High CO2 Capture Capacity Research Articles

Impact of organic interlayer anions on the CO2 adsorption performance of Mg-Al layered double hydroxides derived mixed oxides

Herein we report a systematical investigation on the promoting effect of the carbon chain length of the intercalated carboxylic anions on the CO2 capture performance of Mg-Al layer double hydroxides (LDHs). A series of organo-LDHs were successfully synthesized via co-precipitation and calcination-rehydration methods. All as-prepared samples were characterized by many techniques including XRD, ATR-FTIR, BET, and TGA. The XRD and ATR-FTIR studies indicated that organic anions were successfully intercalated into LDHs. The influence of some important parameters such as calcination temperature, adsorption temperature, and coating with (Li-Na-K)NO3 molten salt was investigated. The results exhibited that when the number of carbon is greater than 10, the CO2 capture capacity steadily increased with the increase in carbon number. After coating with 55mol% (Li-Na-K)NO3 molten salt, the CO2 uptake of LDH-C16 sample with high Mg/Al ratios can be increased up to 3.25mmol/g. The CO2 adsorption/desorption cycling stability was also studied using temperature swing adsorption, which showed a stable CO2 capture performance even after 22 cycles. Considering its high CO2 capture capacity and good cycling stability, this novel CO2 adsorbent is very promising in the sorption-enhanced water gas shift (SEWGS) processes.

One-pot carbonization enrichment of nitrogen in microporous carbon spheres for efficient CO2 capture

Nitrogen-enriched porous carbon spheres are made by a one-pot carbonization process by decorating melamine–formaldehyde with resorcinol and hexamethylenetetramine, exhibiting high CO2 capture capacities of 4.34 mmol g−1 at 25 °C and 2.76 mmol g−1 at 75 °C.

CO2 capture performance of cement-modified carbide slag

A novel and low-cost synthetic CO2 sorbent for calcium looping process, cement-modified carbide slag (CMCS), was synthesized from carbide slag, aluminate cement and by-product of biodiesel by combustion. The effects of synthesis conditions such as combustion temperature, combustion duration, hydration, by-product of biodiesel and cement addition and regeneration temperature on CO2 capture performance of CMCS were investigated. The comprehensively optimum preparation conditions of CMCS were obtained. The highest CO2 capture capacity is 0.62 g/g after 10 cycles, which is 2.18 times as high as that of carbide slag. The addition of aluminate cement improves the CO2 capture performance of CMCS, while excessive aluminate cement is adverse for CO2 capture due to the reduced CaO content in CMCS. The addition of by-product of biodiesel contributes to a uniform sol mixing of carbide slag and cement. The CMCS exhibits higher carbonation and calcination rates than CS. The porous and stable pore structure leads to the better CO2 capture performance and cyclic stability of CMCS.

Trimodal nanoporous silica as a support for amine-based CO2 adsorbents: Improvement in adsorption capacity and kinetics

A trimodal nanoporous silica (TS) having unique trimodal pore structure viz., internal mesopores, textural mesopores and interconnected macropores, has been functionalized with amine using two different methods covalent grafting and wet impregnation. Both were studied as nanocomposite sorbents for CO2 capture. The effects of the amine loading, immobilization processes and the type of support were investigated. Commercially available silica gel (SG) with a purely mesoporous structure was studied as the support for the amine in order to compare differences in pore structure and amine loading with differences in CO2 adsorption capacity and kinetics. Amine-grafted TS exhibited much faster CO2 adsorption kinetics at 35°C than amine-grafted SG. At the same amine loading, amine-impregnated TS showed higher CO2 adsorption capacity and faster CO2 adsorption kinetics than amine-impregnated SG. The CO2 adsorption capacity of amine-impregnated TS increased as the amine loading increased until 70%, with the highest value of 172mg/g, while the amine-impregnated SG reached the highest CO2 adsorption capacity of only 78mg/g at 40% amine loading. More importantly, amine-impregnated as-prepared TS exhibited even higher CO2 capture capacity than amine-impregnated TS when the amine loading was below 60%. Results suggest that amine-modified trimodal nanoporous silica sorbents meet the challenges of current CO2 capture technology.

