Academic literature on the topic 'Room Temperature CO2 Adsorption'

In this paper, the adsorption of heavy metals by biomass, namely dry garlic stem, an environmentally-friendly and natural adsorbent, were studied．The efficiency of the adsorbent was studied under different experimental conditions by varying parameters such as pH, initial concentration and contact time using batch adsorption technique. The results show that at pH 5.50, room temperature, the adsorption time 90 min and the amount of garlic stem 0.5 g, Co2+ have the maximum adsorption capacity. The maximum adsorption capacity of the Co2+ on garlic stem is 14.9 mg/g. At pH 9.50, the adsorption time 90 min and the amount of garlic stem 0.7g, Cd2+ have the maximum adsorption at the same temperature. The maximum adsorption of the Cd2+ is 20.90 mg/g. At pH 10.0, the adsorption time 150 min and the amount of garlic stem 0.3g, Ni2+ have the maximum adsorption at the same temperature. The dry garlic stem is a efficient adsorbent in removing cobalt, cadmium and nickel from aqueous solution.

MgO/Mg(OH)2-based materials have been intensively explored for CO2 adsorption due to their high theoretical but low practical CO2 capture efficiency. Our previous study on the effect of H2O wetting on CO2 adsorption in MgO/Mg(OH)2 nanostructures found that the presence of H2O molecules significantly increases (decreases) CO2 adsorption on the MgO (Mg(OH)2) surface. Furthermore, the magneto-water-wetting technique is used to improve the CO2 capture efficiency of various nanofluids by increasing the mass transfer efficiency of nanobeads. However, the influence of magneto-wetting to the CO2 adsorption at nanobead surfaces remains unknown. The effect of magneto-water-wetting on CO2 adsorption on MgO/Mg(OH)2 nanocomposites was investigated experimentally in this study. Contrary to popular belief, magneto-water-wetting does not always increase CO2 adsorption; in fact, if Mg(OH)2 dominates in the nanocomposite, it can actually decrease CO2 adsorption. As a result of our structural research, we hypothesized that the creation of a thin H2O layer between nanograins prevents CO2 from flowing through, hence slowing down CO2 adsorption during the carbon-hydration aging process. Finally, the magneto-water-wetting technique can be used to control the carbon-hydration process and uncover both novel insights and discoveries of CO2 capture from air at room temperature to guide the design and development of ferrofluid devices for biomedical and energy applications.

Although mesoporous silica materials have been widely investigated for many applications, most silica materials are made by calcination processes. We successfully developed a convenient method to synthesize mesoporous materials at room temperature. Although the silica materials made by the two different methods, which are the calcination process and the room-temperature process, have similar specific surface areas, the silica materials produced with the room-temperature process have a significantly larger pore volume. This larger pore volume has the potential to attach to functional groups that can be applied to various industrial fields such as CO2 adsorption. This mesoporous silica with a larger pore volume was analyzed by TEM, FT-IR, low angle X-ray diffraction, N2-adsorption analysis, and CO2 adsorption experiments in comparison with the mesoporous silica synthesized with the traditional calcination method.

Magnesium oxide (MgO) has been investigated as a wet mineral carbonation adsorbent due to its relatively low adsorption and regeneration temperatures. The carbon dioxide (CO2) capture efficiency can be enhanced by applying external force on the MgO slurry during wet carbonation. In this study, two aerosol-processed MgO nanoparticles were tested with a commercial MgO one to investigate the external force effect on the wet carbonation performance at room temperature. The MgO nano-adsorbents were carbonated and sampled every 2 h up to 12 h through forced and non-forced wet carbonations. Hydrated magnesium carbonates (nesquehonite, artinite and hydromagnesite) were formed with magnesite through both wet carbonations. The analyzed results for the time-dependent chemical compositions and physical shapes of the carbonation products consistently showed the enhancement of wet carbonation by the external force, which was at least 4 h faster than the non-forced carbonation. In addition, the CO2 adsorption was enhanced by the forced carbonation, resulting in a higher amount of CO2 being adsorbed by MgO nanoparticles than the non-forced carbonation, unless the carbonation processes were completed. The adsorbed amount of CO2 was between the maximum theoretical amounts of CO2 adsorbed by nesquehonite and hydromagnesite.

In this study, mesoporous polyimide aerogels with carboxyl were successfully synthesized by the co-polymerization method at room temperature from pyromellitic dianhydride and 1,3,5-triaminophenoxybenzene, 3,5-diaminobenzoic acid, and 2,2′-dimethyl-4,4′-diaminobiphenyl. Compared to previously reported porous organic polymer materials, this aerogel has the advantage of a simple and efficient synthesis method. The thermal decomposition temperatures of the obtained polyimide aerogels are all above 400 °C and have excellent thermal stability. Among them, the largest specific surface area is 62.03 m2/g. Although the surface area of this aerogel is not large enough, it has considerable CO2 adsorption properties. The adsorption capacity of CO2 is up to 11.9 cm3/g, which is comparable to those of previously reported porous materials. The high CO2 adsorption is attributed to the abundance of carboxyl groups in the polyimide networks. The mild and convenient synthesis method and high CO2 adsorption capacity indicate that the polyimide aerogel with carboxyl is suitable as a good candidate material for CO2 adsorption.

Supported ionic liquid (IL) [bmim][CF3SO3] on SiO2 was prepared, characterized and its potential evaluated for CO2 capture via adsorption and desorption studies using gas adsorption analyzer. The physical and chemical properties were determined using N2 adsorption/desorption and CO2-TPD analysis. The increasing IL loading caused a drastic decrease in the surface area as well as pore volume due to the confinement of IL within the micropore and mesopore area. However, the increasing IL loading increased the basicity of the sorbent which significantly enhanced CO2 chemisorption. Supported [bmim][CF3SO3] on SiO2 revealed the physical and chemical adsorption of CO2 and resulted in a remarkable CO2 adsorption capacity at atmospheric pressure and room temperature (66.7 mg CO2/gadsorbent) which has great potential in industrial applications.

Sepoilite was surface-modified by the mixture of ethanolamine and n, n-dimethyl ethanolamine. The XRD, SEM, FT-IR, BET and TGA were used to characterize the material structure and the adsorption property in CO2. The results showed that the weight percentage of CO2 adsorption rose from 4.01% for pure sepoilite to 19.28% for the modified sepoilite at room temperature.

Due to high regeneration energy demands for amine absorption processes for post-combustion CO2 capture, alternative technologies such as adsorption processes using solid adsorbents have been considered. Other practical issues such as corrosion of equipment and loss of solvent can be avoided with adsorption processes. Fixed bed adsorption processes, in which CO2 adsorption and adsorbent regeneration are performed successively in a vessel packed with adsorbent, are the most common adsorption processes. However, in fixed bed temperature swing adsorption (TSA) processes, large columns and long heating and cooling times would be needed. Fixed bed pressure swing adsorption (PSA) processes use electrical energy, which is more expensive than thermal energy in a power plant. Therefore, the feasibility of moving bed adsorption processes including fluidised-bed, co-current and counter-current systems is investigated. In these systems, the adsorbent continuously circulates from a CO2 adsorber to a regenerator. The adsorbents considered are a supported amine adsorbent, activated carbon and zeolite 13X. Numerical simulations of moving bed TSA cycles for CO2 capture have been carried out. The effects of influential parameters in the process have been assessed via sensitivity analyses. It was found that counter-current beds with supported amine adsorbent give the best overall performance. Compared to an amine absorption process, it was found that a moving bed TSA process without heat integration requires the same heat consumption per unit mass of CO2 captured. There is a potential for a lower heat consumption in moving bed TSA processes if, similarly to amine absorption processes, heat integration is carried out or if the CO2 working capacity of the adsorbent can be increased.

