CO2 Desorption Kinetics Research Articles

Efficient CO2 Desorption Catalysts: from Material Design to Kinetics Analysis and Application Evaluation

Catalytic amine-solvent regeneration has been validated as an energy-saving strategy for CO2 chemisorption by boosting reaction kinetics under mild conditions. The upscale performance evaluation and long-term durability are indispensable steps for industrial application but have been scarcely reported thus far. Here, we report a ZrO2/Al2O3 pack catalyst that possesses strong metal oxide-support interactions, a porous structure, active and stable Zr–O–Al coordination, promoted proton transfer and a 40.7% decrease in the energy activation of carbamate decomposition, which significantly accelerates CO2 desorption kinetics. The upscale experiment and cost evaluation based on industrial flue gas revealed that the use of packing catalysts can reduce energy consumption by 27.56% and optimize the overall cost by 10.49%. The active sites present excellent stability in alkaline solvents. This work is the first to investigate the ability of high-technology readiness (technology readiness level at 6 (TRL 6)) for catalytic amine-solvent regeneration, providing valuable insights for potential applications involving efficient CO2 capture with catalyst assistance.

Underlying Roles of Polyol Additives in Promoting CO2 Capture in PEI/Silica Adsorbents.

Solid-supported amines having low molecular weight branched poly(ethylenimine) (PEI) physically impregnated into porous solid supports are promising adsorbents for CO2 capture. Co-impregnating short-chain poly(ethylene glycol) (PEG) together with PEI alters the performance of the adsorbent, delivering improved amine efficiency (AE, mol CO2 sorbed/mol N) and faster CO2 uptake rates. To uncover the physical basis for this improved gas capture performance, we probe the distribution and mobility of the polymers in the pores via small angle neutron scattering (SANS), solid-state NMR, and molecular dynamic (MD) simulation studies. SANS and MD simulations reveal that PEG displaces wall-bound PEI, making amines more accessible for CO2 sorption. Solid-state NMR and MD simulation suggest intercalation of PEG into PEI domains, separating PEI domains and reducing amine-amine interactions, providing potential PEG-rich and amine-poor interfacial domains that bind CO2 weakly via physisorption while providing facile pathways for CO2 diffusion. Contrary to a prior literature hypothesis, no evidence is obtained for PEG facilitating PEI mobility in solid supports. Instead, the data suggest that PEG chains coordinate to PEI, forming larger bodies with reduced mobility compared to PEI alone. We also demonstrate promising CO2 uptake and desorption kinetics at varied temperatures, facilitated by favorable amine distribution.

Amine-functionalized macroporous resin for direct air capture with high CO2 capacity in real atmospheric conditions: Effects of moisture and oxygen

Direct air capture (DAC) is an important negative carbon emission technology that has attracted increasing attention. Amine-functionalized porous CO2 adsorbents are promising materials for DAC because of their high CO2 capacities, fast adsorption and desorption kinetics, and low energy costs during regeneration. In this study, inexpensive macroporous resins with high specific surface areas and pore volumes were selected as carriers of tetraethylenepentamine (TEPA) or polyethyleneimine (PEI). Their DAC performances in relation to their microstructures were explored under different humidity and oxygen conditions. Moisture simultaneously enhanced the CO2 capacity and slowed the adsorption/desorption process. Oxygen did not react with the resin and amine under ambient conditions, but physically adhered to the active sites of the adsorbents and caused a slight decrease in the CO2 uptake capacity. The optimized material reached adsorption equilibrium in 7269 s with CO2 uptake capacity of 5.4 mmol g−1 and desorbed CO2 in 1611 s with CO2 desorption capacity of 5.0 mmol g−1. After five cycles, the materials retained 82.2 % of the adsorption capacity. The findings indicate that amine-functionalized macroporous resins are promising DAC adsorbents under atmospheric conditions.

Sulfur Migration Enhanced Proton-Coupled Electron Transfer for Efficient CO2 Desorption with Core-Shelled C@Mn3O4.