Preparation and performance of potassium-based sorbent using SnO2 for post-combustion CO2 capture

Potassium-based sorbents using γ-Al2O3 or TiO2 as a support or an additive material have disadvantages in terms of their thermal stability and cyclic CO2 capture. To overcome the shortcomings of these sorbents, a novel potassium-based sorbent (KSnI30) using SnO2 was developed in this study. The KSnI30 sorbent formed only K2CO3 and SnO2 phases without any inactive alloy species even after calcination at high temperatures (500–700 °C), indicating the good thermal stability of the KSnI30 sorbent regardless of the calcination temperature. Furthermore, the KSnI30 sorbent has an excellent regeneration property (above 98 %), as well as high CO2 capture capacities (89–94 mg CO2/g sorbent). Its excellent regeneration property is due to the formation of a KHCO3 phase without by-products during CO2 sorption. These results of the present study demonstrate that the SnO2 shows promise as a new support or an additive material to replace TiO2 and γ-Al2O3 in the preparation of a regenerable potassium-based sorbent for post-combustion CO2 capture with good thermal stability and excellent regeneration property.

The effect of fly ash on reactivity of calcium based sorbents for CO2 capture

Calcium looping technology is considered one of the potential technologies for CO2 capture. However, the rapid decay in CO2 capture capacity of calcium based sorbents is still of great concern. To reduce the decay and maintain high performance of CO2 capture is extremely attracted by researchers, especially in an environmentally friendly way at low cost. Efforts have been made to seek an effective method to enhance CO2 capture performance of calcium based sorbents by use of coal fly ash. CO2 capture performance is improved for sorbents modified with fly ash after pretreatment such as grinding and calcination. Calcium based sorbents hydrated with fly ash under acidic condition present increased reactivity and achieve high CO2 capture capacity attributed to improved microstructure and formation of supporting products such as Ca12Al14O33 and CaSiO3, while sorbents modified under basic condition do not enhance CO2 capture performance but present more stability during calcination/carbonation cycles.

Ether Functionalized Choline Tethered Amino Acid Ionic Liquids for Enhanced CO2 Capture

Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to their low toxicity, biodegradability, and fast reactivity toward CO2. The ionic nature of amino acid ILs can raise an environmental issue if the cation counterpart becomes toxic to the aquatic ecosystems, and they can become potential atmospheric pollutants. In this regard, choline based ILs are known to be promising scaffolds for the development of less toxic amino acid ILs. However, the existing choline amino acid ILs are highly viscous, limiting their applicability as solvents. Ether functionalized choline based amino acid ILs with a novel series of less toxic green ILs were explored with reduced viscosity and high CO2 capture capacity. A simple, economic, clean, and environmentally benign method was utilized for the synthesis of novel choline based amino acid ILs using a commercially available and economical starting material, 2-(dimethylamino)ethanol (deanol, a human dietary food supplement). These ILs have l...

Mechanical Modification of Naturally Occurring Limestone for High-Temperature CO2 Capture

The rapid decrease of CO2 capture capacity is one of the most challenging problems hindering the use of naturally occurring limestone in the calcium looping process. In this work, the mechanical modification method (dry planetary ball milling) was used to improve the cyclic CO2 capture performance of naturally occurring limestone. Low-cost Bayer aluminum hydroxide sourced from the industrial-scale production of alumina from bauxite ore was used as the precursor of the inert support to enhance the CO2 sorption stability of the ball-milled sorbents. It was found that the CO2 uptake of the milled sorbents could be further improved by increasing the ball-milling time because this generated more amounts of fine particles. Moreover, the pellets produced from ball-milled limestone powder possessed a relatively high CO2 capture capacity of 0.252 g/g in the 25th cycle, which is nearly 1.3 times the capture capacity of naturally occurring limestone powder. This indicates that the combination of mechanical modificat...

Role of Hydrogen Peroxide Preoxidizing on CO2 Adsorption of Nitrogen-Doped Carbons Produced from Coconut Shell

In this work, the coconut shell was preoxidized by hydrogen peroxide, before it was treated by the ammoxidation process and potassium hydroxide activation to synthesize nitrogen-doped porous carbons. The resulting sorbents exhibit significantly higher nitrogen content and narrow microporosity than the control sample without H2O2 pretreatment. Consequently, these sorbents are found to demonstrate high carbon dioxide uptake at 1 bar, such as 4.47 mmol g–1 at 25 °C and 6.79 mmol g–1 at 0 °C. In addition, these sorbents possess high CO2/N2 selectivity, stable reusability, high initial heat of CO2 adsorption, and high dynamic CO2 capture capacity under simulated flue gas conditions. These superior CO2 adsorption properties make them highly competitive among all the carbonaceous adsorbents for CO2 capture.

