Toward the Development and Deployment of Large-Scale Carbon Dioxide Capture and Conversion Processes

Carbon capture, utilization and sequestration systems design and operation optimization: Assessment and perspectives of artificial intelligence opportunities

Carbon capture, utilization, and sequestration (CCUS) is a promising solution to decarbonize the energy and industrial sectors to mitigate climate change. An integrated assessment of technological options is required for the effective deployment of CCUS large-scale infrastructure between CO2 production and utilization/sequestration nodes. However, developing cost-effective strategies from engineering and operation perspectives to implement CCUS is challenging. This is due to the diversity of upstream emitting processes located in different geographical areas, available downstream utilization technologies, storage sites capacity/location, and current/future energy/emissions/economic conditions. This paper identifies the need to achieve a robust hybrid assessment tool for CCUS modeling, simulation, and optimization based mainly on artificial intelligence (AI) combined with mechanistic methods. Thus, a critical literature review is conducted to assess CCUS technologies and their related process modeling/simulation/optimization techniques, while evaluating the needs for improvements or new developments to reduce overall CCUS systems design and operation costs. These techniques include first principles- based and data-driven ones, i.e. AI and related machine learning (ML) methods. Besides, the paper gives an overview on the role of life cycle assessment (LCA) to evaluate CCUS systems where the combined LCA-AI approach is assessed. Other advanced methods based on the AI/ML capabilities/algorithms can be developed to optimize the whole CCUS value chain. Interpretable ML combined with explainable AI can accelerate optimum materials selection by giving strong rules which accelerates the design of capture/utilization plants afterwards. Besides, deep reinforcement learning (DRL) coupled with process simulations will accelerate process design/operation optimization through considering simultaneous optimization of equipment sizing and operating conditions. Moreover, generative deep learning (GDL) is a key solution to optimum capture/utilization materials design/discovery. The developed AI methods can be generalizable where the extracted knowledge can be transferred to future works to help cutting the costs of CCUS value chain.

Integrated CO2 capture and electrochemical upgradation: the underpinning mechanism and techno-chemical analysis

Coupling post-combustion CO2 capture with electrochemical utilization (CCU) is a quantum leap in renewable energy science since it eliminates the cost and energy involved in the transport and storage of CO2. However, the major challenges involved in industrial scale implementation are selecting an appropriate solvent/electrolyte for CO2 capture, modeling an appropriate infrastructure by coupling an electrolyser with a CO2 point source and a separator to isolate CO2 reduction reaction (CO2RR) products, and finally selection of an appropriate electrocatalyst. In this review, we highlight the major difficulties with detailed mechanistic interpretation in each step, to find out the underpinning mechanism involved in the integration of electrochemical CCU to achieve higher-value products. In the past decades, most of the studies dealt with individual parts of the integration process, i.e., either selecting a solvent for CO2 capture, designing an electrocatalyst, or choosing an ideal electrolyte. In this context, it is important to note that solvents such as monoethanolamine, bicarbonate, and ionic liquids are often used as electrolytes in CO2 capture media. Therefore, it is essential to fabricate a cost-effective electrolyser that should function as a reversible binder with CO2 and an electron pool capable of recovering the solvent to electrolyte reversibly. For example, reversible ionic liquids, which are non-ionic in their normal forms, but produce ionic forms after CO2 capture, can be further reverted back to their original non-ionic forms after CO2 release with almost 100% efficiency through the chemical or thermal modulations. This review also sheds light on a focused techno-economic evolution for converting the electrochemically integrated CCU process from a pilot-scale project to industrial-scale implementation. In brief, this review article will summarize a state-of-the-art argumentation of challenges and outcomes over the different segments involved in electrochemically integrated CCU to stimulate urgent progress in the field.