Transforming hazardous species into active sites by ingenious material design was a promising and positive strategy to improve catalytic reactions in industrial applications. To synergistically address the issue of sluggish CO2 desorption kinetics and SO2-poisoning solvent of amine scrubbing, we propose a novel method for preparing a high-performance core-shell C@Mn3O4 catalyst for heterogeneous sulfur migration and in situ reconstruction to active -SO3H groups, and thus inducing an enhanced proton-coupled electron transfer (PCET) effect for CO2 desorption. As anticipated, the rate of CO2 desorption increases significantly, by 255%, when SO2 is introduced. On a bench scale, dynamic CO2 capture experiments reveal that the catalytic regeneration heat duty of SO2-poisoned solvent experiences a 32% reduction compared to the blank case, while the durability of the catalyst is confirmed. Thus, the enhanced PCET of C@Mn3O4, facilitated by sulfur migration and simultaneous transformation, effectively improves the SO2 resistance and regeneration efficiency of amine solvents, providing a novel route for pursuing cost-effective CO2 capture with an amine solvent.

Utilizing ZrO2 as an Alkali Metal-Based Adsorbent Support to Lower Energy Consumption in Direct Air Capture

Alkali metal-based adsorbents are used in the direct air capture of CO2, but the process is hindered by high energy demands, mainly due to the slow adsorption and desorption kinetics of CO2, This necessitates the use of a catalytic support like ZrO2 to reduce the energy barrier associated with the reaction. This study uses both density functional theory and experimental approaches to explore how ZrO2 support interacts with H2O during the carbonation reaction. The findings suggest that the presence of [ZrO(OH)]+ and OH- on the monoclinic ZrO2 (001) surface greatly speeds up the dissociation of H2O, reducing energy use in CO2 capture and increasing thermal efficiency. The catalytic role of ZrO2 is further confirmed through analyses using thermogravimetric-mass spectrometry (TG-MS) and X-ray photoelectron spectroscopy (XPS).

Solid acid catalysts for low-temperature regeneration of non-aqueous sorbents: An innovative technique for energy-efficient CO2 capture processes

Chemical absorption of CO2 from flue gases by using aqueous amine sorbents is regarded as the most mature and effective technology for reducing CO2 emissions, but the high energy cost of sorbent regeneration has so far greatly limited its industrial application. One of the best strategies developed by researchers in recent years to reduce energy requirements is to improve CO2 desorption kinetics by adding catalysts during sorbent regeneration. Moreover, non-aqueous sorbents have recently been gaining increasing attention as alternatives to conventional aqueous amines as they have the potential to lower the energy demand for sorbent regeneration. In this paper, we propose an innovative technique that combines and further develops these two emerging technologies, non-aqueous absorbent and catalyst-assisted regeneration, to enable less energy-intensive CO2 capture processes. In particular, in this screening study, we evaluate the regeneration behaviour of a CO2-saturated solution of 2-(2-aminoethoxy)ethanol (DGA) in diethylene glycol monomethyl ether (DEGMME) when heated to 85 °C in the absence and presence of different types of solid acid catalysts. In order to assess the potential benefits of this innovative technique over conventional systems, the results obtained were compared with the desorption performance of an aqueous solution of DGA under the same operating conditions and with the same catalysts, which highlighted the possibility of obtaining rapid desorption at relatively low temperatures when conducted with suitable acid catalysts using amines in organic diluents.

Mesoporous MgO enriched in Lewis base sites as effective catalysts for efficient CO2 capture

Capturing CO2 has become increasingly important. However, wide industrial applications of conventional CO2 capture technologies are limited by their slow CO2 sorption and desorption kinetics. Accordingly, this research is designed to overcome the challenge by synthesizing mesoporous MgO nanoparticles (MgO-NPs) with a new method that uses PEG 1500 as a soft template. MgO surface structure is nonstoichiometric due to its distinctive shape; the abundant Lewis base sites provided by oxygen vacancies promote CO2 capture. Adding 2 wt % MgO-NPs to 20 wt % monoethanolamine (MEA) can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by ∼3000% and can increase the CO2 absorption capacity within the breakthrough time by ∼3660%. The data suggest that MgO-NPs can accelerate the rate and increase CO2 desorption capacity by up to ∼8740% and ∼2290% at 90 °C, respectively. Also, the excellent stability of the system within 50 cycles is verified. These findings demonstrate a new strategy to innovate MEA absorbents currently widely used in commercial post-combustion CO2 capture plants.

