Search Results (33)

The synthesis of high performance catalysts for the catalytic wet oxidation (CWO) of N-methyldiethanolamine (MDEA) in water remains a challenge, and is a topic of considerable importance in relation to sustainability. In this paper, a Ru-CN_x/CeO₂ catalyst was synthesized through a modified impregnation process for the CWO of MDEA, exhibiting a high activity of 80% COD removal at 180 °C and 2.5 MPa. EPR, Raman, and XPS characterizations revealed that the CN_x species facilitated the reduction in Ru⁴⁺ to Ru⁰ species and enhanced the Ru–Ce interaction to form a high-density Ru-O-Ce structure with Ce³⁺ sites, which strongly correlate to the generation of oxygen vacancies. The oxygen vacancies enabled the adsorption and activation of the oxygen, generating active species (h⁺, ·O₂⁻, and ·OH) that effectively oxidized the MDEA during the catalytic reaction. Full article

In chemical absorption for carbon capture, the regeneration heat is a key factor determining solvent regeneration energy consumption, and the sterically hindered amine 2-amino-2-methyl-1-propanol (AMP) has great potential for application. In this paper, a CO₂ reaction heat measurement system designed and constructed by our team was used to perform a comparative study on AMP and monoethanolamine (MEA). Moreover, five additives—MEA, diglycolamine (DGA), diethanolamine (DEA), methyldiethanolamine (MDEA), and piperazine (PZ)—were introduced into AMP-based solutions to investigate the promotion performance of these blended solvents. The results revealed that although AMP exhibited a slower absorption rate compared to MEA, it demonstrated a higher CO₂ loading capacity and cyclic capacity, as well as a lower reaction heat, making it advantageous in terms of regeneration energy consumption. At the same total concentration, the absorption capacity of blended solutions (excluding AMP-MEA solutions) was generally lower than that of single-component AMP solutions. Among these additives, MEA and PZ could enhance the absorption rate clearly yet increase the reaction heat at the same time; DGA and DEA could decrease the overall absorption performance. Generally, AMP-MDEA solutions showed the best desorption performance, with the 15 wt% AMP + 5 wt% MDEA mixture demonstrating the lowest regeneration heat and good cyclic capacity. Full article

The increase in atmospheric CO₂ caused by human activities has driven the development of technologies to capture this gas before it reaches the atmosphere. This study analyzed CO₂ sorption using amine-based solvents, such as methyldiethanolamine (MDEA), diethylenetriamine (DETA), triethanolamine (TEA), and monoethanolamine (MEA) in 40 wt.% aqueous solutions, under high-pressure conditions (initial pressure: 500 psia) and room temperature (30 °C), in both non-stirred and stirred systems. Piperazine (PZ), a heterocyclic compound, was tested as an additive to improve the kinetics of the CO₂ sorption process. Kinetic and thermodynamic analyses were conducted to evaluate the efficiency of each amine-based solution in terms of reaction rate and CO₂ loading capacity. MEA and TEA exhibited higher reaction rates, while DETA and MDEA were the most thermodynamically efficient due to the highest CO₂ loading capacity. The PZ kinetic behavior depended on the equipment used; in the non-stirred system, no kinetic effect was observed, while in the stirred system, this effect was appreciable. Additionally, a corrosivity study revealed that MEA, a primary amine, was the most corrosive, whereas TEA, a tertiary amine, was the least corrosive. Full article

Traditional alkanolamine absorption methods for CO₂ capture suffer from significant absorbent loss and high regeneration energy consumption. To address this issue, novel blended alkanolamine formulations based on monoethanolamine (MEA), methyldiethanolamine (MDEA) and 2–amino–2–methyl–1–propanol (AMP) were investigated. Based on the optimization of CO₂ absorption conditions, a low–temperature and high–efficiency microwave heating desorption method for CO₂ was proposed, and the microwave heating desorption process of a CO₂ alkanolamine absorption solution was optimized. The results show that when the mass ratio of monoethanolamine (MEA), methyldiethanolamine (MDEA) and 2–amino–2-methyl–1–propanol (AMP) was 4:5:1, the composite alkanolamine solution with a concentration of 20% had the best absorption effect at an absorption temperature of 30 °C. The desorption efficiency of this group of formulations at 95 °C reached 89% in 4 min. Compared with the traditional heating desorption method, the CO₂ desorption rate of the microwave heating method at 95 °C increased by 62%, the desorption time was significantly shortened, and the energy consumption was significantly reduced. This study provides a new research direction for the efficient and low-energy desorption of CO₂ by blended alkanolamine. Full article