Design and Synthesis of N-Doped Porous Carbons for the Selective Carbon Dioxide Capture under Humid Flue Gas Conditions

The design of novel porous solid sorbents for carbon dioxide capture is critical in developing carbon capture and storage technology (CCS). We have synthesized a series of nitrogen-rich porous organic polymers (POPs) from crosslinking melamine and pyrrole monomers. The final polymer's nitrogen content was tuned by varying the melamine ratio compared to pyrrole. The resulting polymers were then pyrolyzed at 700 °C and 900 °C to produce high surface area nitrogen-doped porous carbons (NPCs) with different N/C ratios. The resulting NPCs showed good BET surface areas reaching 900 m² g^-1. Owing to the nitrogen-enriched skeleton and the micropore nature of the prepared NPCs, they exhibited CO₂ uptake capacities as high as 60 cm³ g^-1 at 273 K and 1 bar with significant CO₂/N₂ selectivity. The materials showed excellent and stable performance over five adsorption/desorption cycles in the dynamic separation of the ternary mixture of N₂/CO₂/H₂O. The method developed in this work and the synthesized NPCs' performance towards CO₂ capture highlight the unique properties of POPs as precursors for synthesizing nitrogen-doped porous carbons with a high nitrogen content and high yield.

CO2 /N2 Separation on Highly Selective Carbon Nanofibers Investigated by Dynamic Gas Adsorption

The development of highly selective adsorbents for CO2 is a key part to advance separation by adsorption as a viable technique for CO2 capture. In this work, polyacrylonitrile (PAN) based carbon nanofibers (CNFs) were investigated for their CO2 separation capabilities using dynamic gas adsorption. The CNFs were prepared by electrospinning and subsequent carbonization at various temperatures ranging from 600 to 1000 °C. A thorough investigation of the CO2 /N2 selectivity resulted in measured values of 53-106 at 1 bar and 25 °C on CNFs carbonized at 600, 700, or 800 °C. Moreover, the selectivity increased with lower measurement temperatures and lower CO2 partial pressures, reaching values up to 194. Further analysis revealed high long-term stability with no degradation over 300 cycles and fast adsorption kinetics for CNFs carbonized at 600 or 700 °C. These excellent properties make PAN-based CNFs carbonized at 600 or 700 °C promising candidates for the capture of CO2 .

Efficient imidazolium ionic liquid as a tri-functional robust catalyst for chemical fixation of CO2 into cyclic carbonates

The recent increase in CO₂ levels has had an extensive impact on the environment; hence an effective catalyst for chemical CO₂ fixation into value-added products is demanded. This work demonstrates a simple approach towards the chemical fixation of CO₂ to cyclic carbonates without solvent, metal and additives using one-pot synthesized tri-functional-imidazolium bromide ionic liquid. Herein, synthesized tri-functional-imidazolium-based ionic liquids, namely 3-(2-hydroxyethyl)-1-vinyl-1H-imidazole-3-ium bromide ([VIMEtOH][Br] (24 and 72 h)), 3-(2-hydroxyethyl)-1-vinyl-1H-imidazole-3-ium hydroxyl ([VIMEtOH][OH]) and poly 3-(2-hydroxyethyl)-1-vinyl-1H-imidazole-3-ium bromide (poly [VIMEtOH][Br]), were used for the comprehensive investigation of chemical fixation of CO₂ into cyclic carbonates and their physiochemical properties. In case of [VIMEtOH][Br] ionic liquid, it displayed time-dependent synthesis dissolution in the reaction system. This study found that [VIMEtOH][Br]-72 ionic liquid is not dissolved in the reaction system. The effect on the catalytic efficiency of the presence of functional groups in ionic liquids such as N-vinyl (-CC-N), acidic proton of imidazolium (-C (2)-H) and hydroxyl (-OH) along with bromide anion and the reaction conditions are systematically investigated. For CO₂ fixation, 99.6% conversion of propylene oxide with an excellent selectivity of propylene carbonate (≥99%) over [VIMEtOH][Br]-72 catalyst (at 120 °C, 2 MPa, 2 h) was observed without co-catalyst, metal and solvent. Also, it demonstrated an excellent wide substrates scope of epoxide and all reactions were performed on gram-scalable, which are potential prospects for industrial use.