Energy-efficient and water-saving sorbent regeneration at near room temperature for direct air capture

This study reports energy-efficient and water-saving microwave-accelerated regeneration of sorbent (MARS) for dilute carbon capture from the ambient air. The experimental studies indicated that the CO2 desorption rate from the chemisorbents increased with microwave output under near-isothermal conditions at near room temperature. The reduced activation energy of MARS, i.e., 20–28 kJ/mol, indicated enhanced CO2 desorption kinetics by microwave-induced rotational–vibrational (rovibrational) coupling transitions, primarily due to the highly polarized feature of the carbamate (CO2-PEI). The instant and selective delivery of microwave energy to the targeted polarized C–N bonds at room temperature is particularly advantageous for energy-efficient direct air capture. The experimental results also demonstrated a good working capacity of 0.6–1.4 mmol of CO2/g and a promising rapid MARS-DAC process with microwave swing. As it does not require steam regeneration and heat exchanger, a simple MARS process is attractive for CO2 capture in water-stressed regions.

Real-time monitoring of CO2 gas using inverse opal photonic gel containing Poly(2-(dimethylamino)ethylmethacrylate

With the rapid progression of global climate changes and air pollution in recent years, there has been growing interest in the sensing and monitoring of CO2 gas. In the present study, an inverse opal photonic gel (IOPG) colorimetric sensor is demonstrated that is capable of real-time monitoring of CO2 gas in an open system without the necessity of a power supply. The IOPGs are fabricated via the opal-templated photo-polymerization of monomer mixtures of hydroxyethyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) or 2-(dimethylamino)propyl methacrylamide (DMAPMAm), followed by template removal. When the IOPG sensor is immersed in water with a steady flow of mixed CO2/N2 gas at various ratios, the CO2 molecules dissolve in the water and are converted to carbonate anions, which subsequently bind to the amino groups of pDMAEMA to build up osmotic pressure, thus leading to swelling of the IOPG. A comparison of the sensing and recovery capabilities of the two types of IOPG indicates that the pDMAEMA-containing IOPG exhibits a limit of detection below 1.2%, and 2.6 times faster CO2 desorption kinetics compared to the pDMAPMAm-containing IOPG. The swelling behavior of the CO2-responsive IOPG is rigorously investigated at various pH values, and temperatures by analyzing the reflectance spectra of the IOPG in the visible wavelength range. The usefulness of the pDMAEMA-IOPG as a real-time CO2 sensor was confirmed by applying it to various carbonated drinks.

Supercritical carbon dioxide enhanced natural gas recovery from kerogen micropores

As the global energy demand increases, a sustainable and environmentally friendly methane (CH4) extraction technique must be developed to assist in the transition off of fossil fuels. In recent years, supercritical carbon dioxide (CO2) has been poised as a candidate for enhanced gas recovery (EGR) from CH4-rich source rocks, potentially with the reservoir serving as a carbon sink for CO2. However, the underlying molecular-scale mechanisms of CO2-EGR processes are still poorly understood. Using constant chemical potential molecular dynamics (CμMD), this study investigates the CH4 recovery process via supercritical CO2 injection into immature (Type I-A) and overmature (Type II-D) kerogens in real-time and at reservoir conditions (365 K and 275 bar). A pseudo-second order (PSO) rate law was used to quantify the adsorption and desorption kinetics of CO2 and CH4. The kinetics of simultaneous adsorption/desorption are rapid in immature kerogen due to better connected pore volume facilitating fluid diffusion, whereas in overmature kerogen, the structural heterogeneity hinders fluid diffusion. Estimated second order kinetic rate coefficients reveal that CO2 adsorption and CH4 desorption in Type I-A are about two times and an order of magnitude faster, respectively, compared to those of in Type II-D. Furthermore, overmature Type II-D kerogen contains inaccessible micropores which prevent full recovery of CH4. For every CH4 molecule replaced, at least two and six CO2 molecules are adsorbed in Type-II-D and Type I-A kerogens, respectively. Overall, this study shows that CO2 injection can achieve 90 % and 65 % CH4 recovery in Type I-A and Type II-D kerogens, respectively.

Evidencing Pt-Au alloyed domains on supported bimetallic nanoparticles using CO desorption kinetics

We explored here the possibility to use CO desorption kinetics monitored by IR spectroscopy as a tool to characterize the mixing of Au and Pt atoms at the surface of supported nanoparticles. CO desorption of CO monitored at 50 °C showed that a bimetallic sample exhibited an intermediate behavior between those of monometallic Au and Pt samples, reflecting the alloyed nature of the nanoparticles. Our data also show that alumina-supported Au nanoparticles led to the formation of surface carbonates at 50 °C, possibly formed through Boudouard reaction (2 CO → C + CO2), in contrast to the case of the Pt-based sample.