This study employs Density Functional Theory (DFT) calculations and traditional all-atom Molecular Dynamics (MD) simulations to reveal atomistic insights into a task-specific Deep Eutectic Solvent (DES) supported by graphene oxide with the aim of mimicking its application in the natural gas desulfurization process. The DES, composed of N,N,N′,N′-tetramthyl-1,6-hexane diamine acetate (TMHDAAc) and methyldiethanolamine (MDEA) supported by graphene oxide, demonstrates improved efficiency in removing hydrogen sulfide from methane. Optimized structure and HOMO-LUMO orbital analyses reveal the distinct spatial arrangements and interactions between hydrogen sulfide, methane, and DES components, highlighting the efficacy of the DES in facilitating the separation of hydrogen sulfide from methane through DFT calculations. The radial distribution function (RDF) and interaction energies, as determined by traditional all-atom MD simulations, provide insights into the specificity and strength of the interactions between the DES components supported by graphene oxide and hydrogen sulfide. Importantly, the stability of the DES structure supported by graphene oxide is maintained after mixing with the fuel, ensuring its robustness and suitability for prolonged desulfurization processes, as evidenced by traditional all-atom MD simulation results. These findings offer crucial insights into the molecular-level mechanisms underlying the desulfurization of natural gas, guiding the design and optimization of task-specific DESs supported by graphene oxide for sustainable and efficient natural gas purification. Full article

Hydrogen is an industrial raw material both for the production of chemicals and for oil refining with hydrotreating. It is the subject of increasing attention for its possible use as an energy carrier and as a flexible energy storage medium. Its production is generally accomplished in Steam Methane Reforming (SMR) plants, where a gaseous mixture of CO and H₂, with a limited number of other species, is obtained. The process of production and purification generates relevant amounts of carbon dioxide, which needs to be removed due to downstream process requirements or to limit its emissions to the atmosphere. A work by IEAGHG focused on the study of a state-of-the-art Steam Methane Reforming plant producing 100 kNm³/h of H₂ and considered chemical absorption with MethylDiEthanolAmine (MDEA) solvent for removing carbon dioxide from the PSA tail gas in a baseline scheme composed of the absorber, one flash vessel and the regeneration column. This type of process is characterized by high energy consumption, in particular at the reboiler of the regeneration column, usually operated by employing steam, and modifications to the baseline scheme can allow for a reduction of the operating costs, though with an increase in the complexity of the plant. This work analyses three configurations of the treatment section of the off gas obtained after the purification of the hydrogen stream in the Pressure Swing Adsorption unit with the aim of selecting the one which minimizes the overall costs so as to further enhance Carbon Capture and Storage in non-power industries as well. Full article

This study explores the stability of electrodeposited copper catalysts utilized in electrochemical CO₂ reduction (ECR) across various amine media. The focus is on understanding the influence of different amine types, corrosion ramifications, and the efficacy of pulse ECR methodologies. Employing a suite of electrochemical techniques including potentiodynamic polarization, linear resistance polarization, cyclic voltammetry, and chronopotentiometry, the investigation reveals useful insights. The findings show that among the tested amines, CO₂-rich monoethanolamine (MEA) exhibits the highest corrosion rate. However, in most cases, the rates remain within tolerable limits for ECR operations. Primary amines, notably monoethanolamine (MEA), show enhanced compatibility with ECR processes, attributable to their resistance against carbonate salt precipitation and sustained stability over extended durations. Conversely, tertiary amines such as methyldiethanolamine (MDEA) present challenges due to the formation of carbonate salts during ECR, impeding their effective utilization. This study highlights the effectiveness of pulse ECR strategies in stabilizing ECR. A noticeable shift in cathodic potential and reduced deposit formation on the catalyst surface through periodic oxidation underscores the efficacy of such strategies. These findings offer insights for optimizing ECR in amine media, thereby providing promising pathways for advancements in CO₂ emission reduction technologies. Full article

A series of cationic waterborne polyurethane (CWPU) emulsions was synthesized with isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) as hard segments; polyol (N210) and polyethylene glycol (PEG-2000) as soft segments; N-methyldiethanolamine (MDEA) as a hydrophilic chain extender; and trimethylolpropane (TMP) as a crosslinker. Then, the effects of the R-value, MDEA content, and TMP content on the properties of the CWPU emulsion, film, and fabric treatment were investigated. The results indicated that when the R-value was 3.0, the MEDA content accounted for 4.0% of the solid and the TMP content accounted for 1.0% of the solid. CWPU has excellent storage stability. Applying it to the fixing treatment of the viscose fiber fabrics can effectively improve the color fastness to rubbing, elasticity, surface smoothness, and anti-static properties. Full article