Next steps for solvent-based CO2 capture; integration of capture, conversion, and mineralisation

In this perspective, we detail how solvent-based carbon capture integrated with conversion can be an important element in a net-zero emission economy. Carbon capture and utilization (CCU) is a promising approach for at-scale production of green CO2-derived fuels, chemicals and materials. The challenge is that CO2-derived materials and products have yet to reach market competitiveness because costs are significantly higher than those from conventional means. We present here the key to making CO2-derived products more efficiently and cheaper, integration of solvent-based CO2 capture and conversion. We present the fundamentals and benefits of integration within a changing energy landscape (i.e., CO2 from point source emissions transitioning to CO2 from the atmosphere), and how integration could lead to lower costs and higher efficiency, but more importantly how CO2 altered in solution can offer new reactive pathways to produce products that cannot be made today. We discuss how solvents are the key to integration, and how solvents can adapt to differing needs for capture, conversion and mineralisation in the near, intermediate and long term. We close with a brief outlook of this emerging field of study, and identify critical needs to achieve success, including establishing a green-premium for fuels, chemicals, and materials produced in this manner.

Study on Selected Metal-Organic Framework-Based Catalysts for Cycloaddition Reaction of CO2 with Epoxides: A Highly Economic Solution for Carbon Capture and Utilization

The level of carbon dioxide in the atmosphere is growing rapidly due to fossil fuel combustion processes, heavy oil, coal, oil shelter, and exhausts from automobiles for energy generation, which lead to depletion of the ozone layer and consequently result in global warming. The realization of a carbon-neutral environment is the main focus of science and academic researchers of today. Several processes were employed to minimize carbon dioxide in the air, some of which include the utilization of non-fossil sources of energy like solar, nuclear, and biomass-based fuels. Consequently, these sources were reported to have a relatively high cost of production and maintenance. The applications of both homogeneous and heterogeneous processes in carbon capture and storage were investigated in recent years and the focus now is on the conversion of CO2 into useful chemicals and compounds. It was established that CO2 can undergo cycloaddition reaction with epoxides under the influence of special catalysts to give cyclic carbonates, which can be used as value-added chemicals at a different level of pharmaceutical and industrial applications. Among the various catalysts studied for this reaction, metal-organic frameworks are now on the frontline as a potential catalyst due to their special features and easy synthesis. Several metal-organic framework (MOF)-based catalysts were studied for their application in transforming CO2 to organic carbonates using epoxides. Here, we report some recent studies of porous MOF materials and an in-depth discussion of two repeatedly used metal-organic frameworks as a catalyst in the conversion of CO2 to organic carbonates.

Conditions for the Joint Conversion of CO2 and Syngas in the Direct Synthesis of Light Olefins Using In2O3–ZrO2/SAPO-34 Catalyst

The conditions for promoting the joint conversion of CO₂ and syngas in the direct synthesis of light olefins have been studied. In addition, given the relevance for the viability of the process, the stability of the In₂O₃–ZrO₂/SAPO-34 (InZr/S34) catalyst has also been pursued. The CO+CO₂ (CO_x) hydrogenation experimental runs were conducted in a packed bed isothermal reactor under the following conditions: 375–425 °C; 20–40 bar; space time, 1.25–20 g_catalyst h mol_C^–1; H₂/(CO_x) ratio in the feed, 1–3; CO₂/(CO_x) ratio in the feed, 0.5; time on stream (TOS), up to 24 h. Analyzing the reaction indices (CO₂ and CO_x conversions, yield and selectivity of olefins and paraffins, and stability), the following have been established as suitable conditions: 400 °C, 30 bar, 5–10 g_cat h mol_C^–1, CO₂/CO_x = 0.5, and H₂/CO_x = 3. Under these conditions, the catalyst is stable (after an initial period of deactivation by coke), and olefin yield and selectivity surpass 4 and 70%, respectively, with light paraffins as byproducts. Produced olefin yields follow propylene > ethylene > butenes. The conditions of the process (low pressure and low H₂/CO_x ratio) may facilitate the integration of sustainable H₂ production with PEM electrolyzers and the covalorization of CO₂ and syngas obtained from biomass.

