Spain) was performed by determining the trace element content in airborne PM10 in a sampling campaign from July 2001 to July 2002. Samples were collected in a heavy traffic area with a high volume air sampler provided with a PM10 cutoff inlet. The levels of 16 elements (Al, Ba, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) were quantified after collecting the PM10 on Teflon-coated glass fiber filters (GFF). Regarding the PM10, 32% exceedance of the proposed PM10 daily limit was obtained, some of them corresponding to summer and autumn periods. The limit values of toxic trace elements from US-EPA, WHO, and EC were not exceeded, considering Zaragoza as a moderately polluted city under the current air quality guidelines. The contribution of anthropogenic sources to atmospheric elemental levels was reflected by the high values of enrichment factors for Zn, Pb, and Cu compared to the average crustal composition. Statistical analyses also determined the contribution of different sources to the PM10, finding that vehicle traffic and anthropogenic emissions related to combustion and industrial processes were the main pollutant sources as well as natural sources associated with transport of dust from Africa for specific dates. Regarding the influence of meteorological conditions on PM10 and trace elements concentrations, it was found that calm weather conditions with low wind speed favor the PM10 collection and the pollution for trace elements, suggesting the influence of local sources.

The modeling of breakthrough curves obtained in the adsorption of phenanthrene as model compound on different activated carbons is described. All the runs were performed in a fixed bed reactor at atmospheric pressure, with a process temperature of 150 °C and low contaminant concentrations. Therefore, experimental conditions were similar to the observed in the flue gases of energy generation systems. This work is mainly focused on the study of how adsorbent characteristics (surface area and micropore size distribution) influence the kinetics of the adsorption process. First, equilibrium values are found from the breakthrough curves and they are satisfactory fitted to the Freundlich isotherm. Using the obtained equilibrium values together with the linear driving force model as kinetic expression, the breakthrough curve modeling is achieved. It was found that this model fits all the breakthrough curves and it is a useful tool for modeling purposes. Values for the phenanthrene surface and effective diffusion coefficients are calculated and reported, and a relationship with the microporosity is found. As it was expected, it is observed that the phenanthrene molecule finds kinetic restrictions for the diffusion in those carbons with narrow microporosity, especially in those with a mean pore diameter close to the molecular size.

Three-ring polycyclic aromatic hydrocarbons (PAH) are one of the most abundant PAH groups emitted during coal combustion. Four of themacenaphthene (Ac), phenanthrene (Phe), fluorene (Fu), and anthracene (An)have been listed by the U.S. EPA as priority pollutants. The aim in this paper is to study the abatement of this particular group of three-ring PAH from hot gas emissions during energy generation in coal combustion. The three-ring PAH adsorption capacities are related to the morphological and chemical properties of the 16 sorbents used in this work. Single and multiple linear regressionsprincipal component regression (PCR)were applied in this study. The main conclusions reached are, first, that the micropore volume is the most determinant parameter for removal of these PAHs and, second, that the adsorption of three-ring PAH by sorbents from waste hot gas emissions is inversely proportional to their volatility: the lower the PAH volatility, the higher the adsorbent adsorption capacity. The adsorption isotherms show that Phe and An, both examples of PAH with three aromatic rings, behave similarly. However, their behavior differs from that of Ac and Fu, compounds in which only two of their three rings exhibit an aromatic nature.

The aim of this paper is to investigate the effects that the incorporation of limestone to the feed may have on polyaromatic hydrocarbon (PAH) emissions during coal atmospheric fluidized bed combustion (AFBC). The study was performed at a combustion temperature of 850 °C, an oxygen excess percentage of 10%, and a total air velocity of 0.24 m/s (around twice the minimum fluidization velocity of the heaviest solid) in a laboratory scale pilot plant with a fluidized bed reactor (7 cm i.d., 76 cm height). The emissions of 16 PAH's (listed by the US Environmental Protection Agency as priority pollutants) were analyzed considering their feeding and their fluidized bed nature. The samples analyzed were taken from a cyclone, a condenser, a Teflon filter (1-micron pore size), and XAD-2 resin. After sonication extraction with dimethylformamide (DMF) as the solvent, the 16 PAH's were analyzed by fluorescence spectroscopy (FS) in the synchronous mode. The results obtained show that not all the PAH's could be detected and that the highest PAH content was emitted when a limestone bed was used. Wih regard to the PAH gas/solid partitioning emissions, most of them were concentrated on the solid phase when limestone coal blend was added to the reactor, while most of the emissions were produced in the gas phase when only coal was fed. To assess a possible Ca catalytic role, additional combustion experiments were performed through feeding coal (without limestone) to the bed obtained from coal-limestone blend feed. Finally, the influence of the calcite porosity and the Ca presence on PAH formation, emission, and distribution are also reported and discussed.