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One of the crucial steps for the conversion of CO2 into polymers is the catalytic formate to oxalate coupling reaction (FOCR). Formate can be obtained from the (electro)catalytic reduction of CO2, while oxalate can be further processed toward building blocks for modern plastics. In its 175 year history, multiple parameters for the FOCR have been suggested to be of importance. Yet, no comprehensive understanding considering all those parameters is available. Hence, we aim to assess the relative impact of all those parameters and deduce the optimal reaction conditions for the FOCR. We follow a systematic two-stage approach in which we first evaluate the most suitable categorical variables of catalyst, potential poisons, and reaction atmospheres. In the second stage, we evaluate the impact of the continuous variables temperature, reaction time, catalyst loading, and active gas removal within previously proposed ranges, using a response surface modeling methodology. We found KOH to be the most suitable catalyst, and it allows yields of up to 93%. Water was found to be the strongest poison, and its efficient removal increased oxalate yields by 35%. The most promising reaction atmosphere is hydrogen, with the added benefit of being equal to the gas produced in the reaction. The temperature has the highest impact on the reaction, followed by reaction time and purge rates. We found no significant impact of catalyst loading on the reaction within the ranges reported previously. This research provides a clear and concise multiparameter optimization of the FOCR and provides insight into the reaction cascade involving the formation and decomposition of oxalates from formate., Critical assessment of parameters in the formate to oxalate reaction using design of experiments and response surface model methodology in CO2 for materials processing.

Compressed energy storage (CES) of air, CO2, or H2 in porous formations is a promising means of energy storage to abate the intermittency of renewable energy production. During operation, gas is injected during times of excess energy production and extracted during excess demands to drive turbines. Storage in saline aquifers using CO2 as a cushion or working gas has numerous advantages over typical air storage in caverns. However, interactions between CO2 and saline aquifers may result in potential operational limitations and have not been considered. This work utilizes reactive transport simulations to evaluate the geochemical reactions that occur during injection and extraction operational cycles for CES in a porous formation using CO2 as a cushion gas. Simulation results are compared with similar simulations considering an injection-only flow regime of geologic CO2 storage. Once injected, CO2 creates conditions favorable for dissolution of carbonate and aluminosilicate minerals. However, the dissolution extent is limited in the cyclic flow regime where significantly smaller dissolution occurs after the first cycle such that CO2 is a viable choice of cushion gas. In the injection-only flow regime, larger extents of dissolution occur as the fluid continues to be undersaturated with respect to formation minerals throughout the study period and porosity increased uniformly from 24.84% to 33.6% throughout the simulation domain. For the cyclic flow conditions, porosity increases nonuniformly to 31.1% and 25.8% closest and furthest from the injection well, respectively.

Hydrogenothrophic biomethanation of CO2 is an attractive alternative method for either to increase biogas production or upgrading biogas in biogas plants as a carbon capture and utilization (CCU) technology. the use of various packaging materials providing efficient cell immobilization can increase hydrogenotrophic biomethanation efficiency. For this purpose, the effect of two packing materials (ceramic ball and glass pipe) on hydrogenotrophic biomethanation efficiency were investigated. It was found that glass pipe outcompeted ceramic ball in terms of both H-2 utilisation efficiency (55% for ceramic ball and 85% for the glass pipe), high CH4 content in the headspace (65% for ceramic ball and 78% for the glass pipe) and methane formation rates (MFR: 3.9 and 4.8 m(CH4)(3)/m(reactor)(3)/day for ceramic ball and glass pipe, respectively). [GRAPHICS] ., Ege UniversityEge University [17/CSUAM/002], This research was funded by Ege University Grant No 17/CSUAM/002 directed by Prof. Azbar.

The impact of alkali promotion on the CO2 hydrogenation activity and selectivity over 1 %Ru/Al2O3 catalyst was investigated varying the type of metal (Li, Na, K) and precursor salt (carbonates vs. nitrates) while keeping constant the equivalent weight load. Catalysts prepared by sequential impregnations of Ru and alkali precursors on highly resistant γ-Al2O3 spheres (1 mm) were characterized by XRD, BET, H2 chemisorption, PSD, FT-IR, CO2-TPD, H2-TPRx and CO2 catalytic hydrogenation tests at atmospheric pressure under continuous flow conditions in the temperature range 200–430 °C. It was found that both CO2 capture capacity and methanation activity of Ru/Al2O3 catalyst were simultaneously increased only via doping with Li (nitrate), which largely reacted with alumina to form a mixed spinel phase. Therefore, Li-Ru/Al2O3 catalyst was successfully tested as a dual functional material operating the cyclic chemical looping process of CO2-capture followed by its methanation under alternating flow conditions at a fixed temperature as low as 230 °C.

Dimethyl ether is one of the most promising alternative fuels under consideration worldwide. Both the conventional indirect DME synthesis and the improved direct DME synthesis process are constrained by thermodynamics, which results in limited product yield, extensive separations and large recycle streams. Sorption enhanced DME synthesis is a novel process for the production of DME. The in situ removal of H2O ensures that the oxygen surplus of the feed no longer ends up in CO2 as is the case for direct DME synthesis. As a result CO2 can be converted directly to DME with high carbon efficiency, rather than being the main byproduct of DME production. The sorption enhanced DME synthesis process is a promising intensification, already achieving over 80 % single-pass CO2 conversion for a non-optimized system. The increased single-pass conversion requires less downstream separation and smaller recycle streams, especially for a CO2-rich feed. A key optimization parameter for the process performance is the adsorption capacity of the system. This capacity can be improved by optimizing the reactive adsorption conditions and the regeneration procedure. In this work, a detailed modelling study is performed to investigate the impact of various process parameters on the operating window and the interaction between different steps in a complete sorption enhanced DME synthesis cycle, and to compare its performance to other direct DME synthesis processes. The development of sorption enhanced DME synthesis, with its high efficiency carbon conversion, could play a significant role in the energy transition in which the carbon conversion will become leading.

CO(2)emissions from the steel industry are amongst the most difficult to abate, since carbon is used as a stoichiometric reducing agent in most steel mills. This carbon ends up as a CO/CO(2)mixture in the steel mill gases, which are combusted to generate heat, electricity, and more CO2. Strategies to capture and store (CCS), utilize (CCU) or avoid CO(2)in steel production exist, but are highly dependent on the availability of renewable electricity for the production of low-carbon H-2. Steel mill gas contains energy, and can thus be re-used more easily than combustion gas or process gas from the cement industry. In this study, we evaluate several strategies to reduce CO(2)emissions in the steel industry and rank them according to their renewable electricity requirement. We propose the following steps: (1) shut down the steel plant's power plant, since it produces electricity with a carbon intensity that is even higher than coal-based power plants; (2) replace steel mill gas with natural gas to generate heat within the steel mill; (3) recover the reducing gases, H(2)and CO, from the steel mill gases:e.g., using pressure swing adsorption to obtain a H-2-rich stream from COG, and sorption-enhanced water gas shift to obtain a H-2-rich stream and a pure CO(2)stream from BFG and BOFG; (4) the recovered H(2)converts some of the CO(2)to methanol, excess CO(2)is stored. The proposed CCUS scenario can retrofit existing infrastructure, uses proven technology and reduces CO(2)emissions by 70% for a marginal renewable electricity demand. Other energy-intensive alternatives have the potential to reduce CO(2)emissions by 85%, but require an order-of-magnitude more renewable electricity.