Hydrothermal synthesis of N-doped spherical carbon from carboxymethylcellulose for CO2 capture

Spherical carbonaceous adsorbents (CSn) with micro-porosity developed for CO2 capture were prepared by a simple hydrothermal carbonization of carboxymethylcellulose (CMC) in the presence of urea, and activated in a high temperature N2 atmosphere. The effects of specific surface area, pore structure, and N content on the CO2 adsorption capacity were systematically investigated. Urea was found to react with surface carbonyl groups and other intermediate products generated by CMC hydrothermal carbonization, which produced highly spherical morphologies that also exhibited some ordered lattice structures. The particle size of N-doped CSn was larger than that of particles prepared without urea. Nitrogen was mainly present in pyridine (N-6), pyrrolic/pyridone (N-5) and quaternary (N-Q) forms. The high CO2 capture capacity was produced by a combination of N-doping and developing micro-pore structures. At an adsorption pressure of 1bar, the capacity was dominated by the micro-porosity. However, during initial, lower pressures the N content dominated the CO2 adsorption capacity.

Preparation and characterization of chemically activated carbon materials for CO2capture

Activated carbon (AC) has attracted considerable interest because of its low cost, availability, facile tunability, and thermal stability. In this work, chemically activated carbon materials were prepared with different amounts of KOH (i.e., AC/KOH ratios of 1:1, 1:2, 1:3, and 1:4). The specific surface area and micropore volume were analyzed via N2 adsorption- desorption isotherms at 77 K. The CO2 adsorption capacity was investigated by CO2 adsorption-desorption isotherms at 298 K and 1 bar. The indoor CO2 capture capacities of the samples were examined in a manufactured chamber at the laboratory scale. The K2-AC sample exhibited a large specific surface area (1507 m2/g) and high total pore volume (0.670 cm3/g) and micropore volume (0.580 cm3/g). The prepared KOH-AC samples exhibited a high CO2 capture capacity of 144.5 mg/g (at an AC/KOH ratio of 1:2). Therefore, we proved that the CO2 capture capacity is significantly affected by chemical activation.

Adsorption of CO2 by Petroleum Coke Nitrogen-Doped Porous Carbons Synthesized by Combining Ammoxidation with KOH Activation

The goal of our research is developing an efficient and cost-effective carbonaceous CO2 sorbent. Using petroleum coke as the precursor, porous nitrogen-doped carbons were prepared by combining ammoxidation with KOH activation. The as-synthesized samples possess highly developed microporosities and large nitrogen loadings. High CO2 adsorption capacities of 3.76–4.57 mmol/g at 25 °C and 5.80–6.62 mmol/g at 0 °C under atmospheric pressure were achieved. Specifically, the sample prepared under mild temperature (650 °C) and low KOH/precursor ratio (KOH/precursor = 2) shows a CO2 uptake of 4.57 mmol/g at 25 °C, among the highest achieved for nitrogen-doped porous carbons. This high CO2 capture capacity can be attributed to the synergistic effect of nitrogen doping and high narrow microporosity of the sorbent. However, experimental evidence suggests that nitrogen doping contributes less than narrow microporosity. Additionally, the CO2/N2 selectivity and CO2 heats of adsorption of the sorbent are as high as 22 an...

Enhanced CO2 Capture Capacity of Nitrogen-Doped Biomass-Derived Porous Carbons

Nitrogen-doped porous carbons obtained from coconut shell by urea modification and KOH activation are found to exhibit very high CO2 uptake at 1 bar, almost 5 mmol g–1 at 25 °C and over 7 mmol g–1 at 0 °C, respectively. The high CO2 uptake of the sorbent can be ascribed to its high microporosity and nitrogen content. In addition, these sorbents possess high CO2/N2 selectivity, stable cyclic ability, high initial heat of CO2 adsorption, fast adsorption kinetics, and high dynamic CO2 capture capacity under simulated flue gas conditions. When combined with the low cost of the coconut-shell precursor, these properties make them exceptionally attractive sorbent candidates for CO2 capture.

