CO2 N2 Research Articles

Dynamics of impure CO2 and composite oil in mineral nanopores: Implications for shale oil recovery and gas storage performance

Evaluating the application effectiveness of impure CO2 in shale reservoirs is a prerequisite for reducing CO2 purification costs. Therefore, molecular dynamics simulations were applied to study the influential mechanisms of impurity gases, mineral types and oil components on impure CO2 enhanced oil recovery (impure CO2-EOR) and gas storage (GS). The orientation force between H2S and polar oil components and the strong adsorption of H2S on mineral walls improve the solubility and diffusivity of impure CO2 in shale oil. Moreover, the induction force between H2S and CO2 carry additional CO2 to walls, and the hydrogen bonds formed between H2S and walls further enhance oil–gas competitive adsorption, resulting in more adsorbed oil being stripped and more H2S/CO2 being sequestered. N2 hinders the dissolution of H2S/CO2 into shale oil and the diffusion of desorbed oil towards the center of nanopores. Therefore, the EOR and GS performances in nanopores are positively and negatively correlated with the proportion of H2S and N2 in impure CO2, respectively. Both EOR and GS performances of impure CO2 decrease sequentially in illite, quartz, and kerogen nanopores, because the strong adsorption of shale oil on kerogen walls causes oil molecules to arrange tightly and dissolve in kerogen. It weakens the solubility and diffusivity of impure CO2 in shale oil, and also increases the resistance of impure CO2 to displace adsorbed and dissolved oil. By contrast, illite walls have the weakest adsorption on shale oil and the largest number of hydrogen bonds formed with H2S. The increase of heavy component content further enhances the interaction between oil molecules and the adsorption of shale oil on wall, thereby weakening the effects of various impure CO2-EOR mechanisms.

Dynamic CO2 separation performance of nano-sized CHA zeolites under multi-component gas mixtures

To identify and evaluate promising adsorbents for CO2 separation, we synthesized CHA zeolites with different cations (Na+, K+, Cs+) and crystal sizes (45 nm – CHA45 and 500 nm – CHA500), and evaluated their explored CO2 adsorption performance from CO2/N2/He and CO2/CH4/He mixtures. Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations predicted CO2, N2, and CH4 adsorption isotherms and CO2 mobilities, respectively, which were compared to experimental data. Breakthrough curve analysis was used to assess the CO2 dynamic adsorption performance. The breakthrough curve analysis shows the smaller crystal sizes (45 nm) enhance the CO2 separation due to shorter interacrystalline diffusion pathways. Notably, Cs-CHA45 removed 2.2 times more CO2 from CO2/N2/He than Cs-CHA500. K-CHA45 showed the highest CO2/N2 selectivity (108) and achieved 841mmol g−1 for CO2 capture from N2 and 721mmol g−1 for CO2 from CH4. These findings underscore the potential of CHA nanocrystals for effective CO2 separation in various applications.

Comprehensive investigation of flue gas component separation and CO2 sequestration in water-saturated porous media of subsurface formation

Flue gas poses subsurface direct storage inefficiency due to its high non-CO2 content, while surface separation, desulfurization and denitrification processes require additional equipment and financial resources. To address these challenges, flue gas subsurface component separation and CO2 sequestration within aquifer were proposed in this paper. CO2 migrates notably slower than N2, leading to the gathering of N2 at gas flooding front and the occurrence of CO2 hysteresis during flue gas filtration within the aquifer. The phenomenon, characterized by gas composition deviations from the original injection mole fractions of N2 and CO2, is referred to as the flue gas component separation. Numerical simulation results indicate that the solubility difference between N2 and CO2 is the primary force driving the separation of components, and the asynchronous filtration velocities of the gas and aqueous phases further promote the separation. Thus, simultaneous N2 separation and CO2 storage can achieve by the optimized gas-water alternate injection, and the efficiencies of N2 separation and CO2 storage are inversely correlated. Increasing N2 mole fraction within the injected flue gas enhances the efficiency of N2 separation, while having a slight effect on CO2 storage. Water vapor in flue gas condenses and integrates into the liquid phase, while O₂ component is produced slightly later than N₂, leading to a marginal reduction in N₂ separation efficiency. The synergistic influences of aquifer temperature and pressure exhibit bidirectionality, stemming from the shift between the dominant factors between CO2 dissolution and gas sweep efficiency. Conditions of relatively lower aquifer temperatures and moderate pressures, particularly in medium permeability aquifers, are more favorable for enhancing N₂ separation and CO₂ storage. This proposal method holds the potential for efficient subsurface separation of flue gas components and concurrent underground storage of CO2, thereby contributing to the reduction of greenhouse gas emissions and mitigation of climate change.