Le réchauffement climatique, résultant essentiellement des émissions anthropiques de dioxyde de carbone, demeure un sujet de grande préoccupation. Le captage et la séquestration du dioxyde de carbone est une solution viable permettant de prévoir une baisse des émissions de CO2 issues des importantes sources ponctuelles qui impliquent la combustion des carburants fossiles. Dans cette perspective, les systèmes aqueux d’alcanolamines offrent une solution prometteuse à court terme pour la capture du CO2 dans les installations de production d'électricité. Cependant, ces systèmes sont confrontés à divers accrocs opératoires tels que les limitations d’équilibre, les grandes quantités d’énergie requises pour la régénération, les pertes en solvant et la corrosion prononcée des installations, pour ne citer que ces quelques inconvénients. L’eau étant la principale cause de ces complications, une mesure à prendre pourrait être le remplacement de la phase aqueuse par un solvant plus stable. Les liquides ioniques à température ambiante, dotés d’une haute stabilité thermique et pratiquement non-volatils émergent en tant que candidats prometteurs. De plus, grâce à leur nature ajustable, ils peuvent être apprêtés conformément aux exigences du procédé. La substitution de la phase aqueuse dans les processus utilisant l’alcanolamine par les liquides ioniques à température ambiante ouvre une opportunité potentielle pour une capture efficace du CO2. Un aspect remarquable de ces systèmes serait la cristallisation du produit résultant de la capture du CO2 (c-à-d, le carbamate) au sein même du liquide ionique qui non seulement déjouerait les contraintes d’équilibre mais également pourvoirait une opportunité intéressante pour la séparation des produits. Étant donné le peu d’information disponible dans la littérature sur la viabilité des systèmes utilisant la combinaison d’amine et de liquide ionique, l’étude proposée ici a pour but d’apporter une meilleure compréhension sur l’efficacité à séparer le CO2 d’un mélange de type postcombustion à travers une approche plus systématique. À cet effet, des liquides ioniques à base d’imidazolium ([Cnmim][Tf2N], [Cnmim][BF4], [Cnmim][Otf]) ont été choisis. Deux alcanolamines, à savoir, le 2-amino-2-methyl-1-propanol (AMP) et le diéthanolamine (DEA) ont été examinées en détail afin d’explorer la capture du CO2 et les possibilités de régénération qu’offre un système amine-liquide ionique. Les résultats ont révélé l’intérêt de la combinaison DEA-liquide ionique étant donné que ce système pourrait aider à réduire de manière significative l’écart entre les températures d’absorption et de régénération, promettant ainsi une perspective attrayante en termes d’économie d’énergie. En outre, les liquides ioniques ont également été scrutés du point de vue de leur nature hydrophobe/hydrophile afin d’étudier le comportement corrosif du mélange amine-liquide ionique au contact d’échantillons d’acier au carbone. Bien que l’utilisation des liquides ioniques hydrophiles ait aidé à abaisser la vitesse de corrosion jusqu’à concurrence de 72%, l’emploi de liquides ioniques hydrophobes s’avère plus efficace, car annulant quasiment le phénomène de corrosion même dans un environnement riche en CO2. Dans le cas des mélanges immiscibles comme DEA-[hmim][Tf2N], une agitation continue s’avère nécessaire afin d’assurer une dispersion prolongée des gouttelettes d’amine émulsifiées au sein de liquides ioniques et ainsi atteindre une vitesse de capture optimale.
Global warming, largely resulting from anthropogenic emissions of carbon dioxide, continues to remain a matter of great concern. Carbon capture and storage (CCS) is a viable solution to ensure a prevised fall in CO2 emissions from large point sources involving fossil fuel combustion. In this context, aqueous alkanolamine systems offer a promising near-term solution for CO2 capture from power generation facilities. However, these face several operational hitches such as equilibrium limitations, high regeneration energy requirement, solvent loss, and soaring corrosion occurrence. The main culprit in this respect is water and, accordingly, one feasible practice may be the replacement of aqueous phase with some stable solvent. Room-temperature ionic liquids (RTILs), with high thermal stability and practically no volatility, are emerging as promising aspirants. Moreover, owing to the tunable nature of ionic liquids, RTIL phase can be adapted in accordance with the process requirements. Replacing aqueous phase with RTIL in case of alkanolamine based processes provided a potential opportunity for efficient CO2 capture. The most striking aspect of these schemes was the crystallization of CO2-captured product (carbamate) inside the RTIL phase that not only helped evade equilibrium constraints but also rendered a worthy opportunity of product separation. Since there is little information available in the literature about the viability of amine-RTIL systems, the proposed research was aimed at better understanding CO2 separation proficiency of these fluids through a more systematic approach. Imidazolium RTILs ([Cnmim][Tf2N], [Cnmim][BF4], [Cnmim][Otf]) were chosen for this purpose. Two alkanolamines, 2-amino-2-methyl-1-propanol (AMP) and diethanolamine (DEA) were examined in detail to explore CO2 capture and regeneration capabilities of amine-RTIL systems. The results revealed the superiority of DEA-RTIL combination as this scheme could help significantly narrow the gap between absorption and regeneration temperatures thus promising a sparkling prospect of attenuating energy needs. Furthermore, ionic liquids were scrutinized in reference to their hydrophobic/hydrophilic nature to study the corrosion behaviour of carbon steel in amine-RTIL media. Though hydrophilic ionic liquids helped decrease corrosion occurrence up to 72%, hydrophobic RTIL appeared to be the most effective in this regard, virtually negating the corrosion phenomenon under CO2 rich environment. In case of immiscible blends like DEA-[hmim][Tf2N], continual agitation appeared to be a necessity to ensure a prolonged dispersion of amine in the RTIL phase and, thereby, to attain an optimal capture rate.

Adsorption on proper adsorbents is one of the commonly used technologies to capture carbon dioxide. Zeolites, such as 13X, exhibit good adsorption capacity and selectivity towards CO₂. Compared with CO₂ capture from large point sources with high concentration of CO₂, direct capture from the ambient air plays a better role in the reduction of greenhouse gases. On the other hand, greenhouse crops can be benefited from CO₂ enrichment, typically around 1000 ppm. By applying temperature swing adsorption to ambient air, CO₂ concentration can be enriched from 400 ppm to about 1000 ppm, which can then be directly used for greenhouse CO₂ enrichment. The proposed method not only helps the capture of CO₂ from air but also provides an enriched CO₂ stream to greenhouses. In this study, the performance of zeolite 13X was evaluated in a fixed bed reactor for enriching ambient CO₂ concentration from 400 ppm to 1000 ppm by temperature swing adsorption under different operating conditions such as ambient temperature and moisture content. Results showed that 13X performed well for both CO₂ adsorption and desorption, and an enrichment factor of 3 can be reached, demonstrating the feasibility of the proposed TSA method. A lower adsorption temperature and a higher desorption temperature would result in a higher enriched CO₂ concentration. Finally, economic analyses have been carried out to compare the unit cost of proposed method for capturing one tonne CO₂ with the cost of other air capture technologies and the cost of CO₂ supply in current greenhouse operations. The unit cost of CO₂ enrichment by temperature swing adsorption seems to be quite competitive if the adsorption and desorption capacity of the currently tested adsorbent could be increased by six times to the level as reported in the literature.

