Ethanolamine Research Articles

Industrial test of post combustion CO2 capture by reactive absorption with two new solvents in natural gas power plant

The post-combustion chemical decarbonization process is one of the key technology selections for the low-carbon development of natural gas power plants. The high energy consumption of amine regeneration is hindering its commercial application. In this paper, two new mixed amines solvent 15%Diethylaminoethanol (DEEA) +9% Piperazine (PZ)+ 6% Monoethanolamine (MEA) named DT01-3 and 22% 1,4-butanediamine (BDA)+ 4% N-Methyldiethanolamine (MDEA) + 4% 2-Amino-2-methyl-1-propanol (AMP) named DT02-2 are verified by the 3000Nm3/h industrial demonstration system. The steady state condition was gradually established by adjusting the main parameters such as flue gas flow rate, absorber inlet flue gas temperature, solvent circulation flow rate, regeneration tower operation pressure, steam flow rate and so on with the goal of maintaining ≥90% of the capture efficiency. The results show that the CO2 capture efficiency of DT01-3 and DT02-2 is 91.23% and 90.81% respectively. The regeneration heat consumption is 3.65 GJ/tCO2 and 3.73 GJ/tCO2. The amines consumption is 0.95kg/tCO2,1.1kg/tCO2. The operating cost of DT01-3 and DT02-2 is 336.37 CNY/t,346.04 CNY/t, which is 20.94%,18.68% lower compared with MEA.

POPs to COFs by post-modification: CO2 chemisorption and dissolution.

Porous organic polymers (POPs) and covalent organic frameworks (COFs) are hierarchical nano materials with variable applications. To our knowledge, this is the first report of a post-modified, non-renewable, DMSO-soluble M-POP/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) upon atmospheric H2O/CO2 trapping after 48 h, forming a DBUH+·HCO3- adduct, as verified by solution carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. The success of the post-modification resulting from aldehyde enriched POPs was proven spectroscopically. The accessible functional group was reacted with excess monoethanolamine (MEA) resulting in the formation of M-POP. Away from CO2 physisorption, only few examples have been reported on the chemisorption process. One such example is the ethylene diamine-functionalized E-COF, capable of capturing CO2via carbamation. This was evidenced by several qualitative measurements including colorimetry and conductivity, which showed an unprecedented water solubility for a 2D COF material. The crystallinity of COFs as a result of post-modification was proven by powder X-ray diffraction (PXRD).

Enhancements of monoethanolamine CO2 absorption rate and degradation in the presence of nickel nanoparticles catalysts

In the study of the catalytic effect of nickel nanoparticles (NiNPs) on amine-based CO2 capture systems, monoethanolamine (MEA) was subjected to a CO2 loading at greatly varying concentrations (3–30 wt%) at two temperatures (20 °C and 50 °C) for the first time in a lab study to the best of our knowledge. This study shows that NiNPs can enhance the rate of CO2 absorption into MEA and that its enhancement is greater at 20 °C than at 50 °C. Solutions were loaded with CO2 until full saturation and the mass gain was recorded. At 20 °C the overall enhancement ranged between 4.0–7.4% with the optimum (>7.0%) observed at concentrations of 5 wt% and 20 wt% of MEA with NiNPs. In addition, there were large reductions in the time that it takes to fully saturate the MEA with CO2, (up to a 42% reduction) and there were differences in peak loading (molCO2/molmea) between the NiNPs solution and the control (without NiNPs) (of up to 12.5% for the same time at 20 °C and 30 wt% of MEA with NiNPs). For the first time to the best of our knowledge, the degradation of MEA with and without NiNPs was studied; an oxidative degradation experiment (30 wt%, 0.4 molCO2/molmea, 7.5 mL/min CO2, 0.35 L/min air, 55 °C) based on typical absorber conditions and a thermal degradation experiment based on typical stripper conditions (30 wt%, 0.5 molCO2/molmea, 135 °C) were carried out. Gas chromatography-mass spectrometry was used to identify and quantify the major degradation compounds. It is found that NiNPs increase the rate of both oxidative and thermal degradation.