Experimental and kinetics investigations of low-concentration CO2 adsorption on several amine-functionalized adsorbents

The rapid cleanup of endogenous CO2 has become a necessity in environmental control and life support systems (ECLSSs), to ensure crew safety and long-term task execution. The extensively used non-regenerable LiOH and soda lime adsorbents, although exhibit high CO2 storage capacities and fast kinetics, can hardly fulfill the demands of reduced launch weight and storage volume in the space- and load-limited ECLSSs. New CO2 adsorbents with desirable attributes including high CO2 uptakes, good selectivity, facile regeneration, fast adsorption and desorption kinetics, and good multicycle stability are urgently needed. We developed amine-functionalized adsorbents by loading tetraethylenepentamine (TEPA) on mesoporous supports of activated carbon (AC), aluminum oxide (AO) and silica gel (SG). The adsorbents were characterized by N2 adsorption-desorption, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) to study their microstructural properties. CO2 adsorption capacities and kinetic performance of the adsorbents with different supports and various amine loadings (10–50 wt%) were evaluated in 2%CO2 at 20 °C. The effects of support and amine loading on the structure-performance relationships of the adsorbents were demonstrated. The TEPA-SG-20 adsorbent (20 wt% TEPA loaded on silica gel support) exhibits the highest CO2 adsorption capacity of 1.90 mmol CO2/g and the maximum amine efficiency of 0.48 mmol CO2/mmol N. TEPA-SG-20 also exhibits fast CO2 adsorption kinetics, and the Avrami fractional order kinetic model provides a satisfactory correlation of the experimental CO2 uptakes. Furthermore, the TEPA-SG-20 adsorbent can be efficiently regenerated at 110 °C with a great regeneration efficacy of 97%. The desired adsorbent also exhibits good working stability with a low loss-in-capacity of 4.32% in 10 consecutive cycles. The good CO2 adsorption performance of TEPA-SG-20 is associated with the excellent microstructural properties such as high surface area, great pore volume and uniform dispersion of amine species. Overall, the desired TEPA-SG-20 adsorbent shows promise for low-concentration CO2 removal in ECLSSs.

A systematic analysis of the dynamics of microwave- and conventionally-assisted swing adsorption on zeolite 13X and an activated carbon under post-combustion carbon capture conditions

This work presents a detailed parametric experimental work on the feasibility of microwave regeneration of two commercial adsorbents in a dynamic carbon capture swing adsorption system. A synthetic flue gas (15% v/v CO2 in N2) dry or with 15% relative humidity was selected, along with Norit R2020CO2 activated carbon and zeolite 13X. A purpose-modified experimental apparatus was used to compare microwave-assisted and conventional thermal swing regeneration. The impact of operating parameters on the dynamic process performance was measured for microwave and conventional heating. Parameters considered were type of adsorbent, flue gas composition, quantity of adsorbent (and bed size), and time of full regeneration, on CO2 capture capacity, recovery, purity and desorption kinetics. Results showed that microwave-assisted regeneration presents advantages over its conventional equivalent, as CO2 purity, recovery, and productivity were found to be higher under the former for the two adsorbents studied. For the time needed to achieve 50, 80, 90, and 99% regeneration, the benefits of microwave regeneration over conductive regeneration increased with an increase in sample size. Under the wet gas feed, Norit R2020CO2 and zeolite 13X showed an appreciably higher working capacity with microwave regeneration than with conventional regeneration (39.68 and 24.23% higher, respectively). Under the dry gas feed, the two adsorbents also maintained a higher working capacity with microwave heating as opposed to conductive heating (9.36 and 20.39% higher, respectively). The larger working capacity observed with microwave-assisted regeneration is attributed to the better regeneration.

Synergetic effect of multicomponent additives on limestone when assessed as a thermochemical energy storage material

The effect of adding both Al2O3 and ZrO2 to limestone (CaCO3) to enhance the cyclic stability and reaction kinetics of endothermic CO2 desorption and exothermic CO2 absorption is investigated. The formation of CaZrO3 and Ca-Al-O compounds, e.g. CA5Al6O14, is evident, which enables a substantial >80% capacity retention over 50 calcination/carbonation cycles. The additives enable fast reaction kinetics where an 80% energy storage capacity is reached within 20–30 min, which is attributed to the synergetic effect of having both Ca-Zr-O and Ca-Al-O ternary additives present. The inert nature of the formed compounds prevents sintering of the particles, whilst allowing ion migration throughout the crystal structures, catalysing the carbonation reaction.

