High CO2 Capture Research Articles

Spray-assisted layer-by-layer self-assembly of tertiary-amine-stabilized gold nanoparticles and graphene oxide for efficient CO2 capture

Carbon capture and storage (CCS) is the process of capturing carbon dioxide (CO2) produced from the combustion of fossil fuels. CO2 is a major contributor to global warming and should be removed after combustion. The objective of this research is to design a CO2 capture membrane consisting of tertiary-amine-stabilized gold nanoparticles (Au NPs), graphene oxide (GO), and polyelectrolytes. A high CO2 capture ability is most important for designing a CO2 capture membrane that can maintain a high gas permeance. Multilayer films were fabricated using an automatic spray-assisted layer-by-layer (LbL) machine. The polar affinity of polyelectrolytes assisted the CO2 capture of tertiary amines. The randomly oriented and loosely stacked GO layers not only helped align the Au NPs in the polyelectrolyte matrix, but also helped maintain the permeance of N2. Thus, we successfully fabricated a CO2 adsorptive multilayer nanocoating with a maximum CO2/N2 selectivity of 48.48 while maintaining the N2 permeance at 1204.25 GPU.

Preparation of carbon-based monolithic CO2 adsorbents with hierarchical pore structure

Various porous solid sorbents in the form of powder or monoliths have been developed over the last years, as a promising solution for reducing CO2 emissions. Although powder sorbents, due to higher porosities and efficient mass transport, exhibit higher capacities compared with monoliths, several factors limit their suitability for practical application. The most prominent is their low bulk density, which makes them difficult to handle and poses health risks due to dust inhalation. In this work, we prepared robust hierarchically porous carbon-based monoliths based on a simple three-step approach with the focus on combining efficient CO2 adsorption and transport with easy handling for practical applications. The approach is based on incorporation of polystyrene nanoparticles (PS NPs) and expanded graphite (EG) into a nitrogen-rich precursor, which is polymerized to form 3D monoliths. Incorporation of thermally unstable PS NPs or thermally stable EG enables us to control the formation of macropores during a precarbonization step, while variation of KOH concentration and mixing intensity during a subsequent activation step controls the formation of micropores. The resulting hierarchically porous monoliths with high nitrogen contents exhibited CO2 uptake capacities reaching 6.52 mmol g−1 at 273.15 K and 1 bar, which is among the highest reported for porous carbon monoliths. In addition, the materials also exhibited good reversibility of CO2 adsorption over several cycles with simple regeneration under mild conditions. Considering the high CO2 capture performance together with improvements in sorbent properties such as easy handling and reusability, the presented sorbents are promising candidates for practical applications.

Rapid, simple and sustainable synthesis of ultra-microporous carbons with high performance for CO2 uptake, via microwave heating

A one step microwave pyrolysis-activation method has been developed for the preparation of activated carbons from biomass with high CO2 capture efficiency (5.3 mmol g−1) by employing a low impregnation ratio (1) of KOH and K2CO3. The high microwave susceptibility identified by the dielectric properties enabled the preparation of a series of activated carbons in short processing times (<6 min), and the pyrolysis-activation simultaneously enhanced the formation of ultra-micropores leading to high CO2 uptake at 15 and 100% CO2 in the temperature range of 0–100 °C. The high CO2/N2 selectivity of up to 36 the adsorptive capacities were directly correlated to a pore size of ~0.7 nm, which favoured CO2 uptake up to 5.3 and 4.5 mmol g−1 at 1.1 bar and 0 °C and an uptake of 3.7 and 3.3 at 25 °C for activated samples with KOH and K2CO3, respectively. The activated carbons presented in this study are the first examples of samples that have been prepared by this simple and rapid method, which represents a 96.66% reduction in the processing times in comparison to conventional heating routes, and the CO2 uptake is comparable to the largest reported in literature for activated carbons. The outstanding uptake and selectivity, the simple synthesis using microwave technology in addition to the utilisation of a waste biomass as a carbon precursor, satisfy the requirements for the development of new and more sustainable energy environmental processes.

