CO2 storage properties of nanostructured carbons by a microwave plasma reactor

Nanostructured carbon was successfully produced by methane cracking in a relatively low-energy cold plasma reactor designed in-house. A followed thermal treatment was carried out to further enhance its porosity. The modified plasma carbon was then employed for CO2 adsorption at 25°C. The as-synthesized plasma carbon and the modified carbon were characterized by BET surface area/pore size analyzer, Raman spectra, and transmission electron microscopy (TEM). The results show thermal modification pronouncedly improves BET surface area and porosity of PC due to opening up of accessible micro-/mesopores in the graphitic structure and by the removal of amorphous carbons around the graphite surface. The modified PC displays a higher adsorption capacity at 25°C than that of the commercial activated carbon reported. The low hydrogen storage capacity of the modified PC indicates that it can be considered for CO2 removal in syngas

Production of spherical mesoporous molecularly imprinted polymer particles containing tunable amine decorated nanocavities with CO2 molecule recognition properties

Novel spherical molecularly imprinted polymer (MIP) particles containing amide-decorated nanocavities with CO2 recognition properties in the poly[acrylamide-co-(ethyleneglycol dimethacrylate)] mesoporous matrix were synthesized by suspension polymerization using oxalic acid and acetonitrile/toluene as dummy template and porogen mixture, respectively. The particles had a maximum BET surface area, SBET, of 457 m2/g and a total mesopore volume of 0.92 cm3/g created by phase separation between the copolymer and porogenic solvents. The total volume of the micropores (d < 2 nm) was 0.1 cm3/g with two sharp peaks at 0.84 and 0.85 nm that have not been detected in non-imprinted polymer material. The degradation temperature at 5% weight loss was 240–255 °C and the maximum equilibrium CO2 adsorption capacity was 0.56 and 0.62 mmol/g at 40 and 25 °C, respectively, and 0.15 bar CO2 partial pressure. The CO2 adsorption capacity was mainly affected by the density of CO2-philic NH2 groups in the polymer network and the number of nanocavities. Increasing the content of low-polar solvent (toluene) in the organic phase prior to polymerization led to higher CO2 capture capacity due to stronger hydrogen bonds between the template and the monomer during complex formation. Under the same conditions, molecularly imprinted particles showed much higher CO2 capture capacity compared to their non-imprinted counterparts. The volume median diameter (73–211 μm) and density (1.3 g/cm3) of the produced particles were within the range suitable for CO2 capture in fixed and fluidized bed systems

Rapid synthesis of MCM-41 and SBA-15 by microwave irradiation: promising adsorbents for CO2 adsorption

It is known that the world scenario is one of constant search for sustainable technologies that can reduce the emission of carbon dioxide (CO2) in the atmosphere. This is because CO2 is seen as the main responsible for the increase in the generation of greenhouse gases, which leads to global warming and climate change. The development of efficient adsorbents for CO2 capture is a current challenge. MCM-41 and SBA-15 were synthesized in a microwave reactor and used as adsorbents in this work. Microwave irradiation presents itself as an easy synthesis strategy with less preparation time and energy requirement. The silica synthesis period was extremely reduced (1 h) at a temperature of 60 and 80 °C in the microwave reactor, obtaining silica with good textural and chemical properties. The CO2 adsorption isotherms were performed at 0, 25, and 40 °C at 1 bar. The MCM-41 and SBA-15 present favorable results for CO2 capture processes, showing that pure silica synthesized by microwave already obtains promising results, reaching a maximum adsorption capacity of 2.16 mmol g−1 (1 bar—0 °C) and a good fit for the Langmuir, DsL and Toth models. Furthermore, to increase CO2 adsorption, the mesoporous silica was also modified via impregnation with branched polyethylene diamine (PEI) or tetraethylenepentamine (TEPA). It is worth mentioning that microwave irradiation reduced the synthesis steps and improved the properties and adsorption capacity of the silica. This work opens new opportunities in the efficient preparation of materials that require optimizing the adsorbent synthesis process.The authors thank you to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, National Council for Scientific and Technological Development, Brazil) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Higher Education Personnel Improvement Coordination, Brazil, CAPES—financing code 001) for financial support. This research was also funded by the Ministry of Science, Innovation and Universities (Spain), Grants Nos. RTI2018-099668-B-C22 and PID2021-126235OB-C32, and projects UMA18-FEDERJA-126 and P20_00375 of Junta de Andalucía and FEDER funds. // Funding for open access publishing: Universidad Málaga/CBUA

ZSM-5/Silicalite-1 core-shell beads as CO₂ adsorbents with increased hydrophobicity