Current and future perspectives on catalytic-based integrated carbon capture and utilization

There exist several well-known methods with varying maturity for capturing carbon dioxide from emission sources of different concentrations, including absorption, adsorption, cryogenics and membrane separation, among others. The capture and separation steps can produce almost pure CO₂, but at substantial cost for being conditioned for transport and final utilization, with high economical risks to be considered. A possible way for the elimination of this conditioning and cost is direct CO₂ utilization, whether on-site in a further process but within the same plant, or in-situ, coupling both capture and conversion in the same unit. This approach is usually called integrated carbon capture and utilization (ICCU) or integrated carbon capture and conversion (ICCC), and has lately started receiving considerable attention in many circles. As CO₂ is already industrially employed in other sectors, such as food preservation, water treatment and conversion to high added-value chemicals and fuels such as methanol, methane, etc., among others, it is of great interest to explore the global ICCC approach. Catalytic-based processes play a key role in CO₂ conversion, and different technologies are gaining great attention from both academia and industry. However, the 'big picture of ICCU' and in which technology the efforts should focus on at large scale is still unclear. This review analyzes some promising concepts of ICCU specifically on CO₂ catalytic conversion, highlighting their current commercial relevance as well as challenges that have to be faced today and in the next future.

Biocatalytic Reduction of Formaldehyde to Methanol: Effect of pH on Enzyme Immobilization and Reactive Membrane Performance

Thermodynamic stabled CO2 molecules can be biocatalytically reduced to methanol via three cascade dehydrogenases (formate, formaldehyde and alcohol) with the aid of cofactor as the electron donor. In this study, Alcohol dehydrogenase (EC 1.1.1.1), the third step of the cascade enzymatic reaction which catalyzed formaldehyde (CHOH) to methanol (CH3OH) will be immobilized in an ultrafiltration membrane. The enzyme will be immobilized in the support layer of a poly(ether)sulfone (PES) membrane via a technique called fouling induced enzyme immobilization. The objective of this study is to evaluate the effect of varying pH (acid (pH 5), neutral (pH 7) and alkaline (pH 9)) of the feed solution during immobilization process of ADH in the membrane in terms of permeate flux, observed rejection, enzyme loading and fouling mechanism. The experiment was conducted in a pressure driven, dead-end stirred filtration cell. Reaction conversion and biocatalytic productivity will be also evaluated. The results showed that permeate flux for acid solution were the lowest during immobilization. High concentration polarization and fouling resistance cause lower observed rejection for pH 7 and 9. Enzyme loading for pH 5 give 73.8% loading rate which is the highest compared to 62.4% at pH 7 and 70.1% at pH 9. Meanwhile, the conversion rate during the reaction shows that reaction on fouled membrane showed more than 90% conversion for pH 5 and 7. The fouling model predicted that irreversible fouling occurs during enzyme immobilization at pH 7 with standard blocking mechanism while reversible fouling occurs at pH 5 and 9 with intermediate and complete blocking, respectively. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

Since the industrial revolution, the rapid growth and development of global industries have depended largely upon the utilization of coal-derived chemicals, and more recently, the utilization of petroleum-based chemicals. These developments have followed a linear economy model (produce, consume, and dispose). As the world is facing a serious threat from the climate change crisis, a more sustainable solution for manufacturing, i.e., circular economy in which waste from the same or different industries can be used as feedstocks or resources for production offers an attractive industrial/business model. In nature, biological systems, i.e., microorganisms routinely use their enzymes and metabolic pathways to convert organic and inorganic wastes to synthesize biochemicals and energy required for their growth. Therefore, an understanding of how selected enzymes convert biobased feedstocks into special (bio)chemicals serves as an important basis from which to build on for applications in biocatalysis, metabolic engineering, and synthetic biology to enable biobased processes that are greener and cleaner for the environment. This review article highlights the current state of knowledge regarding the enzymatic reactions used in converting biobased wastes (lignocellulosic biomass, sugar, phenolic acid, triglyceride, fatty acid, and glycerol) and greenhouse gases (CO₂ and CH₄) into value-added products and discusses the current progress made in their metabolic engineering. The commercial aspects and life cycle assessment of products from enzymatic and metabolic engineering are also discussed. Continued development in the field of metabolic engineering would offer diversified solutions which are sustainable and renewable for manufacturing valuable chemicals.