The Effects of Synthesis Conditions on the Carbon Capture Capacity of Polyethylenimine Impregnated Protonated Titanate Nanotubes

Capture and storage of carbon dioxide emitted from power plants, which burn fossil fuels, is one of the best ways to mitigate climate change. Polyethylenimine (PEI) impregnated protonated titanate nanotubes (PEI-PTNTs) are efficient amine-modified solid adsorbents for post combustion carbon capture. This study is to investigate the effects of synthesis conditions of titanate nanotubes on the carbon capture capacity of PEI-PTNTs. PTNTs are synthesized using hydrothermal treatment of TiO2 anatase powder at different temperatures and in different days, followed by washing with dilute HCl solution and deionized water. PEI-PTNTs are prepared by loading PEI (M.W. = 10,000) onto PTNTs at a weight ratio of 1:1 using a wet impregnation process. PTNTs and PEI-PTNTs are characterized using transmission electron microscopy, porosity and surface area analysis, powder X-ray diffraction, and Fourier transform infrared spectroscopy. CO2 adsorption is conducted at 75 °C using simulated flue gas, and CO2 desorption is performed at 110 °C by purging the adsorbent with dry nitrogen gas. CO2 adsorption experiments demonstrate that the PEI-PTNTs synthesized at 130 °C within 3 or 5 days, have the highest CO2 capture capacity. These optimized PEI-PTNTs have a significant potential to capture CO2 from power plants.

Robust Metal-Triazolate Frameworks for CO2 Capture from Flue Gas.

Construction of thermally and chemically robust metal-organic frameworks (MOFs) is highly desirable for postcombustion CO2 capture from flue gas containing water vapor and other acidic gases. Here we report a strategy based on appending amino groups to the triazolate linkers of MOFs to achieve exceptional chemical stability against aqueous, acidic, and basic conditions. These MOFs exhibit not only CO2/N2 thermodynamic adsorption selectivity as high as 120 but also CO2/H2O kinetic adsorption selectivity up to 70,featuring distinct adsorptive sites at the channel center for CO2 and at the corner for H2O, respectively. The best performing MOF in this series features low regeneration energy, high CO2 capture utility under humid conditions, and decent cycling performance for mimic flue gas.

The effect of incorporation Mg ions into the crystal lattice of CaO on the high temperature CO2 capture

The influence of doping Mg ions into the crystal lattice of CaO on the CO2 adsorption has been investigated. The stronger Ca-O-Mg interactions promote the electron transfer capacity and oxygen vacancy generation, which are highly advantageous to capture CO2. The high CO2 adsorptive performance are also attributed to the uniform nano-sized grains and optimized pore size distribution. The theoretical estimation of adsorption energy verifies that doping Mg ions into the crystal lattice of CaO renders the surface O atom rearrangement. Furthermore, the analysis of bond length, Mulliken population, difference electron density, and partial density of states provides evidence for the donation of more electrons to the adsorbing CO2 by Mg ions entering into the CaO lattice, indicating the stronger interaction between C atoms in CO2 molecule and surface O atom in CaO. The Mg ions in the calcium-based sorbent prepared by sol-gel method enter into the CaO crystal lattice, which exhibits the highest adsorption capacity and the best multicycle stability among all the as-prepared samples (a sorption capacity at the 20th cycle of 0.45 g−CO2/g-ads).

Synthesis of hierarchical porous carbon from waste &lt;i&gt;Camellia oleifera&lt;/i&gt; shell with high carbon dioxide adsorption capacity

A porous carbon material with hierarchical micropore-mesopore structure was prepared from waste Camellia oleifera shell by a simple ZnCl2 chemical activation technique. The surface morphology and textural properties of prepared carbon materials were characterised by scanning electron microscope (SEM) and N2 adsorption/desorption measurement. The carbon product exhibits high specific surface area and pore volume of 2,933 m2/g and 1.59 cm3/g, respectively, which are the highest values among carbon materials prepared from various biomass materials reported to date. This carbon material exhibited a CO2 uptake of 134 mg/g at 25°C and 1 atm pressure, which is one of the highest CO2 capture capacities among carbon materials prepared from a variety of biomass materials reported so far under the same experimental conditions. The adsorbent regeneration can be achieved by a facile argon purge and the material showed stable performance in 5 CO2 consecutive adsorption-desorption test cycles.