Influence of Supercritical Conditions on Isothermal Adsorption Capacity Calculation of Methane and Model Optimization.

The study of isothermal adsorption models for coal and methane under supercritical conditions helps us to understand the gas content distribution in coal seams and improve gas management in coal mines. Coal samples from the Hebi mine and Longshan coal mine were selected for this research. Using the weight method, isothermal adsorption curves of supercritical methane at temperatures of 308, 313, and 318 K were measured. The adsorption phase density of supercritical methane was obtained by using the intercept method and model fitting, and the absolute adsorption capacity of methane was calculated. Simultaneously, the pore volume and specific surface area of the coal samples were tested, and the isothermal adsorption model for supercritical methane was studied and optimized. The results indicate that using mercury intrusion, low-temperature N2, and low-temperature CO2 adsorption methods for testing coal sample pore structures allows for multiscale characterization of the coal pore structure. Based on the Gibbs excess adsorption theory, the phase density of methane obtained from the intercept method and model fitting effectively represent the isothermal adsorption curve of supercritical methane. By combination of the specific surface area and pore volume distribution of the coal with the absolute adsorption capacity of methane, the number of methane adsorption layers on the coal surface was calculated to be between 1.11 and 1.3 layers. This suggests that the isothermal adsorption model for supercritical methane on coal is not solely micropore filling or single molecular layer adsorption but primarily single molecular layer adsorption with concurrent micropore filling adsorption. Based on this adsorption mechanism, an L-DA isothermal adsorption model for supercritical methane on coal was established. The L-DA isothermal model shows good fitting results and effectively explains the adsorption characteristics of supercritical methane on coal.

A Robust Adenine-Based Microporous Metal-Organic Framework with Hydrophobic Alkyl Groups and Abundant Lewis Basic Sites for CO2/N2 Separation.

The development of a chemically robust metal-organic framework (MOF) with appropriate pore nanospace for efficient CO2 capture and separation from flue gas under humid conditions is sought after. Herein, an adenine-based microporous MOF, Cu-AD-SA, bearing abundant Lewis basic sites and alkyl groups has been utilized to capture and separate CO2 from CO2/N2 gas mixtures. The introduction of alkyl groups enable Cu-AD-SA with high chemical stability. The confined pore nanospace involving small pore size and functionalized pore surface decorated by Lewis basic amino and alkyl groups bestows the framework with stronger CO2 affinity versus N2, thus resulting in a high CO2/N2 separation performance even at high operating temperature (323 K) and humidity (80%), as evidenced by breakthrough experiments. Moreover, molecular modeling studies were implemented to establish the adsorption mechanism, in which the ditopic aliphatic carboxylic acids and adenine linkers collaboratively play a vital role in the separation of CO2/N2 gas mixtures via C-H···OCO2, CCO2···O, CCO2···N, and CCO2···π interactions.

Perinatal asphyxia leads to acute kidney damage and increased renal susceptibility in adulthood.