Evaluating CO2 Capture Performance of Trisolvent MEA-BEA-AMP with Heterogeneous Catalysts in a Novel Bench-Scale Pilot Plant.

To reduce the huge energy cost of CO2 capture technology applicable in industry, the CO2 absorption-desorption performance was conducted in a novel bench-scale pilot plant with hot water as a heat source. The trisolvent MEA(monoethanol amine)-BEA(butylethanol amine)-AMP(2-amino-2-methyl-1-propanol) was prepared at a specific concentration to analyze the CO2 capture performance and compared with 5 M MEA as the benchmark. Meanwhile, several solid acid catalysts, blended H-ZSM-5/γ-Al2O3(1/2), or HND-8, were packed in the desorber, and the solid base catalyst, CaCO3 or CaMg(CO3)2, was packed in the absorber with random packing. The CO2 absorption efficiency (AE), cyclic capacity (CC), and heat duty (HD) were tested onto MEA-BEA-AMP and MEA under various operating conditions. Experimental results indicated that the performance of 4.3 mol/L MEA-BEA-AMP was significantly better than 5 M MEA under both catalytic and noncatalytic operation. The most energy efficient combination of this study was discovered as 0.3 + 2 + 2 mol/L MEA-BEA-AMP, with 50 g (CaCO3/CaMg(CO3)2) in the absorber and 150 g H-ZSM-5/γ-Al2O3(1/2) in the desorber. The heat duty reached as low as 2.4 GJ/tCO2 at a FG of 7.0 L/min and a FL of 70 mL/min. These results were highly applicable in an industrial amine scrubbing pilot plant for CO2 capture.

Preparation, and Evaluation of waste ground tyre rubber as Antioxidant, Antibacterial Activity and anticorrosion inhibitor for N80 steel in 0.1N H3PO4

In this work, polybutadiene (PBD) was prepared from waste tires. The halogenated of polybutadiene was grafted with mono, di, and triethanolamine, the grafting was studied by X-ray diffraction and scanning electron microscopy. And according to the thermal characteristics (TGA and DSC), the produced compound was thermally stable up to 202 °C. Using potentiodynamic polarization techniques, the adsorption and corrosion inhibiting effects of three grafting polymers on N80 steel in 0.1 N H3PO4 as aggressive environments were measured at four different temperatures: 25, 35, 45, and 55°C. The prepared polymers have excellent inhibition efficiency at high temperatures. The pBut-g-mono ethanol amine is the corrosion inhibitor that is most effective in all tested temperatures. The adsorption behavior of the polymers was found to follow the Langmuir isotherm, and the values ​​of the free energy variation illustrate the mixed types of adsorptions occurring on the N80 surface. Tafel curves indicate that the tested polymers act as mixed anodic and cathodic inhibitors. In contrast, indicates that all tested modifying polymers had antioxidant capability.

Amino-modified ZIF-8 for enhanced CO2 capture: Synthesis, characterization and performance evaluation

The urgent need for sustainable and innovative approaches to mitigate the increasing levels of atmospheric CO2 necessitates the development of efficient methods for its removal. In this study, we focus on the new, innovative approach for synthesis and functionalization of metal-organic framework (MOF) ZIF-8 in one step at room temperature to enhance its capacity for CO2 capture. Specifically, we investigated the impact of four amino-compounds, namely tetraethylenepentamine (TEPA), hexadecylamine (HDA), ethanolamine (ELA), and cyclopropylamine (CPA), on the chemical structure, size, surface area and porosity, and CO2 capturing of ZIF-8 powder. By varying concentrations of the amino-compounds, we examined their influence on the ZIF-8 properties. Our findings demonstrate that each amino-compound and its respective concentration exhibit distinct effects on the characteristics of ZIF-8. Notably, the ZIF-8 sample functionalized with the highest presented concentration of TEPA exhibited significant improvement in CO2 trapping efficiency, with a 33.3% enhancement. Moreover, least concentrated samples with added HDA or CPA demonstrated notable improvements with enhancements of 46.6% and 18.6%, respectively. These results highlight the potential of simple synthesis and functionalization techniques for MOFs in enhancing their CO2 capture capabilities. The findings from this study offer new opportunities for the development of strategies to mitigate CO2 emissions using MOFs.