Efficient carbon dioxide capture by nitrogen and sulfur dual-doped mesoporous carbon spheres from polybenzoxazines synthesized by a simple strategy

Nitrogen and sulfur dual-doped ordered mesoporous carbon has been synthesized from a novel polybenzoxazine using resorcinol, 2-aminothiazole, formaldehyde and different ampliphilictriblock copolymers by a simple one-pot strategy. The structure, morphology, and elemental compositions of the carbon was characterized using X-ray diffraction, raman spectroscopy, field emission scanning electron spectroscopy, and X-ray photoelectron spectroscopry. The effect of carbonization temperature, type of soft template and soft template concentration on the textural properties and CO2 adsorption capacity of porous carbon spheres has been studied. By varying the synthesis conditions, ordered mesoporous N, S dual-doped carbon with improved mesoporosity, specific surface areas of up to 910 m2/g and pore volume of 0.42 cm3/g were achieved. CO2 adsorption results revealed that the synthesized carbon possesses excellent performance as an absorbent for CO2 capture at 1.0 bar (4.25 and 3.17 mmol/g at 273 and 298 K, respectively). Apart from the micropores, presence of both nitrogen and sulfur elements are also necessary for achieving a high CO2 capture performance.

Impact of load changes on the carbonator reactor of a 1.7 MWth calcium looping pilot plant

This work analyses the performance of a Calcium Looping (CaL) carbonator reactor that captures CO2 from a power plant operating under large load changes. Several experimental campaigns have been conducted in La Pereda 1.7 MWth CaL pilot plant where the carbonator inlet flue gas velocity varied between 2.0 and 5.3 m/s, leading to large changes in the particles entrainment rate and the solids inventory. These tests showed that CaL systems using circulating fluidized bed reactors are highly flexible. Modest gas velocities translate into high CO2 capture efficiencies because circulation rates equivalent to CaO/CO2 molar ratios ~10–12 can still be maintained, while carbonator solids inventories are relatively large. Under high carbonator gas velocities, a sorbent with high CO2 carrying capacity is necessary to guarantee high CO2 capture efficiencies. In these conditions, the recirculation of a fraction of the exiting particles towards the bottom of the carbonator proved to be useful for moderating the solids circulation rate between reactors, increasing the particles residence time in the carbonator and sustaining high CO2 capture efficiencies. For load increases, staging the flue gas entering the carbonator helped to sustain high CO2 capture efficiencies thanks to maintaining the solids inventory at the bottom of the reactor.

Thickness controllable hypercrosslinked porous polymer nanofilm with high CO2 capture capacity

Thickness controllable porous polymer nanofilm with superior gas storage capacity has gradually emerged as promising adsorbents for capture of CO2, due to extremely high surface area and micro-scale pore. In this work, we have developed a novel and facile strategy to fabricate thickness controllable two or three dimensional ordered porous nanofilm based on poly(styrene-butyl acrylate), in combination with covalently layer by layer (LBL) self-assemble process and hypercrosslinked post-treatment. Abundant microporous structures and a small number of mesoporous structures are formed in hypercorsslinked nanofilm and corresponding surface area derived from Brunauer-Emmett-Teller method (BET) were determined to be 605.7 m2/g. The capacity of CO2 capture was also measured, which reach up to 53.6 wt% (12.2 mmol/g) at 273 K/1 bar, which is comparable to highest record. We have found that all the as prepared nanofilm with different thickness exhibited apparently enhanced micro- and meso-porosity after hypercrosslinking. Moreover, with the increase of thickness of nanofilm, the adsorption capacity decreases gradually, as well as the CO2 adsorption capacity. An excellent recycling capacity for CO2 capture have also found for this porous polymer nanofilm via repetitive adsorption-desorption assay. Our work confirmed that thickness controllable porous polymer nanofilm with superior CO2 capture capacity can be fabricated by a very simple strategy which can meet the challenges of the current CO2 capture and storage technology.