CO₂ transformed into CO is the initial step in the manufacturing of carbon-neutral products. Herein, the supported iron-oxide (FeOₓ) nanoparticles are investigated for the reverse water gas shift (RWGS) reaction from 200 °C to 400 °C under atmospheric conditions. The effect of the catalyst support is investigated by comparing unsupported and supported FeOₓ on Co₃O₄ and γ-Al₂O₃ supports. The FeOₓ/Co₃O₄ catalytic system displayed a high selectivity to CO (>99 %), a 1.4-fold CO₂ conversion increase over bare Co₃O₄ support and a 20-times improvement over FeOₓ/γ-Al₂O₃. The superior catalytic activity of FeOₓ/Co₃O₄ is attributed to the reducibility of Co₃O₄ under the reaction conditions and generation of oxygen vacancies. This in turn affected the electronic properties of the FeOₓ catalyst and as a result improved its catalytic activity for the RWGS reaction. To confirm the effect of oxygen vacancies in Co₃O₄ and the observed metal-support interaction (MSI), we performed electrochemical characterizations of the FeOₓ/Co₃O₄ catalyst. Under both anodic and cathodic polarization, the catalytic activity decreased by over 10 % due to the in-situ change in the oxidation state of Co₃O₄ during polarization, thus affecting the MSI effect between FeOₓ and Co₃O₄. Our study demonstrates that the application of electrochemical methods for studying the MSI effect in heterogeneous catalysts is a powerful and informative in-situ tool.

International audience; This study focuses on thermochemical H2O and CO2-splitting processes using non-stoichiometric metal oxides and concentrated solar energy to produce solar fuels. The redox process involves two distinct reactions: (i) a thermal reduction at high temperature of the oxide with creation of oxygen vacancies in its crystallographic structure, resulting in released O2; (ii) a re-oxidation of the metal oxide by H2O and/or CO2, yielding H2 and/or CO. Hierarchically-ordered porous ceria materials offer high potential for solar-driven thermochemical fuel production based on two-step redox cycles for H2O and CO2-splitting. The emergence of additive manufacturing processes allows to develop architected reactive materials with 3D-ordered geometry and hierarchical structure (porosity gradient), able to enhance the volumetric solar absorptivity and provide homogeneous heating of the oxygen carrier. The investigation of additive-manufactured ordered porous ceria monoliths made from 3D-printed polymer scaffolds was performed in a solar reactor.In comparison with reticulated ceria foams, an improvement of the oxygen yields was achieved with 3D-ordered porous structures. A low total pressure during the reduction step (inducing low pO2) favored the reduction extent and associated fuel yields. The fuel production rate during the exothermal oxidation step was enhanced by decreasing the temperature and by increasing the CO2 partial pressure. In addition, since the oxidation step is a surface-controlled reaction, a natural pore former (woody biomass) was used to create µm-size pores within the struts of ceria scaffolds. This enhanced the oxidation kinetics with a maximal CO production rate of 4.9 mL/min/g and fuel yield up to 333 µmol/g (with a reduction step at 1400 °C under ~0.10 bar of total pressure). Thus, using a 3D-ordered open-cell geometry with addition of micro-scale porosity in the struts enhanced the thermochemical performance.

Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al2O3 into the Cu-based catalyst stabilize the CuO crystalline structure and introduce basic sites on the ternary as-synthesized catalyst. In contrast, the as-prepared CuZn- and Cu-based materials contain a higher amount of superficial Cu0 and Cu1+ species. The CuZnAl-catalyst exhibited enhanced catalytic performance for the CO and H2 production, reaching a Faradaic efficiency (FE) towards syngas of almost 95% at −0.89 V vs. RHE and a remarkable current density of up to 90 mA cm−2 for the CO2 reduction at −2.4 V vs. RHE. The physico-chemical characterizations confirmed that the pyramidal mesoporous structure of this material, which is constituted by a high pore volume and small CuO crystals, plays a fundamental role in its low diffusional mass-transfer resistance. The CO-productivity on the CuZnAl-catalyst increased at more negative applied potentials, leading to the production of syngas with a tunable H2/CO ratio (from 2 to 7), depending on the applied potential. These results pave the way to substitute state-of-the-art noble metals (e.g., Ag, Au) with this abundant and cost-effective catalyst to produce syngas. Moreover, the post-reaction analyses demonstrated the stabilization of Cu2O species, avoiding its complete reduction to Cu0 under the CO2 electroreduction conditions.

The electrochemical reduction of CO2 to fuels or commodity chemicals is a reaction of high interest for closing the anthropogenic carbon cycle. The role of the electrolyte is of particular interest, as the interplay between the electrocatalytic surface and the electrolyte plays an important role in determining the outcome of the CO2 reduction reaction. Therefore, insights on electrolyte effects on the electrochemical reduction of CO2 are pivotal in designing electrochemical devices that are able to efficiently and selectively convert CO2 into valuable products. Here, we provide an overview of recently obtained insights on electrolyte effects and we discuss how these insights can be used as design parameters for the construction of new electrocatalytic systems., The electrochemical reduction of CO2 to fuels and chemicals can potentially close the carbon cycle. Here, the authors discuss the importance of the electrolyte in determining the outcome of the reaction. They highlight recently obtained insights on electrolyte effects and discuss how the electrolyte choice can be used as a design parameter for more efficient electrocatalytic systems.

Power-to-Methane (PtM) can provide flexibility to the electricity grid while aiding decarbonization of other sectors. This study focuses specifically on the methanation component of PtM in 2050. Scenarios with 80–95% CO2 reduction by 2050 (vs. 1990) are analyzed and barriers and drivers for methanation are identified. PtM arises for scenarios with 95% CO2 reduction, no CO2 underground storage and low CAPEX (75 €/kW only for methanation). Capacity deployed across EU is 40 GW (8% of gas demand) for these conditions, which increases to 122 GW when liquefied methane gas (LMG) is used for marine transport. The simultaneous occurrence of all positive drivers for PtM, which include limited biomass potential, low Power-to-Liquid performance, use of PtM waste heat, among others, can increase this capacity to 546 GW (75% of gas demand). Gas demand is reduced to between 3.8 and 14 EJ (compared to ∼20 EJ for 2015) with lower values corresponding to scenarios that are more restricted. Annual costs for PtM are between 2.5 and 10 bln€/year with EU28’s GDP being 15.3 trillion €/year (2017). Results indicate that direct subsidy of the technology is more effective and specific than taxing the fossil alternative (natural gas) if the objective is to promote the technology. Studies with higher spatial resolution should be done to identify specific local conditions that could make PtM more attractive compared to an EU scale.

Hydrogen represents a versatile energy carrier with net zero end use emissions. Power-to-Liquid (PtL) includes the combination of hydrogen with CO2 to produce liquid fuels and satisfy mostly transport demand. This study assesses the role of these pathways across scenarios that achieve 80–95% CO2 reduction by 2050 (vs. 1990) using the JRC-EU-TIMES model. The gaps in the literature covered in this study include a broader spatial coverage (EU28+) and hydrogen use in all sectors (beyond transport). The large uncertainty in the possible evolution of the energy system has been tackled with an extensive sensitivity analysis. 15 parameters were varied to produce more than 50 scenarios. Results indicate that parameters with the largest influence are the CO2 target, the availability of CO2 underground storage and the biomass potential. Hydrogen demand increases from 7 mtpa today to 20–120 mtpa (2.4–14.4 EJ/yr), mainly used for PtL (up to 70 mtpa), transport (up to 40 mtpa) and industry (25 mtpa). Only when CO2 storage was not possible due to a political ban or social acceptance issues, was electrolysis the main hydrogen production route (90% share) and CO2 use for PtL became attractive. Otherwise, hydrogen was produced through gas reforming with CO2 capture and the preferred CO2 sink was underground. Hydrogen and PtL contribute to energy security and independence allowing to reduce energy related import cost from 420 bln€/yr today to 350 or 50 bln€/yr for 95% CO2 reduction with and without CO2 storage. Development of electrolyzers, fuel cells and fuel synthesis should continue to ensure these technologies are ready when needed. Results from this study should be complemented with studies with higher spatial and temporal resolution. Scenarios with global trading of hydrogen and potential import to the EU were not included.

