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With the rising levels of atmospheric CO2, electrochemistry shows great promise in decarbonizing industrial processes by converting CO2 into valuable products through scalable and sustainable technologies. In this framework, the present study investigates the solar-driven CO2 reduction toward carbon monoxide, achieved by the integration between the electrochemical reactor and dye-sensitized solar cells (DSSCs), both in experimental and modeling perspectives. COMSOL® Multiphysics 6.3 was used to develop a detailed finite element method model of the electrochemical cell integrated with a photovoltaic module, validated with the experimental results that demonstrated a strong correlation. A 2D model was designed, incorporating cathode and anode regions divided by an ion-exchange membrane. The model includes platinum foil and silver nanoparticles as catalysts for the oxygen evolution reaction and CO2 reduction reaction, respectively. Integration with the fundamental equations of the DSSCs was simulated to analyze the solar-driven CO2 reduction behavior under solar irradiance variations, offering a valuable tool for optimizing operating conditions and predicting the device performance under different environmental conditions. The integrated device successfully produces CO with a faradaic efficiency of 73.85% at a current density of J = 3.35 mA/cm2 under 1 sun illumination, with the result validated and reproduced by the mathematical model. Under reduced illumination conditions of 0.8 and 0.6 suns, faradaic efficiencies of 68.5% and 64.1% were achieved, respectively. [ABSTRACT FROM AUTHOR]

Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO2 over the last decade, the search for a robust and cost‐effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO2 with high efficiency and low cost. Two polystyrene‐based anion exchange resins, AmberlystTM A26‐Cl (A26‐Cl) and AmberliteTM IRA‐400‐Cl (IRA400‐Cl), were compared. The results demonstrated the catalysts' remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco‐friendly method for cyclic carbonate production using waste CO2. A Design of Experiment (DoE) approach was implemented to optimize the catalytic cycloaddition of CO2. The reaction scale‐up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost‐effective, scalable method for converting CO2 into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates. [ABSTRACT FROM AUTHOR]

Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO2 over the last decade, the search for a robust and cost‐effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO2 with high efficiency and low cost. Two polystyrene‐based anion exchange resins, AmberlystTM A26‐Cl (A26‐Cl) and AmberliteTM IRA‐400‐Cl (IRA400‐Cl), were compared. The results demonstrated the catalysts' remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco‐friendly method for cyclic carbonate production using waste CO2. A Design of Experiment (DoE) approach was implemented to optimize the catalytic cycloaddition of CO2. The reaction scale‐up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost‐effective, scalable method for converting CO2 into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates. [ABSTRACT FROM AUTHOR]

Cyclic organic carbonates are defined as key compounds for a sustainable chemical economy. Their synthesis from CO2 under mild conditions is a useful way to valorise this greenhouse gas as carbon source. Even if a wide range of catalysts were described to promote the carbon dioxide cycloaddition into epoxides, only few ones concern enzymatic systems. The zinc–l‐histidine active site of carbonic anhydrase inspired the present work, pointing out that the imidazole moiety of the amino acid ligand has a crucial role. An extensive study was undertaken to establish the structure–activity relationship of imidazole derivatives, zinc salts, and their respective catalytic activity in the CO2 cycloaddition reaction. The effect of aromatic, alkyl, or iodine substituents and their position in N‐heterocycles were highlighted. A synergic effect was noted when combining imidazole compounds with zinc salts. The optimization of reaction conditions emphasised the in situ ZnI2–1‐methylimidazole catalytic system, which is selective toward cyclic styrene carbonates and efficient under solvent‐free mild conditions (50 °C, atmospheric CO2 pressure). Once reusing tests confirmed the catalytic system robustness, the reaction scope was enlarged to several epoxides resulting in 84%–99% yields of their corresponding cyclic carbonates. [ABSTRACT FROM AUTHOR]

This study introduces a metal-free binary catalytic system for coupling CO2 with cyclohexane oxide (CHO) under mild conditions, allowing for tunable product selectivity. Using trans-cyclohexane diol (trans-CHD) and phosphazene superbase (P4) as catalysts, the system selectively produces cyclic carbonates and oligocarbonates at 1 bar CO2 pressure and 80 °C. By adjusting the catalyst ratio, varying proportions of cis-cyclohexane carbonate (cis-CHC), trans-cyclohexane carbonate (trans-CHC), and oligocarbonate are achieved, with 51 mol% CHO conversion and respective selectivities of 36%, 31%, and 33%. The catalytic efficiency and precise control of product outcomes underscore this system's potential. [ABSTRACT FROM AUTHOR]

