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The hydrogenation of magnesite to CH 4 and MgO offers a powerful approach for CO 2 direct utilization. To deepen the understanding of the reaction mechanisms, (Mg 5 (CO 3) 4 (OH) 2 (H 2 O) 4 was selected as a model compound to gain insights into carbonate hydrogenation. A novel Ni/Fe/ZrO 2 catalyst with ferromagnetic properties was employed to facilitate the magnetic separation of the catalyst from the solid products. Thermodynamic simulation and experiments were conducted to address key issues such as gas evolution during catalytic hydrogenation, the effects of catalyst on CH 4 selectivity, and the separation of solid products and catalyst. The results indicate that lower temperatures favor CH 4 formation, whereas higher temperatures favor CO formation. Increasing Ni loading can enhance the CH 4 selectivity. With the presence of 10Ni/Fe/ZrO 2 catalyst, 100% CH 4 selectivity can be achieved at 300 °C. Moreover, 10Ni/Fe/ZrO 2 catalyst exhibits high magnetic responsiveness, facilitating the solid separation and the recycle of the catalyst. • A novel route for the hydrogenation of magnesite to produce CH 4 and MgO is proposed. • A ferromagnetic Ni/Fe/ZrO 2 catalyst enables efficient separation of the catalyst and product. • Low temperature favors CH 4 formation, while high temperature favors CO formation. • 100% CH 4 selectivity can be achieved at 300 °C with the presence of 10Ni/Fe/ZrO 2. [ABSTRACT FROM AUTHOR]

This study presents a novel microwave-assisted dry reforming of methane (MW-DRM) method, significantly enhancing syngas (H 2 +CO) production at a lower temperature of 400 °C. Compared to conventional heating dry reforming of methane (CH-DRM) processes, MW-DRM achieves higher conversion rates of CH 4 (84.6%) and CO 2 (85.7%) at a lower temperature of 500 °C, significantly reducing energy consumption. The CsRu/CeO 2 catalyst exhibited excellent stability under microwave heating, maintaining high conversion rates and selectivity for 8 h. Detailed characterization using XRD, BET surface analysis, Raman spectroscopy, TEM, and CO chemisorption revealed insights into the structural changes of the catalyst, highlighting the selective impact of microwave heating on the catalyst structure. This study provides a promising approach for sustainable and cost-effective syngas and hydrogen production, aligning with greenhouse gas reduction goals. [Display omitted] • Dry reforming of methane is conducted under microwave conditions. • Microwave-enhanced DRM demonstrated high efficiency. • Compared to CH-DRM, MW-DRM achieves the same activity at 200 °C lower. • CsRu/CeO 2 catalyst demonstrated high stability in DRM. [ABSTRACT FROM AUTHOR]

Chemical looping combustion is a highly efficient CO2 separation technology without direct contact between combustion air and fuel. A metal oxide is used as an oxygen carrier in dual fluidized beds to generate clean CO2. The use of biomass is the focus of current research because of the possibility of negative CO2 emissions and the utilization of biogenic carbon. The most commonly proposed OC are natural ores and residues, but complete combustion has not yet been achieved. In this work, the direct utilization of CLC exhaust gas for methane synthesis as an alternative route was investigated, where the gas components CO, CH4 and H2 are not disadvantageous but benefit the reactions in a methanation step. The whole process chain, the coupling of an 80 kWth pilot plant with gas cleaning and a 10 kW fluidized bed methanation unit were for this purpose established. As OC, ilmenite enhanced with limestone was used, combusting bark pellets in autothermal operation at over 1000 °C reaching high combustion efficiencies of up to 91.7%. The fuel reactor exhaust gas was mixed with hydrogen in the methanation reactor at 360 °C and converted with a methane yield of up to 97.3%. The study showed especially high carbon utilization efficiencies of 97% compared to competitor technologies. Based on the experimental results, a scale-up concept study showed the high potential of the combination of the technologies concerning the total efficiency and the adaptability to grid injection. [ABSTRACT FROM AUTHOR]

2,5-furandicarboxylic acid (FDCA), one of the most important building blocks, has attracted tremendous concerns, and the routes for FDCA synthesis from non-edible hemicellulose are of vital importance from the views of the circular economy. Herein, a multistep process towards hemicellulose-to-FDCA conversion is proposed, including hemicellulose-to-furfural conversion and sequential oxidation to furoic acid (FA), following with cesium furoate (FA-Cs) preparation and its direct carboxylation with carbon dioxide (CO2). The overall conversion yield of the targeted FDCA product towards the hemicellulose-to-FDCA pathway reaches 29.6%. Many efforts are made on the direct carboxylation reaction of FA-Cs with CO2 using Cs2CO3 as a catalyst. Results show that FDCA with 56.47% yield is achieved via direct carboxylation of FA-Cs at 290 °C for 12 h with 40 mL/min of flowing CO2. Different from the previous reports, it is demonstrated that drying methods of FA-Cs show significant effects on the yield and properties of the targeted FDCA product. It is found that the conventional drying method is more suitable than the vacuum drying method. From the putative reaction mechanism, the roles of CO2 and Cs2CO3 are elucidated. CO2 plays a direct role in carboxylation reaction, and excessive Cs2CO3 can deteriorate FDCA yield due to the occurrence of decomposition. Interestingly, biochar generated during carboxylation reaction is a promising potential adsorbent, which can efficiently adsorb methylene blue with a removal rate of 96% and an adsorption amount of 80 mg/g. This present work can provide an integrated strategy for both hemicellulose valorization and CO2 utilization in future. [ABSTRACT FROM AUTHOR]

The rapid expansion of reservoir fractures and the enlargement of the area affected by working fluids can be accomplished solely through fracturing operations of oilfield working fluids in geological reservoirs. Supercritical CO2 is regarded as an ideal medium for shale reservoir fracturing owing to the inherent advantages of environmental friendliness, excellent capacity, and high stability. However, CO2 gas channeling and complex propagation of fractures in shale reservoirs hindered the commercialization of Supercritical CO2 fracturing technology. Herein, a simulation method for Supercritical CO2 fracturing based on cohesive force units is proposed to investigate the crack propagation behavior of CO2 fracturing technology under different construction parameters. Furthermore, the shale fracture propagation mechanism of Supercritical CO2 fracturing fluid is elucidated. The results indicated that the propagation ability of reservoir fractures and Mises stress are influenced by the fracturing fluid viscosity, fracturing azimuth angle, and reservoir conditions (temperature and pressure). An azimuth angle of 30° can achieve a maximum Mises stress of 3.213 × 107 Pa and a crack width of 1.669 × 10−2 m. However, an apparent viscosity of 14 × 10−6 Pa·s results in a crack width of only 2.227 × 10−2 m and a maximum Mises stress of 4.459 × 107 Pa. Additionally, a weaker fracture propagation ability and reduced Mises stress are exhibited at the fracturing fluid injection rate. As a straightforward model to synergistically investigate the fracture propagation behavior of shale reservoirs, this work provides new insights and strategies for the efficient extraction of shale reservoirs. [ABSTRACT FROM AUTHOR]