Accelerated carbonation is a carbon utilization option which allows the manufacturing of useful products, employing CO2-concentrated or -diluted emission sources and waste streams such as industrial or other processing solid residues, in a circular economy perspective. If properly implemented, it may reduce the exploitation of virgin raw materials and their associated environmental footprint and permanently store CO2 in the form of Ca and/or Mg carbonates, thus effectively contributing to climate change mitigation. In this perspective article, we first report an overview of the main mineral carbonation pathways that have been developed up to now, focusing on those which were specifically designed to obtain useful products, starting from different alkaline feedstocks. Based on the current state of the art, we then discuss the main critical issues that still need to be addressed in order to improve the overall feasibility of mineral carbonation as a CCUS option, as well as research needs and opportunities.

Producción Científica, The present work reviews the role of biogas as advanced biofuel in the renewable energy system, summarizing the main raw materials used for biogas production and the most common technologies for biogas upgrading and delving into emerging biological methanation processes. In addition, it provides a description of current European legislative framework and the potential biomethane business models as well as the main biogas production issues to be addressed to fully deploy these upgrading technologies. Biomethane could be competitive due to negative or zero waste feedstock prices, and competitive to fossil fuels in the transport sector and power generation if upgrading technologies become cheaper and environmentally sustainable., Unión Europea - (URBIOFIN project 745785, H2020-BBI-JTI-2016), Junta de Castilla y León y Fondo Europeo de Desarrollo Regional (FEDER) - (grant CLU 2017-09)

Negative emission technologies have recently received increasing attention due to climate change and global warming. One among them is bioenergy with carbon capture and storage (BECCS), but the capture process is very energy intensive. Here, a novel pathway is introduced, based on second-generation biofuels followed by carbon circulation in an indefinitely closed chain, effectively resulting in a sink. Instead of using an energy-intensive conventional CCS process, the application of an on-board solid oxide fuel cell (SOFC) running on biofuels in an electric vehicle (FCEV) could result in negative emissions by capturing a concentrated stream of CO2, which is readily stored in a second tank. A CO2 recovery system at the fuel station then takes the CO2 from the tank to be transported to storage locations or to be used for local applications such as CO2-based concrete curing and synthesis of e-fuels. Incorporating CO2 utilization technologies into the FCEVs-SOFC system can close the carbon loop, achieving carbon neutrality through feeding the CO2 in a reverse-logistic to a methanol plant. The methanol produced is also used in SOFCs, leading to an infinite repetition of this carbon cycle till a saturation stage is reached. It is determined this pathway will reach typical Cradle-to-Grave negative emissions of 0.515 ton CO2 per vehicle, and total negative CO2 emission of 138 Mt for all passenger cars in the EU is potentially achievable. All steps comprise known technologies with medium to high technology readiness level (TRL) levels, so principally this system can readily be applied in the mid-term.

Dimethyl carbonate (DMC) has recently gained popularity due to its environmentally friendly status and multiple applications in which it is able to replace more toxic chemicals. Among its several commercial synthesis production routes, the ethylene carbonate (EC) transesterification shines as a CO2 consuming process. However, other factors such as the high emitting synthesis of EC precursors hinder its environmental capabilities. Methanol oxycarbonylation is a mature DMC non-CO2 consuming synthesis route with the potential to indirectly utilize the greenhouse gas throughout the synthesis of its intermediates. In this work, we propose a DMC production superstructure using the methanol oxycarbonylation route with the aim of consuming CO2 in both the synthesis gas (syngas) and methanol synthesis stages. Results show that the integration of methanol and syngas synthesis with the DMC production process vastly decreases both the cost and emission with respect to the unintegrated case. However, the addition of a Reverse Water Gas Shift (RWGS) reactor further decreases the emission down to a minimum of 1.019. kg CO2-eq/kg DMC, resulting in a 54 % decrease in the indicator compared with the direct CO2 utilization route. In comparison with other routes, utilization of this DMC in blends with gasoline manages to reduce the GWP of using the fuel mix to a potential 16 %. The authors gratefully acknowledge financial support from the project PROMETEO2020/064. The authors would also like to thank «Generalitat Valenciana: Conselleria de Educación, Investigación, Cultura y Deporte» for the Ph.D grant (ACIF/2016/ 062).

Production of synthetic natural gas (SNG) offers an alternative way to valorize captured CO2 from energy intensive industrial processes or from a dedicated CO2 grid. This paper presents an energy-efficient way for synthetic natural gas production using captured CO2 and renewable hydrogen. Considering several renewable hydrogen production sources, a techno-economic analysis was performed to find a promising path toward its practical application. In the paper, the five possible renewable hydrogen sources (photo fermentation, dark fermentation, biomass gasification, bio photolysis, and PV electrolysis) were compared to the two reference cases (steam methane reforming and water electrolysis) from an economic stand point using key performance indicators. Possible hydrogen production capacities were also considered for the evaluation. From a technical point of view, the SNG process is an efficient process from both energy efficiency (about 57%) and CO2 conversion rate (99%). From the evaluated options, the photo-fermentation proved to be the most attractive with a levelized cost of synthetic natural gas of 18.62 €/GJ. Considering the production capacities, this option loses its advantageousness and biomass gasification becomes more attractive with a little higher levelized cost at 20.96 €/GJ. Both results present the option when no CO2 credit is considered. As presented, the CO2 credits significantly improve the key performance indicators, however, the SNG levelized cost is still higher than natural gas prices.

A novel process configuration for sorption-enhanced methanation (SEM) based on the technology of dual interconnected fluidized beds was recently proposed. The idea consists of a chemical looping system where in one reactor (the methanator), catalytic methanation occurs simultaneously with H2O capture by a suitable sorbent to drive the equilibrium towards methane formation, while in another reactor (dehydrator), the regeneration of the sorbent takes place. In this work, two possible H2O sorbents for such a SEM process were tested under simulated SEM conditions. The sorbents were a granular CaO obtained from natural limestone, which reacts with H2O to form Ca (OH)2, and an attrition-resistant spherical 3A-zeolite, which physically adsorbs H2O. Each test consisted of 10 complete hydration/dehydration cycles in a lab-scale twin fluidized bed device. The temperature range investigated for hydration was 200–300 °C, while that for dehydration was 350–450 °C. CaO showed a decay of the steam capture capacity with the number of cycles, induced by the irreversible carbonation of the sorbent with CO2. By contrast, the zeolite had a more stable behavior in all conditions. The presence of a high CO2 concentration reduced the steam capture capacity of both sorbents, but this effect was more evident for CaO, because of the abovementioned carbonation reaction. For the zeolite, results suggest that CO2 competes with H2O for adsorption in the sorbent. In-bed particle fragmentation was limited for CaO and absent for the zeolite. On the whole, results indicate that both sorbents can be used for the SEM process. The zeolite shows a better asymptotic capture capacity than CaO and it is not affected by deactivation during the cycles, though it is a more expensive material.

A rise in atmospheric carbon dioxide levels, following years of burning fossil fuels, has brought about increase in global temperatures and climate change due to the green-house effect. As such, recent efforts aimed at addressing this problem have been directed to the use of carbon dioxide as an inexpensive and non-toxic single carbon source for making chemical products. Herein, we report the use of tetrazolyl complexes as catalysts precursors for hydrogenation of carbon dioxide. Specifically, tetrazolyl compounds bearing phosphorus-sulfur bonds have been synthesized with the view of using these as phosphorus-nitrogen bidentate tetrazolyl ligands that can coordinate to iridium(III) thereby forming heteroatomic five-member complexes. Interestingly, reacting the phosphorus-nitrogen bidentate tetrazolyl ligands with iridium dimer led to serendipitous isolation of chiral-at-metal iridium(III) half-sandwich complexes instead. The complexes were obtained via prior formation non-chiral iridium half-sandwich complexes. The complexes undergo initial phosphorus-sulfur bond heterolysis of the precursor ligands, which then ultimately results in new half-sandwich iridium complexes featuring monodentate phosphine co-ligands with proton responsive functionalities. Conditions necessary to significantly affect the rate of phosphorus-sulfur bond heterolysis in the precursor ligand and the subsequent coordination to iridium have been reported. The complexes served as catalyst precursors and exhibited activity in carbon dioxide and bicarbonate hydrogenation in excellent catalytic activity, at low catalyst loadings, producing concentrated formate solutions exclusively. Catalyst precursors with proton responsive phosphines were found to influence catalytic activity when present as racemates, while ease of dissociation of the ligand from the iridium centre was observed to influence activity in spite of the presence of electron-donating ligands. A test for homogeneity indicated that hydrogenation of carbon dioxide proceeded by homogenous means. Subsequently, the mechanism of the reaction by the iridium catalyst precursors was studied using proton NMR techniques. This revealed that a chiral-at-metal iridium hydride species generated in situ, served as the active catalyst.