The deep eutectic solvent (DES) has emerged in recent years as a valuable medium for converting CO2 into valuable chemicals because of its easy availability, stability, and safety, and its capability to dissolve carbon dioxide. CO2 valorization in DES has evolved rapidly over the past 20 years. As well as being used as solvents for acid/base‐promoted CO2 conversion for the production of cyclic carbonates and carbamates, DESs can be used as reaction media for electrochemical CO2 reduction for formic acid and CO. Among these products, cyclic carbonates can be used as solvents and electrolytes, carbamate derivatives include the core structure of many herbicides and pesticides, and formic acid and carbon monoxide, the C1 electrochemical products, are essential raw materials in the chemical industries. An overview of the application of DESs for CO2 valorization in recent years is presented in this review, followed by a compilation and comparison of product types and reaction mechanisms within the different types of DESs, and an outlook on how CO2 valorization will be developed in the future. [ABSTRACT FROM AUTHOR]

The thermodynamically and kinetically sluggish electrocatalytic C−N coupling from CO2 and NO3− is inert to initially take place while typically occurring after CO2 protonation, which severely dwindles urea efficiency and carbon atom economy. Herein, we report a single O‐philic adsorption strategy to facilitate initial C−N coupling of *OCO and subsequent protonation over dual‐metal hetero‐single‐atoms in N2−Fe−(N−B)2−Cu−N2 coordination mode (FeN4/B2CuN2@NC), which greatly inhibits the formation of C‐containing byproducts and facilitates urea electrosynthesis in an unprecedented C‐selectivity of 97.1 % with urea yield of 2072.5 μg h−1 mgcat.−1 and 71.9 % Faradaic efficiency, outperforming state‐of‐the‐art electrodes. The carbon‐directed antibonding interaction with Cu−B is elaborated to benefit single O‐philic adsorption of CO2 rather than conventional C‐end or bridging O,O‐end adsorption modes, which can accelerate the kinetics of initiated C−N coupling and protonation. Theoretical results indicate that the O‐monodentate adsorption pathway benefits the thermodynamics of the C−N coupling of *OCO with *NO2 and the protonation rate‐determining step, which markedly inhibits CO2 direct protonation. This oriented strategy of manipulating reactant adsorption patterns to initiate a specific step is universal to moderate oxophilic transition metals and offers a kinetic‐enhanced path for multiple conversion processes. [ABSTRACT FROM AUTHOR]

The construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long‐standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO2‐to‐CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso‐tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br2] (2,2′‐bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non‐sacrificial electrodes. The reaction can be directly scaled up to gram‐scale and operates effectively at a CO2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO2 reduction is key in the formation of the [Ni(bpy)(CO)2], which is proposed as the catalytic intermediate responsible for the C−C bond formation in the carbonylation steps. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen vacancy and isolated Ti3+ embed into interface of a Z-scheme heterojunction. • Calcination precisely regulated oxygen vacancy and isolated Ti3+ in the interface. • The interface showed superior photocatalytic CO 2 reduction activity to reported ones. • The interfacial modification greatly promoted CO 2 activation and reduction activity. Exploring the real force that drives the separation of Coulomb-bound electron-hole pairs in the interface of heterojunction photocatalysts can establish a clear mechanism for efficient solar energy conversion efficiency. Herein, the formation of oxygen vacancy (Ov) and isolated Ti3+ was precisely regulated at the interface of g-C 3 N 4 /TiO 2 Z-scheme heterojunction (g-C 3 N 4 /Ov-Ti3+-TiO 2) by optimizing the opening degree of the calcination system, showing excellent production rate of CO and CH 4 from CO 2 photoreduction under visible light. This photocatalytic system also exhibited prominent stability. Combining theoretical calculation and characterization, the introduction of Ov and isolated Ti3+ on the interface could construct a charge transfer channel to break the forbidden transition of n → π*, improving the separation process of photoexcited electron-hole pairs. The photoexcited electrons weakened the covalent interaction of C O bonds to promote the activation of adsorbed inert CO 2 molecules, significantly reducing the energy barrier of the rate-limiting step during CO 2 reduction. This work demonstrates the great application potential of reasonably regulating heterojunction interface for efficient photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