Graphitic nanoplatelets (GnPs), edge‐selectively carboxylated graphitic nanoplatelets (ECGnPs), are functionalized with a carboxylic acid at the edge increasing their surface area, and are highly dispersible in various solvents. However, there is a limit in that the basal plane remains intact because it is functionalized only in the part where the radical is generated at the edge. Here, we activate ECGnPs to have porous structures by flowing CO2 at 900 °C. Etching of the ECGnPs structure was performed through the Boudouard reaction, and the surface area increased from 579 m2 g−1 to a maximum of 2462 m2 g−1. In addition, the pore structure was investigated with various adsorption gases (CH4, Ar, CO2, H2, and N2) according to the reaction time. This study provides the overall green chemistry in that it utilizes CO2 from manufacturing to activation compared to the process of activating with conventional chemical treatment. [ABSTRACT FROM AUTHOR]

Synthesis of monomer‐recyclable polyesters solely from CO2 and bulk olefins holds great potential in significantly reducing CO2 emissions and addressing the issue of plastic pollution. Due to the kinetic disadvantage of direct copolymerization of CO2 and bulk olefins compared to homopolymerization of bulk olefins, considerable research attention has been devoted to synthesis of polyester via the ring‐opening polymerization (ROP) of a six‐membered disubstituted lactone intermediate, 1,2‐ethylidene‐6‐vinyl‐tetrahydro‐2H‐pyran‐2‐one (휹‐L), obtained from telomerization of CO2 and 1,3‐butadiene. However, the conjugate olefin on the six‐membered ring of 휹‐L leads to serious Michael addition side reactions. Thus, the selective ROP of 휹‐L, which can precisely control the repeating unit for the production of polyesters potentially amenable to efficient monomer recycling, remains an unresolved challenge. Herein, the first example of selective ROP of 휹‐L is reported using a combination of organobase and N,N′‐Bis[3,5‐bis(trifluoromethyl)phenyl]urea as the catalytic system. Systematic modifications of the substituent of the urea show that the presence of electron‐deficient 3,5‐bis(trifluoromethyl)‐phenyl groups is the key to the extraordinary selectivity of ring opening over Michael addition. Efficient monomer recovery of oligo(휹‐L) is also achieved under mild catalytic conditions. [ABSTRACT FROM AUTHOR]

The experimental data over CuO/ZnO/ZrO2 catalyst for a wide range of operating conditions were used to develop the kinetics of the reaction CO2 hydrogenation to methanol. Three kinetic models such as the power law model, the Graaf kinetic model, and the Park kinetic model were tested against the experimental data. Both the mechanistic models have been developed based on the Langmuir‐Hinshelwood‐Hougen‐Watson approach and are specific only to the methanol synthesis from CO/CO2 hydrogenation. In an attempt to reduce the number of parameters in the two models, the abridged forms of these models were also tried. Overall, 25 kinetic rate equations were tested and the best‐fit kinetic rate expression with optimized parameters was worked out. Both the integral and differential methods of kinetic analysis were employed and their efficacy in finding the best‐fit expression was compared. The MATLAB built‐in function fminsearch was employed to perform the regression of the data. The Graaf model in its parent form, but with the new optimized values of the parameters, was found to be the best‐fit rate model. The Graaf kinetics, with re‐estimated parameters, could be helpful in designing and simulating a methanol synthesis reactor operating on CO2 and H2 feed and utilizing a CuO/ZnO/ZrO2 catalyst. [ABSTRACT FROM AUTHOR]

This study aimed to propose a method for producing 1,4-butanediol (1,4-BDO) from inedible lignocellulosic biomass (e.g., kenaf). The process involved high-pressure CO2-catalyzed hydrolysis and dehydration to obtain furfural from kenaf and the conversion of furfural into 1,4-BDO. In the furfural production process, the yield of furfural increased with increasing temperature and reaction time, but a further increase in reaction time led to the formation of unwanted byproducts such as humins. The highest furfural yield (based on kenaf) was 3.78 mg g−1 at 220 °C with a 10-min reaction time. Further, furfural can be converted to 1,4-BDO using a bifunctional Pt/TiO2–ZrO2 catalyst. The 1,4-BDO yield (based on kenaf) achieved potentially with the Pt/TiO2–ZrO2 catalytic system was 3.22 mg g−1. The sequential conversion of kenaf biomass to valuable chemicals showcases a sustainable approach, aligning with global efforts toward reduced environmental impact. [ABSTRACT FROM AUTHOR]

Multifunctional metallo‐/ionic‐covalent organic polymers (TCTB@Zn‐iCOPs) were constructed through one‐pot multicomponent reaction in a deep eutectic solvent at room temperature. The structures of various TCTB@Zn‐iCOPs were characterized, demonstrating their successful integration of multiple sites and excellent structural stability. Then TCTB@Zn‐iCOPs were employed to transform atmospheric CO2 into cyclic carbonates. The results showed that satisfactory product yields were obtained under mild and additive‐free conditions, with a high TOF value of 101 h−1; furthermore, the optimized TCTB@Zn‐iCOP2 exhibited excellent versatility in catalyzing the cycloaddition reactions between various substituted epoxides and CO2, and its activity did not significantly decrease after being reused for five times. Compared with previously reported nonmetallic iCOPs, the TCTB@Zn‐iCOP2 shows significantly improved activity and stability. Finally, DFT calculations were conducted along with a comparison of energy barriers for possible reaction paths, gaining an in‐depth understanding of the synergistic catalytic mechanism involving multiple sites. [ABSTRACT FROM AUTHOR]