Today, climate change caused by global warming has become a worldwide problem with increasing greenhouse gas (GHG) emissions. Carbon capture and storage technologies have been developed to capture carbon dioxide (CO2), however, CO2 storage and utilization technologies are relatively less developed. In this light, we have reported efficient CO2 decomposition results using a nonperovskite metal oxide, SrFeCo0.5Ox, in a continuous-flow system. In this study, we report enhanced efficiency, reliability under isothermal conditions, and catalytic reproducibility through cyclic tests using SrFeO3&minus, d. This ferrite needs an activation process, and 3.5 vol% H2/N2 was used in this experiment. Activated oxygen-deficient SrFeO3&minus, d can decompose CO2 into carbon monoxide (CO) and carbon (C). Although SrFeO3&minus, d is a well-known material in different fields, no studies have reported its use in CO2 decomposition applications. The efficiency of CO2 decomposition using SrFeO3&minus, d reached &sup3, 90%, and decomposition (&sup3, 80%) lasted for approximately 170 min. We also describe isothermal and cyclic experimental data for realizing commercial applications. We expect that these results will contribute to the mitigation of GHG emissions.

Within the context of energy transition scenarios towards renewable resources, superstructure optimization is implemented for the synthesis of sustainable and efficient Power-to-Syngas processes. A large number of reactors (i.e. reverse water-gas-shift, steam reforming, dry reforming, tri-reforming, methane partial oxidation reactor, water electrolyzer) and separators (e.g. PSA, TSA, cryogenics, membranes, gas-liquid scrubbing) \textcolor{blue}{are included within a single MILP framework, accounting for typical operating conditions of each process-unit, under the specified simplifying assumptions. Power is minimized in the context of sustainable feedstocks: water and biogas or carbon dioxide from direct air-capture. The objective function adds the thermal to the electrical contribution to the total power, the latter being weighted by a pseudo-price of null -- i.e. sustainable, in-house electricity production -- or unitary value -- i.e. electricity purchased, possibly generated from non-sustainable sources. simultaneous operations of multiple reactor-technologies is allowed to identify possible synergies. With biogas and null value of the pseudo-price, the results identify plant configurations mainly run via electricity, which constitutes up to $97\%$ of the total power for co-operating partial oxidation of methane and water electrolysis. Alternatively, lower total demands are attained at the expenses of thermal duty when electricity is penalized: the endothermic reactors are operated. With carbon dioxide, the total power demand dramatically increases due to the large consumptions of direct-air capture and water electrolysis. The resulting topologies always favor membrane separation, adsorption and cryogenics over absorption technologies.

Global climate change is a worldwide concern that requires the dramatic reduction of greenhouse gases. Innovation in sustainable technologies for CO2 utilization to other high value products is therefore an emerging and rising field. It was found that CO2 as a sole carbon source can be converted to CH4 (higher than 97%) in a system consisted of anaerobic granular sludge, water and zero valent scrap iron. In this system (zero valent scrap iron, anaerobic granular sludge and CO2), pre-exposure of zero valent scrap iron to green tea resulted in a higher conversion rate and total CH4 production compared to bare zero valent scrap iron response. At the abiotic system (no anaerobic sludge) the zero valent scrap iron pre-treated with green tea also showed around 10% higher H2 production as well as higher final pH compared to zero valent scrap iron. The dominant crystalline product of the process both at the abiotic and at the biological system was siderite (FeCO3). It is likely that the formation of siderite on the zero valent scrap iron outer surface have reduced the amount of H2 release from zero valent scrap iron, shielding the substrate for methanogens. The presence of green tea compounds can form an iron-tannate complex with iron ions and this can possibly decrease or slow down the siderite layer, as a result more H2 was released when zero valent scrap iron was pre-exposed to green tea. Anaerobic spent filtered media was independently added to zero valent scrap iron to examine the effect of extracellular enzymes, however slight increase of the H2 production rate was found. The examined system combines potential solutions for two environmental problems; production of siderite derived from zero valent scrap iron for environmental applications and utilization of CH4 generated from CO2 for energy purposes.

We compare different approaches for the preparation of carbon monoxide-rich synthesis gas (syngas) for Fischer&ndash, Tropsch (FT) synthesis from carbon dioxide (CO2) using a self-consistent design and process simulation framework. Three alternative methods for suppling heat to the syngas preparation step are investigated, namely: allothermal from combustion (COMB), autothermal from partial oxidation (POX) and autothermal from electric resistance (ER) heating. In addition, two alternative design approaches for the syngas preparation step are investigated, namely: once-through (OT) and recycle (RC). The combination of these alternatives gives six basic configurations, each characterized by distinctive plant designs that have been individually modelled and analyzed. Carbon efficiencies (from CO2 to FT syncrude) are 50&ndash, 55% for the OT designs and 65&ndash, 89% for the RC designs, depending on the heat supply method. Thermal efficiencies (from electricity to FT syncrude) are 33&ndash, 41% for configurations when using low temperature electrolyzer, and 48&ndash, 59% when using high temperature electrolyzer. Of the RC designs, both the highest carbon efficiency and thermal efficiency was observed for the ER configuration, followed by POX and COMB configurations.

The use of herbal medicine has increased tremendously over the last decades, generating a considerable amount of herbal medicine waste. Pyrolysis is a promising option to dispose of biomass and organic waste such as herbal medicine waste. Herein, an activated carbon-supported Pt catalyst (Pt/AC) and carbon dioxide (CO2) were applied to the pyrolysis of real herbal medicine waste to develop a thermal disposal method to prevent the formation of benzene derivatives that are harmful to the environment and human health. When using the Pt/AC catalyst in the pyrolysis of the herbal medicine waste at 500 &deg, C, the generation of benzyl species was suppressed. This was likely because the Pt catalytic sites accelerate a free radical mechanism that is dominant in the thermal cracking of carbonaceous substances. However, the employment of CO2 (instead of typically used N2) as a pyrolysis medium for the herbal medicine waste pyrolysis did not decrease the concentrations of benzyl compounds contained in the pyrolytic products of the herbal medicine waste. This study might help develop a method to thermally dispose of agricultural biowaste, preventing the formation of harmful chemicals to the environment and human beings.

Recent advances in modular nuclear reactors could facilitate the use of irradiation to produce fuels and chemicals using anthropogenic CO2. One of the challenges in CO2 conversion reactions is the stability or low reactivity of CO2. Chemical activation of CO2 via thermochemical or electrochemical approaches contributes to the high energy intensity of CO2 conversion reactions. Activation of the CO2 molecule via irradiation at significantly lower temperatures may now allow us to use heterogeneous CO2-bearing waste gas streams and low-carbon emitting nuclear energy resources to produce high value chemicals and fuels in a distributed manner. In this paper, we review the radiolytic behavior of CO2 and particularly, irradiation pathways relevant for producing fuels and chemicals using CO2, technological advances and research directions for advancing radiolytic conversion of CO2 to chemicals and fuels.