The rising amount of greenhouse gases has been contributing to global warming and, subsequently, climate change. Industries such as refineries and power plants emit a significant amount of CO2 into the atmosphere. It is imperative to curb anthropogenic CO2 emissions, and hence, in this effort, we explore the utilization of a refinery emission stream to produce value‐added chemicals. The chosen emission stream for the said purpose is a typical flue gas stream from refineries. Following the capture step, this CO2 stream has been leveraged for subsequent valorization processes. Two strategies have been proposed in this paper to valorize the captured carbon dioxide. The first strategy employs the tri‐reforming process with a refinery‐specific fuel gas stream as the co‐reactant. The resulting syngas from tri‐reforming has been converted to chemicals such as methanol (MET) and ethanol. Furthermore, to improve the amount of CO2 valorized, another approach with green hydrogen has been considered. The second strategy aims at direct hydrogenation of the captured CO2 stream to produce MET and ethanol. The proposed strategies analyze the feasibility of valorizing captured CO2 from flue gas to MET and ethanol in terms of gross margin per feed and percentage of CO2 valorization. The performance assessment and analysis of the proposed processes have been carried out using simulations in Aspen Plus® that exhibited up to 74% valorization of CO2 into valuable chemicals. [ABSTRACT FROM AUTHOR]

The properties of amorphous calcium carbonate (ACC) and its transformations to crystalline polymorphs are frequently studied in aqueous systems and in small quantities. In this study, synthetic calcium carbonate stones are created from bulk ACC and crystalline polymorphs, which were precipitated from gaseous CO2, at a gradient of end pH. Some of the ACCs hardened into stones which are durable against an abrasion and impact test, while some of the ACCs create fragile, friable stones. When ACCs which transform to durable stones and those which transform into fragile stones were subject to calorimetry, significant differences were observed. These stones, synthesized from gaseous CO2, can be used as a storage reservoir for utilized CO2 in construction and other infrastructure applications. [ABSTRACT FROM AUTHOR]

Research has focused on the threat of global warming-induced climate change to modern human civilization. Carbon dioxide (CO2) is a primary greenhouse gas that causes global warming. Current efforts have focused on using CO2 as a raw source for producing value-added chemicals. Among the different CO2 conversion processes, the Sabatier process, also known as "CO2 methanation," is an effective approach, particularly if H2 is generated by renewable energy sources. In this process, methane (CH4) and water (H2O) are produced from CO2 and H2 using different transition-metal-based catalysts. Although numerous studies have been conducted to assess the significance of CO2 methanation, quantitative analysis of the publication trends in this research field is still lacking. This review presents the global research landscape of CO2 methanation over the last 20 years (2000–2022). The Web of Science (WoS) database was used to extract 1657 publications, and the VOSviewer software was used for bibliometric investigations. Bibliometric analysis revealed that 77.53% of the papers were published within the past 5 years (2018–2022). The International journal of hydrogen energy is leading journal publishing research articles about CO2 methanation followed by Applied Catalysis B. This study conducted a statistical analysis on the influence of leading countries, institutions, journals, authors, and top keywords in the field of CO2 methanation. Additionally, future research directions and findings of the most cited publications are discussed. Because the CO2 methanation reaction requires a highly stable and active catalyst, a brief introduction and major challenges of these catalysts are also reviewed. We hope that bibliometric findings will help scholars to understand this field of research more effectively and comprehensively. [ABSTRACT FROM AUTHOR]

In this study, the effect of the cell density of monolithic catalysts was investigated and further mathematically modeled on cordierite supports used in CO2 methanation. Commercial cordierite monoliths with 200, 400, and 500 cpsi cell densities were coated by immersion into an ethanolic suspension of Ni/CeO2 active phase. SEM–EDS analysis confirmed that, owing to the low porosity of cordierite (surface area < 1 m2 g−1), the Ni/CeO2 diffusion into the walls was limited, especially in the case of low and intermediate cell density monoliths; thus, active phase was predominantly loaded onto the channels' external surface. Nevertheless, despite the larger exposed surface area in the monolith with high cell density, which would allow for better distribution and accessibility of Ni/CeO2, its higher macro-pore volume resulted in some introduction of the active phase into the walls. As a result, the catalytic evaluation showed that it was more influenced by increments in volumetric flow rates. The low cell density monolith displayed diffusional control at flow rates below 500 mL min−1. In contrast, intermediate and high cell density monoliths presented this behavior up to 300 mL min−1. These findings suggest that the interaction reactants-catalyst is considerably more affected by a forced non-uniform flow when increasing the injection rate. This condition reduced the transport of reactants and products within the catalyst channels and, in turn, increased the minimum temperature required for the reaction. Moreover, a slight diminution of selectivity to CH4 was observed and ascribed to the possible formation of hot spots that activate the reverse water–gas shift reaction. Finally, a mathematical model based on fundamental momentum and mass transfer equations coupled with the kinetics of CO2 methanation was successfully derived and solved to analyze the fluid dynamics of the monolithic support. The results showed a radial profile with maximum fluid velocity located at the center of the channel. A reactive zone close to the inlet was obtained, and maximum methane production (4.5 mol m−3) throughout the monolith was attained at 350 °C. Then, linear streamlines of the chemical species were developed along the channel. [ABSTRACT FROM AUTHOR]