Perinatal asphyxia (PA) poses a significant threat to multiple organs, particularly the kidneys. Diagnosing PA-associated kidney injury remains challenging, and treatment options are inadequate. Furthermore, there is a lack of long-term follow-up data regarding the renal implications of PA. In this study, 7-day-old male Wistar rats were exposed to PA using a gas mixture (4% O2; 20% CO2 in N2 for 15 min) to investigate molecular pathways linked to renal tubular damage, hypoxia, angiogenesis, heat shock response, inflammation, and fibrosis in the kidney. In a second experiment, adult rats with a history of PA were subjected to moderate renal ischemia-reperfusion (IR) injury to test the hypothesis that PA exacerbates renal susceptibility. Our results revealed an increased gene expression of renal injury markers (kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin), hypoxic and heat shock factors (hypoxia-inducible factor-1α, heat shock factor-1, and heat shock protein-27), proinflammatory cytokines (interleukin-1β, interleukin-6, tumor necrosis factor-α, and monocyte chemoattractant protein-1), and fibrotic markers (transforming growth factor-β, connective tissue growth factor, and fibronectin) promptly after PA. Moreover, a machine learning model was identified through random forest analysis, demonstrating an impressive classification accuracy (95.5%) for PA. Post-PA rats showed exacerbated functional decline and tubular injury and more intense hypoxic, heat shock, proinflammatory, and profibrotic response after renal IR injury compared with controls. In conclusion, PA leads to subclinical kidney injury, which may increase the susceptibility to subsequent renal damage later in life. In addition, the parameters identified through random forest analysis provide a robust foundation for future biomarker research in the context of PA.NEW & NOTEWORTHY This article demonstrates that perinatal asphyxia leads to subclinical kidney injury that permanently increases renal susceptibility to subsequent ischemic injury. We identified major molecular pathways involved in perinatal asphyxia-induced renal complications, highlighting potential targets of therapeutic approaches. In addition, random forest analysis revealed a model that classifies perinatal asphyxia with 95.5% accuracy that may provide a strong foundation for further biomarker research. These findings underscore the importance of multiorgan follow-up for perinatal asphyxia-affected patients.

Novel monolithic catalysts for the hydrotreating of oleic acid

Alumina-supported palladium and molybdenum carbide monolithic catalysts were tested in the hydrodeoxygenation of oleic acid. Anodized aluminum monoliths were used as the substrate of the structured catalysts. The Pd catalyst was synthetized by wet impregnation, and the Mo2C sample was prepared in situ using the temperature-programmed carburization methodology. The monolithic catalysts were characterized by X-ray diffraction, N2 sorption analysis, CO chemisorption and scanning electron microscopy. The catalytic tests were carried out in a continuous tubular reactor at temperatures between 553 and 633 K, with a hydrogen pressure of 30 atm. Both catalysts showed to be active, reaching a conversion of oleic acid higher than 92% at 633 K. The deoxygenation reactions using the Mo2C catalyst were suppressed, favoring the saturation of carbon-carbon double bonds and the stearic acid formation. On the other hand, oleic acid hydrodeoxygenation was promoted when using the palladium-based catalyst, forming undecane and tridecane alkanes.

Optimizing oil recovery with CO2 microbubbles: A study of gas composition

Microbubbles represent a feasible method for enhancing oil recovery (EOR). To further investigate microbubble displacement and interaction mechanisms between gas and oil, in this study, EOR experiments were conducted on normal (NB) and microbubble (MB) CO2 and CO2–N2 mixtures using NMR. The CO2 flooding process and the mechanism of microbubble CO2-oil interaction were examined, the contributions of small and large pores to oil recovery and CO2 storage were quantified. Importantly, economic benefits were analyzed under different injection conditions for the first time. The results show CO2 injection formed a stable displacement front and the maximum oil recovery was obtained from MB CO2. The oil swelling and “jamin effect” increased MB CO2 sweep area and the efficiency of small pore utilization was 20.9 % higher than NB CO2. Compared to CO2 injection, the oil recovery gradually decreased with increasing N2 concentration due to the reduced sweep area. The maximum CO2 storage efficiency achieved under MB CO2 injection was 35.92 %. Economic analysis revealed that MB CO2-EOR could provide significant economic benefits of approximately US $492.5 per ton of CO2 injected. This study provides data for the commercial application of microbubble technology.

Box–Behnken modeling of biodiesel production from Botryococcus braunii microalgae

AbstractThis research aimed to model and optimize the growth factors and enhance the lipid yield from Botryococcus braunii microalgae, and to design a system for obtaining biodiesel from these lipids as this does not compromise food security. Botryococcus braunii, grown on a modified Chu‐13 medium, reached the stationary phase after 27 days with a maximum cell count of 265 × 104 cells mL−1 after 27 days and maximum biomass yield of 725 mg L−1 after 30 days on modified Chu‐13 medium, which was higher than growth on Basal SAG medium. The maximum lipid content (18.47%) and lipid yield (4.46 mg L−1day) were obtained when B. braunii was cultivated on modified Chu‐13 medium after 30 days. Gas chromatography (GC) analysis for the lipids indicated that the highest percentages of SFAs (51.03%) and lowest percentages of monounsaturated fatty acids (MUFAs) (36.47%) and polyunsaturated fatty acids (PUFAs) (12.49%) were obtained by culturing B. braunii on modified Chu‐13 medium. The effect of different growth parameters (N2 level, NaHCO3, and CO2 concentrations) on growth yield was modeled by using D‐optimal design response surface methodology (RSM).