The authors would like to thank Cyprus University of Technology for covering the open access fees. A new approach for CO2 utilization (as a sole carbon source) to acetic acid and other VFAs under ambient conditions using zero valent iron and anaerobic granular sludge was examined by methanogens inhibition. Zero Valent Iron when is anaerobically oxidized generates H2 that can be utilized along with CO2 by homoacetogens in the anaerobic granular sludge for the production of acetic acid or other VFAs. However, methanogens in anaerobic sludge act antagonistically with homoacetogens and therefore the main goal of this study is to examine strategies to inhibit methanogenesis and to enrich homoacetogens. Based on this, several strategies were investigated such as the exposure of (a) anaerobic granular sludge to low pH, (b) the short exposure of anaerobic granular sludge to heat, (c) addition of bromoethanesulfonate under various concentrations and (d) exposure of anaerobic granular sludge to salinity 30–90 g NaCl/L. The highest performance (2,020 mg/L of acetic acid) was found when anaerobic granular sludge was exposed to 50 mM of bromoethanesulfonate at 100 g/L (ZVI), pH 6–6.5, after 12 days whereas, the short exposure of anaerobic granular sludge to heat at 100 g/L ZVI at pH 6–6.5 resulted in 1,290 mg/L of acetic acid. The operation of this system in pH 5–6 generated less VFAs compared to operation at pH 6–6–5. The daily regulation of pH to 3 was not practical as the pH was increased to 6.5 due to abiotic anaerobic oxidation of ZVI and this resulted in CH4 production and propionic acid generation. The exposure of anaerobic granular sludge to ZVI and 30 g NaCl/L as well as to seawater resulted in production of CH4 (around 28% of the headspace) and mainly production of acetic acid (550–850 mg/L). The increased in salinity to 60 and 90 g NaCl/L resulted in reduction of CH4 and VFAs however, a more diverse range of VFAs was produced. Exposure of anaerobic granular sludge to heat and then to CO2 and ZVI resulted in an increase of Clostridium sensu stricto to 65.9% and the same genus was increased when anaerobic sludge was exposed to bromoethanesulfonate and ZVI.

Underground gas storage reservoirs (UGSRs) are used to keep the natural gas supply smooth. Native natural gas is commonly used as cushion gas to maintain the reservoir pressure and cannot be extracted in the depleted gas reservoir transformed UGSR, which leads to wasting huge amounts of this natural energy resource. CO2 is an alternative gas to avoid this particular issue. However, the mixing of CO2 and CH4 in the UGSR challenges the application of CO2 as cushion gas. In this work, the Donghae gas reservoir is used to investigate the suitability of using CO2 as cushion gas in depleted gas reservoir transformed UGSR. The impact of the geological and engineering parameters, including the CO2 fraction for cushion gas, reservoir temperature, reservoir permeability, residual water and production rate, on the reservoir pressure, gas mixing behavior, and CO2 production are analyzed detailly based on the 15 years cyclic gas injection and production. The results showed that the maximum accepted CO2 concentration for cushion gas is 9% under the condition of production and injection for 120 d and 180 d in a production cycle at a rate of 4.05 kg/s and 2.7 kg/s, respectively. The typical curve of the mixing zone thickness can be divided into four stages, which include the increasing stage, the smooth stage, the suddenly increasing stage, and the periodic change stage. In the periodic change stage, the mixed zone increases with the increasing of CO2 fraction, temperature, production rate, and the decreasing of permeability and water saturation. The CO2 fraction in cushion gas, reservoir permeability, and production rate have a significant effect on the breakthrough of CO2 in the production well, while the effect of water saturation and temperature is limited.

Carbon Capture and Utilization (CCU) is an emerging field proposed for emissions mitigation and even negative emissions. These potential benefits need to be assessed by the holistic method of Life Cycle Assessment (LCA) that accounts for multiple environmental impact categories over the entire life cycle of products or services. However, even though LCA is a standardized method, current LCA practice differs widely in methodological choices. The resulting LCA studies show large variability which limits their value for decision support. Applying LCA to CCU technologies leads to further specific methodological issues, e.g., due to the double role of CO2 as emission and feedstock. In this work, we therefore present a comprehensive guideline for LCA of CCU technologies. The guideline has been development in a collaborative process involving over 40 experts and builds upon existing LCA standards and guidelines. The presented guidelines should improve comparability of LCA studies through clear methodological guidance and predefined assumptions on feedstock and utilities. Transparency is increased through interpretation and reporting guidance. Improved comparability should help to strengthen knowledge-based decision-making. Consequently, research funds and time can be allocated more efficiently for the development of technologies for climate change mitigation and negative emissions., Frontiers in Energy Research, 8, ISSN:2296-598X

This review aims to give more understanding of the selection and development of oxygen carrier materials for chemical looping. Chemical looping, a rising star in chemical technologies, is capable of low CO2 emissions with applications in the production of energy and chemicals. A key issue in the further development of chemical looping processes and its introduction to the industry is the selection and further development of an appropriate oxygen carrier (OC) material. This solid oxygen carrier material supplies the stoichiometric oxygen needed for the various chemical processes. Its reactivity, cost, toxicity, thermal stability, attrition resistance, and chemical stability are critical selection criteria for developing suitable oxygen carrier materials. To develop oxygen carriers with optimal properties and long-term stability, one must consider the employed reactor configuration and the aim of the chemical looping process, as well as the thermodynamic properties of the active phases, their interaction with the used support material, long-term stability, internal ionic migration, and the advantages and limits of the employed synthesis methods. This review, therefore, aims to give more understanding into all aforementioned aspects to facilitate further research and development of chemical looping technology.

In the course of dark fermentative hydrogen production, a complex gaseous mixture with significant quantity of CO2 is formed. Hence, proper separation of H2 and CO2 is required for adequate utilization of hydrogen gas in fuel cell applications. Technological solutions for the removal of CO2 can be designed by using gas separation membranes. Nevertheless, contemporary systems should be concerned with the consecutive valorization of carbon dioxide, as well. In this review article, the membrane-based technologies aiming at the effective separation of CO2 and biohydrogen (bioH2) will be evaluated, along with concise discussion and perspectives of integrative schemes offering alternatives for the biologically-mediated (fermentative, bioelectrochemical and algal) conversion of carbon dioxide into value-added substances, such as methane, hydrocarbons, etc. With this analysis, the objective was to bring the most important aspects of membrane-assisted biohydrogen downstream technology under one cover and give insights to recent advancement and possible future research directions.

Carbon capture and utilization (CCU) may offer a response to climate change mitigation from major industrial emitters. CCU can turn waste CO2 emissions into valuable products such as chemicals and fuels. Consequently, attention has been paid to petrochemical industries as one of the best options for CCU. The largest industrial CO2 removal monoethanol amine-based plant in Iran has been simulated with the aid of a chemical process simulator, i.e., Aspen HYSYS&reg, v.10. The thermodynamic properties are calculated with the acid gas property package models, which are available in Aspen HYSYS&reg, The results of simulation are validated by the actual data provided by Kermanshah Petrochemical Industries Co. Results show that there is a good agreement between simulated results and real performance of the plant under different operational conditions. The main parameters such as capture efficiency in percent, the heat consumption in MJ/kg CO2 removed, and the working capacity of the plant are calculated as a function of inlet pressure and temperature of absorber column. The best case occurred at the approximate temperature of 40 to 42 &deg, C and atmospheric pressure with CO2 removal of 80.8 to 81.2%, working capacity of 0.232 to 0.233, and heat consumption of 4.78 MJ/kg CO2.

The economics of CO2 utilization are discussed from a critical perspective, with a concise analysis of the state-of-the-art of economics in power-to-X (methanol, methane). The main elements of the analysis of the economics are commented to provide guidelines on how to interpret the techno-economic results in the area of CO2 utilization. It remarks the need of a careful analysis of the specific context, and of the limits of the evaluation, in order to go beyond the just use of the results without a proper analysis of how the data support the conclusions, their limits and applicability. Case examples discussed in a more detail regard the CO2 to methanol or methane conversion, from the perspective of highlighting possible issues or limits rather than to indicate which results are more valuable, which is out of the scope of this contribution.

