Maximum CO2 Adsorption Capacity Research Articles

Effects of the Adsorbent Preparation Method for CO2 Capture from Flue Gas Using K2CO3/Al2O3 Adsorbents

The effect of the preparation method on the CO2 adsorption capacity of K2CO3/Al2O3 adsorbents is examined. The multi-step impregnation (MI) method enables uniform dispersion of active species (K2CO3) in the broad macropores without blocking narrower mesopores. This facilitates higher loading of accessible K2CO3 for CO2 adsorption and, hence, higher adsorption capacity. The single-step impregnation (SI) method suffers from blockage of narrower mesopores by excessive growth of K2CO3. This limits the CO2 accessibility toward active species in the porous structure because of the formation of larger active species aggregates. For 50 wt % K2CO3/Al2O3 prepared by MI and SI methods, the maximum CO2 adsorption capacity at CO2 partial pressure of 8 kPa is found to be 3.12 and 2.1 mmol/g, respectively. The regeneration efficiency of 50MI and 50SI are observed to be nearly 65 and 56%, respectively, at 130 °C in multi-cycle testing. The experimental data for CO2 adsorption were described by the Langmuir isotherm, and the isosteric heat as a function of fractional coverage of the adsorbent was evaluated by means of the van’t Hoff equation. The isosteric heat showed a decreasing trend with an increase in the surface coverage of the adsorbent. From the results, it is concluded that the adsorbent prepared by the MI method shows better performance because of its tunable textural and morphological properties to achieve higher CO2 adsorption capacity.

Porous sulfur-doped titanate as the support of tetraethylenepentamine for CO2 capture

Porous sulfur-doped titanate was synthesized by hydrothermal method as the support of amine for CO2 capture. Tetraethylenepentamine (TEPA) was selected as the modifier to enhance CO2 adsorption capacity and selectivity by the introduction of chemisorptions. The physicochemical properties of raw and TEPA modified sulfur-doped titanate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), as well as low temperature N2 adsorption. CO2 adsorption and desorption were investigated by a fixed bed reactor system and temperature programmed desorption (TPD), respectively. With the maximum TEPA loading of 45wt%, the maximum CO2 adsorption capacity reached 3.58mmol/g at 70°C. The adsorption capacity for CO2 remained almost the same after cyclic regeneration experiments. Ultimately, the results of characterization and experiments were summarized to understand the CO2 adsorption–desorption mechanism.

Adsorption of carbon dioxide by sodium hydroxide-modified granular coconut shell activated carbon in a fixed bed

In the present work, commercial coconut shell activated carbon was impregnated with alkaline NaOH to investigate the efficiency of modified activated carbon for CO2 adsorption in a fixed-bed column adsorption system. The modification parameters, such as the NaOH concentration (24–48%) and dwelling time (1–4 h), were also investigated. The results showed that a 32% NaOH concentration with a 3 h dwelling time provided the best CO2 adsorption capacity. Later, the modified activated carbon was characterized by nitrogen adsorption–desorption, scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of the CO2 % in the feed, the adsorption temperature, the feed flow rate and the amount of adsorbent in the column were investigated in the adsorption experiments. The maximum CO2 adsorption capacity in this study was 27.10 mg/g at 35 °C. This study also suggests that NaOH-modified activated carbon is a state-of-the-art adsorbent for CO2 adsorption.

Calorimetric study of the CO2 adsorption on carbon materials

Given the great interest in the CO2 removal and decreasing their impact on the environment, in this work, a calorimetric study of CO2 adsorption on different activated carbons was performed. For this purpose, we used two methodologies for the determination heat of CO2 adsorption: determination of CO2 isotherms at different temperatures and adsorption calorimetry. The heats determined by these two techniques were compared. In this regard, carbonaceous materials of granular and monolithic types were prepared, characterized, and functionalized for carbon dioxide adsorption. As precursor material, African palm stones that were activated with H3PO4 and CaCl2 at different concentrations was used. The obtained materials were functionalized in gas phase with NH3 and liquid phase with NH4OH, with the intention to incorporate the surface basic groups (amines or nitrogen groups) and subsequently were studied for CO2 adsorption at 273 K and atmospheric pressure. For characterization of these materials, the following techniques are used: N2 adsorption at 77 K and immersion calorimetry in different solvents. The experimental results show the obtaining of micropores and mesoporous (moderately) materials, with surface area between 430 and 1,425 m2 g−1 and pore volumes between 0.17 and 0.53 cm3 g−1. It was determined that there is a difference between the heats of CO2 adsorption obtained by the techniques employed. This deviation between the values corresponds to the methodological difference between the two experiments. In this work, we obtained a maximum adsorption capacity of CO2, which is greater than 334 mg CO2 g−1 at 273 K and 1 bar in carbon materials with moderate surface area and pores volume.