Purpose: Herein, we examined C. necator for its production of bioplastic under mixotrophic fermentation. The mixotrophic process utilized dual carbon sources of mixed CO2 and glucose for the production of PHB. Methods: C. necator was optimized through adaptive laboratory evolution under a mixed carbon sources of CO2 and glucose. The isolated mutant was then studied for its ability to co-utilize glucose and CO2 carbon sources for growth and for PHB production. Experimental design based on central composition design was implemented to optimize PHB production under mixotrophic fermentation. Parameters effecting PHB accumulation including CO2 and glucose substrate ratio, cell dosage and aeration were studied. Results: Under optimized mixotrophic batch process, 0.22 g/L of PHB and 28% PHB content was reached from mixed carbon sources. Further CO2 and glucose co-feeding strategy optimization in mixotrophic fed-batch, PHB titer was elevated to 0.41 g/L. Conclusion: Overall, this study offered a promising alternative for CO2 valorization through the mixotrophic conversion of CO2 and glucose to PHB by C. necator, which could provide basis in future Bio-CCU technology development for climate change mitigation. [ABSTRACT FROM AUTHOR]

CuOx/LaCoO3 systems have been studied for the rWGS reaction under thermal assisted photocatalytic conditions within low temperature range of 180–330 ºC. CuOx species deposited from chemical reduction method over LaCoO3 homogeneously covered the perovskite surface. The reduction pretreatment before reaction leads to the partial Co reduction and the complete reduction of Cu. A significant improvement on CO production has been attained upon Cu incorporation. In addition, upon UV–vis irradiation the CO production is also enhanced. Best results have been obtained for 5 wt% Cu. The highest synergistic effect was observed for the lowest temperature, for which catalytic contribution is negligible. Thus, a good compromise is attained at 300 ºC for which a CO production of 5.45 mmol/h·g and 92 % selectivity, showing a good synergistic effect between thermo and thermo-photocatalytic activity.

Abstract Background Industrial biomanufacturing of value-added products using CO2 as a carbon source is considered more sustainable, cost-effective and resource-efficient than using common carbohydrate feedstocks. Cupriavidus necator H16 is a representative H2-oxidizing lithoautotrophic bacterium that can be utilized to valorize CO2 into valuable chemicals and has recently gained much attention as a promising platform host for versatile C1-based biomanufacturing. Since this microbial platform is genetically tractable and has a high-flux carbon storage pathway, it has been engineered to produce a variety of valuable compounds from renewable carbon sources. In this study, the bacterium was engineered to produce resveratrol autotrophically using an artificial phenylpropanoid pathway. Results The heterologous genes involved in the resveratrol biosynthetic pathway—tyrosine ammonia lyase (TAL), 4-coumaroyl CoA ligase (4CL), and stilbene synthase (STS) —were implemented in C. necator H16. The overexpression of acetyl-CoA carboxylase (ACC), disruption of the PHB synthetic pathway, and an increase in the copy number of STS genes enhanced resveratrol production. In particular, the increased copies of Vv STS derived from Vitis vinifera resulted a 2-fold improvement in resveratrol synthesis from fructose. The final engineered CR-5 strain produced 1.9 mg/L of resveratrol from CO2 and tyrosine via lithoautotrophic fermentation. Conclusions To the best of our knowledge, this study is the first to describe the valorization of CO2 into polyphenolic compounds by engineering a phenylpropanoid pathway using the lithoautotrophic bacterium C. necator H16, demonstrating the potential of this strain a platform for sustainable chemical production.

With the rising levels of atmospheric CO2, electrochemistry shows great promise in decarbonizing industrial processes by converting CO2 into valuable products through scalable and sustainable technologies. In this framework, the present study investigates the solar-driven CO2 reduction toward carbon monoxide, achieved by the integration between the electrochemical reactor and dye-sensitized solar cells (DSSCs), both in experimental and modeling perspectives. COMSOL® Multiphysics 6.3 was used to develop a detailed finite element method model of the electrochemical cell integrated with a photovoltaic module, validated with the experimental results that demonstrated a strong correlation. A 2D model was designed, incorporating cathode and anode regions divided by an ion-exchange membrane. The model includes platinum foil and silver nanoparticles as catalysts for the oxygen evolution reaction and CO2 reduction reaction, respectively. Integration with the fundamental equations of the DSSCs was simulated to analyze the solar-driven CO2 reduction behavior under solar irradiance variations, offering a valuable tool for optimizing operating conditions and predicting the device performance under different environmental conditions. The integrated device successfully produces CO with a faradaic efficiency of 73.85% at a current density of J = 3.35 mA/cm2 under 1 sun illumination, with the result validated and reproduced by the mathematical model. Under reduced illumination conditions of 0.8 and 0.6 suns, faradaic efficiencies of 68.5% and 64.1% were achieved, respectively.