Performance of the carbonator and calciner during long-term carbonate looping tests in a 1 MWth pilot plant

Carbon capture and utilization/storage is an effective means to reduce CO2 emissions from power and energy intensive industries. Carbonate looping is a 2nd generation post-combustion CO2 capture technology using solid sorbents that form carbonates when reacting with CO2. This technology has economic benefits caused by the low efficiency penalty and the low cost of the sorbent. Autothermal continuous operation of this process at high CO2 capture rates has been successfully proven in several pilot plants up to 1.7 MWth. The 1 MWth pilot plant in Darmstadt has been operated for more than 2000 h with long periods of steady-state conditions, which allows the evaluation of the performance of the reactor system during long-term operation. This paper presents complementary results of these pilot tests focussing on the performance of the carbonator and calciner reactors. A high carbonator efficiency above 80 % is possible in the temperature range of 650–675 °C with a specific solid inventory above 700 kg/m2 combined with either a high sorbent looping ratio of 16 molCa/molCO2 or a high make-up ratio of 0.13 molCa/molCO2. A calcination efficiency of 90 % can be achieved by a calciner space time above 6 min, if the calciner temperature is 30 K above the equilibrium temperature at the prevailing CO2 concentration. Heating of the sorbent entering the calciner consumes almost half of the thermal fuel input.

Proposal of ultra-high-efficiency zero-emission power generation systems

Solid oxide fuel cell (SOFC) and protonic ceramic fuel cell (PCFC) have strong features that enables high efficiency power generation and efficient CO2 capture. Applying these technologies to the fossil fuel and biomass power generation, we can realize ultra-high efficiency zero-emission power generation by capturing liquefied CO2 (LCO2) for easy transport and utilization (CCU) or storage(fossil fuel CCS and bio-energy CCS: BECCS). In this study, we propose LCO2 capture ultra-efficient power generation systems consist of multi-stage SOFC/PCFC, oxygen or hydrogen transport membrane, CO2 cooling and liquidizing units driven by exhaust heat and generated power by fuel cells. Net power generation efficiency is estimated through heat mass balance analysis. As the results for natural gas, proposed PCFC system is suitable and expected 64.7 %LHV net power generation efficiency with more than 99 vol% LCO2 capture. For biogas direct supply case, net power generation efficiency of proposed PCFC system is 57%LHV with 99 vol% capture of CO2 in the air. These results indicates that proposed systems have quite strong potential that enables ultra-high efficient CO2-free fossil fuel power generation with CCS and CO2-reduction biomass fuel power generation with BECCS.

Pre‐Carbonization: An Efficient Route to Improve the Textural and Gas Sorption Properties of Nitrogen‐Enriched Nanoporous Polytriazine

AbstractAn unprecedented approach to improve the CO2 capture capacity by heating nitrogen enriched nanoporous polytriazine (NENP‐1) below the carbonization (pre‐carbonization) temperature has been invented. The NENP‐1 heated at 350 °C for 2 h (assigned as NENP‐1‐350) in argon atmosphere has improved specific surface area (SABET) marginally from 840 (NENP‐1) to 880 m2 g−1 (NENP‐1‐350). However, there was a substantial increase in the CO2 capture capacity from 22.9 (NENP‐1) to 33.8 wt% (NENP‐1‐350) measured at 0 °C and 1 bar. Although, both the specimens have comparable SABET, the NENP‐1‐350 has larger pore volume of 1.10 cm3 g−1 (as compared to 0.71 cm3 g−1 in NENP‐1) and larger pore size distribution (PSD) along with the higher isosteric heat of adsorption that contributed for such a high CO2 capture capacity. Unlike the CO2 capture capacity in the NENP‐1‐350, there was only marginal increase in the hydrogen storage capacity from 2.30 to 2.47 wt% and methane sorption capacity from 1.8 to 1.9 wt% measured at −196 and 0 °C, respectively, as compared to the NENP‐1.