Le reformage à la vapeur couplé à la sorption in-situ d’un composant du milieu réactionnel (sorption-enhanced steam reforming, SESR) est un procédé d’avant-garde qui permet simultanément la production d’hydrogène de très haute pureté et la capture du CO2. L'objectif principal de ce travail est le développement de nouveaux sorbants pour le CO2 applicables à hautes températures et l’étude de leur application dans SESR. Deux nouvelles méthodes de synthèse ont été proposées pour synthétiser du zirconate de lithium (Li2ZrO3), zirconate de sodium (Na2ZrO3) ainsi que des matériaux à base d’oxyde de calcium (CaO), trois catégories de sorbants capables de réagir avec le CO2 à hautes températures. L’application du Li2ZrO3 à la capture du CO2 a démontré une augmentation de l’activité du matériau produit par une nouvelle méthode de synthèse combinant un surfactant et traitement à ultrasons, comparativement au Li2ZrO3 préparé par une méthode avec surfactant seulement (sans ultrasons) ou par la méthode conventionnelle (mélange des composants en phase liquide). Néanmoins, pour des pressions partielles en CO2 inférieures à 0,75 bar, la faible cinétique de sorption du CO2 obtenue par le Li2ZrO3 limite son application au procédé SESR. En considérant l’amélioration des propriétés de sorption obtenue en appliquant la méthode combinée surfactant/ultrasons à la synthèse du Li2ZrO3, la même technique a été aussi appliquée à la synthèse du Na2ZrO3. Des résultats inattendus ont été pourtant obtenus. Le Na2ZrO3 développé par la nouvelle technique a été moins actif durant les cycles sorption/régénération que celui produit par la méthode conventionnelle, de par la faible résistance de sa structure poreuse à de très hautes températures. La nouvelle méthode de synthèse combinée surfactant/ultrasons a été aussi appliquée pour la synthèse de CaO stabilisé par du zirconium (Zr). Un rapport Zr/Ca de 0,303 a été trouvé optimal pour la production d’un sorbant présentant la meilleure stabilité et activité pour la capture de CO2. Dans les conditions sévères d’opération, les résultats ont généralement indiqué une capacité de sorption du CaO stabilisé supérieure à celle du CaO pure. Dans le but de réduire les coûts de production des sorbants, une source moins chère de CaO (calcaire naturel) a été utilisée en combinaison avec une nouvelle méthode de synthèse qui consiste dans l’acidification du calcaire par de l’acide citrique suivie par une calcination en deux étapes (argon et air). Doté d’une structure hautement poreuse, le CaO produit a révélé une stabilité nettement meilleure par rapport au calcaire, ainsi qu’une capacité accrue de sorption du CO2. La même technique de synthèse a été aussi utilisée pour développer plusieurs matériaux à base de CaO stabilisé par divers oxydes métalliques (Al, Zr, Mg et Y), afin d’améliorer la stabilité du sorbant dans les conditions opérationnelles sévères, particulièrement les hautes températures de régénération en présence de CO2. CaO stabilisé par l’aluminium (Al) ou le zirconium (Zr) a démontré une meilleure activité comparativement aux autres matériaux synthétisés, inclusivement dans des conditions sévères d’opération. L’application de ces deux types de sorbants au vaporeformage du méthane (SESMR) a été ensuite étudiée dans un réacteur à lit fixe. Pour minimiser les limitations diffusionnelles, deux matériaux hybrides sorbant-catalyseur ont été développés. NiO-CaO stabilisé par Zr, préparé par la méthode combinée surfactant/ultrasons, dont le contenu en NiO est de 20.5 % (masse) a montré une efficacité dans la production d’hydrogène de 92% lors du premier cycle de reformage, ce qui est remarquablement plus élevée que le rendement d’équilibre en H2 pour le procédé traditionnel de vaporeformage du méthane (SMR) ( 70%). La méthode acidification/calcination en deux étapes a été utilisée pour produire le deuxième matériau hybride (NiO-CaO stabilisé par Al). L’application du matériau contenant 25 % (masse) de NiO a conduit à une efficacité moyenne de production d’hydrogène de 97.3%, démontrant ainsi son grand potentiel pour le SESMR. Les résultats de ce projet de recherche ont clairement démontré que le procédé SESR est une alternative très avantageuse au procédé traditionnel de reformage à la vapeur (sans séparation in-situ de CO2) pour la production d’hydrogène de très haute pureté. Le matériau hybride sorbant-catalyseur NiO-CaO stabilisé par Al a démontré une excellente activité à long terme, en confirmant son potentiel élevé pour application dans le procédé SESMR.
Sorption-enhanced steam reforming (SESR) is a forefront technology to produce H2 clean fuel, which integrates both CO2 capture and H2 production in a single process. The main objective of this work is to develop novel high-temperature CO2 sorbents and to investigate their application in SESR operation. Special attention was given to lithium zirconate (Li2ZrO3), sodium zirconate (Na2ZrO3) and calcium oxide (CaO)-based materials, as most famous high temperature CO2 sorbents, by applying two novel synthesis techniques. The application of Li2ZrO3 in CO2 capture sorption showed an increase in activity of the material prepared by surfactant template/sonication method compared to Li2ZrO3 prepared by simple surfactant template method (without sonication) or conventional wet-mixing route. Nevertheless, porous Li2ZrO3 still suffered from slow kinetics of CO2 sorption at low CO2 partial pressure (below 0.75 bar), which can limit its application for SESMR operation. Taking into consideration the improvement of Li2ZrO3 sorption properties, the same surfactant template/sonication technique was then applied to develop porous Na2ZrO3. The behavior of the new developed Na2ZrO3 was unexpected. The samples prepared by surfactant template/sonication technique were found to be less active than the conventional Na2ZrO3 during cyclic operation, due to the low resistivity of the pore structure at the very high temperature treatment required for calcination. The same surfactant template/sonication was also applied to develop Zr-stabilized CaO sorbents. An optimum Zr/Ca ratio of 0.303 was found to maximize the stability and CO2 capture activity of the proposed Zr-stabilized CaO sorbent. The results generally showed a better CO2 capture ability of Zr-stabilized CaO sorbent in comparison with pure CaO in severe cyclic operating conditions. With the purpose of reducing the cost of sorbent production, a cheaper source of CaO (natural limestone) was also considered and a novel synthesis technique (limestone acidification by citric acid followed by two-step calcination (in Ar and air atmospheres)) was applied in order to prepare highly porous CaO structure with unique CO2 capture ability. The results revealed a much better stability and CO2 sorption activity of the developed sorbent compared to natural limestone. The same technique was employed to develop a number of metal oxide (Al, Zr, Mg and Y)-stabilized CaO sorbents in order to enhance sorbent stability in severe operating conditions, i.e., high temperature regeneration in the presence of CO2. Al and Zr-stabilized CaO showed the best activity during both mild and severe operating conditions. The performance of the developed CO2 sorbents providing the best performance in CO2 capture (Zr-stabilized and Al-stabilized CaO) were then investigated experimentally in the sorption enhanced steam methane reforming (SESMR) using a fixed-bed reactor. To minimize the diffusional limitations, a hybrid catalyst-sorbent was developed for both sorbents. The application of Zr-stabilized CaO-nickel hybrid catalyst with 20.5 wt% NiO loading, prepared by surfactant-template/sonication method, resulted in 92% H2 production efficiency for the initial SESMR cycle, which is remarkably higher than traditional steam methane reforming (SMR) equilibrium H2 yield (70 %). The second developed hybrid sorbent-catalyst (Al-stabilized CaO-NiO) was prepared using limestone acidification coupled with two-step calcination technique. The long-term application of the hybrid catalyst containing 25 wt% NiO led to an average H2 production efficiency of 97.3%, proving its high efficiency in the SESMR process. In summary, the results of this thesis show that the SESR process is as an efficient alternative of traditional steam reforming for production of highly pure H2. The Al-stabilized CaO-NiO hybrid sorbent-catalyst showed an excellent activity over long-term operation, thus confirming its very high potential for use in the SESMR process.

To deal with the Greenhouse Gases emissions increase, CO2 post-combustion capture linked to its storage is a promising technological solution. Different methods are currently developed, including the adsorption which is this study’s core interest. This work concerns the use of a TSA process (Temperature Swing Adsorption) for CO2 post-combustion capture. This process is an adsorber based on indirect heating (steam condensation) and cooling (water circulation) by means of an internal heat-exchanger (no contact between the coolant and the adsorbant). This study takes experimental and numerical approaches. From the preliminary experiments, the 5A zeolite was selected. Different operating conditions (inlet gas composition, desorption temperature, purge flow rate, periods of cycles, pre-cooling / pre-heating steps,…) were then tested from a mixture N2-CO2 in order to obtain an optimal compromise between the performance criteria. Then, other configurations were tested within a numerical model validated from previous experiments. In the adsorption step, the inlet gas temperature and the initial bed temperature have very little influence on the performances of the adsorber. Due to a parametric study done for cycle experiments, optimal operating conditions, in particular with a pre-cooling step, were determined for this specific application. The results obtained are very encouraging as they underline comparable performances with the reference process ones, the amine absorption
Face à l’augmentation des émissions de gaz à effet de serre, le captage post-combustion du CO2 associé à son stockage est une solution technologique prometteuse. Différentes méthodes sont actuellement développées dont l’adsorption qui fait l’objet de cette étude. Ce travail concerne l’utilisation d’un procédé TSA (Temperature Swing Adsorption) pour le captage post-combustion du CO2. Ce procédé fait appel à un adsorbeur équipé d’un échangeur interne permettant un chauffage (vapeur d’eau) et refroidissement (circulation d’eau) indirects (pas de contact entre le caloporteur et l’adsorbant). Ce travail s’appuie à la fois sur une partie expérimentale et numérique. A partir des premières expériences, la zéolithe 5A a été sélectionnée. Différentes conditions opératoires (composition de l’alimentation, température de désorption, débit de purge, durée du cycle, étapes de pré-refroidissement / pré-chauffage,…) ont alors été testées à partir d’un mélange N2-CO2 afin d’obtenir un compromis optimal entre les critères de performance. D’autres configurations ont ensuite été testées au moyen d’un modèle numérique préalablement validé à partir d’expériences. En phase d’adsorption, la température d’alimentation et la température initiale du lit n’ont que peu d’influence sur les performances de l’adsorbeur. Grâce à une étude paramétrique effectuée pour des cycles, des conditions opératoires optimales, notamment avec une étape de pré-refroidissement, ont été déterminées pour cette application spécifique. Les résultats ainsi obtenus sont tout à fait encourageants puisqu’ils ont permis de mettre en évidence des performances comparables à celles des procédés de référence d’absorption par amine

