CO2 Adsorption on Modified Mesoporous Silicas: The Role of the Adsorption Sites (original) (raw)
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CO2 Adsorption on the N- and P-Modified Mesoporous Silicas
Nanomaterials
SBA-15 and MCM-48 mesoporous silicas were modified with functionalized (3-aminopropyl)triethoxysilane (APTES) by using the post-synthesis method, thus introducing N- and P-containing groups to the pore surface. The structure of the newly synthesized modifiers (aldimine and aminophosphonate derivatives of (3-aminopropyl)triethoxysilane and their grafting onto the porous matrix were proved by applying multinuclear NMR and FTIR spectroscopies. The content of the grafted functional groups was determined via thermogravimetric analysis. The physicochemical properties of the adsorbent samples were studied by nitrogen physisorption and UV–Vis spectroscopy. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The modified silicas displayed an enhanced adsorption capacity compared to the initial material. The 13C NMR spectra with high-power proton decoupling proved the presence of physically captured CO2. A value of 4.60 mmol/g was achieved for the MCM-48 material g...
Engineering of Silica Mesoporous Materials for CO2 Adsorption
Materials
Adsorption methods for CO2 capture are characterized by high selectivity and low energy consumption. Therefore, the engineering of solid supports for efficient CO2 adsorption attracts research attention. Modification of mesoporous silica materials with tailor-made organic molecules can greatly improve silica’s performance in CO2 capture and separation. In that context, a new derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, possessing an electron-rich condensed aromatic structure and also known for its anti-oxidative properties, was synthesized and applied as a modifying agent of 2D SBA-15, 3D SBA-16, and KIT-6 silicates. The physicochemical properties of the initial and modified materials were studied using nitrogen physisorption and temperature-gravimetric analysis. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The three modified materials displayed a higher capacity for CO2 adsorption than the initial ones. Among the studied sorbe...
Tuning the textural properties of HMS mesoporous silica. Functionalization towards CO2 adsorption
Microporous and Mesoporous Materials, 2018
HMS mesoporous silica materials were prepared using different amines as structure directing agents. Textural properties showed a clear dependence on the molecule used, with too long and too short amines yielding significantly distorted structures. CO 2 adsorbents were obtained by loading additional amino groups on supports before (as made) or after removing the structure directing agent (extracted and calcined). Organic loading was performed by grafting with diethylenetriaminetrimethoxysilane (DT) and by impregnation with polyethyleneimine (PEI). CO 2 adsorption analyses showed a higher CO 2 uptake and amine efficiency (defined as the molar ratio CO 2 /N) for uniformly-structured adsorbents. Besides, as-made materials showed the best CO 2 adsorption properties due to a synergistic effect between loaded amines and those already present in the support. The influence of adsorption temperature, operation cycles and CO 2 concentration was also studied. A maximum CO 2 uptake of 4.19 mmol CO 2 /g (184 mg CO 2 /g) was registered in pure CO 2 (90 ºC, 1 bar), while a value of 1.80 mmol CO 2 /g was found in direct air capture conditions (400 ppm CO 2 , 45ºC, 1 bar).
Effect of the amine type on thermal stability of modified mesoporous silica used for CO2 adsorption
Journal of Thermal Analysis and Calorimetry, 2018
In this study, the preparation by grafting of amino-functionalized SBA-15 molecular sieves was carried out. Aminofunctionalized molecular sieves were synthesized using a silane coupling agent and different types of amination reagents which react with modified SBA-15. These composites were characterized by FT-IR spectroscopy, X-ray diffraction at low angles, nitrogen physisorption at 77 K, and evaluated by the adsorption of CO 2 and its temperature-programmed desorption-TPD. Thermal stability was investigated by TGA and DTA methods. In the view of a possible use of these aminofunctionalized molecular sieves as sorbents for CO 2 removal, their adsorption-desorption properties towards CO 2 were also investigated by the TPD method. The mass loss of amino-functionalized molecular sieves above 215°C was due to the oxidation and decomposition of amino propyl functional groups. This means that these composites could be used for adsorption of CO 2 at temperatures below 215°C. The adsorption of CO 2 and its temperature programmed desorption using thermogravimetry were studied for amino-functionalized molecular sieves at 60°C. The evolved gases during the adsorption-desorption of CO 2 on amino-functionalized molecular sieves were identified by online mass spectrometry coupled with thermogravimetry. CO 2 adsorption isotherms of functionalized samples at 60°C showed that both the adsorption capacity (mg CO 2 /g adsorbent) and the efficiency of amino groups (mol CO 2 /mol NH 2) depend on the type of amination reagents and the amount of organic compound used.
Functionalised micro-/mesoporous silica for the adsorption of carbon dioxide
Microporous and Mesoporous Materials, 2007
SBA-16 silica was synthesised using the tri-block copolymer F127 as a surfactant. The copolymer was eliminated by calcination to 823 K or extraction with ethanol. These materials were functionalised with the diamine (CH 3 O) 3 Si-(CH 2 ) 3 -NH-(CH 2 ) 2 -NH 2 by post-synthesis grafting. TGA and DRIFT infrared spectroscopy revealed that the copolymer was not removed completely by extraction. For both methods the cubic pore structure of the synthesised silica remained intact which was corroborated by nitrogen isotherms and TEM measurements. The adsorption of carbon dioxide was studied with microcalorimetry at 300 K and up to 35 bars. The grafted silica samples show high enthalpies [À(90-100) kJ mol À1 ] at low pressures for the carbon dioxide adsorption. This was attributed to the initial interactions of the gas with the amine modified silica surface. With increasing carbon dioxide pressures the enthalpies decreased to values close to those observed with the non-grafted silica. The amounts of CO 2 adsorbed at 30 bar were $6.5 mmol g À1 for the non-grafted silica samples and 5.4 (extracted sample) and 4.6 mmol g À1 adsorbent (calcined sample) for the grafted silica materials, respectively.