Background: Industrial biomanufacturing of value-added products using CO2 as a carbon source is considered more sustainable, cost-effective and resource-efficient than using common carbohydrate feedstocks. Cupriavidus necator H16 is a representative H2-oxidizing lithoautotrophic bacterium that can be utilized to valorize CO2 into valuable chemicals and has recently gained much attention as a promising platform host for versatile C1-based biomanufacturing. Since this microbial platform is genetically tractable and has a high-flux carbon storage pathway, it has been engineered to produce a variety of valuable compounds from renewable carbon sources. In this study, the bacterium was engineered to produce resveratrol autotrophically using an artificial phenylpropanoid pathway. Results: The heterologous genes involved in the resveratrol biosynthetic pathway—tyrosine ammonia lyase (TAL), 4-coumaroyl CoA ligase (4CL), and stilbene synthase (STS) —were implemented in C. necator H16. The overexpression of acetyl-CoA carboxylase (ACC), disruption of the PHB synthetic pathway, and an increase in the copy number of STS genes enhanced resveratrol production. In particular, the increased copies of VvSTS derived from Vitis vinifera resulted a 2-fold improvement in resveratrol synthesis from fructose. The final engineered CR-5 strain produced 1.9 mg/L of resveratrol from CO2 and tyrosine via lithoautotrophic fermentation. Conclusions: To the best of our knowledge, this study is the first to describe the valorization of CO2 into polyphenolic compounds by engineering a phenylpropanoid pathway using the lithoautotrophic bacterium C. necator H16, demonstrating the potential of this strain a platform for sustainable chemical production. [ABSTRACT FROM AUTHOR]

Composite materials have been widely used because of their superior properties compared to those of the original material. Separation of the constituent materials is not easy in the recycling process, and such an effort lowers economic viability. As such, this study employed a pyrolysis as a valorizing method for the composite material. Disposable paper cup waste (DPCW) was chosen as the model compound for paper-plastic composites. To offer green/sustainable features, CO2 was employed as a raw and reactive material in the pyrolysis process. It was proved that DPCW primarily composed of cellulose (outer layer) and polyethylene (inner layer). In the single-stage and multistage pyrolysis of DPCW, the CO2 reactivity in the homogeneous reaction of CO2 and DPCW-derived volatiles was not rapid. To accelerate the reaction kinetics governing the reactivity of CO2, the catalytic pyrolysis of DPCW over Ni/SiO2 was performed. The formation of syngas increases significantly, suggesting that CO2 reactivity was catalytically enhanced. The generation of syngas (enhanced by CO2) was inversely related to the DPCW oil generation, indicating that more carbon was assigned from the oil to the gaseous pyrogenic products. The study results would offer a strategic means to valorize paper-plastic composites and CO2 into energy through pyrolysis. [ABSTRACT FROM AUTHOR]

Zinc(II) Schiff base complexes with different substituents at 5, 5' positions have been synthesized to study the effect of the electronic environment of the metal towards the cycloaddition reaction between CO2 and epoxide. The complexes have been characterized by FT‐IR, XPS, NMR, electronic spectroscopy, LC–MS, and TGA. We have used density functional theory to study the electronic structure of the Zn(II) complexes and modelled the electronic spectra and the mechanism of catalysis. Results obtained from DFT and LC–MS indicate the dimeric structures for all the complexes except ZnL4. The monomeric ZnL4 has the strongest electron withdrawing group, i. e. −NO2 at 5, 5' positions along with two labile water molecules attached to the Zn center. The dimeric complexes exhibit good to moderate yield for cycloaddition reaction to styrene carbonate under solvent‐free conditions and a relatively low reaction temperature of 80 °C, with CO2 pressure of ~1 atm. The best yield has been achieved by ZnL4. Different rate‐determining steps are captured by the DFT studies for dimeric and monomeric complexes. Without taking any preventing measure of dimerization by attaching the bulky tBu groups, relatively lesser catalytic amounts of all the complexes have shown yields of cyclic carbonate between 53–74 %, depending on the nature of the substituent present. [ABSTRACT FROM AUTHOR]