The overall objective of this thesis is to evaluate the fundamentals of current low concentration CO2 separation technologies and to provide an alternate method using adsorption technology with existing as well as new adsorbents. Two different applications for the adsorption of CO2 are explored; Direct Air Capture (DAC) and excimer gas purification. The investigation of aerogels as possible adsorbent for these applications was also explored. The first application, DAC of CO2 using adsorbents, addresses climate change by reducing the amount of atmospheric CO2 levels that are directly correlated to global warming. Because of DAC being carbon negative, this field has gained significant attention in the literature. DAC as a CO2 reduction strategy was approached in two ways: 1. Chapter 2 investigates capturing and concentrating CO2 from 0.04% in the air to 95% to be able to sequester it into the ground. This research began by doing an adsorbent selection using pure gas gravimetric measurements on seven different commercially available type X zeolites that were determined to have potential for this separation. Breakthrough experiments were then carried out with the most promising zeolite by perturbing the bed with compressed ambient air. In the process studied, a basic four step temperature vacuum swing adsorption (TVSA) cycle was investigated comprising the following steps: pressurization, adsorption, blowdown, and desorption. Four different regeneration temperatures were tested along with four different gas space velocities. With this cycle configuration, CO2 was concentrated to 95% from 0.04% with total capture fractions as high as 81%. This study highlighted methods to reduce the energy consumption per ton of CO2 captured in the system as well as the potential of using low Si/Al ratio faujasite structured zeolites in DAC of CO2 for greenhouse gas reduction. 2. Chapter 3 expands on the research of Chapter 2 by capturing CO2 from 0.04% in the air and concentrating it to high purity CO2 levels where the cost for operating the process will be reimbursed through the value of the produced CO2. The goal of this research was to increase the CO2 to as high as possible because the purer the CO2, the more valuable it is. This research started by conducting an in-depth investigation into the pure gas adsorption of CO2, N2, O2, and Ar on the most promising zeolite from Chapter 2. The data was then fitted to the TD-Toth model which allowed for the evaluation of the TVSA cycle and showed the potential of reducing the pressure and/or elevating the temperature during the blowdown step in order to produce high purity CO2. To confirm this, the TVSA cycle was run on a fixed bed breakthrough experiment where high purity CO2 was produced between a concentration of 99.5% and 99.96% by lowering the blowdown pressure. By controlling the blowdown temperature, the concentration of the product was increased from 99.8% to 99.95%, however with a significant loss of CO2. This effect of N2, O2, and Ar desorbing during the blowdown step with CO2 desorbing during the evacuation step is shown graphically by measuring the concentration and flow rate of the exiting gas species. The results from this study show the potential for producing a valuable product of high purity CO2 from atmospheric concentrations. The second application in this thesis that is explored in Chapter 4 is the purification of trace impurities of CO2, CF4, COF2, and O2 from F2, Kr, and Ne for applications in excimer lasers. Due to the incompatibility of many adsorbents to F2 and HF, aluminas and polymeric adsorbents were selected as potentially compatible materials. To increase the compatibility of these adsorbents, the use of a cryo-cooler was determined to be feasible to precool the feed stream before separation, which increases the adsorption capacity and compatibility of the material to F2 and HF. To determine the adsorption potential in the low concentration of these adsorbents, the concentration pulse chromatographic technique was chosen to determine the Henry’s Law constants of CO2, CF4, and O2. This data was then plotted on the van’t Hoff plot and extrapolated to colder temperatures to determine the benefit of using a cryo-cooler. From this study, it was determined that HayeSep Q was the best polymeric adsorbent with significant adsorption of CO2 at temperatures below -50˚C while being the best performing CF4 adsorbent. AA-300 was the best performing alumina in this study while having significant adsorption of CF4 at temperatures below -135˚C. However, from a compatibility standpoint, both of these materials need to be tested to determine their robustness in the presence of F2 and HF at room and reduced temperatures. Chapters 5 & 6 in this thesis explore the fundamentals of adsorption on aerogels as a prelude to using aerogels as possible adsorbents for DAC of CO2. This investigation into aerogels looks at silica aerogels and carbon aerogels, which are both industrially produced and explores their adsorption with relation to like materials such as silica gel and activated carbons. Both of these Chapters utilize experimentally determined adsorption isotherms of CO2, N2, O2, and Ar as well as characterization to determine adsorption trends in the materials. Some major conclusions for silica aerogels were that common surface modifications to make the material more resilient against water adsorption impacts the adsorption of CO2 significantly with roughly 4 fold difference in adsorption capacity. For carbon aerogels some major conclusions were that the adsorption was increasingly dominated by the heterogeneous nature of the surface at lower pressures and increasingly dominated by the pore size at the higher pressures. Both chapters discuss the adsorption of air along with ideas such as the influence of gas thermal conductivity in the pores with respects to adsorption. L'objectif général de cette thèse est d'évaluer les principes fondamentaux des technologies actuelles de séparation du CO2 à faible concentration et de fournir une méthode alternative utilisant la technologie d’adsorption avec des adsorbants actuels ainsi que d'en découvrir de nouveaux. Deux applications différentes pour l'adsorption du CO2 ont été explorées; la capture directe dans l’air ambient (CAD) et la purification des gaz excimères, ainsi que la recherche d'aérogels comme adsorbant possible pour ces applications. La première application, le CAD du CO2 utilisant des adsorbants, pourrait répondre aux changements climatiques puisque les niveaux de CO2 atmosphérique sont directement corrélés au réchauffement climatique. Dernièrement, le CAD a fait l'objet d'une attention particulière en tant que stratégie de réduction du CO2, par conséquent, deux voies différentes ont été explorées dans cette thèse: 1. Le chapitre 2 étudie la capture et la concentration du CO2 de 0,04% dans l'air à 95% afin de pouvoir l’enfermer dans la terre. Pour ce faire, une sélection d'adsorbant a été effectué en utilisant des mesures gravimétriques à gaz pur sur sept zéolithes de type X disponibles dans le commerce qui ont été déterminés comme ayant un potentiel pour cette séparation. Des expériences révolutionnaires ont ensuite été réalisées avec la zéolite la plus prometteuse en perturbant le lit avec de l'air ambiant comprimé. Dans le processus étudié, un cycle basique à quatre étapes d’adsorption modulée en température et pression (AMTP) a été étudié, comprenant les étapes suivantes: pressurisation, adsorption, purge et désorption. Quatre températures de régénération différentes ont été testées ainsi que quatre vitesses spatiales de gaz différents. Avec cette configuration de cycle, le CO2 était concentré à 95% de 0,04% avec des fractions de capture totales aussi élevées que 81%. Cette étude a mis en évidence des méthodes pour réduire la consommation d'énergie par tonne de CO2 captée dans le système ainsi que le potentiel d'utilisation de zéolithes structurées à base de faujasite à faible rapport Si/Al dans le CAD du CO2 pour la réduction des gaz à effet de serre. 2. Le chapitre 3 approfondit les recherches du chapitre 2 en capturant le CO2 de 0,04% dans l'air et en le concentrant à des niveaux de très haute pureté où le processus sera remboursé par la valeur du CO2 produit. L'objectif de cette partie était d'augmenter la pureté du CO2 le plus possible car plus le CO2 est pur, plus il est précieux. Une enquête approfondie sur l'adsorption de gaz pur de CO2, N2, O2 et Ar sur la zéolite la plus prometteuse du chapitre 2. Les données ont ensuite été ajustées au modèle TD-Toth qui a permis d'évaluer le cycle AMTP et a montré le potentiel de réduire la pression et/ou d'élever la température pendant l'étape de purge afin de produire du CO2 de haute pureté. Pour confirmer cela, le cycle AMTP a été fait par le biais d’une expérience dans un lit fixe où du CO2 de haute pureté a été produit entre une concentration de 99,5% et 99,96% en abaissant la pression de purge. En contrôlant la température de purge, la concentration du produit est passée de 99,8% à 99,95%, mais avec une perte importante de CO2. Cet effet de la désorption de N2, O2 et Ar pendant l'étape de purge avec la désorption du CO2 pendant l'étape d'évacuation est illustré graphiquement en mesurant la concentration et le débit des espèces de gaz sortant. Les résultats de cette étude montrent le potentiel de production d'un produit précieux de CO2 de haute pureté à partir des concentrations atmosphériques. La deuxième application de cette thèse qui est explorée au Chapitre 4 est la purification des traces d'impuretés de CO2, CF4, COF2 et O2 de F2, Kr et Ne pour des applications dans les lasers à excimère. En raison de l'incompatibilité de nombreux adsorbants avec le F2 et le HF, les alumines et les adsorbants polymères ont été sélectionnés comme matériaux potentiellement compatibles. Pour augmenter la compatibilité de ces adsorbants, l'utilisation d'un cryoréfrigérant a été jugée possible pour pré-refroidir le flux d'alimentation avant la séparation, ce qui augmente la capacité d'adsorption et la compatibilité du matériau en F2 et HF. Pour déterminer le potentiel d'adsorption dans la faible concentration de ces adsorbants, la technique de chromatographie pulsée de concentration a été choisie pour déterminer les constantes de la loi de Henry de CO2, CF4 et O2. Ces données ont ensuite été tracées sur le graphique van’t Hoff et extrapolées à des températures plus froides pour déterminer les avantages de l’utilisation d’un cryoréfrigérant. À partir de cette étude, il a été déterminé que HayeSep Q était le meilleur adsorbant polymère avec une adsorption significative de CO2 à des températures inférieures à -50 ° C tout en étant l'adsorbant CF4 le plus performant. L'AA-300 était l'alumine la plus performante de cette étude tout en ayant une adsorption significative de CF4 à des températures inférieures à -135 °C. Cependant, du point de vue de la compatibilité, ces deux matériaux doivent être testés pour déterminer leur robustesse en présence de F2 et de HF à température ambiante et réduite. Les chapitres 5 et 6 explorent les principes fondamentaux de l'adsorption sur les aérogels en prélude à l'utilisation d'aérogels comme adsorbants possibles pour le CAD du CO2. Cette enquête sur les aérogels examine les aérogels de silice et les aérogels de carbone, qui sont tous les deux fabriqués industriellement et explore leur adsorption par rapport à des matériaux similaires tels que le gel de silice et les charbons actifs. Ces deux chapitres utilisent des isothermes d'adsorption déterminés expérimentalement de CO2, N2, O2 et Ar ainsi que la caractérisation pour déterminer les tendances d'adsorption dans les matériaux. Certaines conclusions majeures pour les aérogels de silice étaient que les modifications de surface courantes pour rendre le matériau plus résistant à l'adsorption d'eau ont un impact significatif sur l'adsorption de CO2 avec une différence d'environ 4 fois dans la capacité d'adsorption. Pour les aérogels de carbone, certaines conclusions majeures étaient que l'adsorption était de plus en plus dominée par la nature hétérogène de la surface à des pressions plus faibles et de plus en plus dominée par la taille des pores aux pressions plus élevées. Les deux chapitres discutent de l'adsorption d'air ainsi que des idées telles que l'influence de la conductivité thermique du gaz dans les pores en ce qui concerne l'adsorption.