Mesoporous Electrocatalysts with p-n Heterojunctions for Efficient Electroreduction of CO2 and N2 to Urea.

The electrocatalytic synthesis of high-value-added urea by activating N2 and CO2 is a green synthesis technology that has achieved carbon neutrality. However, the chemical adsorption and C-N coupling ability of N2 and CO2 on the surface of the catalyst are generally poor, greatly limiting the improvement of electrocatalytic activity and selectivity in electrocatalytic urea synthesis. Herein, novel hierarchical mesoporous CeO2/Co3O4 heterostructures are fabricated, and at an ultralow applied voltage of -0.2 V, the urea yield rate reaches 5.81 mmol g-1 h-1, with a corresponding Faraday efficiency of 30.05%. The hierarchical mesoporous material effectively reduces the mass transfer resistance of reactants and intermediates, making it easier for them to access active centers. The emerging space-charge regions at the heterointerface generate local electrophilic and nucleophilic regions, facilitating CO2 targeted adsorption in the electrophilic region and activation to produce *CO intermediates and N2 targeted adsorption in the nucleophilic region and activation to generate *N ═ N* intermediates. Then, the electrons in the σ orbitals of *N ═ N* intermediates can be easily accepted by the empty eg orbitals of Co3+ in CeO2/Co3O4, which presents a low-spin state (LS: t2g6eg0). Subsequently, *CO couples with *N ═ N* to produce the key intermediate *NCON*. Interestingly, it was discovered through in situ Raman spectroscopy that the CeO2/Co3O4 catalyst has a reversible spinel structure before and after the electrocatalytic reaction, which is due to the surface reconstruction of the catalyst during the electrocatalytic reaction process, producing amorphous active cobalt oxides, which is beneficial for improving electrocatalytic activity.

Insight into the mechanism of helium enrichment in natural gas from the Bohai Bay basin, China: Chemical and isotopic composition perspectives

Helium (He) is an important societal resource, yet its enrichment mechanism is unclear in the Bohai Bay Basin, despite the presence of He-rich (He > 0.1% v/v) gas. A comprehensive analysis of 112 sets of chemical and isotopic data from natural gases in the literature was conducted to further elucidate the source and accumulation mechanism of He in this basin. Natural gas is categorized into five groups based on CO2 and N2 abundances: N2 gas (CO2+N2 ≥ 95%, CO2 < N2), high-purity CO2 gas (CO2+N2 ≥ 95%, CO2 > N2), low-purity CO2 gas (50 ≤ CO2+N2 < 95%, CO2 > N2), low-purity HC gas (15 ≤ CO2+N2 < 50%) and high-purity HC gas (CO2+N2 < 15%). δ13C–CO2 (−8.3 to −3.0‰) and 3He/4He (1.66–6.45 Ra, where Ra is the atmospheric 3He/4He) suggest a mantle origin of CO2 in N2 and CO2 gases. The δ13C–CO2 of N2 gas (−8.3‰) is lighter than that of high-purity CO2 gas (−6.2 to −3.4‰), indicating CO2 dissolution and mineralization. A positive correlation between He and CH4 content in the N2 and high-purity CO2 gases suggests water-derived CH4 capture during CO2 migration. Similarly, the positive correlation between He and N2 content across all samples indicates water-derived N2 capture during gas migration. A mixture of mantle and crust-derived He is indicated by 3He/4He ratio (0.06–6.45 Ra). Two distinct types of He-rich gas were identified: He-rich N2 gas (3He/4He = 3.1–3.2 Ra) and He-rich HC gas (3He/4He = 0.36–0.48 Ra). He enrichment in N2 gas is attributed to water-derived He capture and concurrent loss of CO2 during mantle-derived CO2 migration. He-rich HC gas formation results from He-rich N2 gas dilution with hydrocarbons. The findings provide theoretical support for exploring He-rich natural gas in this basin and offer valuable insights into He enrichment mechanisms in comparable sedimentary basins globally.