Enhancing the formation of eco-friendly CO2 adsorbent through utilizing the RSM technique and implementation of PAN/PU electrospinning and radiation-grafted approaches

In this research, the original, efficient, novel NF-PAN/PU-GMA-EA nanocomposite was fabricated and used as an adsorbent to remove carbon dioxide from methane. For this purpose, two cheap polymers, including industrial polyacrylonitrile (PAN) and industrial polyurethane (PU) were used to prepare NF-PAN nanofibers under the electrospinning method. Then, the synthesis procedure was performed by grafting glycidyl methacrylate (GMA) onto NF-PAN nanofibers and ethanolamine (EA), diethylamine (DEA), and triethylamine (TEA) as the modified agents. In addition, the response surface methodology based on the central composite design experiments was developed to predict adsorption capacity. The aforementioned approach determined the impacts of GMA monomer (10–30%); gamma radiation at doses (10–50 kGy); and amine concentrations (40–100%). The results showed that ethanolamine was the best amine to modify the surface of NF-PAN/PU nanofibers. The highest adsorption was obtained equal to 2.95 mmol CO2/g adsorbents at a radiation dose of 28.03 kGy, 25.77% GMA and 66.45% EA. The results described that the variation from micro to nanoscale increases the adsorption capacity. Also, a significant increase in the adsorption capacity in the radiation-grafted adsorbent was observed equally to be 73.15% higher than the non-irradiated adsorbent. The adsorption capacity was decreased by about 9% after four adsorption and desorption cycles (regeneration at 80 °C and 15 min), indicating the proper performance of the novel eco-friendly synthesized adsorbents.

A low energy-consuming phase change absorbent of MAE/DGM/H2O for CO2 capture

The concept of phase change absorbents has been widely studied as a novel and low-energy consumption option for CO2 capture. This work screened diethylene glycol dimethyl ether (DGM) from 17 physical solvent species as a better phase change accelerator for absorbents of 2-(methylamino)ethanol (MAE)-physical solvent-H2O. Then, the optimized mass ratio of 30:49:21 for MAE-DGM-H2O solution was investigated with phase change behaviors, CO2 absorption–desorption performance, cyclic capacity, and energy consumption. The experimental results showed that the cyclic CO2 capacity reached 1.32 mol/L and the CO2-rich phase made up only 50.4 % of the total volume for the 30 wt%MAE-49 wt%DGM-21 wt%H2O, as well as its regenerative energy consumption was 40 % lower than that of 30 wt% monoethanolamine (MEA) solution. Also, the viscosity and surface tension gap of the CO2-rich phase and CO2-lean phase for the optimized absorbent were studied. It was observed that those gaps increase with the increasing mass ratio of DGM. In addition, the possible phase change mechanism was proposed by using the dipole moment values of components calculated by Gaussian (B3LYP/6-31G) coupled with 13C NMR spectra.

Carbon dioxide absorption using monoethanolamine, piperazine and n-metil-2-pirolidon solvents under counter current regime in packed column reactor

In this research the carbon dioxide absorption using Monoethanolamine (MEA), Piperazine (PZ) and N-Metil-2-pirolidon (NMP) solvents and their different blends (MEA/NMP, PZ/NMP, MEA/PZ) in packed column reactor filled with Raschig rings was investigated and compared for efficient carbon dioxide absorption. The process was followed in a countercurrent regime under a liquid flow rate of 200 mL/min, gas flow rate of 2.5 L/min, and CO2 concentration of 50,000 ppm. Carbon dioxide removal efficiency (%), absorption capacity (mol CO2/mol solvent), overall mass transfer coefficient (1/min) and absorption rate (mol/l.s) were monitored. The highest obtained values for carbon dioxide removal efficiency, absorption capacity and overall mass transfer coefficient were 57.5%, 0.148 mol CO2/mol solvent and 2.178 min−1 respectivelly when 0.03 M MEA/0.07 M PZ in a hybrid system was used. It was concluded that PZ blends with MEA were successful absorbent as the organic physical solvent whereas NMP didn't show improving effect in blends with MEA on the absorption efficiency.