Zeolites are commonly used for selective CO2 adsorption from biogas and flue gas. One of the biggest challenges for zeolites in this application is the presence of water vapour in the raw gas streams. While zeolites with low Si/Al ratio typically display high CO2 adsorption, they are hydrophilic and H2O competes for adsorption on the active sites. On the other hand, zeolites with high Si/Al ratio are hydrophobic, but display lower CO2 adsorption capacities. In order to overcome this limitation and to combine the high CO2 adsorption capacity of low Si/Al zeolites and the hydrophobicity of high Si/Al zeolites into a single material, we designed and synthesized novel core-shell zeolitic beads comprising a ZSM-5 core and a Silicalite-1 shell. Two different strategies were employed to synthesize these macroscopic core-shell beads. In both approaches, the initial step was the synthesis of binderless ZSM-5 beads with hierarchical porosity using resin beads as hard template. In the first strategy, a shell of Silicalite-1 was synthesized on the external surface of the calcined ZSM-5 beads, yielding Sil-ZSM-A core-shell beads (0.84 ± 0.12 mm). In the second strategy, the Silicalite-1 shell was synthesized without first removing the polymeric template from the ZSM-5 beads, resulting in core-shell composite beads that after calcination yielded Sil-ZSM-B core-shell beads (0.73 ± 0.14 mm). Characterization by SEM, XRD, XRF, ICP-AES and N2 physisorption indicated that both Sil-ZSM-A and Sil-ZSM-B beads displayed the desired zeolitic core-shell structure with hierarchical porosity. Both core-shell beads showed the anticipated increase in hydrophobicity. The most promising results were obtained with Sil-ZSM-A beads, which displayed a 40% decrease in H2O adsorption capacity at 20% relative humidity (RH) and a 28% decrease at max RH compared to the parent ZSM-5 beads. At the same time, their CO2 adsorption capacity (1.94 mmol/g at 1 bar) decreased only slightly compared to the parent ZSM-5 beads (2.13 mmol/g at 1 bar). These results indicate that these core-shell beads present the desired combination of the high CO2 adsorption capacity of the ZSM-5 core with the hydrophobicity of the Silicalite-1 shell. This is a promising feature for application in the adsorption of CO2 from water-containing streams.</p

MgO-based adsorbents for CO2 adsorption: Influence of structural and textural properties on the CO2 adsorption performance

MgO-based adsorbents for CO2 adsorption: Influence of structural and textural properties on the CO2 adsorption performanceA series ofMgO-based adsorbents were prepared through solution–combustion synthesis and ball-milling process. The prepared MgO-based powders were characterized using X-ray diffraction, scanning electron microscopy, N2 physisorptionmeasurements, and employed as potential adsorbents for CO2 adsorption. The influence of structural and textural properties of these adsorbents over the CO2 adsorption behaviour was also investigated. The results showed that MgO-based products prepared by solution–combustion and ball-milling processes, were highly porous, fluffy, nanocrystalline structures in nature, which are unique physico-chemical properties that significantly contribute to enhance their CO2 adsorption. It was found that the MgO synthesized by solution combustion process, using a molar ratio of urea to magnesium nitrate (2:1), and treated by ball-milling during 2.5 hr (MgO-BM2.5h), exhibited the maximum CO2adsorption capacity of 1.611 mmol/g at 25°C and 1 atm, mainly via chemisorption. The CO2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area, total pore volume, pore size distribution and crystallinity. The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO2 adsorption–desorption times, without any significant loss of performance, that supports the potential of MgO-based adsorbent. The results confirmed that the special features of MgO prepared by solution–combustion and treated by ball-milling during 2.5 hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO2 capture technologies

Hybrid Two-step Preparation of Nanosized MgAl Layered Double Hydroxides for CO₂ Adsorption

Hybrid Two-step synthesis method for preparation of MgAl LDHs materials for CO2 adsorption has been employed because of the features of fast micromixing and enhanced mass transfer by using a ‘T-mixer’ reactor. MgAl LDHs with different morphologies were successfully obtained by three different synthesis routes: ultrasonication-intensified in ‘T-mixer’ (TU-LDHs), conventional co-precipitation (CC-LDHs) and ultrasonic-intensified in ‘T-mixer’ pretreatment followed by conventional co-precipitation (TUC-LDHs). The synthesized samples characterized by the XRD showed that LDHs formed a typical layered double hydroxide structure and no other impurities were identified in the compound. The SEM and TEM analyses also confirmed that the size distribution of TUC-LDHs was relatively uniform (with an average size of approximate 100 nm) and layered structure was clearly visible. The BET characterization indicated that such LDHs had a large surface area (235 m2 g−1), which makes it a promising adsorbent material for CO2 capture in practical application. It can be found that the CO2 adsorption capacities of TU-LDHs, CC-LDHs and TUC-LDHs at 80°C were 0.30, 0.22 and 0.28 mmol g−1, respectively. The CO2 adsorption capacities of TU-LDHs, CC-LDHs and TUC-LDHs at 200°C were 0.33, 0.25 and 0.36 mmol g−1, respectively. The order of CO2 adsorption capacity to reach equilibrium at 80°C seen in Avrami model is: TU-LDHs > TUC-LDHs > CC-LDHs. The CO2 adsorption/desorption cycling test reveals that TU-LDHs and TUC-LDHs have good adsorption stability than CC-LDHs