Na primeira parte do trabalho, foram investigados materiais ativos para eletro-oxidar etanol e acetaldeído seletivos para a rota C2 (Carbono 2) e, também, ativos para eletro-oxidar hidrogênio molecular, visando a aplicação em células a combustível de hidrogênio indireto. Neste tipo de célula, um processador de combustível externo desidrogena o etanol e os produtos desta reação, contendo H2, acetaldeído e, possivelmente, etanol residual, são direcionados para alimentar o ânodo. Neste sentido, o eletrocatalisador anódico pode ser ativo para a eletro-oxidação de etanol residual, bem como acetaldeído, mas este deve catalisar a reação via C2 com o objetivo de evitar a formação de espécies que envenenam a superfície catalítica (CO ou CHx), ou seja, a ligação C-C deve permanecer intacta. Os eletrocatalisadores bimetálicos foram formados por M/Pt/C (onde M = W, Ru ou Sn) e os produtos reacionais foram analisados por DEMS On-line. Os resultados mostraram que Ru/Pt/C e Sn/Pt/C apresentaram maiores taxas de reação global, no entanto, eles não foram seletivos. Por outro lado, W2/Pt3/C foi mais seletivo para a rota C2, dada a não formação de CH4 e CO2. Além disso, este material também foi ativo e estável para a eletro-oxidação de H2, mesmo na presença de acetaldeído, o que o torna um potencial catalisador para aplicação no ânodo de células a combustível de hidrogênio indireto. Na segunda parte do trabalho, o objetivo foi relacionado com o estudo de eletrocatalisadores seletivos para a rota C1 (Carbono 1). A oxidação eletroquímica do etanol e de seus produtos reacionais foram investigados por DEMS on-line em temperatura ambiente e intermediária (245oC). Para temperatura ambiente, utilizou-se solução aquosa de ácido sulfúrico (H2SO4) e, para temperatura intermediária, utilizou-se ácido sólido (CsH2PO4) como eletrólito. Os eletrocatalisadores investigados foram formados por SnOxRuOx-Pt/C e Pt/C. Em temperatura ambiente, os resultados de polarização potenciodinâmica mostraram uma maior atividade eletrocatalítica para o material SnOxRuOx-Pt/C, com eficiência de corrente para formação de CO2 de 15,6% contra 15,2% para Pt/C, sob condições estagnantes, sem controle por transporte de massa. O stripping de resíduos reacionais, após a eletro-oxidação de etanol bulk, sob condições de fluxo, mostraram o acúmulo de espécies com 1 átomo de carbono (CO e CHx) que causam o bloqueio dos sítios ativos e são oxidadas eletroquimicamente somente em mais altos potenciais (ca. 1,0 V). Por outro lado, as curvas de polarização a 245oC mostraram maiores valores de eficiências de correntes para formação de CO2 (45% para Pt/C em ambos potenciais 0,5 V e 0,8 V contra 36% e 50% para SnOxRuOx-Pt/C em 0,5 V e 0,8 V respectivamente) quando comparado com os valores obtidos em temperatura ambiente, mas com atividades similares para SnOxRuOx-Pt/C e Pt/C. Para ambos os eletrocatalisadores, os estudos de espectrometria de massas a 245oC evidenciaram que as rotas eletroquímicas ocorrem em paralelo com rotas puramente químicas, envolvendo catálise heterogênea, de decomposição do etanol, produzindo H2 e CO2 como produtos majoritários.
In the first part of this study were investigated active materials to electro-oxidize ethanol and acetaldehyde selective for the C2 route (Carbon 2), besides active to electro-oxidize molecular hydrogen, in order to apply into indirect hydrogen fuel cells. In this type of cell, ethanol can be dehydrogenated in the external fuel processor and the products generated in this reaction, containing H2, acetaldehyde and, possibly, unreacted ethanol are used to feed the fuel cell anode. Therefore, the anode electrocatalyst has to be active to electro-oxidize residual ethanol and acetaldehyde, however, it has to catalyze the reaction via C2 route aiming to avoid the species formation that poison the catalyst surface (CO and CHx), in the other words, the C-C bond should remain intact. The bimetallic electrocatalysts were formed by W, Ru and Sn-modified Pt nanoparticles. The reaction products were followed by on-line differential electrochemical mass spectrometry (DEMS) experiments. The results showed that Ru/Pt/C and Sn/Pt/C presented higher overall reaction rate when compared to the other studied materials, however, they were non-selective. On the other hand, W/Pt/C with high W content was more selective to the C2 route, evidenced by the absence of the DEMS signals for molecules with one carbon atom such as CH4 and CO2. Additionally, this material was active and stable for H2 electro-oxidation even in the acetaldehyde presence, what turns it into a potential electrocatalyst for application in the anode of indirect hydrogen fuel cells. In the second part of this work, we investigated conditions and electrocatalysts selective to the C1 route. The ethanol electro-oxidation and its reaction products were investigated by on-line DEMS at room and intermediate temperature. At room, and intermediate temperature (245oC), the electrolytes were aqueous sulfuric acid and solid-state acid (CsH2PO4), respectively. The catalysts investigated were SnOxRuOx-Pt/C and Pt/C. The results of potentiodynamic polarizations at room temperature showed much higher electrocatalytic activity for the SnOxRuOx-Pt/C material, with current efficiency for CO2 formation of 15.6% against 15.2% for Pt/C under stagnant conditions. The reaction residues stripping after the ethanol electro-oxidation, under continuous flow conditions, showed the accumulation of species containing 1 carbon atom (CO and CHx), which are oxidized just at high potentials (ca. 1.0 V) and they cause the obstruction of the active sites. On the other hand, the polarization curves at 245oC showed higher values of current efficiencies (45% for Pt/C for both potentials 0.5 V and 0.8 V against 36% and 50% to SnOxRuOx-Pt/C at 0.5 V and 0.8 V respectively) for the CO2 formation than at ambient condition, however, with similar activities for SnOxRuOx-Pt/C and Pt/C. For both electrocatalysts, in parallel with the electrochemical pathways, heterogeneous chemical catalysis of ethanol decomposition also takes place, producing H2 and CO2, as major products.