Potassium β–alanine – A promising agent for reducing carbon capture cost via electrochemically mediated amine regeneration

Electrochemically mediated amine regeneration (EMAR) for CO2 capture is a promising substitute for traditional organic amine–based CO2 capture by replacing the thermal process with electricity. To avoid problems such as oxidative degradation, toxicity, volatilization, and precipitation of organic amine absorbent, potassium β–alanine was suggested as an absorbent using EMAR process for the first time in this study. The CO2 absorption performance under different copper loading and chemical reactions were studied, and cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and the Taffel extrapolation method were used to study the electrochemical characterization. Compared to the benchmark monoethanolamine (MEA) system, a smaller potential difference between oxidation and reduction peak was acquired in the potassium β–alanine system, of which the energy consumption was only 44.1% of the MEA system at the current of 100 A/m2. The cathode Faraday efficiency in the potassium β–alanine system was 101.9% higher than that in the MEA system at the current density of 25 A/m2. Furthermore, the result of scanning electron microscope of the electrode surface after desorption showed that potassium β–alanine absorbent improved the inhomogeneity of the electrode surface and was in favor of uniform current distribution. Overall, potassium β–alanine can be used as a more environmentally friendly absorbent in the EMAR system and has great potential to further reduce the actual energy consumption and improve the Faraday efficiency and cycling performance.

A technical and environmental comparison of novel silica PEI adsorbent-based and conventional MEA-based CO2 capture technologies in the selected cement plant

The cement industry accounts for almost 7 % of anthropogenic carbon dioxide emissions globally. Therefore, it is imperative to identify innovative solutions to mitigate carbon dioxide emissions from the cement industry.This study aims to evaluate and compare the technical and environmental aspects of integrating two post-combustion carbon capture processes (CCS) into a cement plant: the conventional monoethanolamine (MEA)-based CCS process and the novel silica-alkoxylated polyethyleneimine (SPEI)-based CCS process. Three scenarios were considered: (i) a reference cement plant without CCS, (ii) the conventional MEA-based CCS system integrated into a cement plant and (iii) the novel SPEI-based CCS system integrated into a cement plant. The technical evaluation results showed that the regeneration energy requirements for the conventional MEA and novel SPEI-based CCS processes were 3.53 GJ/tonne CO2 and 2.36 GJ/tonne CO2, respectively, to achieve a capture rate of 90 %. However, the performance of MEA-based carbon capture processes can be improved by using advanced amine formulations that offer lower regeneration heat requirements at 3.3 GJ/tonne CO2, although this is still higher than the SPEI-based carbon capture processes.The novel SPEI-based CCS process showed superior environmental performance compared to the conventional MEA-based CCS process. The endpoint single score was conducted which showed that the SPEI-based CCS process had a lower impact on human health, ecosystems, and resources (7 %, 9 %, and 26 % lower, respectively) compared to the MEA-based CCS process.

Corrosion performance of carbon/stainless steel in amine‐based solvents under different conditions for CO2 chemical absorption process