Carbon capture, utilization, and storage supply chain is recently acknowledged as a crucial method to limit global warming. There is a notable desire to optimize supply chains simultaneously with respect to economic and environmental factors, and the development of a mathematical model integrating the life cycle assessment into source-sink matching is missing in the existing literature. The present work means to fill this gap by using a bi-objective mixed-integer linear programming problem. The case study for this research focuses on a real-life scenario in Germany where carbon dioxide is captured from flue gas and transported to be stored or/and used. The total profit and life cycle GHG reduction are maximized. The results show that the profit per unit of sequestered CO2 decreases from 2014 to −€332 as the rate of life cycle GHG reduction increases from −873 to 52 MtCO2eq/year. The findings from the model can provide valuable knowledge that can be utilized in various countries at different levels, such as at regional, state, and national levels. This knowledge can also assist decision-makers in selecting more sustainable solutions when designing carbon capture, utilization, and storage systems. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2) and methane (CH 4) are highly hazardous air pollutants that pose significant threats to the environment and human health and contribute indirectly to global warming. The dry reforming of methane (DRM) reaction has been investigated in numerous applications, including hydrogen production and catalytic converters. Catalytic DRM is one of the most effective approaches for utilizing CO 2 and CH 4 in syngas, which has garnered a lot of scholarly attention as a model reaction throughout the past couple of decades. Previous studies have extensively investigated the development of catalysts for DRM, with a particular emphasis on noble metal catalysts, catalyst configuration, and the influence of process parameters. However, despite the current understanding, there still needs to be a research gap in comprehending the synergistic interactions between catalytic activity and physicochemical features. Addressing this gap is of utmost importance. Therefore, a state-of-the-art review that clarifies new advancements for specific recently developed catalytic DRM systems with a complete evaluation and the synergistic link to physicochemical properties and their correlation with catalyst deactivation is critically urgent. Furthermore, in this study, we emphasized Ni-based catalysts as a promising option for DRM, given their potential, wide availability, and cost-effectiveness, owing to their high activity. Also, we discussed the limitations associated with this particular active metal. Additionally, this review integrates informetric analysis, employing robust search resources such as Web of Science. This analysis provides valuable insights into the DRM reaction, facilitating a deeper understanding of research trends and developments. This review can serve as a critical reference for scientists and experts engaged in mitigating CO 2 and CH 4 using DRM reactions and supports the academic and industrial sectors in their research and development efforts by contributing to developing well-designed catalysts suitable for future applications. [Display omitted] • A comprehensive review of the role of catalytic properties for Dry Reforming of Methane (DRM). • Rational and suitable design of catalysts for DRM were addressed. • Metal-support interaction, particle size, basicity, oxygen vacancies, reducibility, and porosity were elucidated. • Current challenges and future perspectives for DRM developments have been proposed. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) reaction is advantageous in producing syngas with a low H2/CO, relevant to many industries. Effect of contact time on catalytic activity and carbon deposition is studied for DRM using Ni−Al catalysts, along with the effect of metal loading, reaction temperature, and reactant partial pressure (CO2/CH4). Maximum CH4 conversion (58 %) and CO2 (59 %) were achieved at a higher contact time of 4.009 kg‐cat. h/kgCH4. A maximum of 46 % CH4 conversion was achieved at 1023 K with a contact time of 0.134 kg‐cat. h/kgCH4. Higher CH4 and CO2 conversion were achieved with an excellent H2 and CO yield due to the RWGS reaction with increased metal (Ni) loading (10–30 wt. %). When the reactant partial pressure (CO2) changed from 0.1–0.3, the CH4 conversion increased whereas CO2 conversion decreased. FESEM images revealed the formation of whisker‐like carbon fibers for all loadings. For the best syngas output and stability in a Ni‐based catalyst, a combination of a basic support (alumina) at a higher contact time (~4.009 kg‐cat. h/kgCH4) and a CO2/CH4 ratio of 1–1.5 at a moderate temperature of 873 K may provide best CO2 adsorption with minimal coking. [ABSTRACT FROM AUTHOR]

CO2 mineralization products are often heralded as having outstanding potentials to reduce CO2-eq. emissions. However, these claims are generally undermined by incomplete consideration of the life cycle climate change impacts, material properties, supply and demand constraints, and economic viability of CO2 mineralization products. We investigate these factors in detail for ten concrete-related CO2 mineralization products to quantify their individual and global CO2-eq. emissions reduction potentials. Our results show that in 2020, 3.9 Gt of carbonatable solid materials were generated globally, with the dominant material being end-of-life cement paste in concrete and mortar (1.4 Gt y-1). All ten of the CO2 mineralization technologies investigated here reduce life cycle CO2-eq. emissions when used to substitute comparable conventional products. In 2020, the global CO2-eq. emissions reduction potential of economically competitive CO2 mineralization technologies was 0.39 Gt CO2-eq., i.e., 15% of that from cement production. This level of CO2-eq. emissions reduction is limited by the supply of end-of-life cement paste. The results also show that it is 2 to 5 times cheaper to reduce CO2-eq. emissions by producing cement from carbonated end-of-life cement paste than carbon capture and storage (CCS), demonstrating its superior decarbonization potential. On the other hand, it is currently much more expensive to reduce CO2-eq. emissions using some CO2 mineralization technologies, like carbonated normal weight aggregate production, than CCS. Technologies and policies that increase recovery of end-of-life cement paste from aged infrastructure are key to unlocking the potential of CO2 mineralization in reducing the CO2-eq. footprint of concrete materials. [ABSTRACT FROM AUTHOR]

As oil and gas companies are one of the major greenhouse gas emitters, they face increasing responsibility to address climate challenges. This highlights the necessity of integrating decarbonization options into their operations to meet global climate objectives. While progress in technologies for capturing, utilizing, and storing CO2 (CCUS technologies) is often attributed to oil and gas companies, CCUS projects in the sector predominantly focus on carbon storage, namely CO2 injection for enhanced oil recovery, which presents limited possibilities. Meanwhile, carbon capture and utilization (CCU) technologies offer a promising avenue for producing valuable products from CO2, a potential that has been underexplored in theory and practice within the oil and gas sector. This study analyzes the development of the full CCU cycle by oil and gas companies, assessing the economic viability of such projects. It includes a content analysis of research materials on CCU deployment and a case study modeling the economic viability of producing methanol from CO2 in Russia. The findings indicate that the estimated minimum price for CO2-based methanol to achieve project payback is USD 1128 per ton, compared to approximately USD 400 per ton for traditional methanol. This price gap underscores the need to foster the development of low-carbon technologies, markets, and measures to support these projects. In the domain of CCU projects, cost-reduction measures could be more applicable, while regulatory measures, such as carbon taxes, currently have a limited impact on the economic viability of these projects. [ABSTRACT FROM AUTHOR]