Cette thèse concerne l’étude de la réaction photoélectrochimique de réduction du CO2 (PEC CO2RR) sur le semi-conducteur de type p CuCo2O4 en abordant le rôle cocatalytique des RTIL à base d'imidazolium par microscopie photoélectrochimique à balayage (SPECM). Le CuCo2O4 a été étudié dans différents électrolytes supports, notamment une solution aqueuse, une solution de mélange binaire (25 vol.% [C2mim][BF4]/H2O et 25 vol.% [C4mim][BF4]/H2O) et des liquides ioniques pur pour explorer par SPECM le rôle des RTIL dans les performances des PEC. Un courant de photoréduction significativement amélioré sous l'éclairage UV-vis et visible est obtenu dans une solution à 25 vol.% [C2mim][BF4]/H2O. Seul le CO généré par la PEC CO2RR a été détecté sur une fibre optique à double sonde - ultra-microélectrode (OF-UME) développée au laboratoire et sur une électrolyse en volume sous illumination. La formation de CO à des potentiels plus positifs que la valeur thermodynamique est rapportée ici et il est clairement indiqué que la réduction directe du CO2 à la surface de l'électrode n'est pas le mécanisme. Un schéma de réaction possible pour la PEC CO2RR par l'intermédiaire de [C2mim]+ est proposé. Ainsi, nos résultats ont démontré pour la première fois le rôle cocatalytique de [C2mim]+ pour le PEC CO2RR. En outre, la CO2RR électrochimique a également été étudiée sur divers catalyseurs de métaux de transition, d'azote et de carbone (M–N–Cs). 25%Fe25%Co–N–C a montré la meilleure performance parmi les M–N–Cs étudiés. La présence de sites Co a fourni un effet synergique pour la génération de microcubes distribués riches en Fe, qui agissent comme des sites actifs dans la CO2RR électrochimique
This thesis studies photoelectrochemical CO2 reduction reaction (PEC CO2RR) on p-type semiconductor CuCo2O4 addressing the cocatalytic role of imidazolium based RTILs by scanning photoelectrochemical microscopy (SPECM). CuCo2O4 was studied in different solvent supporting electrolyte systems including: aqueous solution (0.1 M KHCO3 and 0.1 M Na2SO4), binary mixture solution (25 vol.% [C2mim][BF4]/H2O and 25 vol.% [C4mim][BF4]/H2O) and pure RTILs ([C2mim][BF4], [C4mim][BF4]) to explore by SPECM the role of RTILs in CuCo2O4 semiconductor PEC performance. Significantly enhanced photoreduction current under both UV-vis and visible light illumination is reported in 25 vol.% [C2mim][BF4]/H2O solution. Only CO generated from PEC CO2RR was detected using an in-situ detection method based on a home-made dual tip optical fiber-ultramicroelectrode (OF-UME) and from bulk electrolysis under illumination. The formation of CO at potentials more positive than the thermodynamic value clearly points out that direct CO2 reduction on the electrode surface is not the mechanism. A possible reaction scheme for the PEC CO2RR mediated by [C2mim]+ is proposed. Thus, our results have demonstrated for the first time the cocatalytic role of [C2mim]+ for the PEC CO2RR. In addition, electrochemical CO2RR has also been studied on various synthesized transition metal–nitrogen–carbon catalysts (M–N–Cs) by rotating disk electrode. 25%Fe25%Co–N–C exhibited the best performance among the studied M–N–Cs in this thesis. The presence of Co sites in that catalyst provided synergic effect for the generation of distributed Fe-rich microcubes, which act as active sites in electrochemical CO2RR

The 2°C target for global warming had been under severe scrutiny in the run-up to the climate negotiations in Paris in 2015 (COP21). Clearly, with a remaining carbon budget of 470–1,020 GtCO2eq from 2015 onwards for a 66% probability of stabilizing at concentration levels consistent with remaining below 2°C warming at the end of the 21st century and yearly emissions of about 40 GtCO2 per year, not much room is left for further postponing action. Many of the low stabilization pathways actually resort to the extraction of CO2 from the atmosphere (known as negative emissions or Carbon Dioxide Removal [CDR]), mostly by means of Bioenergy with Carbon Capture and Storage (BECCS): if the biomass feedstock is produced sustainably, the emissions would be low or even carbon-neutral, as the additional planting of biomass would sequester about as much CO2 as is generated during energy generation. If additionally carbon capture and storage is applied, then the emissions balance would be negative. Large BECCS deployment thus facilitates reaching the 2°C target, also allowing for some flexibility in other sectors that are difficult to decarbonize rapidly, such as the agricultural sector. However, the large reliance on BECCS has raised uneasiness among policymakers, the public, and even scientists, with risks to sustainability being voiced as the prime concern. For example, the large-scale deployment of BECCS would require vast areas of land to be set aside for the cultivation of biomass, which is feared to conflict with conservation of ecosystem services and with ensuring food security in the face of a still growing population.While the progress that has been made in Paris leading to an agreement on stabilizing “well below 2°C above pre-industrial levels” and “pursuing efforts to limit the temperature increase to 1.5°C” was mainly motivated by the extent of the impacts, which are perceived to be unacceptably high for some regions already at lower temperature increases, it has to be taken with a grain of salt: moving to 1.5°C will further shrink the time frame to act and BECCS will play an even bigger role. In fact, aiming at 1.5°C will substantially reduce the remaining carbon budget previously indicated for reaching 2°C. Recent research on the biophysical limits to BECCS and also other negative emissions options such as Direct Air Capture indicates that they all run into their respective bottlenecks—BECCS with respect to land requirements, but on the upside producing bioenergy as a side product, while Direct Air Capture does not need much land, but is more energy-intensive. In order to provide for the negative emissions needed for achieving the 1.5°C target in a sustainable way, a portfolio of negative emissions options needs to minimize unwanted effects on non–climate policy goals.

AbstractWith the increase in energy prices and the drive to reduce carbon emission, this paper presents an investigation of the use of smart office environments to monitor and evaluate the sustainability and behaviour of employees and the utilisation of space and resources. This paper presents analysis of data in an office environment in a company in Derby city to attempt to understand the behaviour of employees, pattern of work, power consumption and performance of heating and air-conditioning systems. Data from occupancy, room temperature, CO2, humidity, lighting, air temperature, windows status are all collected and analysed. The data also included external environmental conditions. The results indicate some correlation between CO2 levels and the number of employees. They also show correlation between outside and inside environmental conditions. In addition, the utilisation of space was also monitored, and the results demonstrate low utilisation during most days, this was due to Covid-19 and to working from home and off-site patterns. However, the data is found useful to inform future decisions about the actual space needed for normal working conditions.