International Journal of Molecular Sciences
The ordered mesoporous silica MCM-48 with cubic Ia3d structure was synthesized using the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) as a template agent and tetraethylorthosilicate (TEOS) as a silica source. The obtained material was first functionalized with (3-glycidyloxypropyl)trimethoxysilane (KH560); further, two types of amination reagents were used: ethylene diamine (N2) and diethylene triamine (N3). The modified amino-functionalized materials were characterized by powder X-ray diffraction (XRD) at low angles, infrared spectroscopy (FT-IR) and nitrogen adsorption–desorption experiments at 77 K. Characterization from a structural point of view reveals that the ordered MCM-48 mesoporous silica has a highly ordered structure and a large surface area (1466.059 m2/g) and pore volume (0.802 cm3/g). The amino-functionalized MCM-48 molecular sieves were tested for CO2 adsorption–desorption properties at different temperatures using thermal program desorption (TPD). ...
Amine-Grafted Mesoporous Silica for CO2 Capture
Latin American Applied Research - An international journal
Three-aminopropyltriethoxysilane modified MCM-41 mesoporous silicas were synthesized by grafting the organic groups on the support surface, using different molar ratios of SiO2:Aminosilane. The synthesized solids were characterized by N2 adsorption, XRD, FTIR and TG-DTA. MCM-41 has a specific surface area of about 1500 m2/g, while that of the functionalized materials falls around 600 m2/g, showing a tendency to decrease as the content of the functionalizing agent grows. The N2 adsorption isotherms of pure and functionalized materials are characteristic of mesoporous type IV materials. The structural properties were studied by FTIR and XRD. TG-DTA studies allow analyzing the thermal stability of the materials and determining the deposited amine content. The aminosilane modified mesoporous silica materials increase the CO2 adsorption capacity compared to that of the pure MCM-41. The results obtained are well interpreted by Freundlich physicochemical model and the model parameters show...
Journal of Porous Materials, 2020
In this study, the preparation of some large-pore ordered mesoporous silicas using a proper surfactant with different swelling agents was carried out. The synthesis of conventional SBA-15 was modified to obtain pore-expanded materials, with pore diameters up to 10 nm. To use a micelle swelling agent with a moderate swelling ability, three swelling agents were selected: 1-phenyl-decane (Dec), butyl benzene (BB), and mesitylene (Mes). These syntheses aimed to achieve a pore diameter enlargement but at the same time to avoid the formation of heterogeneous and/or poorly defined nanostructure of silica. The CO 2 adsorbents were obtained by post-synthesis functionalization treatments carried out by grafting with 3-aminopropyl triethoxysilane. The CO 2 adsorption/desorption experiments showed that carbon dioxide sorption capacities depend on the textural characteristics and the temperature used for the adsorption process. Good CO 2 adsorption capacities were obtained for all prepared adsorbents, especially for SSBA-15-Mes-sil and SSBA-15-BB-sil samples. At 50 °C, the SSBA-15-Mes-sil sample has an adsorption capacity of 3.58 mmol CO 2 /g SiO 2 , and an efficiency of amino groups of 0.99 mmol CO 2 /mmol NH 2. The results of adsorption capacities are comparable or even superior with the ones reported in literature for mesoporous silica functionalized with different amines. After nine adsorption-desorption cycles, the performance of the SSBA-15-Messil adsorbent is relatively stable, with a low decrease in the adsorption capacity (0.1 mmol/g of CO 2 , i.e., 2.8% of initial capacity). These studies show the potential of mesoporous silica for carbon dioxide capture.
Amine-modified ordered mesoporous silica: Effect of pore size on carbon dioxide capture
Chemical Engineering Journal, 2008
Three mesoporous silica materials with different pore sizes (33 Å for small pore size MCM-41; 38 Å for SBA-12; 71 Å for large pore size SBA-15) and pore connectivity (2D for MCM-41 and SBA-15-type materials; 3D for SBA-12 material) were prepared and functionalized with aminopropyl (AP) ligands by post-synthesis treatment. The materials were characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and nitrogen adsorption/desorption experiments. The carbon dioxide sorption on modified mesoporous molecular sieves was investigated by using of microbalances at 25 • C, and the influence of pore size and pore architecture on CO 2 sorption was discussed. The large pore silica, SBA-15, showed the largest carbon dioxide sorption capacity (1.5 mmol/g), relating to highest amine surface density in this material. On the other hand, three-dimensional accessibility of amine sites inside the pores of SBA-12 silica resulted in a faster response to CO 2 uptake in comparison with MCM-41 and SBA-15 molecular sieves.
Adsorption of Carbon Dioxide into Amine Functionalized Ordered Mesoporous Materials
The adsorption of carbon dioxide on amino silanes-functionalized MCM-41 and SBA-15 materiais is reported. The functionalization of mesoporous silicas was made by post-synthesis method, by impregnation of 3-aminopropyltriethoxysilane. The obtained materials were characterized by X-ray diffraction, scanning and transmission electron microscopies, nitrogen adsorption-desorption and X-ray photoelectron spectroscopy measurements. The carbon dioxide adsorption capacities for the samples were carried out under ambient pressures. The obtained results evidenced that amino-silanes with a terminal amine (–NH2) were functionalized through covalent coupling of this group on the surface of the channels in the ordered mesoporous silica, meaning that the amine is anchored on the surface of the bigger pores of the MCM-41 and SBA-15 support. For functionalized materials, the CO2 adsorption capacity of the AMCM-41 increased from 0.18 to 1.1 mmol g−1, whereas for ASBA-15, it was from 0.6 to...