High-temperature CO2 sorption over Li4SiO4 synthesized from diatomite: study of sorption heat and isotherm modeling.

The Li4SiO4 seems to be an excellent sorbent for CO2 capture at post-combustion. Our work contributes to understanding the effect of the natural Algerian diatomite as a source of SiO2 in the synthesis of Li4SiO4 for CO2 capture at high temperature. For this purpose, we use various molar % (stoichiometric and excess) of calcined natural diatomite and pure SiO2. To select the best composition, CO2 sorption isotherms at 500°C on the prepared Li4SiO4 are obtained using TGA measurements under various flows of CO2 in N2. The sorbent having 10% molar SiO2 in diatomite (10%ND-LS) exhibits the best CO2 uptake, probably due to various factors such as the content of the different secondary phases. A comparative study was performed at 400 to 500°C on this selected 10%ND-LS and those with stoichiometric composition obtained with diatomite and pure SiO2. The obtained isotherms show the endothermic character of CO2 sorption. In addition, the evolution of isosteric heat highlights the nature of the involved CO2/Li4SiO4 interactions, by considering the double-shell mechanism. Finally, the experimental sorption isotherms are confronted with some well-known adsorption models to explain the phenomenon occurring over our prepared sorbents. Freundlich and Jensen-Seaton models present a better correlation with the experimental results.

Unusually large microporous HKUST-1 via polyethylene glycol-templated synthesis: enhanced CO2 uptake with high selectivity over CH4 and N2.

Porous solids with highly microporous structures for effective carbon dioxide uptake and separation from mixed gases are highly desirable. Here we present the use of polyethylene glycol (20,000g/mol) as a soft template for the simple and rapid synthesis of a highly microporous Cu-BTC (denoted as HKUST-1). The polyethylene glycol-templated HKUST-1 obtained at room temperature in 10min exhibited a very high Brunauer-Emmett-Teller (BET) surface area of 1904 m2/g, pore volume of 0.87 cm3/g, and average micropore size of 0.84nm. However, conventional HKUST-1 exhibits a BET surface area of 700-1700 m2/g confirming the advantages of using this method. X-ray powder diffraction and electron microscopy analysis confirm the formation of highly crystalline and uniform octahedral particles with sizes ranging from 100nm to 120µm. Adsorption isotherms recorded at temperatures between 273 and 353K and pressures up to 40bar revealed a more favorable adsorption capacity of HKUST-1 for CO2 vs. CH4 and N2 (708mg (CO2)/g, 214mg (CH4)/g and 177mg (N2)/g at 298K and 40bar). The Langmuir, isotherm model, and isosteric heats of adsorption were evaluated. The CO2 interaction at PEG-templated HKUST-1 is physical, exothermic, and spontaneous with DH° = - 6.52kJ/mol, DS° = - 13.72J/mol, and DG° = - 2.43kJ/mol at 298K at 40bar. The selectivities in equimolar mixtures were determined as 53 and 24, respectively, for CO2 over N2 and CH4. CO2 adsorption-desorption tests reveal high adsorbent reusability. The cost-effective and quickly prepared PEG-templated HKUST-1 demonstrates high efficacy as a gas adsorbent, particularly in selectively capturing CO2.

Entropy‐Driven Direct Air Electrofixation

AbstractAccording to the principles of chemical thermodynamics, the catalytic activation of small molecules (like N2 in air and CO2 in flue gas) generally exhibits a negative activity dependence on O2 owning to the competitive oxygen reduction reaction (ORR). Nevertheless, some catalysts can show positive activity dependence for N2 electrofixation, an important route to produce ammonia under ambient condition. Here we report that the positive activity dependence on O2 of (Ni0.20Co0.20Fe0.20Mn0.19Mo0.21)3S4 catalyst arises from high‐entropy mechanism. Through experimental and theoretical studies, we demonstrate that under the reaction condition in the mixed N2/O2, the adsorption of O2 on high‐entropy catalyst contributes to activating N2 molecules characteristic of elongated N≡N bond lengths. As comparison to the low‐ and medium‐entropy counterparts, high entropy can play the second role of attenuating competitive ORR by displaying a negative exponential entropy‐ORR activity relationship. Accordingly, benefiting from the O2, the system for direct air electrofixation has demonstrated an ammonia yield rate of 47.70 μg h−1 cm−2, which is even 1.5 times of pure N2 feedstock (31.92 μg h−1 cm−2), overtaking all previous reports for this reaction. We expect the present finding providing an additional dimension to high entropy that leverages systems beyond the constraint of traditional rules.

