Carbon Capture and Storage (CCS) uses a combination of technologies to capture, transport and store carbon dioxide (CO2) emissions from large point sources such as coal or natural gas-fired power ...plants. Capturing CO2 from ambient air has been considered as a carbon-negative technology to mitigate anthropogenic CO2 emissions in the air. The performance of a mesoporous silica-supported polyethyleneimine (PEI)–silica adsorbent for CO2 capture from ambient air has been evaluated in a laboratory-scale Bubbling Fluidized Bed (BFB) reactor. The air capture tests lasted for between 4 and 14 days using 1kg of the PEI–silica adsorbent in the BFB reactor. Despite the low CO2 concentration in ambient air, nearly 100% CO2 capture efficiency has been achieved with a relatively short gas–solid contact time of 7.5s. The equilibrium CO2 adsorption capacity for air capture was found to be as high as 7.3wt%, which is amongst the highest values reported to date. A conceptual design is completed to evaluate the technological and economic feasibility of using PEI–silica adsorbent to capture CO2 from ambient air at a large scale of capturing 1Mt-CO2 per year. The proposed novel “PEI-CFB air capture system” mainly comprises a Circulating Fluidized Bed (CFB) adsorber and a BFB desorber with a CO2 capture capacity of 40t-CO2/day. Large pressure drop is required to drive the air through the CFB adsorber and also to suspend and circulate the solid adsorbents within the loop, resulting in higher electricity demand than other reported air capture systems. However, the Temperature Swing Adsorption (TSA) technology adopted for the regeneration strategy in the separate BFB desorber has resulted in much smaller thermal energy requirement. The total energy required is 6.6GJ/t-CO2 which is comparable to other reference air capture systems. By projecting a future scenario where decarbonization of large point energy sources has been largely implemented by integration of CCS technologies, the operating cost under this scenario is estimated to be $108/t-CO2 captured and $152/t-CO2 avoided with an avoided fraction of 0.71. Further research on the proposed 40t-CO2/day ‘PEI-CFB Air Capture System’ is still needed which should include the evaluation of the capital costs and the experimental investigation of air capture using a laboratory-scale CFB system with the PEI–silica adsorbent.
•PEI–silica adsorbent capturing CO2 from ambient air evaluated in a BFB reactor.•The equilibrium CO2 adsorption capacity for air capture as high as 7.3wt%.•40t-CO2/day CFB air capture system using PEI–silica adsorbent proposed.•The energy penalty for the proposed air capture system estimated to be 6.6GJ/t-CO2.•The operating cost of the air capture system estimated to be $152/t-CO2 avoided.
Alcohol-containing polymer networks synthesized by Friedel–Crafts alkylation have surface areas of up to 1015 m2/g. Both racemic and chiral microporous binaphthol (BINOL) networks can be produced by ...a simple, one-step route. The BINOL networks show higher CO2 capture capacities than their naphthol counterparts under idealized, dry conditions. In the presence of water vapor, however, these BINOL networks adsorb less CO2 than more hydrophobic analogues, suggesting that idealized measurements may give a poor indication of performance under more realistic carbon capture conditions.
•CO2 capture by PEI–silica adsorbent investigated using a kg-sorbent-scale BFB.•CO2 capture conducted with simulated coal-fired and NGCC flue gases.•Equilibrium capacities stabilized at ca. 11wt% for ...60 cycles under humid condition.•Heat of adsorption determined by energy balance in the fluidized bed and DSC/TGA.•Regeneration heat for the PEI–silica adsorbent noticeably lower than MEA process.
The high performance of polyethyleneimine (PEI)-based solid adsorbent for CO2 capture has been well recognized in thermogravimetric analysis (TGA) and small-scale fixed bed reactors through the measurements of their equilibrium capacities but has not been really demonstrated on larger scales towards practical utilization. In the present study, a laboratory-scale bubbling fluidized bed reactor loaded with a few kg adsorbent is used to evaluate the adsorption performance of PEI–silica adsorbent under different working conditions including with/without the presence of moisture, different gas–solid contact times, initial bed temperatures, and CO2 partial pressures. The adsorption capacities have shown a clear degradation tendency under dry condition. However, they can be stabilized at a high level of 10.6–11.1% w/w over 60 cycles if moisture (ca. 8.8vol%) is present in the gas flow during adsorption and desorption. Breakthrough capacities can be stabilized at the level of 7.6–8.2% w/w with the gas–solid contact time of 13s. The adsorption capacities for the simulated flue gases containing 5% CO2 are only slightly lower than those for the simulated flue gases containing 15% CO2, indicating that the PEI–silica adsorbent is suitable for CO2 capture from flue gases of both coal-fired and natural gas-fired combined cycle power plants. The exothermal heat of adsorption is estimated by the energy balance in the fluidized bed reactor and found to be close (within 10%) to the measured value by TG-DSC. The regeneration heat for the as-prepared PEI–silica adsorbent is found to be 2360kJ/kgCO2 assuming 75% recovery of sensible heat which is well below the values of 3900–4500kJ/kgCO2 for a typical MEA scrubbing process with 90% recovery of sensible heat.