The capture and utilization of carbon dioxide (CO2) as a C1 source for valuable compounds and fuel production are essential in mitigating the escalating atmospheric carbon dioxide. In this context, the present study demonstrates rational integration of an efficient, highly recyclable, and noble-metal-free catalyst for effectively utilizing CO2 to prepare valuable commodity compounds and antibiotics. To achieve this, we anchored catalytically active, alkynophilic Cu(0) nanoparticles (Cu-NPs) with an average size of 10 nm in a high surface area (1079 m2/g), amine-functionalized MOF via the postsynthetic method. The resulting Cu NP-embedded MOF (Cu-NPs/MOF) demonstrates high CO2 uptake and superior catalytic performance for generating 2-oxazolidinones and α-alkylidene cyclic carbonates by CO2 coupling with propargylic amines and alcohols, respectively. More importantly, a facile one-pot preparation of 2-oxazolidinones, antibacterial agents, through a four-component reaction between readily accessible phenylacetylene, acetone, amine, and CO2 has also been accomplished using Cu-NPs/MOF as a catalyst. The high performance of the Cu-NPs/MOF is attributed to the synergistic participation of CO2-philic NH2 groups and catalytic Cu-NPs, rendering selective capture and utilization of carbon dioxide. Further, the Cu-NPs/MOF showed excellent recyclability over six cycles, retaining its catalytic performance and chemical stability. This work highlights the importance of CO2 utilization for one-pot synthesis of valuable 2-oxazolidinones by a four-component reaction involving C–H bond functionalization of phenyl acetylenes at mild conditions. [ABSTRACT FROM AUTHOR]

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Direct synthesis of CH3 COOH from CH4 and CO2 is an appealing approach for the utilization of two potent greenhouse gases that are notoriously difficult to activate. In this Communication, we report an integrated route to enable this reaction. Recognizing the thermodynamic stability of CO2 , our strategy sought to first activate CO2 to produce CO (through electrochemical CO2 reduction) and O2 (through water oxidation), followed by oxidative CH4 carbonylation catalyzed by Rh single atom catalysts supported on zeolite. The net result was CH4 carboxylation with 100 % atom economy. CH3 COOH was obtained at a high selectivity (>80 %) and good yield (ca. 3.2 mmol g-1 cat in 3 h). Isotope labelling experiments confirmed that CH3 COOH is produced through the coupling of CH4 and CO2 . This work represents the first successful integration of CO/O2 production with oxidative carbonylation reaction. The result is expected to inspire more carboxylation reactions utilizing preactivated CO2 that take advantage of both products from the reduction and oxidation processes, thus achieving high atom efficiency in the synthesis.

The present study conceptualizes and simulates a methanol production process through the direct hydrogenation of captured CO2. CuO/ZnO/ZrO2 was employed as the catalyst and Aspen HYSYS was used for the process simulation. Configurational optimization of the process flowsheet was carried out using a step-by-step hierarchical approach. Many alternate flowsheets have resulted, and their capital investment, product cost, and profitability measures were calculated. The discrimination among the competing flowsheets was carried out based on net profit and percent return on investment. The retained flowsheet was further analyzed for optimizing the recycle ratio and evaluating the effect of the price of captured CO2, green H2, natural gas (fuel), and catalyst on the economic performance of the plant. The optimum value of the recycle ratio was computed to be 4.23. Additionally, it was found that the price of H2 is the most important parameter in defining the feasibility and profitability of the process. Mathematical correlations were also developed that relate the profitability and price of the above-mentioned feed materials. [ABSTRACT FROM AUTHOR]

Abstract A novel highly stable aqueous foam was synthesized using CO2, sodium silicate (SS) and anionic surfactant of sodium dodecylbenzene sulfonate. The influence of CO2 foam on the mechanical properties and its underlying mechanisms of foamed backfill material was investigated. The experimental results revealed that the addition of CO2 and SS effectively reduced the drainage of the foam while strengthening the liquid film of the Plateau borders, which stabilizes the foam. The excellent stability is attributable to the gel network developed after SS exposed to CO2, that adhere to the foam surface. Furthermore, due to the interaction between encapsulated CO2 and hydration products, micro CaCO3 formed and filled the pore wall; thus, precast foam forms robust pore structures in the hardened foamed backfill.

As a crucial strategy towards a sustainable chemical industry, the direct synthesis of dimethyl carbonate (DMC) from renewable carbon dioxide (CO2) and methanol (MeOH) is studied using CeO2 nanoparticles modified with 1-butyl-3-methylimidazolium hydrogen carbonate ([BMIm][HCO3]) devoid of stoichiometric dehydrating agents. The synthesized CeO2@-[BMIm][HCO3] catalyst having high thermal stability harnesses the unique physicochemical properties of CeO2 and the ionic liquid to exhibit a DMC yield of 10.4% and a methanol conversion of 16.1% at optimal conditions (pressure of CO2= 5 MPa; temperature=130°C). The catalytic behavior of CeO2@-[BMIm][HCO3] studied with a detailed XRD, XPS, CO2 and NH3-TPD, Raman spectroscopy, TGA, FTIR, SEM and TEM suggests that the synergy between the two catalytic components originating from an increased surface oxygen vacancies boosts the overall catalytic performance. After several recycling tests, the catalyst demonstrated no significant reduction in DMC yield and methanol conversion. This platform is an attractive approach to synthesize thermally stable nanoparticle@ionic liquid that retains and merges the physical attributes of both materials for producing useful bulk chemicals from readily available chemical resources. [ABSTRACT FROM AUTHOR]

Due to the serious ecological problems caused by the high CO2 content in the atmosphere, reducing atmospheric CO2 has attracted widespread attention from academia and governments. Among the many ways to mitigate CO2 concentration, the capture and comprehensive utilization of CO2 through chemical methods have obvious advantages, whose key is to develop suitable adsorbents and catalysts. Frustrated Lewis pairs (FLPs) are known to bind CO2 through the interaction between unquenched Lewis acid sites/Lewis base sites with the O/C of CO2, simultaneously achieving CO2 capture and activation, which render FLP better potential for CO2 utilization. However, how to construct efficient FLP targeted for CO2 utilization and the mechanism of CO2 activation have not been systematically reported. This review firstly provides a comprehensive summary of the recent advances in the field of CO2 capture, activation, and transformation with the help of FLP, including the construction of homogeneous and heterogeneous FLPs, their interaction with CO2, reaction activity, and mechanism study. We also illustrated the challenges and opportunities faced in this field to shed light on the prospective research. [ABSTRACT FROM AUTHOR]