Vinyl-capped cationic waterborne polyurethane (CWPU) was prepared using isophorone diisocyanate (IPDI), polycarbonate diol (PCDL), N-methyldiethanolamine (MDEA), and trimethylolpropane (TMP) as raw materials and hydroxyethyl methacrylate (HEMA) as a capping agent. Then, a crosslinked FPUA composite emulsion with polyurethane (PU) as the shell and fluorinated acrylate (PA) as the core was prepared by core-shell emulsion polymerization with CWPU as the seed emulsion, together with dodecafluoroheptyl methacrylate (DFMA), diacetone acrylamide (DAAM), and methyl methacrylate (MMA). The effects of the core-shell ratio of PA/PU on the surface properties, mechanical properties, and heat resistance of FPUA emulsions and films were investigated. The results showed that when w(PA) = 30~50%, the stability of FPUA emulsion was the highest, and the particles showed a core-shell structure with bright and dark intersections under TEM. When w(PA) = 30%, the tensile strength reached 23.35 ± 0.08 MPa. When w(PA) = 50%, the fluorine content on the surface of the coating film was 14.75% and the contact angle was as high as 98.5°, which showed good hydrophobicity; the surface flatness of the film was observed under AFM. It is found that the tensile strength of the film increases and then decreases with the increase in the core-shell ratio and the heat resistance of the FPUA film is gradually increased. The FPUA film has excellent properties such as good impact resistance, high flexibility, high adhesion, and corrosion resistance. Full article

As the most mature natural gas sweetening process, absorption has always been improved to meet the separation requirement. Recently, ultrasonic irradiation has been proposed as a technique that can intensify CO₂ absorption. However, further studies are still required, particularly focusing on the sonochemical effect. Since the influence of the sonochemical effect on the reaction pathway is still debatable, attention must be given to verifying the influence of ultrasonic irradiation on the chemical reactions of CO₂ absorption. Hence, this work aims to evaluate the influence of $\dot{\mathrm{O}\mathrm{H}}$ radicals generated by the sonochemical effect on the chemical reactions involved during CO₂ absorption using promoter-free methyldiethanolamine (MDEA). For the evaluation, various samples under irradiated and non-irradiated conditions are analyzed using the HPLC characterization technique. The results show that the hypothesis of changing the reaction pathway due to the presence of the sonochemical effect is invalid. However, it can accelerate the generation of hydroxyl radicals ($\dot{\mathrm{O}\mathrm{H}}$) via water sonolysis. Thus, the origin of sonochemistry in aqueous solutions is defined as water sonolysis. The analysis of the CO₂ absorption rate also demonstrates the presence of accelerated chemical reactions (contributed by the $\dot{\mathrm{O}\mathrm{H}}$ radicals), which could potentially make the slow kinetic MDEA more practical for industrial application. Full article

CO₂ sorption–desorption cycles with a methyldiethanolamine (MDEA)/piperazine (PZ) blend have been performed with a rotoevaporator. Similar to other CO₂ separation technologies, the heating involved in MDEA/PZ solvent regeneration is the most energy-intensive step in the overall CO₂ separation process. Thus, this study investigated the desorption kinetics under low-pressure (<200 mbar) and low-temperature conditions in the range from 308 to 363 K with the aim of reducing costs. The CO₂ desorption time to unload the samples from ~2.35 mol/kg to below the threshold of 1 mol/kg was reduced from 500 s at 333 K to 90 s at 363 K. The Avrami–Erofoyev model was found to fit the experimental kinetic data accurately. The Arrhenius law calculations provided an activation energy of the CO₂ desorption process equal to 76.39 kJ/mol. It was demonstrated that the combination of a pressure reduction and the increase in temperature resulted in an enhancement of the desorption kinetics, especially at low temperatures. The combined effect of these two factors resulted in higher desorption kinetics compared to the individual effects of either factor alone. Solvent regeneration at a low temperature was demonstrated to be a valid option when coupled with pressure reduction. Full article

The present study evaluated the environmental impacts of post-combustion CO₂ capture and recovery via membrane–gas absorption processes. We have used SimaPro v.9 packages with the Ecoinvent v3.5 database employing two different methods, ReCiPe 2016 Endpoint (H) and Midpoint (H), considering a fundamental methodological framework to determine the most environmentally friendly experimental condition. Life cycle impact categories were examined and assessed supposing a functional unit of 1 kgCO₂/h recovered. Fourteen environmental impact categories including global warming, ozone depletion, eutrophication, and toxicity potentials have been evaluated within the context of a gate-to-gate approach focusing on only the process stage. Simulation results showed that the maximum liquid flow rate, sweep helium flow rate together with the minimum solvent concentration demonstrated the highest impact on human health, ecosystem, and resources. The usage of pure methyldiethanolamine (MDEA) activated by piperazine as a reactive absorbent provided the lowest environmental impact due to the elimination of the energy needed to heat and evaporate water present in aqueous absorbent solutions and the prevention of the excess water consumption depending on meeting the water needed for reactive absorption of CO₂ in tertiary amine MDEA from simulated humidified flue gas stream. The study highlights the importance of LCA in the determination of an environmentally more sustainable condition during the capture and recovery of post-combustion CO₂ by gas absorption and stripping using membrane contactors in tertiary amine MDEA. Full article