This paper deals with the proposition of a kinetic model for the direct synthesis of DME via CO2 hydrogenation in view of the necessary optimization of the catalytic system, reactor design, and process strategy. Despite the fact that DME synthesis is typically treated as a mere combination of two separated catalytic steps (i.e., methanol synthesis and methanol dehydration), the model analysis is now proposed by taking into account the improvements related to the process running over a hybrid catalyst in a rational integration of the two catalytic steps, with boundary conditions properly assumed from the thermodynamics of direct DME synthesis. Specifically, the CO2 activation step at the metal–oxide interface in the presence of ZrO2 has been described for the first time through the introduction of an ad hoc mechanism based on solid assumptions from inherent studies in the literature. The kinetic modeling was investigated in a tubular fixed-bed reactor operating from 200 to 260 °C between 1 and 50 bar as a function of a gas hourly space velocity ranging from 2500 to 60,000 NL/kgcat/h, in a stoichiometric CO2/H2 feed mixture of 1:3 v/v. A well-detailed elementary mechanism was used to predict the CO2 conversion rate and identify the key reaction pathways, starting with the analysis of the implicated reactions and corresponding kinetic mechanisms and expressions, and finally estimating the main parameters based on an appropriate modeling of test conditions. [ABSTRACT FROM AUTHOR]

Using carbon dioxide as a feedstock for synthesizing organic molecules with added value can contribute to a more sustainable chemical industry since CO2 is an abundant, inexpensive, and nontoxic renewable carbon resource. In this regard, the synthesis of cyclic carbonates and related organic compounds from CO2 as building blocks has been widely studied, and less attention has been paid to their stereocontrolled process. Therefore, this review focuses on the recent development of enantioselective catalysts for the CO2-mediated formation of chiral organic carbonates. [ABSTRACT FROM AUTHOR]

The combined steam-dry reforming (CSDR) of raw bio-oil with NiAl2O4 spinel derived catalyst was studied to establish suitable conditions to combine the objectives of CO2 valorization and sustainable production of syngas with suitable H2/CO ratio for the synthesis of chemicals and fuels. The reactions were carried out in an equipment with two units, for controlled pyrolytic lignin deposition and reforming of the remaining oxygenates in an in-line fluidized bed reactor. The CSDR conditions were: 600–800 ºC; CO2/C molar ratio, 0–1.1; steam/carbon (S/C) molar ratio, 0.5–1.7; space time, 0.125 and 0.250 gcatalyst·h/goxygenates, and time on stream, 6 h. The CO2 conversion is positive in a wide range of operating conditions, and there is always a reduction of CO2 emissions compared to the SR process, even under conditions of CO2 formation. 800 ºC, CO2/C ratio of 1.1, S/C of 1.7 and space-time of 0.250 gcatalyst·h/goxygenates allow attaining near 80% oxygenate conversion, 7% CO2 conversion and 90% syngas yield with H2/CO ratio of 1.6. Lowering the S/C ratio to 0.5 noticeably increases the CO2 conversion (> 23%), but reduces the H2/CO ratio of the syngas produced (< 1). The amount, nature and location of coke were characterized with different techniques (XRD, TPO, N2 adsorption-desorption and SEM), being the amorphous coke derived from oxygenates cracking the main responsible of deactivation. Catalyst stability improves along with temperature and space time, slightly with the CO2/C ratio, but with low effect of S/C ratio.

The CO2‐to‐aromatics process is a chemical reaction that converts carbon dioxide (CO2) into valuable petrochemical, i. e., aromatics (especially, benzene, toluene, and xylene) over the metal/zeolite bifunctional catalytic systems. These aromatics are used in producing plastics, fibers, and other industrial products, which are currently exclusively sourced from fossil‐derived feedstocks. The significance of this process lies in its potential to mitigate climate change by reducing greenhouse gas emissions and simultaneously producing valuable chemicals. Consequently, these CO2‐derived aromatics can reduce the reliance on fossil fuels as a source of feedstocks, which can help to promote a more sustainable and circular economy. Owing to the existence of a wider straight channel favoring the aromatization process, zeolite ZSM‐5 is extensively used to yield aromatics during CO2 hydrogenation over bifunctional (metal/zeolite) catalytic systems. To provide a better understanding of this unique property of zeolite ZSM‐5, this work investigates the impact of particle size and hierarchy of the zeolite and how these govern the reaction performance and the overall selectivity. As a result, an improved understanding of the zeolite‐catalyzed hydrocarbon conversion process has been obtained. [ABSTRACT FROM AUTHOR]