AbstractThe overall corrosion behavior of S304 stainless steel and A3 carbon steel in 30 wt.% MEA (monoethanolamine) and AMP/MEA (2‐amino‐2‐methyl‐1‐propanol / monoethanolamine) blended amine solutions at 40–100°C was investigated. The characterization analysis of the corroded material surfaces was performed, and the changes in the properties of both solvents after long‐term immersion corrosion were measured, including the accumulation of heat stable salts (HSS) and viscosity changes. The results of the long‐term immersion corrosion experiments showed that the corrosion rate of S304 stainless steel was significantly lower than that of A3 carbon steel in both amine solutions. However, the corrosion rate of both materials exhibited a similar trend, initially decreasing and then stabilizing over time. Due to the higher concentration of carbonate ions in the AMP/MEA system, it exhibited better overall corrosion resistance and degradation resistance compared to the MEA system. The main component of the corrosion product on carbon steel was identified as Fe2(OH)2CO3. The electrochemical test results showed that the corrosion current of S304 stainless steel was much smaller than that of A3 carbon steel, and its charge transfer resistance was much higher, indicating that it was less prone to electron loss in the organic amine solutions. Additionally, the AMP/MEA system exhibited superior corrosion resistance. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Effect of organic additives on NO<sub>2</sub> removal in the simultaneous absorption of SO<sub>2</sub> and NO<sub>2</sub> into limestone slurry

When SO<sub>2</sub> and NO<sub>2</sub> are simultaneously absorbed into limestone slurry, the SO<sub>3</sub><sup>2-</sup> (including HSO3 -) ions formed by the hydrolysis of SO<sub>2</sub> enhance the absorption rate of NO<sub>2</sub>. However, NO<sub>2</sub> absorption decreases due to the oxidation of SO<sub>3</sub><sup>2-</sup> in the presence of O<sub>2</sub>. To address this issue, simultaneous absorption was performed by adding organic additives: formic, acetic, propionic acid, monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA). These limestone slurries were denoted FS, AS, PS, MS, DS, and TS, respectively. As the acidity of the organic acid increases, SO<sub>3</sub><sup>2-</sup> oxidation inhibition also increases. Accordingly, the denitrification rate of the slurries with added organic acid was in the order of PS < AS < FS. SO<sub>3</sub><sup>2-</sup> oxidation inhibition by the ethanolamine additives increased with the number of 2-hydroxyethyl. The denitrification rate within 50 min of reaction was in the order of MS < TS < DS, which is attributed to the basicity and SO<sub>3</sub><sup>2-</sup> oxidation inhibition by ethanolamine. The denitrification rate after 50 min of the reaction was in the order of MS < DS < TS, which is presumed to be the result of SO<sub>3</sub><sup>2-</sup> oxidation inhibition and degradation due to the CO<sub>2</sub> absorption rate.

Deep eutectic solvents based on cyclodextrin-monoethanolamine for high-efficiency carbon dioxide capture under high temperature

In this work, a new series of deep eutectic solvents (DESs) based on cyclodextrins (CDs) and monoethanolamine (MEA) was designed firstly for CO2 capture. The effects of CD type, molar ratio, temperature, water content, and CO2 concentration on the absorption ability were investigated. Among these DESs, the sample with the MEAamine:CDhydroxyl molar ratio of three (βCM3) shows excellent absorption property of CO2 under the wide range of temperature (30–110 °C). In particular, high absorption capacity and rate (28.72 wt%, 1 h) is achieved under 80 °C. Meanwhile, cycling performance remains above 90% after 23 time cycles. The hydrogen bond structure and CO2 capture mechanism were demonstrated using FT-IR, NMR and DFT calculation. The circular hydrogen bond composed with hydroxyl of MEA and CD makes DESs more stable. The increase of activation energy of zwitterion intermediate and the decrease of stability of carbamate guarantee the DESs effective absorption CO2 and regeneration. This study provides the experimental and theoretical guidance for potential industrial applications of CO2 capture with novel DESs.

Investigation of CO2 Absorption Rate in Gas/Liquid Membrane Contactors with Inserting 3D Printing Mini-Channel Turbulence Promoters.