The gas sweetening process removes hydrogen sulfide (H₂S) in an acid gas removal unit (AGRU) to meet the gas sales’ specification, known as sweet gas. Monitoring the concentration of H₂S in sweet gas is crucial to avoid operational and environmental issues. This study shows the capability of artificial neural networks (ANN) to predict the concentration of H₂S in sweet gas. The concentration of N-methyldiethanolamine (MDEA) and Piperazine (PZ), temperature and pressure as inputs, and the concentration of H₂S in sweet gas as outputs have been used to create the ANN network. Two distinct backpropagation techniques with various transfer functions and numbers of neurons were used to train the ANN models. Multiple linear regression (MLR) was used to compare the outcomes of the ANN models. The models’ performance was assessed using the mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R²). The findings demonstrate that ANN trained by the Levenberg–Marquardt technique, equipped with a logistic sigmoid (logsig) transfer function with three neurons achieved the highest R² (0.966) and the lowest MAE (0.066) and RMSE (0.122) values. The findings suggested that ANN can be a reliable and accurate prediction method in predicting the concentration of H₂S in sweet gas. Full article

Absorption is one of the most established techniques to capture CO₂ from natural gas and post-combustion processes. Nevertheless, the absorption process frequently suffers from various operational issues, including foaming. The main objective of the current work is to elucidate the effect of degradation product on the foaming behavior in methyldiethanolamine (MDEA) and piperazine (PZ) solution and evaluate the antifoaming performance of polydimethylsiloxane (PDMS) antifoam. The foaming behavior was investigated based on types of degradation product, temperature, and gas flow rate. The presence of glycine, heptanoic acid, hexadecane, and bicine in MDEA-PZ solution cause significant foaming. The presence of hexadecane produced the highest amount of foam, followed by heptanoic acid, glycine and lastly bicine. It was found that increasing the gas flow rate increases foaming tendency and foam stability. Furthermore, increasing temperature increases foaming tendency, but reduces foam stability. Moreover, PDMS antifoam was able to reduce foam formation in the presence of different degradation products and at various temperatures and gas flow rates. It was found that PDMS antifoam works best in the presence of hexadecane with the highest average foam height reduction of 19%. Hence, this work will demonstrate the cause of foaming and the importance of antifoam in reducing its effect. Full article

Exploring new solvents for efficient acid gas removal is one of the most attractive topics in industrial gas purification. Herein, using 2-tertiarybutylamino-2-ethoxyethanol as an absorbent in a packed column at atmospheric pressure was examined for selective absorption of H₂S from mixed gas streams. In the present work, the acid gas load, H₂S absorption selectivity, acid gas removal ratio, amine solution regeneration performance, and corrosion performance were investigated through evaluating experiments absorbing H₂S and CO₂ by using methyldiethanolamine and 2-tertiarybutylamino-2-ethoxyethanol. The experimental results illustrate that the H₂S absorption selective factors were 3.88 and 15.81 by using 40% methyldiethanolamine and 40% 2-tertiarybutylamino-2-ethoxyethanol at 40 °C, respectively, showing that 2-tertiarybutylamino-2-ethoxyethanol is an efficient solvent for selective H₂S removal, even better than methyldiethanolamine. Based on the consideration of cost, we added 5% TBEE to 35% MDEA to form a blended aqueous solvent. To our satisfaction, the blended amine solvent obtained a 99.79% H₂S removal rate and a 22.68% CO₂ co-absorption rate, while using the methyldiethanolamine alone achieved a 98.33% H₂S removal rate and a 23.52% CO₂ co-absorption rate; the blended solvent showed better H₂S absorption efficiency and selectivity. Taken together, this work provides valuable information for a promising alkanolamine for acid gas removal, and the preliminary study has found that the aqueous blend of methyldiethanolamine and 2-tertiarybutylamino-2-ethoxyethanol is an efficient solvent for selective H₂S removal, which not only extends the application field for sterically hindered amines, but also opens up new opportunities in blended solvent design. Full article