Physicochemical Properties and CO<sub>2</sub> Solubility of Tetrabutylphosphonium Carboxylate Ionic Liquids

Four tetrabutylphosphonium carboxylate ionic liquids ([P4444][CA]) were prepared, and their densities, viscosities, refractive indices, and conductivities were measured and correlated with thermodynamic and empirical equations in the temperature range of 298.15-348.15 K. The influence of temperature on these four properties of [P4444][CA] was discussed, and their thermal expansion coefficient values were calculated. The CO2 absorption capacity of [P4444][CA] was studied at 313.15 K and 100 kPa. The results indicated that [P4444][Buty] had the highest CO2 capture capacity among these ionic liquids, with an absorption capacity of 0.4 mol∙mol-1 and balance time of less than 5 min.

CO2Capture by Carbon Aerogel–Potassium Carbonate Nanocomposites

Recently, various composites for reducing CO2emissions have been extensively studied. Because of their high sorption capacity and low cost, alkali metal carbonates are recognized as a potential candidate to capture CO2from flue gas under moist conditions. However, undesirable effects and characteristics such as high regeneration temperatures or the formation of byproducts lead to high energy costs associated with the desorption process and impede the application of these materials. In this study, we focused on the regeneration temperature of carbon aerogel–potassium carbonate (CA–KC) nanocomposites, where KC nanocrystals were formed in the mesopores of the CAs. We observed that the nanopore size of the original CA plays an important role in decreasing the regeneration temperature and in enhancing the CO2capture capacity. In particular, 7CA–KC, which was prepared from a CA with 7 nm pores, exhibited excellent performance, reducing the desorption temperature to 380 K and exhibiting a high CO2capture capacity of 13.0 mmol/g-K2CO3, which is higher than the theoretical value for K2CO3under moist conditions.

Batch fluidized bed test of SATS-derived CaO/TiO2–Al2O3 sorbent for calcium looping

High CO2 capture capacity and attrition resistance are of great significance for CaO-based CO2 sorbents during successive carbonation/calcination cycles. In this study, a novel self-assembly template synthesis (SATS) method is proposed to manufacture a hierarchical structure CaO/TiO2–Al2O3 sorbent, where Ca-rich, Al2O3-supported and TiO2-stabilized in a core–shell microarchitecture. Preparation experiments, including crushing strength and attrition tests of fresh CaO-based CO2 sorbents, confirm the operational feasibility of sorbents to conduct carbonation/calcination cycles in a batch fluidized bed. After 10 cyclic tests, it is interesting that CaO/TiO2–Al2O3 sorbent achieves superior CO2 capture capacity and favorable cyclic stability of 0.78mol CO2/mol CaO, which maintains almost 100% of the initial CO2 capture amount. As for attrition resistance, CaO/TiO2–Al2O3 sorbent performs an appreciable crushing strength of 1.46N and shows a low attrition loss with almost no variation of particle size distribution even after 10 cycles. All the tests are also conducted for CaO and CaO/Al2O3 sorbents for comparison, and the CO2 capture capacity and attrition resistance of the SATS-derived CaO/TiO2–Al2O3 sorbent are highlighted. In addition, it is concluded that the CaO/TiO2–Al2O3 sorbent performs prospective raw material cost in repeated carbonation/calcination cycles, which provides a possible path to realize industrial application.

Nitrogen-doped porous carbon nanofiber webs for efficient CO2 capture and conversion

Nitrogen-doped (N-doped) porous carbon nanofiber webs (CNFWs) have been successfully prepared via one-step carbonization-activation treatment of pre-synthesized polypyrrole (PPy) nanofiber webs (NFWs). In this preparation process, the carbonization of the precursor and further activation with KOH were completed simultaneously. We detailedly investigated the effect of different activation conditions on the textural characteristic of final products. The resultant N-doped porous CNFWs were evaluated not only as adsorbents for CO2 capture, but also as catalysts for CO2 conversion, and results indicated that their textural and chemical properties can be tuned by changing the weight ratio of KOH/PPy and activation temperature. Mildly activated CNFWs (KOH/PPy = 2) obtained at 600 °C (CNFWs-600-2) exhibited relatively high CO2 capture capacities of 6.44 and 4.42 mmol g−1 at 0 °C and 25 °C (1 bar), respectively. Furthermore, the CNFWs-600-2 sample was also found to be metal-, solvent-, halogen-free and high-efficiency catalyst towards the cycloaddition of CO2 to epoxides for the synthesis of cyclic carbonates. Our findings may trigger interest in studies of carbon-based materials on CO2 capture and conversion performance.