Metalloporphyrin and Ionic Liquid-Functionalized Covalent Organic Frameworks for Catalytic CO2 Cycloaddition via Visible-Light-Induced Photothermal Conversion

We report the construction of a porphyrin and imidazolium-ionic liquid (IL)-decorated and quinoline-linked covalent organic framework (COF, abbreviated as COF-P1-1) via a three-component one-pot Povarov reaction. After post-synthetic metallization of COF-P1-1 with Co(II) ions, the metallized COF-PI-2 is generated. COF-PI-2 is chemically stable and displays highly selective CO₂ adsorption and good visible-light-induced photothermal conversion ability (ΔT = 26 °C). Furthermore, the coexistence of Co(II)-porphyrin and imidazolium-IL within COF-PI-2 has guaranteed its highly efficient activity for CO₂ cycloaddition. Of note, the needed thermal energy for the reactions is derived from the photothermal conversion of the Co(II)-porphyrin COF upon visible-light irradiation. More importantly, the CO₂ cycloaddition herein is a "window ledge" reaction, and it can proceed smoothly upon natural sunlight irradiation. In addition, a scaled-up CO₂ cycloaddition can be readily achieved using a COF-PI-2@chitosan aerogel-based fixed-bed model reactor. Our research provides a new avenue for COF-based greenhouse gas disposal in an eco-friendly and energy- and source-saving way.

Process modelling and life cycle assessment coupled with experimental work to shape the future sustainable production of chemicals and fuels

Meeting the sustainable development goals and carbon neutrality targets requires transitioning to cleaner products, which poses significant challenges to the future chemical industry. Identifying alternative pathways to cover the growing demand for chemicals and fuels in a more sustainable manner calls for close collaborative programs between experimental and computational groups as well as new tools to support these joint endeavours. In this broad context, we here review the role of process systems engineering tools in assessing and optimising alternative chemical production patterns based on renewable resources, including renewable carbon and energy. The focus is on the use of process modelling and optimisation combined with life cycle assessment methodologies and network analysis to underpin experiments and generate insight into how the chemical industry could optimally deliver chemicals and fuels with a lower environmental footprint. We identify the main gaps in the literature and provide directions for future work, highlighting the role of PSE concepts and tools in guiding the future transition and complementing experimental studies more effectively.

Carbon neutral manufacturing via on-site CO2 recycling

The chemical industry needs to significantly decrease carbon dioxide (CO₂) emissions in order to meet the 2050 carbon neutrality goal. Utilization of CO₂ as a chemical feedstock for bulk products is a promising way to mitigate industrial emissions; however, CO₂-based manufacturing is currently not competitive with the established petrochemical methods and its deployment requires creation of a new value chain. Here, we show that an alternative approach, using CO₂ conversion as an add-on to existing manufactures, can disrupt the global carbon cycle while minimally perturbing the operation of chemical plants. Proposed closed-loop on-site CO₂ recycling processes are economically viable in the current market and have the potential for rapid introduction in the industries. Retrofit-based CO₂ recycling can reduce annually between 4 and 10 Gt CO₂ by 2050 and contribute to achieving up to 50% of the industrial carbon neutrality goal.