Effect of moisture on the heat capacity and the regeneration heat required for CO2 capture process using PEI impregnated mesoporous precipitated silica

AbstractIn this study, we report the effect of the moisture of polyethylenimine (PEI) impregnated mesoporous precipitated silica used for CO2 adsorption on the heat capacity and the heat required to regenerate the adsorbent. The results indicate that the heat capacity of the absorbent increases as its moisture content increases. The increase in moisture results in the rise of the vaporization heat of water and the elevated heat capacity results in higher sensible heat. For these reasons, the total regeneration heat required for CO2 capture process increases significantly. The adsorbent has a maximum CO2 adsorption capacity at 75 °C. CO2 capture process using PEI impregnated mesoporous precipitated silica requires a minimum energy to regenerate the adsorbent; it reduces 46% of the energy compared to a process using an aqueous MEA 30 wt%, as the process operates at 75 °C.

Adsorption Separation of Carbon Dioxide from Flue Gas by a Molecularly Imprinted Adsorbent

CO2 separation by molecularly imprinted adsorbent from coal-fired flue gas after desulfurization system has been studied. The adsorbent was synthesized by molecular imprinted technique, using ethanedioic acid, acrylamide, and ethylene glycol dimethacrylate as the template, functional monomer, and cross-linker, respectively. According to the conditions of coal-fired flue gas, the influencing factors, including adsorption temperature, desorption temperature, gas flow rate, and concentrations of CO2, H2O, O2, SO2, and NO, were studied by fixed bed breakthrough experiments. The experimental conditions were optimized to gain the best adsorption performance and reduce unnecessary energy consumption in future practical use. The optimized adsorption temperature, desorption temperature, concentrations of CO2, and gas flow rate are 60 °C, 80 °C, 13%, and 170 mL/min, respectively, which correspond to conditions of practical flue gases to the most extent. The CO2 adsorption performance was nearly unaffected by H2O, O2, and NO in the flue gas, and was promoted by SO2 within the emission limit stipulated in the Chinese emission standards of air pollutants for a thermal power plant. The maximum CO2 adsorption capacity, 0.57 mmol/g, was obtained under the optimized experimental conditions, and the SO2 concentration was 150 mg/m(3). The influence mechanisms of H2O, O2, SO2, and NO on CO2 adsorption capacity were investigated by infrared spectroscopic analysis.

Activated Carbon for CO2 Adsorption Obtained through the Chemical Activation of African Palm Stone

In this study, activated carbons were prepared and tested as CO2 adsorbents at a temperature of 273 K and at atmospheric pressure. African palm stone was used as the precursor material, which was initially impregnated with CaCl2 solutions at different concentrations. The textural characterization of activated carbons was performed by nitrogen adsorption at 77 K. The energetic parameters were determined by immersion calorimetry in benzene and water. In addition, the total acidity and basicity were estimated using Boehm titrations. A maximum surface area of 1700 m2 g-1 was obtained with a pore volume of 0.64 cm3 g-1. Immersion calorimetry provided results between -17.95 and -95.75 J g-1 in benzene and between -13.63 and -30.24 J g-1 in water. The materials had a maximum CO2 adsorption capacity of 5.75 mmol CO2 g-1. It was found that the adsorption of gas increased with the total basicity and decreased with acidity. Finally, correlations were established between the textural characteristics, determined by ga...

CO2 Capture with Activated Carbon Grafted by Nitrogenous Functional Groups

Amino/nitro groups were introduced onto the surface of the activated carbon (AC) with nitration followed by reduction in order to improve its adsorption capacity toward CO2. These AC samples were characterized by N2 adsorption/desorption, FTIR, and X-ray photoelectron spectroscopy (XPS). CO2 adsorption properties of the samples were investigated using a self-regulating high-pressure adsorption apparatus. Results showed that the contents of nitrogen on the treated samples’ surface increased from 0% to 1.38 after modification. The maximum CO2 adsorption capacity of the modified samples can reach 19.07 mmol/g at 298 K and 36.0 bar. The adsorbed amounts of CO2 on all samples decreased with an increase in the adsorption temperature, but the extent of the decrease with the modified samples was less than that of the raw AC sample. CO2 adsorption capacities of the modified sample for five cyclic adsorption–desorption runs were found to be nearly identical.