Recent Advances in Anhydrous Solvents for CO2 Capture: Ionic Liquids, Switchable Solvents, and Nanoparticle Organic Hybrid Materials

CO2 capture by amine scrubbing, which has a high CO2 capture capacity and a rapid reaction rate, is the most employed and investigated approach to date. There are a number of recent large-scale demonstrations including the Boundary Dam Carbon Capture Project by SaskPower in Canada that have reported successful implementations of aqueous amine solvent in CO2 capture from flue gases. The findings from these demonstrations will significantly advance the field of CO2 capture in the coming years. While the latest efforts in aqueous amine solvents are exciting and promising, there are still several drawbacks to amine-based CO2 capture solvents including high volatility and corrosiveness of the amine solutions, as well as the high parasitic energy penalty during the solvent regeneration step. Thus, in a parallel effort, alternative CO2 capture solvents, which are often anhydrous, have been developed as the third-generation CO2 capture solvents. These novel classes of liquid materials include: Ionic Liquids (ILs), CO2-triggered switchable solvents (i.e., CO2 Binding Organic Liquids (CO2BOLs), Reversible Ionic Liquids (RevILs)), and Nanoparticle Organic Hybrid Materials (NOHMs). This paper provides a review of these various anhydrous solvents and their potential for CO2 capture. Particular attention is given to the mechanisms of CO2 absorption in these solvents, their regeneration and their processability – especially taking into account their viscosity. While not intended to provide a complete coverage of the existing literature, this review aims at pointing the major findings reported for these new classes of CO2 capture media.

CaO Nanoparticles Coated by ZrO2 Layers for Enhanced CO2 Capture Stability

CaO is an attractive CO2 acceptor, due to its good kinetics and high capture capacity, even under low CO2 concentration conditions. The major problem associated with CaO acceptors is the loss of CO2 capture capacity during cyclic operations. The declining performance of the CaO acceptors is more pronounced in the presence of steam. In this article we propose a method for fabrication of nano-CaO acceptors coated with a ZrO2 layer to improve the stability. The nano-CaO acceptor was prepared by a thermal decomposition method following coating by a sol–gel, incipient wet impregnation, or hydrolysis process. Thermogravimetric analysis of the cyclic process of CO2 carbonation/decarbonation revealed that the nano-CaO acceptors with sol–gel (CaO-SG) and wet impregnation (CaO-IM) coatings have higher CO2 capture capacity and longer lifetime than the uncoated ones. The capture capacity of CaO-IM declined after 14 cycles, whereas CaO-SG remained stable up to 20 cycles. X-ray diffraction, scanning electron microscopy...

Carbon dioxide capture using various metal oxyhydroxide–biochar composites

Innovative and cost-effective methods are needed to capture and store CO2 to reduce anthropogenic impact on global warming. This work produced and characterized aluminum hydroxide, magnesium hydroxide, and iron oxide–biochar composites, and evaluated their ability to capture CO2 at room temperature and atmospheric pressure. Biomass feedstocks were treated with metal ions of a variety of concentrations, and were then pyrolyzed at 600°C. Characterization experiments showed that the process not only turned the biomass into biochar, but also converted the metal ions into metal oxyhydroxide nanoparticles onto the carbon surfaces with the biochar matrix. As a result, the composites, particularly the ones with optimal metal to biomass ratios, had higher CO2 capture capacity than the unmodified biochar. All the composites had relatively large surface area and captured CO2 mainly through physical adsorption. Although Fe2O3–biochar composites had the highest surface area, the AlOOH–biochar composite showed the largest sorption. Thus, both the characteristics of the metal oxyhydroxides and the surface area contributed to the CO2 capture capacity. The maximum adsorption capacity (71mgg−1 at 25°C) by AlOOH–biochar is comparable to commercial adsorbents. The samples had between 90% and 99% desorption at 120°C, so they required low cost regeneration. All these results suggested that biochar-based composites could be a high efficiency and cost-effective adsorbent for CO2 capture.