Massive penetration of renewable energy in the energy systems is required to comply with existing CO2 regulations. Considering current power pools, large shares of renewable energy sources imply strong efficiency and economic penalties in fossil fuel power plants as they are mainly operated to regulate the system and constant shutdowns are expected. Under this framework, the integration of a combined cycle power plant (CCPP) with an energy storage technology such as power to gas (PtG) is proposed to virtually reduce its minimum complaint load through the diversion of instantaneous excess electricity. Power to gas produces hydrogen through water electrolysis, which is later combined with CO2 to produce methane. The main novelty of this study relies in the improved flexibility and economics of combined cycles by means of using power to gas as a tool to reduce the minimum complaint load. The principal objective of the study is the quantification of cost reduction under different scenarios of shutdowns and conventional start-ups. The case study analyses a combined cycle of 400 MWe gross power with a minimum complaint load of 30% that can be virtually reduced to 20% by means of a 40- MWe power-to-gas plant. Eight scenarios are defined to compare the reference case of conventional operation under hot, warm, and cold start-ups with power-to-gas-assisted operation. Additionally, PtG-assisted operation scenarios are analyzed with different loads (30–50–70%). These scenarios also include the consideration of a temporary peak of demand occurring in a period in which dispatch is below the minimum complaint load. Under this situation, the response time of conventional plants is very limited, while PtG-assisted CCPP can rapidly satisfy the peak. The techno-economic model quantifies the required fuel, gross and net power, and emissions as well as total costs and incomes under each scenario and net differential profit in an hourly basis. The analysis of the obtained results does not recommend the operation of the PtG-assisted CCPP at minimum complaint load for hot, warm, or cold start-ups. However, important marginal profits are achieved with the proposed system for part-loads operation over 50% for every sort of start-up, avoiding shutdowns and extending the capacity factor.

The emissions of greenhouse gases, especially CO2, have been identified as the main contributor for global warming and climate change. Carbon capture and storage (CCS) is considered to be the most promising strategy to mitigate the anthropogenic CO2 emissions. This review aims to provide the latest developments of CO2 storage from the perspective of improving safety and economics. The mechanisms and strategies of CO2 storage, focusing on their characteristics and current status, are discussed firstly. In the second section, the strategies for assessing and ensuring the security of CO2 storage operations, including the risks assessment approach and monitoring technology associated with CO2 storage, are outlined. In addition, the engineering methods to accelerate CO2 dissolution and mineral carbonation for fixing the mobile CO2 are also compared within the second section. The third part focuses on the strategies for improving economics of CO2 storage operations, namely enhanced industrial production with CO2 storage to generate additional profit, and co-injection of CO2 with impurities to reduce the cost. Moreover, the role of multiple CCS technologies and their distribution on the mitigation of CO2 emissions in the future are summarized. This review demonstrates that CO2 storage in depleted oil and gas reservoirs could play an important role in reducing CO2 emission in the near future and CO2 storage in saline aquifers may make the biggest contribution due to its huge storage capacity. Comparing the various available strategies, CO2-enhanced oil recovery (CO2-EOR) operations are supposed to play the most important role for CO2 mitigation in the next few years, followed by CO2-enhanced gas recovery (CO2-EGR). The direct mineralization of flue gas by coal fly ash and the pH swing mineralization would be the most promising technology for the mineral sequestration of CO2. Furthermore, by accelerating the deployment of CCS projects on large scale, the government can also play its role in reducing the CO2 emissions.

In this work, in-house synthesized NiMgAl, Ru/NiMgAl, and Ru/SiO2 catalysts and a commercial ruthenium-containing material (Ru/Al2O3com.) were tested for CO2 methanation at 250, 300, and 350 &deg, C (weight hourly space velocity, WHSV, of 2,400 mLN,CO2&middot, g&minus, 1&middot, h&minus, 1). Materials were compared in terms of CO2 conversion and CH4 selectivity. Still, their performances were assessed in a short stability test (24 h) performed at 350 &deg, C. All catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), N2 physisorption at &minus, 196 &deg, C, inductively coupled plasma optical emission spectrometry (ICP-OES), and H2/CO chemisorption. The catalysts with the best performance (i.e., the hydrotalcite-derived NiMgAl and Ru/NiMgAl) seem to be quite promising, even when compared with other methanation catalysts reported in the literature. Extended stability experiments (240 h of time-on-stream) were performed only over NiMgAl, which was selected based on catalytic performance and estimated price criteria. This catalyst showed some deactivation under conditions that favor CO formation (high temperature and high WHSV , i.e., 350 &deg, C and 24,000 mLN,CO2&middot, 1, respectively), but at 300 &deg, C and low WHSV, excellent activity (ca. 90% of CO2 conversion) and stability, with nearly complete selectivity towards methane, were obtained.

The absorption of carbon dioxide from anthropogenic emissions and its utilization as a building block for the synthesis of useful chemicals is gaining increasing interest in recent years as an alternative to the conventional CO2 capture and storage (CCS) technologies. The conversion of carbon dioxide into valuable commodities has the advantage of avoiding the energy penalties of absorbent regeneration, CO2 compression and its disposal underground. In this paper we report a novel semi-continuous technique of CO2 capture from a gas mixture by dilute (0.83 mol dm−3) aqueous solutions of Na2CO3 with a sufficiently high absorption efficiency (about 80%) combined with the nearly quantitative production of high quality CaCO3 and CO2 minimizing the energy requirements since the entire process occurred at room conditions. The highly pure CaCO3 and CO2 recovered by the process are valuable products that have the potential of reducing the costs of the CO2 capture process. The 13C NMR spectroscopy is employed to identify and quantify the species in solution.

The CeO2/CeO2−δ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, followed by CO2 splitting, was considered in this work. This topic concerns one of the emerging and most promising processes for the recycling and valorization of anthropogenic greenhouse gas emissions. The development of redox-active catalysts with enhanced efficiency for solar thermochemical fuel production and CO2 conversion is a highly demanding and challenging topic. The determination of redox reaction kinetics is crucial for process design and optimization. In this study, the solid-state redox kinetics of CeO2 in the two-step process with CH4 as the reducing agent and CO2 as the oxidizing agent was investigated in an original prototype solar thermogravimetric reactor equipped with a parabolic dish solar concentrator. In particular, the ceria reduction and re-oxidation reactions were carried out under isothermal conditions. Several solid-state kinetic models based on reaction order, nucleation, shrinking core, and diffusion were utilized for deducing the reaction mechanisms. It was observed that both ceria reduction with CH4 and re-oxidation with CO2 were best represented by a 2D nucleation and nuclei growth model under the applied conditions. The kinetic models exhibiting the best agreement with the experimental reaction data were used to estimate the kinetic parameters. The values of apparent activation energies (~80 kJ·mol−1 for reduction and ~10 kJ·mol−1 for re-oxidation) and pre-exponential factors (~2–9 s−1 for reduction and ~123–253 s−1 for re-oxidation) were obtained from the Arrhenius plots.