Charge-modulated/electric-field controlled reversible CO2/H2 capture and storage on metal-free N-doped penta-graphene

Abstract Development of advanced materials for the capture and separation of CO2 from the gas mixture is necessary to mitigate the greenhouse effect. In this study, we perform density functional theory computations with long-range dispersion correction to study CO2, H2, CH4 and N2 on the N-doped penta-graphene (PG) sheet under different charge-induced density and applied external electric field. We reveal that the CO2 capture/release process is reversible that can be simply controlled by switching on/off the charged states and electric field of the N-doped PG. The CO2 adsorption is weak on the neutral state of N-doped PG sheet, whereas the adsorption of CO2 can be intensely enhanced under the action of charge-induced density and external electric field. Comparing with the CO2 adsorption, the adsorption species of H2, CH4 and N2 are strikingly weaker signifying that the N-doped PG sheet for CO2 separation from its mixtures with H2, CH4 and/or N2 exhibits efficiently high selectivity by a charge/electric field-controlled. These results might afford new awareness in searching for materials with remarkably high CO2 capture capacity.

Techno – Economic assessment of flexible decarbonized hydrogen and power co-production based on natural gas dry reforming

The need for flexible power plants could increase in the future as variable renewable energy (VRE) share will increase in the power grid. These power plants could balance the increasing strain on electricity grids by renewables. The proposed plant in this paper can adapt to these ramps in electricity demand of the power grid by maintaining a constant feed and producing also high purity hydrogen. Dry methane reforming (DMR) is incorporated into a flexible power plant model and the key performance indicators are calculated from a techno-economic perspective. The net output of the plant is 450 MW with the possibility to lower power production and produce hydrogen, maintaining a high CO2 capture rate (72%). Two cases are compared to the base case to quantify: (i) energy and cost penalties for CO2 capture and (ii) advantages of flexible power plant operation. The levelized cost of electricity (LCOE) for the base case is 67 Euro/MWh, the addition of a carbon capture unit increases it to 82 Euro/MWh. In the case of flexible operation, both the LCOE and levelized cost of hydrogen (LCOH) are calculated and the two depend on the cost allocation factor. The LCOE ranges from 65 to 85 Euro/MWh while the LCOH from 0.15 to 0.073 Euro/Nm3. The DMR power plant presented in Cases 1 and 2 present little advantages in today's market conditions however, the flexible plant (Case 3) can be viable option in balancing VRE.

Enhancement of sintering resistance of CaO-based sorbents using industrial waste resources for Ca-looping in the cement industry

Keeping a high stability and CO2 capture capacity of CaO-based sorbents during the Ca-looping process is still a challenge. The main goal and the innovative idea addressed in this study consists of investigating if solid industrial waste resources such as a coal fly ash (CFA) and a spent Fluid Catalytic Cracking (SFCC) catalyst, can be used as particle spacers to improve the sintering resistance of two CaO-based sorbents. These two inert industrial waste materials are used in the present work for increasing the CaO particles separation and consequently, reducing their coalescence and hindering severe sintering at the high Ca-looping temperatures. There are currently no studies in the literature on the use of industrial SFCC wastes in blends with CaO based sorbents acting as CaO particles spacer with the objective of reducing the Ca-looping sorbents deactivation along the cycles of carbonation-calcination.Despite the mineralogical and textural differences between the CFA and SFCC catalyst industrial wastes, the tests carried out in a fixed bed laboratory reactor showed that the addition of a small fraction of waste to the CaO sorbent (c.a. 10%) seems to be an interesting option to improve the CO2 capture technology efficiency. During the Ca-looping, the volume and stability of sorbent mesopores is essential to achieve higher and stable carbonation conversion values, and since the CFA and SFCC increase the SBET, they contribute to enhance the sintering resistance.The innovative results presented in this study show that the industrial CFA and SFCC wastes have potential to be an economically attractive option thus contributing to reduce the cost of the Ca-looping cycle CO2 capture process, as well as to minimize the adverse environmental impacts of the high volume of industrial wastes generated.

Facile Synthesis of Aromatic Porous Organic Polymer for Highly Selective Capture of CO2 via Enhanced Local Dipole-π and Dipole-Quadrupol Interactions by Adjacent Benzene

A new aromatic porous organic polymeric material named as N-PKIN has been successfully constructed. The electron-rich benzene in its microstructure can donate the electron density to the neighboring indole and carbonyl groups to further enhance the local dipole-π and dipole-quadrupole binding abilities to the CO2 molecules for effectively facilitating the adsorbent to attract CO2 selectively. As a result, this porous organic polymer showed outstanding CO2 absorption capacity and high CO2/N2, CO2/CH4 selectivity. In addition, upon exposure to humid condition, the porous organic polymer still kept high CO2 capture capacity and selectivity. Moreover, we have demonstrated that the CO2 absorption process is fully reversible.