Experimental investigation on CO2 desorption kinetics from MDEA + PZ and comparison with MDEA/MDEA + DEA aqueous solutions with thermo‐gravimetric analysis method

AbstractThe carbon dioxide discharged from fossil fuels combustion products is considered as a major contributor to global warming. The current investigation aimed at CO2 desorption kinetics in 3.25 mol L–1 methyldiethanolamine (MDEA)–0.1 mol L–1 piperazine (PZ) rich amine aqueous solution with thermo‐gravimetric analysis (TGA) method under different heating rates of 2.5, 5, 10, and 20 °C min–1. The kinetics parameters were determined by comparison of 40 mechanism functions with thermal analysis kinetic method. The average activation energy E was 59.16 kJ mol–1, preexponential factor A was 5.54 × 108, and the most probable mechanism function was G(α) = [–ln(1 – α)]3/2. In addition, the kinetic parameters of CO2 desorption process from three rich amine aqueous solutions (MDEA, MDEA + diethanolamine(DEA), MDEA + PZ) were compared and the influence of kinetic parameters was further discussed. The desorption rate models of three rich amine aqueous solutions were established and desorption rates were well predicted. The order of desorption rate inferred from desorption rate model was MDEA > MDEA + DEA > MDEA + PZ. The results indicated that TGA combined with thermal analysis kinetics was an effective and quick method with high accuracy, easy operation, and good repeatability for screening absorbents preliminarily in laboratory. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

A kinetic study of CO2 sorption/desorption of lithium silicate synthesized through a ball milling method

Lithium silicates show high CO2 sorption capacity and excellent cyclic stability at high temperatures. Lithium orthosilicate was synthesized through a planetary ball milling route from LiOH and silica powder and was characterized for its structural and morphological features using TG, DSC, XRD, FTIR and FESEM techniques. Thermogravimetry was employed to study the CO2 sorption capacity of the synthesized sorbent under dynamic, isothermal and cyclic conditions. The material absorbed 30.5 % CO2 and retained its sorption capacity even after 10 cycles. The CO2 sorption and desorption kinetics of the synthesized sorbent were studied using Avrami–Erofeev method and Kissinger–Akahira–Sunose method respectively. The sorption of CO2 on lithium silicate took place by surface chemisorption and diffusion and activation energies required are 79 kJ mol−1 and 109 kJ mol−1 respectively. The activation energy for CO2 desorption increases with the progress in desorption from 91 kJ mol−1 to 146 kJ mol−1.

Ion-exchanged montmorillonite as simple and effective catalysts for efficient CO2 capture

One of the main challenges limiting the widespread industrial use of absorbent-based CO2 capture is the energy intensive solvent regeneration, due to poor CO2 desorption kinetics. The addition of a catalyst can help optimize the CO2 desorption rate at low temperatures and minimize the thermal dependence of CO2 desorption reactions. In this work, we report a new class of inexpensive and abundant montmorillonite clay-based catalysts for this purpose, which can be readily tuned by simple ion-exchange with acid or metal solutions. As an example, in this study montmorillonite was ion-exchanged with an acid, H2SO4 and a metal, Zr. The ion-exchange process substantially increased the BET surface area (up to 10 times), mesoporosity, and surface acidity of the parent montmorillonite without noticeably destroying the clay structure. Solvent regeneration experiments at the moderate temperature of 86 °C showed that the catalysts are effective at low temperature, and increased the CO2 desorption rate by up to 215%, the quantity of desorbed CO2 by up to 79%, and reduced the relative heat duty by up to 44.15% compared to the benchmark amine solution. Additionally, the prepared catalysts could be easily separated by simple filtration, and their stability was confirmed for five cyclic uses. Finally, based on characterizations and experimental results, a plausible reaction mechanism for the ion-exchanged montmorillonite catalyzed CO2 desorption reaction is also presented.