Catalytic performance of La0.3Sr0.7Co0.7Fe0.3O3 (LSCF3773 or LSCF) catalyst for syngas production via two step thermochemical cycles of H2O and CO2 co-splitting was investigated. Oxygen storage capacity (OSC) was found to depend on reduction temperature, rather than the oxidation temperature. The highest oxygen vacancy (Δδ) was achieved when the reduction and oxidation temperature were both fixed at 900 °C with the feed ratio (H2O to CO2) of 3 to 1, with an increasing amount of CO2 in the feed mixture. CO productivity reached its plateau at high ratios of H2O to CO2 (1:1, 1:2, and 1:2.5), while the total productivities were reduced with the same ratios. This indicated the existence of a CO2 blockage, which was the result of either high Ea of CO2 dissociation or high Ea of CO desorption, resulting in the loss in active species. From the results, it can be concluded that H2O and CO2 splitting reactions were competitive reactions. Ea of H2O and CO2 splitting was estimated at 31.01 kJ/mol and 48.05 kJ/mol, respectively, which agreed with the results obtained from the experimentation of the effect of the oxidation temperature. A dual-reactors system was applied to provide a continuous product stream, where the operation mode was switched between the reduction and oxidation step. The isothermal thermochemical cycles process, where the reduction and oxidation were performed at the same temperature, was also carried out in order to increase the overall efficiency of the process. The optimal time for the reduction and oxidation step was found to be 30 min for each step, giving total productivity of the syngas mixture at 28,000 μmol/g, approximately.

The cement and lime industries are responsible for 8% of global CO2 emissions [1]. 35% of this CO2 share comes from fuel combustion to heat and decompose limestone to produce lime or “clinker” in an open atmosphere while the remaining 65% comes from limestone rock itself. Due to the new technology, high grades of both lime and CO2 were obtained faster and at much lower than conventional temperatures and CO2 was fully captured and utilized when using an HEVA reactor for limestone calcination. Clinker, a precursor of cement, was partly obtained at lower temperature when starting from HEVA lime and fine quartz after mechanochemical pretreatment.

Carbon dioxide capture, utilization and storage (CCUS) –including conversion to valuable chemicals-is a challenging contemporary issue having multi-facets. The prospect to utilize carbon dioxide (CO2) as a feedstock for synthetic applications in chemical and fuel industries -through carboxylation and reduction reactions-is the subject of this review. Current statute of the heterogeneously catalyzed hydrogenation, as well as the photocatalytic and electrocatalytic activations of conversion of CO2 to value-added chemicals is overviewed. Envisaging CO2 as a viable alternative to natural gas and oil as carbon resource for the chemical supply chain, three stages of development; namely, (i) existing mature technologies (such as urea production), (ii) emerging technologies (such as formic acid or other single carbon (C1) chemicals manufacture) and (iii) innovative explorations (such as electrocatalytic ethylene production) have been identified and highlighted. A unique aspect of this review is the exploitations of reactions of CO2 –which stems from existing petrochemical plants-with the commodity petrochemicals (such as, methanol, ethylene and ethylene oxide) produced at the same or nearby complex in order to obtain value-added products while contributing also to CO2 fixation simultaneously. Exemplifying worldwide ethylene oxide facilities, it is recognized that they produce about 3 million tons of CO2 annually. Such a CO2 resource, which is already separated in pure form as a requirement of the process, should best be converted to a value-added chemical there avoiding current practice of discharging to the atmosphere. The potential utilization of CO2, captured at power plants, should also been taken into consideration for sustainability. This CO2 source, which is potentially a raw material for the chemical industry, will be available at sufficient quality and at gigantic quantity upon realization of on-going tangible capture projects. Products resulting from carboxylation reactions are obvious conversions. In addition, provided that enough supply of energy from non-fossil resources, such as solar [1], is ensured, CO2 reduction reactions can produce several valuable commodity chemicals including multi-carbon compounds, such as ethylene and acrylic acid, in addition to C1 chemicals and polymers. Presently, there are only few developing technologies which can find industrial applications. Therefore, there is a need for concerted research in order to assess the viability of these promising exploratory technologies rationally.

CO 2 utilization is gaining attention as a greenhouse gas abatement strategy complementary to CO 2 storage. This study explores the techno-environmental performance of CO 2 utilization trough dry reforming of methane into syngas for the production of dimethyl ether (DME). The CO 2 source is a hydrogen production unit at a refinery, where solvent based CO 2 capture is applied. Aspen+ modelling and hybrid life cycle assessment (LCA) is used to assess the techno-environmental performance of this utilization option compared to a reference case without CO 2 capture and a case with CO 2 capture and storage. Results of the technical assessment show that although 94% of the captured CO 2 can be utilised for DME production, only 9% of CO 2 is avoided in the entire process as a result of direct CO 2 formation during DME synthesis and the combustion of syngas to provide the heat demanded by the dry reforming process. Besides, a substantial amount of electricity is required for syngas compression. Consequently, the LCA results indicate that climate change potential (CCP) is reduced by 8% while it is 37% higher than CCP when CO 2 is stored and DME is produced conventionally. Sensitivity analyses are performed on various process conditions. Overall, this study indicates that this utilization route lowers the CCP although the reduction is limited compared to CCS. While the techno-environmental analysis is a useful tool to gain better insights in the performance of CO 2 utilization options, the complex environmental trade-offs make it difficult to draw robust conclusions on the performance.

A study on the mechanochemical activation of the olivine in presence of H2O and under CO2 atmosphere have been approached, focusing both on the structural nature of the transformation and the conversion of CO2 to methane and light hydrocarbons. The mechanochemical process was carried out by high energy laboratory mills, with milling vials properly modified in order to be used as batch reactors. Chemical reactivity and reaction rates were investigated under different experimental conditions, evidencing increased performance with respect to the thermally activated process reported in literature. Mechanical treatment induced H2O and olivine activation, with consequent release of molecular H2 which, in turn, allowed hydrogenation of activated CO2. This last reaction also led, through a competitive process, to the precipitation of carbonate phases, whose composition and structural features were dependent of the CO2/H2O ratio. Fil: Farina, Valeria. Università Degli Studi Di Sassari; Italia Fil: Gamba, Nadia Soledad. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina Fil: Gennari, Fabiana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Garroni, Sebastiano. Università Degli Studi Di Sassari; Italia Fil: Torre, Francesco. Università Degli Studi Di Cagliari; Italia Fil: Taras, Alessandro. Università Degli Studi Di Sassari; Italia Fil: Enzo, Stefano. Università Degli Studi Di Sassari; Italia Fil: Mulas, Gabriele. Università Degli Studi Di Sassari; Italia

The environmental impacts and high long-term costs of poor waste disposal have pushed the industry to realize the potential of turning this problem into an economic and sustainable initiative. Anaerobic digestion and the production of biogas can provide an efficient means of meeting several objectives concerning energy, environmental, and waste management policy. Biogas contains methane (60%) and carbon dioxide (40%) as its principal constituent. Excluding methane, other gasses contained in biogas are considered as contaminants. Removal of these impurities, especially carbon dioxide, will increase the biogas quality for further use. Integrating biological processes into the bio-refinery that effectively consume carbon dioxide will become increasingly important. Such process integration could significantly improve the sustainability of the overall bio-refinery process. The biogas upgrading by utilization of carbon dioxide rather than removal of it is a suitable strategy in this direction. The present work is a critical review that summarizes state-of-the-art technologies for biogas upgrading with particular attention to the emerging biological methanation processes. It also discusses the future perspectives for overcoming the challenges associated with upgradation. While biogas offers a good substitution for fossil fuels, it still not a perfect solution for global greenhouse gas emissions and further research still needs to be conducted.

Several international agreements, focused on regulating greenhouse gases emissions in the atmosphere, were created due to the growing concern about the climate change due to human action. The carbon dioxide (CO2) emissions account for more than 70% of the total greenhouse gases emissions; among the CO2 emitting sectors, electricity generation accounts for 25% of the global emissions. CO2 emissions from Brazilian power plants motivated their mapping, a method was proposed to performance a local market analysis for potential products from CO2 chemical conversion. The forecast behavior of this market for 2030 was also calculated. Among the studied products, methanol, polycarbonates, formic acid and acetaldehyde are the most promising for local manufacture. The States of Sao Paulo, Parana, Amazonas, Bahia, Rio Grande do Sul and Santa Catarina are the most promising regions in terms of potential of CO2 utilization.