Entropy-Driven Direct Air Electrofixation.

According to the principles of chemical thermodynamics, the catalytic activation of small molecules (like N2 in air and CO2 in flue gas) generally exhibits a negative activity dependence on O2 owning to the competitive oxygen reduction reaction (ORR). Nevertheless, some catalysts can show positive activity dependence for N2 electrofixation, an important route to produce ammonia under ambient condition. Here we report that the positive activity dependence on O2 of (Ni0.20Co0.20Fe0.20Mn0.19Mo0.21)3S4 catalyst arises from high-entropy mechanism. Through experimental and theoretical studies, we demonstrate that under the reaction condition in the mixed N2/O2, the adsorption of O2 on high-entropy catalyst contributes to activating N2 molecules characteristic of elongated N≡N bond lengths. As comparison to the low- and medium-entropy counterparts, high entropy can play the second role of attenuating competitive ORR by displaying a negative exponential entropy-ORR activity relationship. Accordingly, benefiting from the O2, the system for direct air electrofixation has demonstrated an ammonia yield rate of 47.70 μg h-1 cm-2, which is even 1.5 times of pure N2 feedstock (31.92 μg h-1 cm-2), overtaking all previous reports for this reaction. We expect the present finding providing an additional dimension to high entropy that leverages systems beyond the constraint of traditional rules.

Photoelectrochemical Proton-Coupled Electron Transfer of TiO2 Thin Films on Silicon.

TiO2 thin films are often used as protective layers on semiconductors for applications in photovoltaics, molecule-semiconductor hybrid photoelectrodes, and more. Experiments reported here show that TiO2 thin films on silicon are electrochemically and photoelectrochemically reduced in buffered acetonitrile at potentials relevant to photoelectrocatalysis of CO2 reduction, N2 reduction, and H2 evolution. On both n-type Si and irradiated p-type Si, TiO2 reduction is proton-coupled with a 1e-:1H+ stoichiometry, as demonstrated by the Nernstian dependence of the Ti4+/3+ E1/2 on the buffer pKa. Experiments were conducted with and without illumination, and a photovoltage of ∼0.6 V was observed across 20 orders of magnitude in proton activity. The 4 nm films are almost stoichiometrically reduced under mild conditions. The reduced films catalytically transfer protons and electrons to hydrogen atom acceptors, based on cyclic voltammogram, bulk electrolysis, and other mechanistic evidence. TiO2/Si thus has the potential to photoelectrochemically generate high-energy H atom carriers. Characterization of the TiO2 films after reduction reveals restructuring with the formation of islands, rendering TiO2 films as a potentially poor choice as protecting films or catalyst supports under reducing and protic conditions. Overall, this work demonstrates that atomic layer deposition TiO2 films on silicon photoelectrodes undergo both chemical and morphological changes upon application of potentials only modestly negative of RHE in these media. While the results should serve as a cautionary tale for researchers aiming to immobilize molecular monolayers on "protective" metal oxides, the robust proton-coupled electron transfer reactivity of the films introduces opportunities for the photoelectrochemical generation of reactive charge-carrying mediators.

Unlocking the Potential of Metal-Doping Fe2O3/Rice Husk Ash Catalysts for Low-Temperature CO-SCR Enhancement.

Transition metal oxides are efficient bifunctional catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) using CO. Nonetheless, their poor activity at lower temperatures constrains broader industrial application. Herein, we propose an optimized Fe2O3-based catalyst through strategic metal doping with Cu, Co, or Ce, which engenders a harmonious balance for the synergistic removal of CO and NOx. Among the developed catalysts, Co-doped Fe2O3, supported by rice husk ash, demonstrates superior low-temperature CO-SCR activity, achieving CO and NOx conversion ratios and N2 selectivity above 98.5% at 100-500 °C. The enhanced catalytic performance is attributed to the catalyst's improved redox properties and acidity, engendered by strong Fe-Ox-Co interactions. Furthermore, the CO-SCR reaction adheres to the Langmuir-Hinshelwood and Eley-Rideal mechanisms. Our findings shed light on the future industrial application of low-temperature CO and NOx near-zero emission technology and provide a strategy for the design of low-cost SCR catalysts.