Synthesis of N-doped microporous carbon via chemical activation of polyindole-modified graphene oxide sheets for selective carbon dioxide adsorption

A polyindole-reduced graphene oxide (PIG) hybrid was synthesized by reducing graphene oxide sheets in the presence of polyindole. We have shown PIG as a material for capturing carbon dioxide (CO2). The PIG hybrid was chemically activated at temperatures of 400–800 ° C, which resulted in nitrogen (N)-doped graphene sheets. The N-doped graphene sheets are microporous with an adsorption pore size of 0.6 nm for CO2 and show a maximum (Brunauer, Emmet and Teller) surface area of 936 m2 g−1. The hybrid activated at 600 ° C (PIG6) possesses a surface area of 534 m2 g−1 and a micropore volume of 0.29 cm3 g−1. PIG6 shows a maximum CO2 adsorption capacity of 3.0 mmol g−1 at 25 ° C and 1 atm. This high CO2 uptake is due to the highly microporous character of the material and its N content. The material retains its original adsorption capacity on recycling even after 10 cycles (within experimental error). PIG6 also shows high adsorption selectivity ratios for CO2 over N2, CH4 and H2 of 23, 4 and 85 at 25 ° C, respectively.

CO2 adsorption properties and thermal stability of different amine-impregnated MCM-41 materials

The adsorption properties of CO2 on MCM-41 mesoporous materials impregnated with ethylenediamine (EDA), tetraethylenepentamine (TEPA) and two kinds of polyethylenimines (PEI600 and PEI1800), respectively, were studied with mass spectrometry (MS) and thermogravimetry (TG) techniques. The sample obtained by impregnating EDA (EDA-MCM-41) showed a low CO2 adsorption capacity due to the ready volatilization of EDA, while those samples prepared by TEPA (TEPA-MCM-41), PEI600 (PEI600-MCM-41) or PEI1800 (PEI1800-MCM-41) exhibit higher adsorption capacity and thermal stability although the adsorption capacity decreased with increasing molecular weight of amines. A maximum CO2 adsorption capacity of 2.7 mmol/g was achieved on the TEPA-MCM-41 with 40% TEPA. When this sample was regenerated at 100°C under pure nitrogen atmosphere, its CO2 adsorption capacity was decreased by 7.4% after ten recycles in contrast to less than 1% for both PEI600-MCM-41 and PEI1800-MCM-41. However, when the regeneration atmosphere was changed to 80% CO2/20% N2, the regeneration temperature should be increased to more than 160°C for all the samples despite that PEI-MCM-41 showed high thermal stability than TEPA-MCM-41.

Mesoporous TiO2 as the support of tetraethylenepentamine for CO2 capture from simulated flue gas

Mesoporous TiO2 (MT) was prepared by a hydrothermal method and used as the supporting material for the immobilization of tetraethylenepentamine (TEPA) to develop a new type of adsorbent for CO2 capture from flue gas. The CO2 adsorption capacity increases with the increase of the TEPA loading amounts. With the maximum TEPA loading of 31 wt% onto the MT sorbent, the maximum CO2 adsorption capacity reached 2.52 mmol of CO2 g−1 of sorbent. In the presence of an appropriate amount of water vapor, the formation of bicarbonate and hydroxylated surface on TiO2 can improve CO2 adsorption capacity from 2.64 to 2.91 mmol g−1. However, an excess of water vapor leads to a decrease in the CO2 adsorption capacity from 2.91 to 2.65 mmol g−1, probably attributed to the adsorption competition between water and CO2. The absorption/regeneration cycle was repeated and the CO2 adsorption capacity decreased from 2.52 to 2.41 mmol g−1 over 5 cycles, almost completely maintained its original CO2 adsorption capacity. In addition, the effect of long-term storage on CO2 adsorption capacity is studied. After approximately one year of storage, the CO2 capacity of the MT–TEPA-31 decreased by 28% compared with the fresh sample.

Preparation and CO2Sorption of a High Surface Area Activated Carbon Obtained from the KOH Activation of Finger Citron Residue

A high surface area activated carbon was synthesized by potassium hydroxide (KOH) activation of Finger Citron residue. The pore structure of the as-synthesized activated carbon was characterized by nitrogen adsorption and its carbon dioxide (CO2) sorption capacities at different conditions were measured under high pressure. The BET surface area and total pore volume of the as-synthesized sample were 2887 m2/g and 1.23 cm3/g, respectively. The dry sample exhibited a CO2 adsorption capacity of 19.21 mmol/g at 276 K and 3.57 MPa. The CO2 adsorption uptake increased considerably when an amount of water was pre-adsorbed onto the sample, possibly as a result of the formation of CO2 hydrate in the pore spaces of the activated carbon. The maximum CO2 adsorption capacity of the wet sample was found to be 29.02 mmol/g at 273 K and 3.57 MPa. Overall, the results reported confirm that Finger Citron residue could prove a promising precursor for high surface area activated carbon and point to the potential application ...