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CO₂ electroconversion is a feasible retrofit for petrochemical plants

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On-site recycling removes several barriers against large-scale CO₂ processing

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CO₂ recycling concept is economically viable in the current market

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On-site recycling has potential to remove 4–10 Gt of CO₂ emissions annually by 2050

Understanding the Effect of Water on CO2 Adsorption

Carbon capture from large sources and ambient air is one of the most promising strategies to curb the deleterious effect of greenhouse gases. Among different technologies, CO₂ adsorption has drawn widespread attention mostly because of its low energy requirements. Considering that water vapor is a ubiquitous component in air and almost all CO₂-rich industrial gas streams, understanding its impact on CO₂ adsorption is of critical importance. Owing to the large diversity of adsorbents, water plays many different roles from a severe inhibitor of CO₂ adsorption to an excellent promoter. Water may also increase the rate of CO₂ capture or have the opposite effect. In the presence of amine-containing adsorbents, water is even necessary for their long-term stability. The current contribution is a comprehensive review of the effects of water whether in the gas feed or as adsorbent moisture on CO₂ adsorption. For convenience, we discuss the effect of water vapor on CO₂ adsorption over four broadly defined groups of materials separately, namely (i) physical adsorbents, including carbons, zeolites and MOFs, (ii) amine-functionalized adsorbents, and (iii) reactive adsorbents, including metal carbonates and oxides. For each category, the effects of humidity level on CO₂ uptake, selectivity, and adsorption kinetics under different operational conditions are discussed. Whenever possible, findings from different sources are compared, paying particular attention to both similarities and inconsistencies. For completeness, the effect of water on membrane CO₂ separation is also discussed, albeit briefly.

A 2-Fold Interpenetrated Nitrogen-Rich Metal-Organic Framework: Dye Adsorption and CO2 Capture and Conversion

A bifunctional ligand strategy for modification of the functional pores is of great significance in the structural design of metal-organic frameworks (MOFs). Herein, a new 2-fold interpenetrated "pillared-layer" 3D Co-MOF, {[Co(HL)(4,4'-bipy)]·DMF·2H₂O}_n (1), was successfully synthesized by using two kinds of ligands, imidazolecarboxylic acid and pyridine. The metal-carboxylic layers are pillared by the 4,4'-bipy ligand, displaying a 3D framework with rectangular 3D channels (high BET surface of 190.9 m² g^-1 and maximum aperture of 3.9 Å) that are decorated with abundant uncoordinated N and O atoms. 1 shows good water stability and thermal stability (320 °C). The proper pores and active sites endowed 1 with a selective adsorption of Congo red in aqueous solution. In addition, a high CO₂ adsorption capacity and an excellent CO₂ chemical conversion were observed.

Hybridization of Fossil- and CO2 -Based Routes for Ethylene Production using Renewable Energy

Carbon capture and utilization (CCU) has recently gained broad interest in the chemical industry. Direct electro- and thermocatalytic technologies are currently the focus of intense research, where the former employs electricity directly to reduce the CO₂ molecule, while the latter comprises hydrogenation of CO₂ in tandem with electrocatalytic water splitting. So far, it remains unclear which of the two is superior, yet this information is considered critical. Focusing on the platform chemical ethylene, the two CCU routes were compared using state-of-the-art performances with the fossil technology considering different power and CO₂ sources. The thermo-route was found to be, at present, economically and environmentally better, yet under the same electrolyzer efficiencies, the electro-route would become superior. CCU routes could substantially improve the carbon footprint of the fossil ethylene (by 236 %) while decreasing at the same time impacts on human health, ecosystem quality, and resources (64, 140, and 80 %, respectively). However, they are economically unattractive even when considering externalities (indirect cost of environmental impacts), that is, 1.7- to 3.9-fold more expensive compared to the current fossil-based analogue. Acknowledging this limitation, the concept of hybridization was applied as a means to smooth the transition towards more sustainable chemicals. Accordingly, it was found that an optimal hybrid plant could produce carbon-neutral (cradle-to-gate) ethylene with a premium of only 30 % over the current market prices by judiciously combining CCU routes with fossil technologies.