An experimental study of the dynamics and mass transfer of a rising bubble

In this work, the rise characteristics of shrinking CO2 and non-shrinking N2 bubbles in distilled water for a wide range of bubble sizes in ellipsoidal and wobbly regime (deq = 1.5 mm to 6.5 mm) have been investigated. For these bubbles, their size, trajectory, and rise velocity have been measured using a moving camera system, while the dissolved CO2 is qualitatively studied using a planar laser-induced fluorescence (P-LIF) technique. We explore the interplay between hydrodynamics and mass transfer using well-studied regimes in bubble behaviour. Our results show that the interrelation between mass transfer and bubble rise dynamics is quasi-steady in nature and strongly dependent on wake-induced effects: shape and path oscillations. Based on an analogy of the two phenomena, we conclude that the behaviour of smaller bubbles (<2 mm) as immobile spheres from a mass transfer perspective is not related to the mobility of the interface, but a lack of surface renewal of dissolved gas at the interface. We propose a mechanistic correlation for calculating the mass transfer coefficient, kL, in this regime of bubble size, using the knowledge of the drag coefficient.

Smart predictive viscosity mixing of CO2–N2 using optimized dendritic neural networks to implicate for carbon capture utilization and storage

Crucial for carbon capture, utilization, and storage (CCUS) initiatives and diverse industries, heat transfer underscores the need for a precise assessment of carbon dioxide (CO2) and nitrogen (N2) viscosities in gaseous blends across various temperatures. This research pioneers an intelligent model by enhancing the dendritic neural regression (DNR) framework, employing the Seagull Optimization Algorithm with Marine Predator Algorithm (SOAMPA) for optimal predictions. Leveraging recent advancements in metaheuristic optimization techniques, the study reveals the superior performance of the novel SOAMPA approach in predictive accuracy, marking a significant breakthrough in predicting CO2-N2 mixture viscosities with implications for advancing CCUS projects and diverse industries. The optimized DNR model, empowered by the modified SOAMPA optimization technique, contributes to estimating the viscosity of N2-CO2 mixture gases. Utilizing inputs like pressure, temperature, mole fraction of N2, and model fraction of CO2, the models are trained and tested on a dataset comprising over 3030 data samples from public literature. Key contributions encompass proposing an optimized DNR approach, introducing the modified SOAMPA technique, and demonstrating its superiority over established optimization methods in conjunction with the traditional DNR model for predicting viscosity based on real experimental datasets.

Stability of potassium-promoted hydrotalcites for CO2 capture over numerous repetitive adsorption and desorption cycles

Hydrotalcite-based adsorbents have demonstrated their potential for CO2 capture, particularly in the sorption-enhanced water-gas shift (SEWGS) process. This study aims to investigate the long-term stability of a potassium-promoted hydrotalcite-based adsorbent (KMG30) over many repetitive cycles under various operating conditions. The stability of the adsorbent, both in terms of its structure and sorption capacity, is examined through multiple consecutive adsorption and desorption cycles. However, it is observed that the capacity for CO2 adsorption decreases when subjected to many repeated cycles of CO2 adsorption followed by N2 flushing, or to many repeated cycles of H2O adsorption followed by N2 flushing. In-depth investigations employing various techniques such as thermogravimetric experiments, XRD, BET, and SEM-EDX analyses were conducted to elucidate the underlying phenomena that can explain this observed behavior. The former can be attributed to aggregation of K2CO3 from the sorbent during the CO2 adsorption and N2 flushing cycles (which can be reversed by re-dispersing the K2CO3 either by exposure to air or by processing the sorbent with cycles of CO2/H2O adsorption followed by N2 flushing), whereas the latter is ascribed to the only partial regeneration of the reactive site (referred to site C in earlier work), most likely associated with K2CO3 modification on MG30. In this case, morphological changes were found to be insignificant. Remarkable stability of KMG30, as known from SEWGS process studies, was confirmed during cycles of CO2 adsorption/steam purge. These findings significantly enhance our understanding of the stability of potassium-promoted hydrotalcite-based adsorbents and provide valuable insights for the design of diverse sorption processes.