To impact carbon emissions, new materials for carbon capture must be inexpensive, robust, and able to adsorb CO2 specifically from a mixture of other gases. In particular, materials must be tolerant ...to the water vapor and to the acidic impurities that are present in gas streams produced by using fossil fuels to generate electricity. We show that a porous organic polymer has excellent CO2 capacity and high CO2 selectivity under conditions relevant to precombustion CO2 capture. Unlike polar adsorbents, such as zeolite 13x and the metal–organic framework, HKUST-1, the CO2 adsorption capacity for the hydrophobic polymer is hardly affected by the adsorption of water vapor. The polymer is even stable to boiling in concentrated acid for extended periods, a property that is matched by few microporous adsorbents. The polymer adsorbs CO2 in a different way from rigid materials by physical swelling, much as a sponge adsorbs water. This gives rise to a higher CO2 capacities and much better CO2 selectivity than for other water-tolerant, nonswellable frameworks, such as activated carbon and ZIF-8. The polymer has superior function as a selective gas adsorbent, even though its constituent monomers are very simple organic feedstocks, as would be required for materials preparation on the large industrial scales required for carbon capture.
Activated carbon adsorbents have been evaluated at high pressure, up to 4 MPa, to determine their applicability for the removal of CO2 from syngas generated from gasification. The CO2 adsorption ...capacity and diffusion mechanism were demonstrated to be dependent upon the adsorbent outgas conditions. Activated carbons have been demonstrated to have higher adsorption capacities than existing absorption systems up to 12 mmol g−1 at 4 MPa, under strong outgas conditions. Adsorption capacities on a weight basis have been demonstrated to be correlated with the surface area and micropore volume of the materials. However, performance on a volumetric basis is less well-defined and is controlled by the form and bulk density of the adsorbent. Complete cyclic regeneration of the adsorbents has been demonstrated by pressure swing regeneration cycles.
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) ethylaminopropyl-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.
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► Amine modified layered double hydroxides were prepared via exfoliation and grafting route. ► CO2 adsorption was studied at 25–80°C and 1bar CO2 pressure. ► Highest CO2 adsorption capacity of 1.75mmolg−1 was achieved at 80°C. ► The Avrami model provided a good fit to the CO2 adsorption isotherms.
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•Silica SBA-15 was functionalized with a primary amine using a new sustainable route.•Supercritical CO2+10%mol EtOH was used to attach 3APTS to silica.•SBET and Vpore gradually ...decreased as 3APTS grafting on silica increased.•scCO2 process is performed at shorter times and lower T than conventional methods.
A new sustainable route to functionalize silica SBA-15 with 3-aminopropyltrimethoxysilane (3APTS) in supercritical CO2 (scCO2) is proposed. The aminosilane/carbamate salt formed (organic salt) by reaction between CO2 and the primary amine group of 3APTS was solubilized in scCO2 by adding 10%mol ethanol as cosolvent. For the first time such a mixture was used to perform the surface functionalization whilst keeping the advantages of performing the reaction in a supercritical fluid at a moderate temperature. Firstly, the phase behaviour of the 3APTS/carbamate+CO2+ethanol was studied to select the process experimental conditions. Then, the functionalization experiments were performed at temperatures of 313 and 333K, pressures ranging from 12.5 to 20.0MPa and concentration values of 3APTS in the modified scCO2 ranging from 0.5 to 3.5×10−3 in molar fraction. The amine functionalized materials were characterized by IR, thermogravimetric analysis, elemental analysis and N2 adsorption isotherms. The effect of pressure and temperature on the amount of 3APTS grafted on silica SBA-15 was not significant. However, as the 3APTS concentration in scCO2 modified with ethanol increased, the grafting density of 3APTS increased gradually and the surface area, pore volume and size of silica SBA-15 were also progressively reduced. The functionalization process in scCO2 was compared to that of the conventional method using toluene. Finally, the performance of the materials for CO2 sorption at low and high-pressure was evaluated. The amine functionalized silica SBA-15 exhibited good CO2 adsorption capacity: 0.7–1.5mmolg−1 at ambient pressure and 8–12mmolg−1 at 4.0MPa. These values indicate the great potential of the amine functionalized silica obtained in scCO2 for carbon capture technology.
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► Amine modified layered double hydroxides were prepared via anionic surfactant-mediated route. ► CO2 adsorption was studied at 25°C and 1bar CO2 pressure. ► Highest CO2 adsorption ...capacity of 1.39mmolg−1 was achieved at 25°C. ► The Avrami model provided a good fit to the CO2 adsorption isotherms.
Amine modified layered double hydroxides were prepared via an anionic surfactant-mediated route followed by monoethanolamine (MEA) extraction. The as-prepared materials were characterized by elemental analysis, X-ray diffraction, thermogravimetric analysis and diffuse reflection infrared Fourier transform spectroscopy. CO2 adsorption was performed in a TG 209 F1 thermogravimetric analyzer. The results showed that amine modified layered double hydroxides were successfully prepared via the anionic surfactant-mediated route but a considerable amount of amino groups were protonated which hindered CO2 adsorption. After MEA extraction, the materials were exfoliated and lost their layered structure. Free amino groups were obtained through the ionic exchange between protonated amine group and ethanolamine. The CO2 adsorption capacity at 25°C reached 1.39mmolg−1 and the amine efficiency was about 0.4. The model derived from carbamate formation mechanism showed good agreement with the experimental data.
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