Homoacetogenesis is an important pathway for bio-utilization of CO2; however, oxygen is a key environmental influencing factor. This study explored the impact of different initial oxygen partial pressures (OPPs) on homoacetogenesis, while implementing low pH regulation enhanced acetic acid (HAc) accumulation under microaerobic conditions. Results indicated that cumulative HAc production increased by 18.2% in 5% OPP group, whereas decreases of 31.3% and 56.0% were observed in 10% and 20% OPP groups, respectively, compared to the control group. However, hydrogenotrophic methanogens adapted to microaerobic environment and competed with homoacetogens for CO2, thus limiting homoacetogenesis. Controlling influent pH 5.0 per cycle increased cumulative HAc production by 18.3% and 18.2% in 5% and 10% OPP groups, respectively, compared with the control group. Consequently, regulating low pH effectively inhibited methanogenic activity under microaerobic conditions, thus increasing HAc production. This study was expected to expand the practical application of homoacetogenesis in bio-utilization of CO2. [ABSTRACT FROM AUTHOR]

Due to the serious ecological problems caused by the high CO2 content in the atmosphere, reducing atmospheric CO2 has attracted widespread attention from academia and governments. Among the many ways to mitigate CO2 concentration, the capture and comprehensive utilization of CO2 through chemical methods have obvious advantages, whose key is to develop suitable adsorbents and catalysts. Frustrated Lewis pairs (FLPs) are known to bind CO2 through the interaction between unquenched Lewis acid sites/Lewis base sites with the O/C of CO2, simultaneously achieving CO2 capture and activation, which render FLP better potential for CO2 utilization. However, how to construct efficient FLP targeted for CO2 utilization and the mechanism of CO2 activation have not been systematically reported. This review firstly provides a comprehensive summary of the recent advances in the field of CO2 capture, activation, and transformation with the help of FLP, including the construction of homogeneous and heterogeneous FLPs, their interaction with CO2, reaction activity, and mechanism study. We also illustrated the challenges and opportunities faced in this field to shed light on the prospective research. [ABSTRACT FROM AUTHOR]

H2‐driven microbial electrosynthesis (MES) is an emerging bioelectrochemical technology that enables the production of complex compounds from CO2. Although the performance of microbial fermentation in the MES system is closely related to the H2 production rate, high‐performing metallic H2‐evolving catalysts (HEC) generate cytotoxic H2O2 and metal cations from undesirable side reactions, severely damaging microorganisms. Herein, a novel design for self‐detoxifying metallic HEC, resulting in biologically benign H2 production, is reported. Cu/NiMo composite HEC suppresses H2O2 evolution by altering the O2 reduction kinetics to a four‐electron pathway and subsequently decomposes the inevitably generated H2O2 in sequential catalytic and electrochemical pathways. Furthermore, in situ generated Cu‐rich layer at the surface prevents NiMo from corroding and releasing cytotoxic Ni cations. Consequently, the Cu/NiMo composite HEC in the MES system registers a 50% increase in the performance of lithoautotrophic bacterium Cupriavidus necator H16, for the conversion of CO2 to a biopolymer, poly(3‐hydroxybutyrate). This work successfully demonstrates the concept of self‐detoxification in designing biocompatible materials for bioelectrochemical applications as well as MES systems. [ABSTRACT FROM AUTHOR]

In this study, the surface and textural properties as well as the catalytic performance of Ni/CeO2 and NiIn/CeO2 catalysts prepared by wet impregnation (WI) and deposition–precipitation (DP) are investigated. The addition of Ni (3.0 wt.%) resulted in a decrease in the specific surface area and pore volume in the case of the WI method, possibly due to a blockage of mesopores. A minimal addition of In (0.25 wt.%) caused a further decrease in the surface area in both cases. XRD analysis showed that Ni deposited on CeO2 by DP resulted in some lattice incorporation, affecting the crystallinity of the support. The H2-TPR profiles altered depending on the different ways of Ni and In introduction. STEM-EDS-derived elemental maps indicated that the Ni and NiIn particles deposited on CeO2 using the DP method were somewhat smaller than in the WI synthesis. A comprehensive CO-DRIFTS analysis proved a direct Ni-In interaction in bimetallic samples, leading to the formation of a surface NiIn alloy. Ni/CeO2 catalysts showed a higher activity in the process of dry reforming of methane (DRM) than the bimetallic counterparts at 650 °C, with the Ni_DP sample performing slightly better. However, the Ni_DP catalyst showed significant coking, which was drastically reduced by the addition of In. The agglomeration of Ni and/or NiIn particles during the 6 h DRM reaction somewhat impaired the catalyst performance. Overall, this study highlights the intricate relationship between the catalyst preparation, surface properties and catalytic performance in the DRM reaction and emphasizes the beneficial role of In addition in reducing the coking of the monometallic catalyst and the critical location and surface morphology of nickel nanoparticles decorated with indium and in contact with ceria. [ABSTRACT FROM AUTHOR]

The preparation of CO2-containing polymers with improved degradation properties is still very challenging. An elegant method for preparing these polymers is to use CO2-containing monomers in ring-opening polymerizations (ROP) which are particularly gentle and energy-saving methods. However, cyclic carbonates are required for this which are not readily available. This paper therefore aims to present the optimization and comparison of two synthesis methods to obtain cyclic carbonates for ROP. Within this work, cyclic styrene carbonate was synthesized from readily available raw materials by using a Jacobsen catalyst for the reaction of styrene oxide and carbon dioxide or an organocatalyst for the transesterification of methyl carbonate with 1-phenyl-1,2-ethanediol. The latter performed with 100% selectivity to the desired styrene carbonate, which was succesfully tested in ROP, producing an amorphous thermoplastic polymer with a TG of 185 °C. [ABSTRACT FROM AUTHOR]

Sustainable hydrogen generation is preferred over production from fossil sources in the context of a carbon‐neutral economy. As a result, production costs for CO2‐based products are estimated to be much higher than those of their fossil equivalents. Hence, it is essential to optimize process chains regarding their hydrogen efficiency. In this study, a concept for the directly coupled production of CO2‐based methanol and formaldehyde in a modified silver catalyst process is evaluated regarding the utilization of H2. Detailed simulations in Aspen Plus allow the comparison to the separately operated synthesis of green methanol and formaldehyde. By directly connecting both production steps, utilization ratios of introduced H2 and CO2 could be improved, reaching values of 98 % and 99 %, respectively. [ABSTRACT FROM AUTHOR]