[EN] In the context of energy conversion efficiency and decreasing greenhouse gas emissions from power generation and energy-intensive industries, membrane technologies for H-2 extraction and CO2 capture and utilization become pronouncedly important. Mixed protonic-electronic conducting ceramic membranes are hence attractive for the pre-combustion integrated gasification combined cycle, specifically in the water gas shift and H-2 separation process, and also for designing catalytic membrane reactors. This work presents the fabrication, microstructure and functional properties of Lanthanum tungstates (La28-xW4+xO54+delta, LaWO) asymmetric membranes supported on porous ceramic and porous metallic substrates fabricated by means of the sequential tape casting route and plasma spray-physical vapor deposition (PS-PVD). Pure LaWO and W site substituted LaWO were employed as membrane materials due to the promising combination of properties: appreciable mixed protonic-electronic conductivity at intermediate temperatures and reducing atmospheres, good sinterability and noticeable chemical stability under harsh operating conditions. As substrate materials porous LaWO (non-substituted), MgO and Crofer22APU stainless steel were used to support various LaWO membrane layers. The effect of fabrication parameters and material combinations on the assemblies' microstructure, LaWO phase formation and gas tightness of the functional layers was explored along with the related fabrication challenges for shaping LaWO layers with sufficient quality for further practical application. The two different fabrication strategies used in the present work allow for preparing all-ceramic and ceramic-metallic assemblies with LaWO membrane layers with thicknesses between 25 and 60 mu m and H-2 flux of ca. 0.4 ml/min cm(2) measured at 825 degrees C in 50 vol% H-2 in He dry feed and humid Ar sweep configuration. Such a performance is an exceptional achievement for the LaWO based H-2 separation membranes and it is well comparable with the H-2 flux reported for other newly developed dual phase cer-cer and cer-met membranes., ProtOMem Project under the BMBF grant 03SF0537 is gratefully acknowledged. Furthermore, the authors thank Ralf Laufs for his assistance in operating the PS-PVD facility. Dr. A. Schwedt from the Central Facility for Electron Microscopy (Gemeinschaftslabor fur Elektronenmikroskopie GFE), RWTH Aachen University is acknowledged for performing the EBSD analysis on the PS-PVD samples.

We investigated CO2 photocatalytic reduction coupling, for the first time in literature, the assets offered by the continuous operating mode using C3N4-TiO2 photo-catalyst embedded in a dense Nafion matrix. The reactor performance was analyzed under UV–vis light in terms of productivity, selectivity and converted carbon. Reaction pressure was specifically investigated for its effect as a “driver” in determining reactor performance, modulating products removal from the reaction volume. In addition, the membrane reactor performance was explored as a function of H2O/CO2 feed molar ratio and contact time. The higher feed pressure (5 bar) led to a lesser MeOH production and a greater amount of HCHO, owing to a hindered desorption, which promoted partial oxidation reactions. Total converted carbon instead did not vary significantly with reaction pressure. Membrane reactor with C3N4-TiO2 photocatalyst resulted more performant than other photocatalytic membrane reactors in terms of carbon converted (61 μmol gcatalyst−1 h−1).

This paper presents a model-based investigation to handle the fundamental issues for the design of co-electrolysis based power-to-methane at the levels of both the stack and system: the role of CO2 in co-electrolysis, the benefits of employing pressurized stack operation and the conditions of promoting internal methanation. Results show that the electrochemical reaction of co-electrolysis is dominated by H2O splitting while CO2 is converted via reverse water-gas shift reaction. Increasing CO2 feed fraction mainly enlarges the concentration and cathode-activation overpotentials. Internal methanation in the stack can be effectively promoted by pressurized operation under high reactant utilization with low current density and large stack cooling. For the operation of a single stack, methane fraction of dry gas at the cathode outlet can reach as high as 30 vol.% (at 30 bar and high flowrate of sweep gas), which is, unfortunately, not preferred for enhancing system efficiency due to the penalty from the pressurization of sweep gas. The number drops down to 15 vol.% (at 15 bar) to achieve the highest system efficiency (at 0.27 A/cm2). The internal methanation can serve as an effective internal heat source to maintain stack temperature (thus enhancing electrochemistry), particularly at a small current density. This enables the co-electrolysis based power-to-methane to achieve higher efficiency than the steam-electrolysis based (90% vs 86% on higher heating value, or 83% vs 79% on lower heating value without heat and converter losses).

The development of highly conductive structured catalysts with enhanced mass- and heat-transfer features is required for the intensification of the strongly exothermic catalytic hydrogenation of CO2 in which large temperature gradients should be avoided to prevent catalyst deactivation and to control selectivity. Therefore, in this work we set out to investigate the preparation of novel structured catalysts obtained from a commercial open cell Ni foam with high pore density (75 ppi) onto which a CeO2 layer was deposited via electroprecipitation, and, eventually, Ru was added by impregnation. Composite Ru/Ce/Ni foam catalysts, as well as simpler binary Ru/Ni and Ce/Ni catalysts were characterized by SEM-EDX, XRD, cyclic voltammetry, N2 physisorption, H2-temperature programmed reduction (TPR), and their CO2 methanation activity was assessed at atmospheric pressure in a fixed bed flow reactor via temperature programmed tests in the range from 200 to 450 °C. Thin porous CeO2 layers, uniformly deposited on the struts of the Ni foams, produced active catalytic sites for the hydrogenation of CO2 at the interface between the metal and the oxide. The methanation activity was further boosted by the dispersion of Ru within the pores of the CeO2 layer, whereas the direct deposition of Ru on Ni, by either impregnation or pulsed electrodeposition methods, was much less effective.

Molten carbonate electrolyzers offer a pathway to capture emitted CO 2 from the flue gas of the power plants and transform this greenhouse gas emission at low energy and high yield instead into a specific, value added, hollow carbon nanofiber product, carbon nanotubes. The present day value of the carbon nanotubes product is ∼10,000 that of proposed, or in place, current carbon tax costs of $30 per ton, strongly incentivizing carbon dioxide removal. The recent progress in high-temperature molten carbonate electrolysis systems for carbon dioxide utilization and the impact these advances have on developing a CO 2 -free fossil fuel power plant for electricity generation is presented. A thermodynamic model analysis is presented for a molten Li 2 CO 3 electrolysis system incorporated within a combined cycle (CC) natural gas power plant to produce carbon nanofibers (CNF) and oxygen. Such a CC CNF plant system is shown to require 219 kJ to convert one mole of CO 2 to carbon, and generates electricity at higher efficiency due to pure oxygen looped back to the gas turbine input from the CO 2 splitting, with the added advantages that (i) the CC CNF plant emits no CO 2 and (ii) all CO 2 is converted to value added carbon nanotubes useful for strong, lightweight construction, batteries and nanoelectronics. Converting to power and ton units, per metric ton of methane fuel consumed the CC CNF plant is thermodynamically assessed to produce 8350 kW h of electricity and 0.75 ton of CNT and emits no CO 2 , while the CC plant produces 9090 kW h of electricity and emits 2.74 ton CO 2 . The required energy balance for a carbon nanotube production from an analogous coal power plant consumes a larger fraction of the coal energy, and encourages co-generation with renewable electric energy.

CO 2 can be converted to useful fuels by electrochemistry method. As an effective strategy to address greenhouse effect and energy storage shortage, electrochemical reduction of CO 2 still needs major improvements on its efficiency and reactivity. This work demonstrates a switchable pH-differential dual electrolyte microfluidic reactor (DEMR) that enhances the thermodynamic property and raises the electrochemical performance based on a laminar flow membrane-less architecture. It is the first time that the CO 2 electrochemical reduction reaction is freed from the hindrances of thermodynamic limitation. DEMR has also achieved a high reactivity and Faradaic efficiency, revealing the potential for larger-scale applications in future urban energy network, such as a carbon-neutral energy conversion system.