Molecular dynamics simulation of carbon dioxide diffusion in NaA zeolite: assessment of surface effects and evaluation of bulk-like properties

Molecular dynamics simulations were carried out for a finite sample of NaA zeolite in contact with bulk carbon dioxide in a wide range of temperatures and CO2 contents. Density and diffusion profiles were obtained to estimate the depth at which the external surfaces of the zeolite affect CO2 diffusion in porous space. The approximate depth of surface effects for NaA zeolite was estimated as ca. 2 nm, though this figure may vary depending on temperature and adsorbed gas density. Diffusion coefficients and diffusion activation energies were calculated for CO2 and Na+ in the bulk-like region of the zeolite. Diffusion activation energy for carbon dioxide demonstrated a non-monotonic dependence on the amount of adsorbed gas.

Designing silica xerogels containing RTIL for CO2 capture and CO2/CH4 separation: Influence of ILs anion, cation and cation side alkyl chain length and ramification

CO₂ separation from natural gas is considered to be a crucial strategy to mitigate global warming problems, meet product specification, pipeline specs and other application specific requirements. Silica xerogels (SX) are considered to be potential materials for CO₂ capture due to their high specific surface area. Thus, a series of silica xerogels functionalized with imidazolium, phosphonium, ammonium and pyridinium-based room-temperature ionic liquids (RTILs) were synthesized. The synthesized silica xerogels were characterized by NMR, helium pycnometry, DTA-TG, BET, SEM and TEM. CO₂ sorption, reusability and CO₂/CH₄ selectivity were assessed by the pressure-decay technique. Silica xerogels containing IL demonstrated advantages compared to RTILs used as separation solvents in CO₂ capture processes including higher CO₂ sorption capacity and faster sorption/desorption. Using fluorinated anion for functionalization of silica xerogels leads to a higher affinity for CO₂ over CH_4. The best performance was obtained by SX- [bmim] [TF₂N] (223.4 mg CO₂/g mg/g at 298.15 K and 20 bar). Moreover, SX- [bmim] [TF₂N] showed higher CO₂ sorption capacity as compared to other reported sorbents. CO₂ sorption and CO₂/CH₄ selectivity results were submitted to an analysis of variance and the means compared using Tukey's test (5%).

Molecular design and experimental study on synergistic catalysts for the synthesis of cyclocarbonate from styrene oxide and CO2

Taking the reaction between styrene oxide and CO₂ to yield cyclocarbonate as the target, the activities of synergistic catalysts, which are composed of Br⁻ and alcohol compounds serving as hydrogen bond donors (HBDs), were predicted by DFT calculations and confirmed by subsequent experiments.

Intensified Electrocatalytic CO2 Conversion in Pressure-Tunable CO2 -Expanded Electrolytes

Multimolar CO₂ concentrations are achieved in acetonitrile solutions containing supporting electrolyte at relatively mild CO₂ pressures (<5 MPa) and ambient temperature. Such CO₂ -rich, electrolyte-containing solutions are termed as CO₂ -eXpanded Electrolytes (CXEs) because significant volumetric expansion of the liquid phase accompanies CO₂ dissolution. Cathodic polarization of a model polycrystalline gold electrode-catalyst in CXE media enhances CO₂ to CO conversion rates by up to an order of magnitude compared with those attainable at near-ambient pressures, without loss of selectivity. The observed catalytic process intensification stems primarily from markedly increased CO₂ availability. However, a non-monotonic correlation between the dissolved CO₂ concentration and catalytic activity is observed, with an optimum occurring at approximately 5 m CO₂ concentration. At the highest applied CO₂ pressures, catalysis is significantly attenuated despite higher CO₂ concentrations and improved mass-transport characteristics, attributed in part to increased solution resistance. These results reveal that pressure-tunable CXE media can significantly intensify CO₂ reduction rates over known electrocatalysts by alleviating substrate starvation, with CO₂ pressure as a crucial variable for optimizing the efficiency of electrocatalytic CO₂ conversion.