Sustainable hydrogen generation is preferred over production from fossil sources in the context of a carbon‐neutral economy. As a result, production costs for CO2‐based products are estimated to be much higher than those of their fossil equivalents. Hence, it is essential to optimize process chains regarding their hydrogen efficiency. In this study, a concept for the directly coupled production of CO2‐based methanol and formaldehyde in a modified silver catalyst process is evaluated regarding the utilization of H2. Detailed simulations in Aspen Plus allow the comparison to the separately operated synthesis of green methanol and formaldehyde. By directly connecting both production steps, utilization ratios of introduced H2 and CO2 could be improved, reaching values of 98 % and 99 %, respectively. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) utilization technologies have emerged as a promising approach to address the direct and indirect consequences of climate change and the need for sustainable resource management. Those innovative technologies aim to capture and utilize CO2 by converting it into valuable products or directly using it as a chemical feedstock in various industries, thus, avoiding their release into the atmosphere. In this study, different CO2 utilization pathways including CO2 to chemicals and fuels, CO2 to building materials, CO2 to enhanced oil recovery (EOR), and CO2 to bio‐products are discussed in terms of their status – economic, environmental and technology readiness level performances. Moreover, various CO2 utilization pathways are comparatively analyzed considering their advantages and drawbacks, CO2 uptake potentials, and overall climate benefits. According to the comparison results, photocatalytic and electrochemical reduction of CO2 along with the bio‐fixation of CO2 are gaining more attention in the recent research and investigations, from the energy intensity and environmental point of view, whereas EOR remains dominant in terms of the scalability, maturity and economic benefits. However, limitations of EOR related to the capacity, life cycle and different geolocations, as well as the complexities of other mature approaches make room for emerging technologies to be more energy‐effective and environmentally friendly. Overall, most of the promising CO2 utilization techniques are either technologically immature or limited in scale to deploy globally. One of the main barriers to reusing CO2 is associated with the high cost of CO2‐based production and the low value of the CO2 market. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The dry reforming of glycerol (GDR) is one of the alternatives for syngas production by utilizing biodiesel byproduct glycerol and CO 2. The development of highly active and stable catalyst is significantly important to achieve GDR process, and the current work provides insights into Co and Fe-doping effects of mesoporous CeO 2 (CoFeCe) catalysts synthesized by the colloidal solution combustion method. The prepared catalysts presented the uniform mesoporous structure, the doping of Co and Fe metals resulted in stronger metal-support interaction. The GDR experimental data were compared with the non-stoichiometric thermodynamic equilibrium values. The conversions of glycerol and CO 2 were increased with increasing the reaction temperatures due to the endothermic GDR reaction, and the H 2 /CO produced in syngas was in the range of 0.7–1.4. Due to the improvement of Co and Fe metals in the mesoporous structure of CeO 2 catalyst, the 7CoFeCe catalyst exhibited excellent and stable GDR performance and no significant signs of deactivation were observed during 76 h test, and the results indicated that the enhanced interaction and high dispersion of Co and Fe in mesoporous CeO 2 catalyst could inhibit carbon formation and promote GDR reaction. [Display omitted] • Co and Fe co-doping on CeO 2 catalyst enhanced GDR reactions. • Increasing in Co-doping improved conversions of glycerol and CO 2 to syngas. • Co–Fe interaction and CeO 2 redox ability inhibited the formation of carbon. • Catalyst with CoFeCe of mole ratio 7: 5:10 exhibited high activity and stability. [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]

For achieving CO2 thermal reduction, a technology combining solid carbon activation and high-temperature CO2 reduction was proposed, named as activated-reduction technology. In this study, this technology is realized by using a circulating fluidized bed and downdraft reactor. Reduced agent parameters (O2/C and CO2 concentration) greatly affect the reduction effect of CO2. In addition, the effect of the activation process on different carbon-based materials can help to broaden the range of carbon-based materials used for CO2 reduction, which is also an important issue. The following three points have been studied through experiments: (1) the influence of the characteristics of the reduced agent (CO2 concentration and O2/C) on CO2 reduction; (2) the performance of different chars in CO2 reduction; and (3) the activation effect of solid carbon. The activation process can develop the pore structure of coal gasification char and transform it into activated char with higher reactivity. The CO concentration in the tail gas is a crucial factor limiting the effectiveness of CO2 reduction, with an experimentally determined upper limit of around 55% at 1200 °C. If CO concentration is far from the upper limit, temperature becomes the significant influencing factor. When the reduced agent O2/C is 0.18, the highest net CO2 reduction of 0.021 Nm3/kg is achieved at 60% CO2 concentration. When the reduced agent CO2 concentration is 50%, the highest net CO2 reduction of 0.065 Nm3/kg is achieved at 0.22 O2/C. Compared with CPGC, YHGC has higher reactivity and is more suitable for CO2 reduction. The activation process helps to reduce the differences between raw materials. [ABSTRACT FROM AUTHOR]

The anthropogenic carbon dioxide (CO2) fixation and various engineering strategies are gaining very significant attention because of the expansion of the net‐zero carbon environment in the atmosphere. Herein, we designed a sodium aluminate@γ‐alumina (NaAlO2@γ‐Al2O3) catalyst by a simple and facile precipitation and impregnation tactics. A series of different weight percentage NaAlO2@γ‐Al2O3 materials were successfully synthesized and well characterized by using advanced analytical and spectroscopic techniques such as TGA, XRD, FE‐SEM, TEM/HR‐TEM, FT‐IR, Raman, TPD, and XPS analysis. The NaAlO2@γ‐Al2O3 catalyst was employed as a competent catalyst for the CO2 fixation under atmospheric pressure reaction conditions. The catalytic activity results evidently revealed that the cycloaddition reaction successfully achieved 94% styrene oxide conversion and 93% selectivity, along with an 87% yield of the styrene carbonate at 120 °C for 6 h. Furthermore, we comprehensively examined the effect of different reaction parameters such as the effect of sodium aluminate amount, co‐catalyst amount, temperature, and time for CO2 fixation reaction. Additionally, different terminal and internal epoxides were tested under optimized reaction conditions and achieved moderate to excellent yield of the desired cyclic carbonate products. Interestingly, a plausible reaction mechanism was proposed for the styrene carbonate synthesis using NaAlO2@γ‐Al2O3 catalyst surface with the support of characterization and experimental results. Remarkably, the NaAlO2@γ‐Al2O3 catalyst could be easily recoverable and successfully recyclable up to six consecutive cycles without declining its initial catalytic activity along with stable structural and physicochemical properties. [ABSTRACT FROM AUTHOR]