Carbon dioxide adsorption performance of N-doped zeolite Y templated carbons

N-Doped microporous carbons are prepared using zeolite NaY as a hard template with furfuryl alcohol/acetonitrile as carbon precursors. CO2 adsorption performances of these carbons are investigated intensively. Structure analysis shows that the replication of zeolite regularity, pore texture and the type of nitrogen functionalities strongly depends on the carbonization temperature. Basic nitrogen functionalities can be efficiently introduced into the carbon framework, which significantly facilitate CO2 uptake via chemical adsorption. The CO2 adsorption isotherms correlated with the Dubinin–Astakhov models, and the isosteric heats of adsorption are calculated using the Clausius–Clapeyron equation. The maximum CO2 adsorption capacity of 10.4 wt% is obtained for the YTC7 carbon due to its high surface area and abundant nitrogen functionalities. CO2 chemical adsorption on the carbons decreases with carbonization temperature due to the decomposition of basic nitrogen functionalities at higher temperature. High CO2 adsorption capacities of up to 9.3 wt% at 25 °C and 4.1 wt% at 70 °C are obtained for the YTC6 carbon. The present study suggests that low temperature vapor deposition of acetonitrile is a promising alternative method of toxic ammonia treatment for CO2 adsorption.

Preparation and CO2 adsorption of amine modified Mg–Al LDH via exfoliation route

In response to the recent focus on reducing carbon dioxide emission, the preparation and characterization of organically functionalized materials for use in carbon capture have received considerable attention. In this paper the synthesis of amine modified layered double hydroxides (LDHs) via an exfoliation and grafting synthetic route is reported. The materials were characterized by elemental analysis (EA), powder x-ray diffraction (PXRD), diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) and thermogravimetric analysis (TGA). Adsorption of carbon dioxide on modified layered double hydroxides was investigated by TGA at 25–80°C. 3-[2-(2-Aminoethylamino) ethylamino]propyl-trimethoxysilane modified MgAl LDH showed a maximum CO2 adsorption capacity of 1.76mmolg−1 at 80°C. The influence of primary and secondary amines on carbon dioxide adsorption is discussed. The carbon dioxide adsorption isotherms presented were closely fitted to the Avrami kinetic model.

Chemical modification of carbon powders with aminophenyl and aryl-aliphatic amine groups by reduction of in situ generated diazonium cations: Applicability of the grafted powder towards CO2 capture

Aminophenyl, p-aminobenzyl and p-aminoethylphenyl groups were grafted at the surface of carbon Vulcan XC72R by spontaneous reduction of the in situ generated diazonium cations from the corresponding amine. X-ray photoelectron spectroscopy and elemental analysis confirmed an amine loading of about 1mmol/g. The grafting of amine functionalities leads to a decrease of specific surface area from 223 to about 110m2/g with a drastic loss of microporosity. Acid–base properties of the surface are also affected by the modification. Aminophenyl grafted groups make the surface more acidic while aryl-aliphatic amines groups tends to render it more basic. The grafted layer shows in each case a good thermal stability up to 250°C. The affinity of the modified powder towards CO2 and N2 has been evaluated by thermal swing adsorption. The maximum adsorption capacity of CO2 of modified carbons is lower than the unmodified carbon but the presence of the amine functionalities involves a better selectivity of the material towards CO2 adsorption in comparison of N2 adsorption.

Adsorptive Removal of Co and Sr Ions from Aqueous Solution by Synthetic Hydroxyapatite Nanoparticles

Hydroxyapatite nanoparticles were synthesized by using the precipitation method with simulated body fluid solution and applied for adsorption of Co2+ and Sr2+ in aqueous solution. The single- and bi-solute adsorption experiments were performed to evaluate the maximum adsorption capacity of hydroxyapatite nanoparticles for Co2+ and Sr2+, the effect of temperature and pH, and the influence of simultaneous presence of other competing metal ion in a binary system. The synthesized hydroxyapatite nanoparticles had high adsorption capacity for Co2+ and Sr2+ due to a high specific surface area. The maximum adsorption capacity and binding energy of Co2+ were higher than those of Sr2+ in single-solute adsorption. The extended Langmuir model was fitted well for bi-solute competitive adsorption of Co2+ and Sr2+ onto the hydroxyapatite nanoparticles. Thermodynamic analysis showed that adsorption occurred spontaneously for both metals and was endothermic for Co2+, but exothermic for Sr2+.