The CO2 absorption by Monoethanolamine (MEA) solutions as chemical absorption was conducted in the membrane gas absorption module with inserting 3D mini-channel turbulence promoters of the present work. A mathematical modeling of CO2 absorption flux was analyzed by using the chemical absorption theory based on mass-transfer resistances in series. The membrane absorption module with embedding 3D mini-channel turbulence promoters in the current study indicated that the CO2 absorption rate improvement is achieved due to the diminishing concentration polarization effect nearby the membrane surfaces. A simplified regression equation of the average Sherwood number was correlated to express the enhanced mass-transfer coefficient of the CO2 absorption. The experimental results and theoretical predictions showed that the absorption flux improvement was significantly improved with implementing 3D mini-channel turbulence promoters. The experimental results of CO2 absorption fluxes were performed in good agreement with the theoretical predictions in aqueous MEA solutions. A further absorption flux enhancement up to 30.56% was accomplished as compared to the results in the previous work, which the module was inserted the promoter without mini channels. The influences of the MEA absorbent flow rates and inlet CO2 concentrations on the absorption flux and absorption flux improvement are also illustrated under both concurrent- and countercurrent-flow operations.

Design and simulate an amine-based CO2 capture process for a steam methane reforming hydrogen production plant

Steam methane reforming (SMR) is a common technique for hydrogen production, however CO2, which is created as a by-product, needs to be captured. Chemical absorption utilizing amine solvents is the most economically practical method of CO2 capturing. Amines are a class of organic compounds that are commonly used as chemical solvents for carbon capture. The effectiveness of a particular amine as a carbon capture solvent depends on its chemical structure and properties. Some commonly used amines for carbon capture include monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). This study aims to simulate SMR hydrogen production plant utilizing amine-based carbon dioxide capture system using Aspen HYSYS V11 software and figure out the efficiency of different chemical solvents in capturing carbon dioxide. The results of this study show that MEA has high efficiency to capture CO2 due to its high reactivity and ability to form a strong chemical bond with CO2. However, it is also highly corrosive and can be costly to regenerate.

Adsorption of Diclofenac from Aqueous Solution by Amine-Functionalized Poly (Acrylonitrile-Co-Acrylic Acid) Microparticles Adsorbent

In this study, the synthesis of poly(acrylonitrile) (PAN) and poly(acrylonitrile-co-acrylic acid) (poly(ACN-co-AAc)) was carried out via redox polymerization, using sodium bisulphate (SBS) and potassium persulphate (KPS) as initiators. Subsequently, the resulting poly(ACN-co-AAc) was functionalized with ethanolamine (ETA) and ethylenediamine (EDA) to utilize as adsorbents for the removal of diclofenac from an aqueous solution. Both unfunctionalized and functionalized poly(ACN-co-AAc) were characterized using Fourier-Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), and Brunauer-Emmett-Teller (BET) analysis. The effects of pH, initial concentration of diclofenac solution, contact time, and adsorbent dosage were investigated during the adsorption process. The isotherm data were best fitted by the Langmuir model, indicating a mono-layered adsorption mechanism. The maximum adsorption capacities obtained from the Langmuir equation were higher for ETA-functionalized poly(ACN-co-AAc) at 120.5 mg/g, as compared to EDA-functionalized poly(ACN-co-AAc) at 80.6 mg/g. The experimental kinetic results showed that the pseudo-second-order model was a good fit for describing the adsorption rate of diclofenac for both ETA-functionalized poly(ACN-co-AAc) and EDA-functionalized poly(ACN-co-AAc), with R2 values of 0.9930 and 0.9906, respectively. This suggests that the chemisorption process is more favourable for the adsorption of diclofenac when using both types of adsorbents.

Research of novel polyamine-based biphasic absorbents for CO2 capture using alkanolamine to regulate the viscosity and mechanism analysis