The chapter is focused on technology of heat and moisture regeneration for ventilation systems. In the first sub-division recent progress in adsorptive technologies for air dehumidification, heating and conditioning is analyzed. In the next sub-divisions results of original researches of authors on adsorptive heat and moisture regeneration are given. The design of adsorptive heat-moisture regenerator for ventilation systems is shown. Its operation and the results of field tests are described. The technology of regeneration of low-potential heat and moisture by composite sorbent ‘silica gel – sodium sulphate' is suggested. Experimental plots of temperature, absolute and relative humidity at the inlet and the outlet of the apparatus and between cassettes with the composite are given. Correlation of flows switch-over time, airflow rate and temperature drop is stated. The relationships temperature efficiency factor vs. dimensionless temperature drop and moisture efficiency factor vs. absolute humidity dimensionless drop are derived with fair accuracy for engineering calculation. Ability of purposeful modification of the above-mentioned characteristics within broad ranges by changing the half-cycle time, the size of the granules of the adsorbent and its amount is revealed. The mathematical model and algorithm for determining the basic parameters of adsorptive regenerator operating processes are developed. The proposed algorithm involves calculating the volume of air passed through the layer of adsorptive heat-storage material, the concentration of water in the airflow at the outlet of the regenerator, the adsorption, the heat of adsorption, the final temperature of the cold air, the air temperature after mixing the cold air from the street and the warm air in the room at the warm end of the regenerator during inflow, calculation of the final concentration of water in the flow at the cold end of the regenerator, the volume of air passing through the layer of heat-accumulating material, adsorption and heat of adsorption, the final temperature of the air at the cold end of the regenerator, the air temperature after mixing of the cold air from the street and the warm air from the room at the cold end of regenerator during outflow, determining the temperature efficiency coefficient, summarized adsorption and maximal adsorption time. The correlation of air temperatures near the warm and cold end of the regenerator, as well as the temperature efficiency factors calculated according to the proposed algorithm and obtained by experimental way is confirmed. The mathematical modeling of the processes of operation of adsorption regenerators based on composites ‘silica gel – sodium sulphate' and ‘sodium acetate' in the conditions of the typical ventilation system of residential premises is carried out. The dependences of the temperature efficiency factor vs. the time of switching air flows and the velocity of air flow, as well as the temperatures of external and internal air under stationary conditions are shown. An optimal composition of composite adsorbents is stated to be 20% of silica gel and 80% of salt, that is, sodium sulphate or sodium acetate. Due to higher value of maximal adsorption composite ‘silica gel – Na2SO4' is shown to be required in half as much as compared with ‘silica gel – CH3COONa'. The results of the research can be used in the development of energy-efficient ventilation systems and devices for residential and warehouse premises.

In the last decade, there is some research on the conversion of CO2 to energy form. CO2 can be converted to value-added chemicals including HCOOH, CO, CH4, C2H4, and liquid hydrocarbons that can be used in various industries. Among the methods, electrochemical methods are of concern regarding their capability to operate with an acceptable reaction rate and great efficiency at room temperature and can be easily coupled with renewable energy sources. Besides, electrochemical cell devices have been manufactured in a variety of sizes, from portable to large-scale applications. Catalysts that optionally reduce CO2 at low potential are required. Therefore, choosing a suitable electrocatalyst is very important. This chapter focused on the electrochemical reduction of CO2 by Zn-Ni bimetallic electrocatalyst. The Zn-Ni coatings were deposited on the low-carbon steel substrate. Electrochemical deposition parameters such as temperature in terms of LPR corrosion rate, microstructure, microcracks, and its composition have been investigated. Then, the electrocatalyst stability and activity, as well as gas intensity and selectivity, were inspected by SEM/EDX analysis, GC, and electrochemical tests. Among the electrocatalysts for CO2 reduction reaction, the Zn65%-Ni35% electrode with cluster-like microstructure had the best performance for CO2 reduction reaction according to minimum coke formation (<10%) and optimum CO and H2 faradaic efficiencies (CO FE% = 55% and H2 FE% = 45%).

Numerous CO2 conversion strategies including thermochemical, photoelectrochemical, electrochemical have been adopted extensively in the last decades. However, the electrochemical CO2 reduction (CO2R) to energy-rich chemicals and fuels remains alternative promising technology owing to its ease of operations with an effective green approach. Compared with other energy conversion technologies, the electrochemical reaction conditions are comparatively mild with the ability to operate the reactions in a room temperature and pressure, thereby bringing better feasibility for alleviating anthropogenic atmospheric CO2 emission that threatens global peace. The reaction processes and directions involved can be controlled freely by tuning reductive potential and temperature. In addition, the process of electrochemical reaction is usually proceeded by reactants to gain or lose electron(s) at the surface of the electrode without the need for redox agents, through which the required electricity is derived from some renewable energy sources (solar, wind, geothermal, etc) which do not generate any additional CO2. This makes electrochemical CO2R a green approach with no generation of contaminants. This chapter, therefore, highlighted different metalorganic frameworks (MOFs) and MOF-based materials for electrocatalytic CO2R to energy-rich chemicals. Various strategies for designing MOFs, challenges, and prospects of MOF materials for better improvement of the CO2R were also discussed.

Activated charcoal was prepared and characterized from residues of coconut peel (CACC) to remove by adsorption the Methyl Orange (AM) dye in aqueous solution. The charcoal was activated with phosphoric acid. The morphology and structure of the pores of the carbon obtained were analyzed by Scanning Electron Microscopy (SEM) and a surface analyzer. The adsorption data were evaluated by the BET, Langmuir and Freundlich isotherms, finding the Langmuir type I model. The surface area of the activated carbon was 526 m2/g with a pore volume of 0.234 cm3/g and an average pore diameter of 1.78 nm, according to BET, which indicates the presence of micropores. The calculated thermodynamic parameters showed that the adsorption of the AM dye in CACC is a spontaneous process at room temperature and that physisorption and chemisorption are probably involved. The adsorption tests were followed by UV–visible spectrophotometry. The effects of the adsorbate concentration (AM) and the heat treatment (450–500°C) with an air atmosphere were investigated, keeping constant the stirring time and the H3PO4/sample weight ratio. The results obtained indicate that the activated carbon obtained could be used as an alternative low-cost adsorbent in the removal of AM from effluents in aqueous solution.

The adsorption of Ni(II) onto blue green marine algae (BGMA) in batch conditions is being investigated. The highest adsorption capacity of BGMA was found to be 42.056 mg/g under ideal testing conditions, where the initial Ni(II) metal ion concentration was adjusted from 25 ppm to 250 ppm. The optimal pH, biomass loading, and agitation rate for maximum Cu(II) ion removal have been determined to be 6, 2 g and 120 rpm, respectively. For the equilibrium condition, 24 hours of contact time is allowed. At room temperature, all of the experiments are conducted. The isotherm has a L shape, based on the equilibrium experimental data. It indicates that there is no considerable competition for active sites between the solvent and Ni(II). There is no strong competition between the solvent and Ni(II) for the active sites of BGMA, indicating that there is no strong competition between the two. It also suggests that the BGMA’s Ni sorption ability is restricted (II). The experimental data is validated using multiple isotherm models, and the mechanism of adsorption is then discovered, as well as the process design parameters. The Fritz-Schlunder-V isotherm model is particularly relevant in defining the mechanism of Ni(II) adsorption under the conditions used in this study, according to modelling studies. This model’s qmax of 41.89 mg/g shows that it matches experimental data more closely.

Abstract Deposition of nanocrystalline TiO2 coatings at low temperatures is becoming more attractive due to the possibility for continuous roll production of coatings for assembly lines of dye-sensitized solar cell at a low cost. In this study, porous nano-TiO2 coatings were deposited by vacuum cold spraying at room temperature on a conducting glass substrate using commercial P25 nanocrystalline TiO2 powder. The microstructure of TiO2 coatings was characterized by field emission scanning electron microscopy and N2 adsorption test. A commercial dye (N719) was adsorbed on the surface of TiO2 particles within the coating to assemble a dye-sensitized solar cell. The cell performance was evaluated employing simulated solar light at an intensity of 100 mW/cm2. The results showed that TiO2 coatings were deposited by the agglomerates of nano-TiO2 powders. The BET test of the as-sprayed TiO2 coatings yielded a porosity of 49% and an average pore size of 17 nm. The assembled solar cell yielded a short-circuit current density of 7.3 mA/cm2 and an energy conversion efficiency of 2.4%. The test result indicates that vacuum cold spraying was a promising method to deposit nanocrystalline TiO2 coating at low temperature applied to the dye-sensitized solar cell.