Gas-fed reactors for CO2 reduction processes are a solid technology to mitigate CO2 accumulation in the atmosphere. However, since it is necessary to feed them with a pure CO2 stream, a highly energy-demanding process is required to separate CO2 from the flue gasses. Recently introduced bicarbonate zero-gap flow reactors are a valid solution to integrate carbon capture and valorization, with them being able to convert the CO2 capture medium (i.e., the bicarbonate solution) into added-value chemicals, such as CO, thus avoiding this expensive separation process. We report here a study on the influence of the electrode structure on the performance of a bicarbonate reactor in terms of Faradaic efficiency, activity, and CO2 utilization. In particular, the effect of catalyst mass loading and electrode permeability on bicarbonate electrolysis was investigated by exploiting three commercial carbon supports, and the results obtained were deepened via electrochemical impedance spectroscopy, which is introduced for the first time in the field of bicarbonate electrolyzers. As an outcome of the study, a novel low-loaded silver-based electrode fabricated via the sputtering deposition technique is proposed. The silver mass loading was optimized by increasing it from 116 μg/cm2 to 565 μg/cm2, thereby obtaining an important enhancement in selectivity (from 55% to 77%) and activity, while a further rise to 1.13 mg/cm2 did not provide significant improvements. The tremendous effect of the electrode permeability on activity and proficiency in releasing CO2 from the bicarbonate solution was shown. Hence, an increase in electrode permeability doubled the activity and boosted the production of in situ CO2 by 40%. The optimized Ag-electrode provided Faradaic efficiencies for CO close to 80% at a cell voltage of 3 V and under ambient conditions, with silver loading of 565 μg/cm2, the lowest value ever reported in the literature so far. [ABSTRACT FROM AUTHOR]

New hypotheses for reusing platforms reaching their end-of-life have been investigated in several works, discussing the potential conversions of these infrastructures from recreational tourism to fish farming. In this perspective paper, we discuss the conversion options that could be of interest in the context of the current energy transition, with reference to the off-shore Italian scenario. The study was developed in support of the development of a national strategy aimed at favoring a circular economy and the reuse of existing infrastructure for the implementation of the energy transition. Thus, the investigated options include the onboard production of renewable energy, hydrogen production from seawater through electrolyzers, CO2 capture and valorization, and platform reuse for underground fluid storage in depleted reservoirs once produced through platforms. Case histories are developed with reference to a typical, fictitious platform in the Adriatic Sea, Italy, to provide an engineering-based approach to these different conversion options. The coupling of the platform with the underground storage to set the optimal operational conditions is managed through the forecast of the reservoir performance, with advanced numerical models able to simulate the complexity of the phenomena occurring in the presence of coupled hydrodynamic, geomechanical, geochemical, thermal, and biological processes. The results of our study are very encouraging, because they reveal that no technical, environmental, or safety issues prevent the conversion of offshore platforms into valuable infrastructure, contributing to achieving the energy transition targets, as long as the selection of the conversion option to deploy is designed taking into account the system specificity and including the depleted reservoir to which it is connected when relevant. Socio-economic issues were not investigated, as they were out of the scope of the project. [ABSTRACT FROM AUTHOR]

Gas fermentation is an upcoming technology to convert gaseous substrates into value-added products using autotrophic microorganisms. The hydrogen-oxidizing bacteria Cupriavidus necator efficiently uses CO2 as its sole carbon source, H2 as electron donor and O2 as electron acceptor. Surplus CO2 is stored in microbial storage material poly-(R)-3-hydroxybutyrate. O2 supply is the most critical parameter for growth and poly-(R)-3-hydroxybutyrate formation. A narrow O2 optimum between ~0.2 and ~4 mg/L was previously reported. Here, a standard benchtop bioreactor was redesigned for autotrophic growth of C. necator on explosive mixtures of CO2, H2 and O2. The bioreactor was equipped with mass flow control units and O2 and CO2 sensors. A controller for automated gas dosage based on a mathematical model including gas mass transfer, gas consumption and sensor response time was developed. Dissolved O2 concentrations were adjusted with high precision to 1, 2 and 4% O2 saturation (0.4, 0.8 and 1.5 mg/L dissolved O2, respectively). In total, up to 15 g/L cell dry weight were produced. Residual biomass formation was 3.6 ± 0.2 g/L under all three O2 concentrations. However, poly-(R)-3-hydroxybutyrate content was 71, 77 and 58% of the cell dry weight with 1, 2 and 4% dissolved O2, respectively. [ABSTRACT FROM AUTHOR]

N‐doped carbon materials can be efficient and cost‐effective catalysts for the electrochemical CO2 reduction reaction (CO2RR). Activators are often used in the synthesis process to increase the specific surface area and porosity of these carbon materials. However, owing to the diversity of activators and the differences in physicochemical properties that these activators induce, the influence of activators used for the synthesis of N‐doped carbon catalysts on their electrochemical performance is unclear. In this study, a series of bagasse‐derived N‐doped carbon catalysts is prepared with the assistance of different activators to understand the correlation between activators, physicochemical properties, and electrocatalytic performance for the CO2RR. The properties of N‐doped carbon catalysts, such as N‐doping content, microstructure, and degree of graphitization, are found to be highly dependent on the type of activator applied in the synthesis procedure. Moreover, the overall CO2RR performance of the synthesized electrocatalysts is not determined only by the N‐doping level and the configuration of the N‐dopant, but rather by the overall surface chemistry, where the porosity and the degree of graphitization are jointly responsible for significant differences in CO2RR performance. [ABSTRACT FROM AUTHOR]