Hydrogen production from methane with CO2 utilization over exsolution derived NiCu/CeO2 catalysts was studied. To form highly dispersed supported bimetallic NiCu particles the Ce0.75(NiCu)0.25O1.75 catalyst precursors (Cu/Ni molar ratio = 0; 0.004; 0.04; 0.25) were prepared by polymerizable complex method with the following reduction at 800 °C. A comparative study of the genesis, textural, structural and morphological properties of materials has been carried out by ex situ and in situ methods. It was shown that Ce0.75(NiCu)0.25O1.75 samples were fluorite-like ceria-based solid solutions with a mesoporous texture. Copper promotion has a positive effect on self-activation and hydrogen yield by improving the reducibility of the catalyst, lowering the exsolution temperature of the Ni2+ cations, and maintaining the concentration of oxygen vacancies. The catalyst of optimal composition NiCu/CeO2 (9.4 wt. % Ni, 0.4 wt. % Cu) formed from Ce0.75(NiCu)0.25O1.75 with Cu/Ni = 0.04 is resistant to coking and provides high hydrogen yield (82%) and CO2 utilization (78%) in steam/CO2 reforming of methane at 850 °C. [ABSTRACT FROM AUTHOR]

This study examined the catalytic activity and stability of transition metal@C (carbon) catalysts in methane pyrolysis for hydrogen and solid carbon production. The carbon support for the catalysts was sustainably synthesized using CO2 as the carbon source. X-ray diffraction analysis was used to confirm the presence of metallic phases in the as-calcined catalysts without requiring an additional H2 reduction step. The apparent activation energies of the catalysts were determined using Arrhenius plots, with Ni@C having the lowest value (71 kJ∙mol−1), followed by Co@C (89 kJ∙mol−1), Fe@C (100 kJ∙mol−1), and Cu@C (122 kJ∙mol−1). The carbon support exhibited an apparent activation energy of 150 kJ∙mol−1, indicating its superior catalytic performance compared with traditional carbon-based catalysts. The reaction order demonstrated first-order reactions, indicating that the rate-determining step is associated with the first C–H bond cleavage in methane. The Ni@C and Co@C catalysts demonstrated promising catalytic activity and stability for methane pyrolysis, with the formation of crystalline carbon and metal particle fragmentation playing crucial roles in enhancing their performance. However, the formation of carbide species contributed to the deactivation of Fe@C. [ABSTRACT FROM AUTHOR]

This study centers on a novel approach of high flexural strength rankinite (3CaO·2SiO2, abbreviated as C3S2) cement benefiting from in-situ formation of aragonite whisker (AW) during carbonation curing. The manufacturing parameters including MgCl2 concentration and reaction temperature play key influence on formation of AW. The results showed that high temperature favored AW formation and AW with length-diameter ratio of 15 ∼ 30 could be generated with concentration of Mg2+/Ca2+ molar ratio of 0.1 at 70 °C. Under this condition, the flexural strength of the C3S2 cement reached 7.5, and 15.6 MPa after 3d and 28d and the corresponding compressive strengths were 30.2 and 71.1 MPa, respectively. The results also showed that 40.9% of CO2 by mass was consolidated in rankinite paste after 48 h, suggesting a promising prospect for calcium silicate-containing waste residue and cement to capture CO2 and simultaneously manufacturing high-performance materia. [ABSTRACT FROM AUTHOR]

Accelerated concrete carbonation is an expanding option for decarbonizing construction. Factors such as concrete mixture design and carbonation environment can influence the maximum CO2 utilization that can be achieved during such a process. A carbonation process designed to utilize a water‐saturated dilute CO2 source wherein 2 < CO2 concentration (v/v%) < 16, was modeled in AspenPlus©. A regression model was developed to correlate CO2 uptake, relative humidity (11%–100%), CO2 concentration ([CO2] = 2—16 v/v%), and temperature (T = 11–74°C) conditions within a carbonation reactor. It was determined that [CO2] was the most significant variable as higher concentrations enhanced CO2 transport through the concrete. The energy use intensity per mass of CO2 utilized (kWh/kgCO2) was determined across a range of processing conditions. As a function of the operational conditions, accelerated carbonation provides a net CO2 reduction of up to 28 kgCO2/tonne of concrete; a reduction of up to ~45% compared to typical formulations. [ABSTRACT FROM AUTHOR]

Opportunity for future green hydrogen development in Nepal comes with end- use infrastructural challenges. The heavy reliance of industries on fossil fuels (63.4%) despite the abundance of hydroelectricity poses an additional challenge to the green transition of Nepal. The presented work aims to study the possibility of storing and utilizing spilled hydroelectricity due to runoff rivers as a compatible alternative to imported petroleum fuels. This is achieved by converting green hydrogen from water electrolysis and carbon dioxide from carbon capture of hard-to-abate industries into synthetic methane for heating applications via the Sabatier process. An economy-of-scale study was conducted to identify the optimal scale for the reference case (Industries in Makwanpur District Nepal) for establishing the Synthetic Natural Gas (SNG) production industry. The techno- economic assessment was carried out for pilot scale and reference scale production unit individually. Uncertainty and sensitivity analyses were performed to study the project profitability and the sensitivity of the parameters influencing the feasibility of the production plant. The reference scale for the production of Synthetic Natural Gas was determined to be 40 Tons Per Day (TPD), with a total capital investment of around 72.15 Million USD. Electricity was identified as the most sensitive parameter affecting the levelized cost of production (LCOP). The 40 TPD plant was found to be price competitive to LPG when electricity price is subsidized below 3.55 NPR/unit (2.7 c/unit) from 12 NPR/unit (9.2 c/unit). In the case of the 2 TPD plant, for it to be profitable, the price of electricity must be subsidized to well below 2 NPR/kWh. The study concludes that the possibility of SNG production in Nepal is profitable and price-competitive at large scales and at the same time limited by the low round efficiency due to conversion losses. Additionally, it was observed that highly favorable conditions driven by government policies would be required for the pilot-scale SNG project to be feasible. [ABSTRACT FROM AUTHOR]