K2CO3 promoted novel Li4SiO4-based sorbents from sepiolite with high CO2 capture capacity under different CO2 partial pressures

CO2 sorption at high temperature is recently attracting increasing attention. In the study, lithium silicate (Li4SiO4) based sorbents were synthesized using sepiolite as silicon source. The effect of the purity, crystallite size, and specific surface area of Li4SiO4 synthesized by different methods on the CO2 sorption performance were studied systematically. Moreover, the CO2 uptake of Li4SiO4 sorbents was improved by using K2CO3. The relationship between the CO2 uptake performance and doping amount of K2CO3 under different CO2 partial pressure was investigated in detail. Results show that the doping amount of K2CO3 was 17.5 wt%, 12.5 wt% and 15 wt%, the CO2 sorption value of synthesized Li4SiO4 samples was 27.67 wt%, 30.69 wt%, 32.95 wt%, respectively. Meanwhile, the K2CO3 promoted mechanism was discussed. Finally, the sorption/desorption cycles were performed under pressure swing sorption (PSA) and temperature swing sorption (TSA) procedures, which displayed high cycling stability after 22 cycles.

Exceptionally High CO2 Capture in an Amorphous Polymer with Ultramicropores Studied by Positron Annihilation.

A series of amorphous melamine-based polymer networks synthesized by Schiff base chemistry (SNW) were successfully prepared by varying the strut length. The pore structure was analyzed by gas adsorption and positron annihilation methods. Positron lifetime measurements indicate the existence of ultramicropores and also larger mesopores in the SNW materials. The sizes of micropores and mesopores are almost the same in these samples, which are about 0.7 and 16.5 nm, respectively. The relative number of micropores increases in the order of SNW-1 < SNW-2 < SNW-3, while the number of mesopores increases in the reverse order. N2 adsorption/desorption measurements also reveal micropores and mesopores in these materials. However, it gives an underestimation of the micropore volume. Benefiting from the abundant nitrogen content and high microporosity, the SNW materials exhibit exceptionally high CO2 capture ability, which reaches a maximum value of 18.3 wt % in SNW-3 at 273 K and 1 bar, followed by SNW-2 and SNW-1. This order is exactly the same as the order of micropore volume revealed by positron annihilation measurement, suggesting that micropores play a crucial role in the CO2 uptake. Our results show that positron can provide more precise information about the structure of micropores and thus can offer an accurate prediction for the adsorption capacity of complex porous materials.

Fabrication of efficient and stable Li4SiO4-based sorbent pellets via extrusion-spheronization for cyclic CO2 capture

Li4SiO4 is a promising solid sorbent for high-temperature CO2 capture due to the high and stable CO2 adsorption performance. It is required to possess good mechanical properties in practical fluidized-bed systems and pelletization is necessary. However, pelletization generally results in a large decline in the CO2 uptake or a continuous loss-in-capacity of Li4SiO4 sorbents in cyclic reactions. In this work, three kinds of Li4SiO4 powders were synthesized and screened, and spherical pellets were further prepared via an extrusion-spheronization technique using polyethylene as a pore-former to develop porous microstructure. Then sorbent pellets were systematically tested on the CO2 adsorption performance, compression strength and attrition resistance. Results shows that the pellets modifying with 20 wt% polyethylene reach and stabilize a CO2 sorption capacity of 0.31 g CO2/g sorbent in the whole 40 tested cycles under typical conditions, which is even higher than that in powder form. Moreover, the pellets are observed to have an outstanding compression strength (27.5 MPa after calcination) and an excellent attrition resistance (only 1.01 wt% mass loss in 10 h-attrition test), which are both far more better than sorbents reported in the literature. The simultaneous physiochemical performances indicate that the prepared Li4SiO4 sorbent pellets could be suitable for high temperature CO2 capture in fluidized-bed reactors.