Abstract While there are numerous experimental data on CO2-brine interfacial tension (IFT), few studies on salinity effects over a wide range of concentrations have been reported. Thus, there is room for further research in understanding the mechanism of the IFT change. The objective of this study is to estimate the effect of salinity on CO2-brine IFT by molecular dynamics (MD) simulations and to gain a better understanding of the phenomenon through microscale insight. IFT of CO2-brine was calculated for a wide range of salinity conditions from pure water to 5 mol/kg NaCl solution at temperatures and pressures from 298 to 473 K and 8 to 20 MPa. To calculate IFT, MD was performed by using the Nosé-Hoover thermostat and the Parrinello-Rahman barostat to keep temperatures and pressures constant. The calculated results show an increasing trend against salinity, which is in good agreement with experimental data from previous studies. For example, the IFT under typical reservoir conditions of 313 K and 10 MPa were 30.0 mN/m for pure water, while 31.9, 34.2, 36.9, 39.4, and 42.6 mN/m for 1, 2, 3, 4, and 5 mol/kg NaCl solutions, respectively. The density distribution of ions in the aqueous phase near the interface and in the bulk region captured the negative adsorption of ions. This enables us to interpret the mechanism of the increase of IFT in light of the Gibbs adsorption isotherm. IFT data calculated in this study is beneficial for estimating and modeling fluid behaviors of CO2-brine systems under a wide range of salinity conditions. In addition, atomic-scale insights would contribute to a better understanding of the interfacial phenomena regarding CO2-brine including high salinity regions.

The chemisorption of a mono-energetic molecular beams of F2 , Cl2, and Br2 onto a room temperature Si(111)-7x7 surface are examined using scanning tunneling microscopy and the resulting adsorbate structures are studied as a function of translational energy/chemisorption mechanism. For F2 chemisorption on Si(111)-7x7, there is no intrinsic physisorption state and therefore no island formation at low incident translational energy1. Instead at low translational energy (0.03eV), we observe that the dominant adsorption sites are single reacted adatoms (Si-F), while at higher translational energy (0.27eV) dimers/neighboring pairs of reacted adatoms are commonly observed. From previous work by the Ceyer2 and Carter3 groups, it is known that at low translational energy, F2 can adsorb via abstraction ( F2 collides, one F atom chemisorbs, the other is ejected into the gas phase), while at higher translational energies, dissociative chemisorption becomes the predominant adsorption mechanism. Our STM experiments, in conjunction with a simple Monte Carlo model, show that at low translational energy, the abstraction mechanism accounts for nearly all chemisorption of F2 because nearly all adsorption sites are single reacted adatoms. At higher translational energy, the dissociative chemisorption mechanism becomes important and the predominance for single site adsorption is greatly reduced while the occurrence of dimers/pairs of reacted adatoms is increased.

Sodium octanoate CH3-(CH2)6-COONa was found to be one of the straight chain aliphatic carboxylates that show good inhibition characteristics towards mild steel. However, as the previously tested concentrations were too high to be applied in the water treatment of secondary circuits, lower concentrations have been investigated in this research. The tested concentrations ranged from 10 to as high as 700 ppm. Potentiodynamic polarization and weight loss tests have been applied at room temperature to study the metal corrosion behaviour in the presence and absence of the tested corrosion inhibitor. The weight loss test simulated the dynamic condition of cooling water as water available at site ‘city water’ was allowed to circulate via pumps through a corrosion test rack in which carbon steel specimens were mounted. Results obtained from both tests were in good agreement. Results revealed that the concentration should not fall below 200 ppm for the tested inhibitor to be effective. The adsorption of inhibitor on the carbon steel surface was found to obey the Langmuir adsorption isotherm model. Thermodynamic parameters of adsorption of the carboxylate have been determined and discussed. The protective film formed due to the presence of the inhibitor at high concentration has been analyzed by Fourier transform infrared (FTIR) spectra. FTIR spectra revealed that octanoate was adsorbed on the steel surface via its functional group.

A substantial body of data is becoming available on "room" temperature catalysts for CO oxidation in CO2 lasers. This data is sometimes confusing and often presented in a form that does not allow the laser system designer to make a confident evaluation of the catalyst for his purpose. It may further be that catalyst cost is not the primary consideration for selection so that performance evaluation becomes increasingly important.

To produce syngas from reforming of jet fuels for fuel-cell-based auxiliary power units, it is necessary to keep the fuel ultra-clean of sulfur. Several Ni-Ce based adsorbents for sulfur cleaning from jet-A fuel under room temperature were developed and tested in fixed bed reactors in this work. The adsorbent preparation procedure and calcination atmosphere were optimized for the highest adsorbent desulfurization capacity. Desulfurization performance due to the ratio of fixed bed column diameter (Dc) and adsorbent particle size (Dp) and liquid hourly space velocity (LHSV) were also investigated in a factorial experiment. The adsorbents can effectively remove sulfur in Jet-A fuel from over 1000 ppmw level to below 30 ppmw. The highest sulfur adsorption capacity achieved is 2.44 mg S/g adsorbent at the breakthrough point of 30 ppmw. To effectively scale up the fixed bed reactor, the LHSV should be kept lower than 0.65 and the Dc/Dp needs to be larger than 124.

A multi-scale method combining the finite volume model (FVM) considering Darcy-Brinkman formulation with grand conical Monte Carlo (GCMC) is built to study the process of CO2 adsorption in 13X zeolite particle bed. The saturation adsorption capacities and adsorption heat in FVM method are calculated by Langmuir model and linear fitting formula, respectively. The GCMC method is used to obtain the parameters of Langmuir model and linear fitting formula. The multi-scale method overcomes the shortcomings of the saturation adsorption capacities restricted by level of experimentation or empirical formula. The relationship between adsorption heat and adsorption amount is also obtained. The value of adsorption heat is no longer treated as the constant value or obtained from the empirical formula. The effects of velocity, particle size, porosity and thermal conductivity of particle on CO2 adsorption in13X zeolite particle bed are investigated. The results show that the saturation adsorption time decreases with increased velocity, porosity and thermal conductivity of particle, while increases with increased particle size. The peak of temperature difference between the solid and gas phase increases with increased inlet velocity, porosity and particle size, while decreases with thermal conductivity of particle. The temperature difference trends uniformity and the peak of temperature difference moves towards to the outlet of adsorption bed with adsorption time processing. The adsorption bed with a higher inlet velocity, porosity and thermal conductivity of particle, and smaller particle size is recommended to improve the adsorption bed performance.

Polymer flooding is one of the most promising EOR methods (Smalley et al. 2018). It is well known and has been used successfully (Pye 1964; Standnes & Skjevrak 2014; Sheng et al. 2015). From a technical perspective we recommend that polymer flooding should be considered as a viable EOR method on the Norwegian Continental Shelf for the following reasons: 1. More oil can be produced with less water injected; this is particularly important for the NCS which are currently producing more water than oil 2. Polymers will increase the aerial sweep and improve the ultimate recovery, provided a proper injection strategy 3. Many polymer systems are available, and it should be possible to tailor their chemical composition to a wide range of reservoir conditions (temperature and salinity) 4. Polymer systems can be used to block water from short circuiting injection production wells 5. Polymer combined with low salinity injection water has many benefits: a lower polymer concentration can be used to reach target viscosity, less mechanical degradation, less adsorption, and a potential reduction in Sor due to a low salinity wettability effect. There are some hurdles when considering polymer flooding that needs to be considered: 1. Many polymer systems are not at the present considered as green chemicals; thus, reinjection of produced water is needed. However, results from polymer degradation studies in the IORCentre indicates that a. High molecular weight polymers are quickly degraded to low molecular weight. In case of accidental release to the ocean low molecular weight polymers are diluted and the lifetime of the spill might be quite short. According to Caulfield et al. (2002) HPAM is not toxic, and will not degrade to the more environmentally problematic acrylamide. b. In the DF report for environmental impact there are case studies using the DREAM model to predict the transport of chemical spills. This model is coupled with polymer (sun exposure) degradation data from the IORCentre to quantify the lifetime of polymer spills. This approach should be used for specific field cases to quantify the environmental risk factor. 2. Care must be taken to prepare the polymer solution offshore. Chokes and vales might be a challenge but can be mitigating according to the results from the large-scale testing done in the IORCentre (Stavland et al. 2021). None of the above-mentioned challenges are server enough to not consider polymer flooding. HPAM is neither toxic, nor bio-accumulable, or bio-persistent and the CO2 footprint from a polymer flood may be significantly less than a water flood (Dupuis et al. 2021). There are at least two contributing factors to this statement, which we will return in detail to in the next section i) during linear displacement polymer injection will produce more oil for the same amount of water injected, hence the lifetime of the field can be shortened ii) polymers increase the arial sweep reducing the need for wells.