Excessive carbon dioxide (CO2) emission has caused problems associated with environmental pollution and climate deterioration. As a consequence, the selective conversion of CO2 into liquid fuels by artificial photosynthesis has gained increasing attention. However, the rational design of photocathode to achieve selective CO2 photoelectroreduction is challenging. Here, we sensitized cuprous oxide (p-nCu2O) loaded on hydroxyl iron oxide (FeOOH) with cobalt-doped cadmium sulfide (Co:CdS) quantum dots to prepare a novel photocathode FeOOH/p-nCu2O/Co:CdS by sequential electrodeposition and chemical bath deposition. The composite photocathode exhibited a larger photovoltage, which is 1.9 times higher than the pristine counterpart, and was efficient for CO2 reduction to produce formic acid with high selectivity of up to 82.9% (Faradaic efficiency). Theoretical calculations revealed that the photocathode out-layer Co:CdS quantum dots had increased binding energy toward the key intermediate *OOCH through additional hybridization orbitals to exclusively favor the formation of formic acid. An impurity energy level was revealed to form by doping Co to the CdS-containing composite, which could reduce the photocathode band gap with improved absorption toward visible light, thus remarkably increasing the photoelectrochemical properties. This is the first work undertaking the energy band structure optimization of the photocathode enabled by elemental doping to improve its photoelectrocatalytic performance. [ABSTRACT FROM AUTHOR]

The catalytic conversion of carbon dioxide is one of the important ways to achieve the goal of carbon neutralization, which can be further divided into electrocatalysis, thermal catalysis, and photocatalysis. Although photocatalysis and electrocatalysis have the advantages of mild reaction conditions and low energy consumption, the thermal catalytic conversion of CO2 has larger processing capacity, better reduction effect, and more complete industrial foundation, which is a promising technology in the future. During the development of new technology from laboratory to industrial application, ensuring the safety of production process is essential. In this work, safety optimization design of equipment, safety performance of catalysts, accident types, and their countermeasures in the industrial applications of CO2 to methanol are reviewed and discussed in depth. Based on that, future research demands for industrial process safety of CO2 to methanol were proposed, which provide guidance for the large-scale application of CO2 thermal catalytic conversion technology. [ABSTRACT FROM AUTHOR]

Aggregate accounts for 60‐80% volume fraction of concrete, which has a great influence on the CO2 emission and performance of concrete. Apart from natural coarse aggregate (NCA), recycled coarse aggregate (RCA) and carbonation recycled coarse aggregate (CRCA) are becoming an important component. This study established a database containing 925 experimental samples of compressive strength (CS) and CO2 emission, which including NCA, RCA, and CRCA concrete respectively. Additionally, the CO2 intensity index was introduced to evaluate the CS and CO2 emission. Machine learning (ML) methods were utilized to establish prediction models for CS, CO2 emissions, and CO2 intensity. The significance of features was analyzed through SHAP and PDP. For the optimization of coarse aggregate mix proportion, the GA and MOPSO algorithms were employed for single and bi-objective optimization designs, respectively. The results indicated that the optimization of coarse aggregate mix proportion can effectively reduce CO2 emission and CO2 intensity of concrete. A CRCA content of 30% is optimal for achieving both enhanced CS and reduced CO2 emissions. The carbonation treatment of RCA presents a viable approach for mitigating CO2 footprint and enhancing the mechanical properties of RCA concrete. The proposed optimization frame can facilitate appropriate decision making for low-carbon concrete design.

Although triblock polycarbonate thermoplastic elastomers (TPEs) have recently attracted great interests due to their biodegradability, insufficient attentions have been paid to improving the elastomeric properties. Through a tandem reaction strategy involving CO2 / allyl glycidyl ether (AGE) / cyclohexene oxide (CHO), poly(cyclohexene carbonate)-b-poly(allyl glycidyl ether carbonate)-b-poly(cyclohexene carbonate) (PCAC) is successfully synthesized using a metal-free Lewis acid-base pair catalyst. The synthesized PCACs are pure well-defined ABA triblock all-polycarbonate, which is supported by 1H NMR, gel permeation chromatography (GPC), and diffusion-ordered spectroscopy (DOSY). A simple modification by grafting alkylthiol chains to PCAC results in excellent TPEs named PCAC-g-S-CaH2a+1 (PCASaC). The synthesized TPEs are characterized by atomic force microscopy (AFM), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and mechanical test. They demonstrate a semi-network and semi-domain phase separation structure, wide service temperature range, good strength, high elongation, and extremely high elastic recovery properties. This low-cost, biodegradable, high-performance TPE shows great potential for applications in biomedical, wearable products, sports equipment, and other fields.

The present study conceptualizes and simulates a methanol production process through the direct hydrogenation of captured CO2. CuO/ZnO/ZrO2 was employed as the catalyst and Aspen HYSYS was used for the process simulation. Configurational optimization of the process flowsheet was carried out using a step-by-step hierarchical approach. Many alternate flowsheets have resulted, and their capital investment, product cost, and profitability measures were calculated. The discrimination among the competing flowsheets was carried out based on net profit and percent return on investment. The retained flowsheet was further analyzed for optimizing the recycle ratio and evaluating the effect of the price of captured CO2, green H2, natural gas (fuel), and catalyst on the economic performance of the plant. The optimum value of the recycle ratio was computed to be 4.23. Additionally, it was found that the price of H2 is the most important parameter in defining the feasibility and profitability of the process. Mathematical correlations were also developed that relate the profitability and price of the above-mentioned feed materials.

This study explores the impact of granular activated carbon (GAC) and L-arginine supplementation on biogas upgrading and acetic acid production employing Clostridium thailandense. GAC and L-arginine concentrations ranged from 0 to 20 g/L and 0 to 5 g/L, respectively, with H2 acting as the electron donor at an H2 to CO2 ratio of 2:1 (v/v). Experiments were conducted at 30 °C with an agitation speed of 150 rpm. Additionally, gene annotation of the C. thailandense genome using Rapid Annotations using Subsystems Technology (RAST) identified genes involved in CO2 to acetic acid conversion. Results indicate that adding 7.5 g/L GAC boosts CH4 purity in biogas, elevating CO2 and H2 consumption efficiencies to 88.3 % and 98.7 %, respectively. This enhancement leads to a CH4 content increase to 93.3 %, accompanied by 0.90 g/L acetic acid production. Conversely, L-arginine demonstrates no significant impact on CO2 conversion. Leveraging RAST, the study identifies hydrogenase genes and NADH-dependent ferredoxin-NADP+ oxidoreductase (Nfn), as crucial for heightened H2 consumption efficiencies and cell growth facilitated by GAC, thus enhancing biogas upgrading efficiency in C. thailandense. This research provides vital insights into optimizing sustainable biogas production through strategic GAC utilization and elucidates the roles of hydrogenase genes and Nfn.