Polyamine nanogel particles spray-coated on carbon paper for efficient CO2 capture in a milli-channel reactor

In this work, we report a proof-of-concept study on CO2 adsorbents synthesized by a thermally initiated free-radical copolymerization and then coated onto carbon paper and poly tetra fluoroethylene via a spray coating approach. A milli-channel reactor was employed to support the obtained materials for efficient CO2 capture with wet conditions, short cooling and heating cycles (303–348 K). CO2 uptake and release performance of the materials were measured and compared with that of the polyamine-based materials prepared by other methods. CO2 adsorption and desorption kinetics can be greatly enhanced when using the spray coating approach, especially for carbon paper as supporter. The CO2 adsorption capacity of the spray-coated carbon paper reaches 80% of its maximum value in only 4.37 ± 0.7 min. Moreover, its adsorption rate (114.6 mg/(g∙min) at 303 K) and desorption rate (239.9 mg/(g∙min) at 348 K) were 81.2% and 81.5% higher than those of the polyamine-impregnated carbon paper, respectively (12% CO2 at atmospheric pressure). Their largest increases of 71% and 67% were achieved by adjusting the concentration of polyamine nanogel particles deposited on the carbon paper surface. The prepared material also presents stable recyclability over 10 wet adsorption–desorption cycles and the aging experiments. The results obtained in this study indicate that the synthesized materials can serve as promising energy-efficient solid adsorbents for CO2 capture.

Solving two environmental issues simultaneously: Waste polyethylene terephthalate plastic bottle-derived microporous carbons for capturing CO2

The treatment of plastic waste is a global issue, and the demand for technologies to reuse or upgrade plastic waste is increasing. In this study, waste polyethylene terephthalate (PET) plastic bottles were used to prepare cost-effective porous carbons, and the prepared carbon materials were tested for capturing CO2. PET plastic bottles were carbonized and activated using KOH or NaOH to develop porous carbons, and their CO2 adsorption behaviors were investigated from both equilibrium and kinetic perspectives. Varying the activation temperature had a significant effect on the textural properties of the prepared carbons. PET-KOH-973, which was prepared by activation with KOH at 973 K, exhibited the highest CO2 uptake of 4.42 mol kg−1 at 298 K and 101.3 kPa among the tested samples. The experimental adsorption data were well fitted to the Langmuir isotherm and pseudo second-order kinetic models, and the CO2 adsorption on the PET-derived porous carbons was mainly related to the pore volumes of the narrow pores under 0.8 nm in diameter. Grand canonical Monte Carlo simulation and density functional theory calculation were also performed to understand adsorption mechanism and selectivity, and the theoretical calculation agreed well with experimental data. The PET-derived porous carbons exhibited not only high CO2 uptake, but also good selectivity of CO2 over N2 and CO, simple regeneration, excellent cyclic stability, and fast CO2 adsorption and desorption kinetics.

Enhancement of CO2 Adsorption Performance on Hydrotalcites Impregnated with Alkali Metal Nitrate Salts and Carbonate Salts

Hydrotalcite is considered to be the potential high-temperature CO₂ sorbent adaptable to operate in 473–673 K. However, pristine hydrotalcite has a lower CO₂ adsorption capacity, which cannot satisfy the industrial requirements. In this work, commercial hydrotalcites (MG60 with a Mg/Al molar ratio of 1.91) were modified through impregnation with two kinds of alkali metal salts (K₂CO₃ and Na/KNO₃) to improve the CO₂ adsorption performance. Because Na/KNO₃ was a mixed salt with a lower melting point of 493 K, the impregnated Na/KNO₃ molten salt in micropores of hydrotalcites would accelerate CO₂ diffusion to enhance CO₂ adsorption and desorption kinetics when it captured CO₂ from the process gas at more than 493 K. By measuring CO₂ adsorption capacity, adsorption and desorption rates, and cyclic adsorption/desorption stability by a thermogravimetric analyzer, the enhancement of CO₂ adsorption performance of impregnated hydrotalcites was evaluated. Furthermore, Raman spectra were used first to explore the CO₂ adsorption enhancement mechanism on impregnated hydrotalcites in addition to IR spectra analysis. By comparison, it was found that the CO₂ adsorption enhancement mechanism was different with two kinds of salts impregnation: Na/KNO₃ promoted MG60 with the alkalinity increase of active sites and having the maximum CO₂ adsorption capacity at 473 K and K₂CO₃ promoted MG60 with the formation of K₂Mg(CO₃)₂ on adsorption active sites and having the maximum CO₂ adsorption capacity at 623 K. The maximum CO₂ adsorption capacities for both impregnated hydrotalcites were up to 1.0 mmol g–¹ under 1 atm CO₂ gas flow, which is more than that of pristine hydrotalcite with less than 0.4 mmol g–¹ at 473–673 K.