Biphasic solvent has attracted widespread attention in CO2 chemical absorption technology due to its significant potential for reducing capture energy consumption. However, the high viscosity of CO2-rich phase after phase split could lead to issues such as high flow resistance, low heat transfer efficiency, and phase separation instability in application. To address these limitations, a strategy of using alkanolamine as a viscosity regulator for biphasic solvents was proposed. Diethanolamine(DEA), an alkanolamine regulator, was introduced to a system of polyamine/amide absorbent, and then a novel biphasic solvent of diethylenetriamine (DETA)/diethanolamine(DEA)/N, N-Dimethylacetamide(DMAC)/water(H2O) was developed. The viscosity of the CO2-rich phase solvent was reduced to 19.02 mPa⋅s, a significant decrease compared to the solution without DEA regulation. The novel solvent exhibited a high cyclic capacity of 2.08 mol/kg, which was 43.4 % higher than that of the solution without DEA, and a desorption rate twice as high as 30 wt% monoethanolamine(MEA). Quantitative 13C Nuclear Magnetic Resonance (NMR) and Molecular Dynamics (MD) simulations revealed the phase split and viscosity regulation mechanisms. It was proved that DETA species, especially carbamates, tend to self-aggregate with each other due to intermolecular hydrogen bonding with the CO2 loading increases, which leads to phase split and high viscosity of the saturated solution. Through DEA regulation, the protonation of carbamates and the generation of HCO3–/CO32– were promoted, which weakened the self-aggregation of carbamates species, decreasing the viscosity and the regeneration energy of saturated CO2-rich phase solution. The regeneration energy reached 2.19 GJ/ton CO2, which exhibited a 42.4 % reduction compared with that of 30 wt% MEA.

Synergetic enhancement of CO2 direct air capture with monoethanolamine-impregnated MIL-101(Cr) MOFs

To mitigate the greenhouse effect caused by the increase of CO2 concentration in the atmosphere, research attention has shifted towards CO2 Direct Air Capture (DAC) techniques. Despite that metal organic frameworks (MOFs) functionalized with various amines are promising to serve as suitable CO2 DAC adsorbent, there is few, if any, reports utilizing monoethanolamine (MEA), the most commonly employed in amine scrubbing technologies, as adsorption active sites. Herein, we have successfully impregnated MEA into MIL-101(Cr), resulting in a notably high CO2 adsorption capacity up to 1.20 mmol/g and an impressive amine utilization efficiency of 23% under low CO2 partial pressure (400 ppm). This improved capture efficiency can be attributed to the presence of hydroxyl groups, which alter the reaction dynamics between CO2 and amine groups. DAC simulation studies predominantly utilize synthetic air to replicate the DAC performance of adsorbents, yet precisely emulating air with artificially mixed gases remains an insurmountable challenge. To overcome this, we designed a system capable of testing DAC performance and employed MEA-impregnated MIL-101(Cr) for DAC testing. The adsorbent achieved pseudo-equilibrium DAC capacities of 2.15 and 1.50 mmol/g under humid and dry conditions, respectively, signifying an enhancement in DAC performance under humid condition. Our study offers novel perspectives for DAC adsorbent research, encompassing both material and equipment considerations.

Evaluating CO2 desorption performance of MEA solution with MnOx/HZ catalytic packings by visualization method

The high energy consumption in the CO2 desorption process is one of the main issues of the chemical absorption method. To address this issue, a MnOx modified HZSM-5 catalyst (MnOx/HZ) was prepared by impregnation method and used as catalytic packing to improve the CO2 desorption rate in the monoethanolamine (MEA) solution. Since the catalytic effects mainly work around the catalytic packing, a visualization method, which can measure the CO2 desorption rate per unit surface area (vCO2/area) of a single packing, is proposed to avoid some uncertain effects occurring as the conventional bubbling method is used. The results showed that the vCO2/area of the MnOx/HZ catalytic packing is 10.06 μmol·cm−2·s−1 at 80 °C, which is 1.78 times of that of HZSM-5 and 15 to 60 times of that of commercial packings. Actually, the MnOx/HZ has more Brønsted and Lewis acid sites than HZSM-5 according to the pyridine adsorption infrared spectroscopy (Py-IR) characterization. As a result, the apparent activation energy (Ea) of the CO2 desorption reaction with the addition of MnOx/HZ can be reduced by 58.6% and 18% compared with the addition of ceramic saddle ring packing and HZSM-5, respectively. However, the catalytic performance of MnOx/HZ packings degrades gradually due to the blockage of micropores by the reaction product, that needs to be settled in the future.