The United States National Aeronautics and Space Administration's (NASA's) mandate is a human mission to Mars in the 2030s and sustained exploration of Mars requires in situ resource utilization (ISRU). Exploiting the Martian water cycle (alongside perchlorate salts that depress water's freezing point to <213 K) and the available 95 vol.% atmospheric CO2, we detail an ultra‐low temperature (255 K) CO2–H2O electrolyzer to produce methane fuel and life‐supporting oxygen on Mars. Our polarization model fit experimental Martian brine electrolyzer performance and predicted CO2 electrolysis occurring at comparatively lower potentials (vs. water electrolysis) on Mars. A hypothetical 10‐cell, 100 cm2 electrode‐area‐per‐cell electrolyzer produced 0.45 g W−1 day−1 of CH4 and 3.55 g W−1 day−1 of O2 at 2 V/cell and 50% electrolyzer faradaic efficiency versus a best‐case production of 2.5 g W−1 day−1 of O2 by the Mars Oxygen in situ Resource Utilization Experiment (MOXIE) from NASA's Mars 2020 mission (MOXIE produces no fuel). Material performance requirements are presented to advance this technology as an energy‐efficient complement to MOXIE. [ABSTRACT FROM AUTHOR]

The application of solar energy to convert CO2 into high‐value chemicals and fuels has been considered a highly desirable approach to relieving the greenhouse effect and energy crisis. However, the exploration of appropriate photocatalysts remains a major challenge. Combining the respective advantages of covalent organic frameworks and metal−organic frameworks to construct covalent metal−organic frameworks (CMOFs) can be a valid strategy to provide efficient, reliable, and eco‐friendly photocatalysts. In this study, a CuI cluster‐based CMOF (JNM‐2) is used as a photocatalyst for CO2 photoreduction under visible‐light irradiation. JNM‐2 exhibits remarkable efficiency in photocatalytic CO2 reduction with high production rates of HCOOH (9019 μmol g−1 h−1) and CO (835 μmol g−1 h−1). The active center, reaction intermediates, and product generation pathways are elucidated by in situ DRIFTS and DFT calculations. This work demonstrates the tremendous possibilities of CMOFs as photocatalysts for CO2 reduction and provides profound insights into the mechanism of CO2 conversion into HCOOH/CO by using a molecularly accurate structural model. [ABSTRACT FROM AUTHOR]

Owing to residual biomass availability, the share of advanced biofuels produced from secondary biomass is forecasted to increase and significantly contribute towards achieving net-zero emissions. The current work investigates bio-methanol production through a new process configuration designed to improve the environmental performance when compared to the state-of-the art technologies (Base Case). The environmental evaluation is conducted according to the Life Cycle Assessment (LCA) methodology. ReCiPe was employed as an impact assessment method with the aid of GaBi software. Depending on the plant geographical location, wooden biomass and exhausted olive pomace were evaluated as biomass sources. A scenario analysis targeting different energy sources was performed as well. The outcome of the environmental evaluation highlights a better performance in eight of a total of nine impact categories studied in the wooden biomass scenarios compared to the exhausted olive pomace. Moreover, two of the CONVERGE technology cases were compared against the Base Case. As the results show, CONVERGE technology registers a lower score in at least six of the impact categories studied. Concerning the total CO2 emissions, CONVERGE exhibits a better performance compared to the Base Case, if the additional amount of CO2 is either stored, sold as a by-product or vented into the atmosphere. [ABSTRACT FROM AUTHOR]

Direct photocatalytic reduction of CO2 has become an highly active field of research. It is thus of utmost importance to maintain an overview of the various materials used to sustain this process, find common trends, and, in this way, eventually improve the current conversions and selectivities. In particular, CO2 photoreduction using plasmonic photocatalysts under solar light has gained tremendous attention, and a wide variety of materials has been developed to reduce CO2 towards more practical gases or liquid fuels (CH4, CO, CH3OH/CH3CH2OH) in this manner. This Review therefore aims at providing insights in current developments of photocatalysts consisting of only plasmonic nanoparticles and semiconductor materials. By classifying recent studies based on product selectivity, this Review aims to unravel common trends that can provide effective information on ways to improve the photoreduction yield or possible means to shift the selectivity towards desired products, thus generating new ideas for the way forward. [ABSTRACT FROM AUTHOR]