Investigation of Ester- and Amide-Linker-Based Porous Organic Polymers for Carbon Dioxide Capture and Separation at Wide Temperatures and Pressures

Organic compounds, such as covalent organic framework, metal–organic frameworks, and covalent organic polymers have been under investigation to replace the well-known amine-based solvent sorption technology of CO2 and introduce the most efficient and economical material for CO2 capture and storage. Various organic polymers having different function groups have been under investigation both for low and high pressure CO2 capture. However, search for a promising material to overcome the issues of lower selectivity, less capturing capacity, lower mass transfer coefficient and instability in materials performance at high pressure and various temperatures is still ongoing process. Herein, we report synthesis of six covalent organic polymers (COPs) and their CO2, N2, and CH4 adsorption performances at low and high pressures up to 200 bar. All the presented COPs materials were characterized by using elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. Physical properties of the materials such as surface areas, pore volume and pore size were determined through BET analysis at 77 K. All the materials were tested for CO2, CH4, and N2 adsorption using state of the art equipment, magnetic suspension balance (MSB). Results indicated that, amide based material i.e. COP-33 has the largest pore volume of 0.2 cm2/g which can capture up to the maximum of 1.44 mmol/g CO2 at room temperature and at pressure of 10 bar. However, at higher pressure of 200 bar and 308 K ester-based compound, that is, COP-35 adsorb as large as 144 mmol/g, which is the largest gas capturing capacity of any COPs material obtained so far. Importantly, single gas measurement based selectivity of COP-33 was comparatively better than all other COPs materials at all condition. Nevertheless, overall performance of COP-35 rate of adsorption and heat of adsorption has indicated that this material can be considered for further exploration as efficient and cheaply available solid sorbent material for CO2 capture and separation.Qatar National Research Fund, National Priorities Research Program grant (NPRP 5-499-1-088)

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 1.76 mmol g−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

Flue gas adsorption by single-wall carbon nanotubes: A Monte Carlo study

Adsorption of flue gases by single-wall carbon nanotubes (SWCNT) has been studied by means of Monte Carlo simulations. The flue gas is modeled as a ternary mixture of N2, CO2, and O2, emulating realistic compositions of the emissions from power plants. The adsorbed flue gas is in equilibrium with a bulk gas characterized by temperature T , pressure p, and mixture composition. We have consid- ered different SWCNTs with different chiralities and diameters in a range between 7 and 20 Å. Our results show that the CO2 adsorption properties depend mainly on the bulk flue gas thermodynamic conditions and the SWCNT diameter. Narrow SWCNTs with diameter around 7 Å show high CO2 adsorption capacity and selectivity, but they decrease abruptly as the SWCNT diameter is increased. For wide SWCNT, CO2 adsorption capacity and selectivity, much smaller in value than for the narrow case, decrease mildly with the SWCNT diameter. In the intermediate range of SWCNT diameters, the CO2 adsorption properties may show a peculiar behavior, which depend strongly on the bulk flue gas conditions. Thus, for high bulk CO2 concentrations and low temperatures, the CO2 adsorption capacity remains high in a wide range of SWCNT diameters, although the corresponding selectivity is moderate. We correlate these findings with the microscopic structure of the adsorbed gas inside the SWCNTs.Ministerio de Economía y Competitividad MAT2013-42934-R y FIS2012-3245

Siliceous foam material and its application in post-combustion carbon capture for NGCC plants: effects of aging conditions

In an effort to reduce the overall energy penalty and capital expenditure associated with carbon capture technologies, a variety of porous solid adsorbents have been developed. The limitations of solid sorbent in large-scale process are related to its CO2 uptake, physicochemical stability, lifecycle, regenerability and operation condition. In this paper, siliceous foam materials were synthesized via a modified microemulsion templating method and functionalized with branched polyethylenimine (PEI). The physical characteristics of synthesized silica adsorbents under different aging conditions were analysed via N2 sorption analysis and Scanned Electron Microscopy (SEM) morphological analysis. CO2 uptake was evaluated by thermogravimetric analyser (TGA). The results show that CO2 uptake is desirable even under low CO2 partial pressure and is predictable with multiple linear regression (MLR) model in the range of examined materials