Efficient 3-aminopropyltrimethoxysilane functionalised mesoporous ceria nanoparticles for CO2 capture

This work described the effect of 3-aminopropyltrimethoxysilane (APTMS) functionalization on the mesoporous ceria nanoparticles (MCNs) toward CO₂ capture. The MCN and APTMS-loaded MCN (APTMS-MCN) were prepared by the sol-gel and impregnation method, respectively. The functionalization of APTMS on the MCN enhanced the CO₂ binding sites which were observed through the formation of carbamate species from the interaction of CO₂ with the NH group. This resulted to the increase of CO₂ adsorption capacity of APTMS-MCN with 10-fold higher than that of pristine MCNs. For MCNs, CO₂ may be adsorbed onto oxygen basic, oxygen vacant, and hydroxyl sites which further formed polydentate, monodentate, bidentate, and hydrogen carbonate species. In addition to these carbonate species, the adsorption of CO₂ on APTMS-MCN has largely occurred through the formation of carbamate species which further enhanced its CO₂ uptake.     

Tetraethylenepentamine-modified mesoporous adsorbents for CO2 capture: effects of preparation methods

Tetraethylenepentamine (TEPA)-modified mesocellular silica foams (MSFs) were fabricated via physical impregnation (MSF-T-x) and chemical grafting (MSF-CT-y) methods. The CO₂ adsorption on these TEPA-modified MSFs was measured by using microbalances at 348?K and their adsorption capacities were observed to be 26.4–193.6?mg CO₂/g-sorbent under ambient pressure using dry 15?% CO₂. It was found that the CO₂ adsorption capacities of MSF-CT-y were smaller than those of MSF-T-x sorbents which may be attributed to their higher density of amine groups. On the contrary, MSF-CT-y exhibited enhanced stability during repeated adsorption-desorption cycles compared to MSF-T-x sorbents. This notable enhancement in the durability of CO₂ adsorption-desorption process was probably attributed to the decreased leaching of TEPA which is chemically bonded to the surface of MSF.     

High and selective CO2 capture by two mesoporous acylamide-functionalized rht-type metal-organic frameworks

Two mesoporous and flexible acylamide-functionalized rht-type MOFs exhibit not only high excess unsaturation CO(2) uptake (157 wt%) at 20 bar and 273 K, but also good selectivity of CO(2)/CH(4) (8.6) and CO(2)/N(2) (34.3). The advantages of acylamide groups for CO(2) capture have been further confirmed by GCMC and first-principles calculations.     

Primary, secondary, and tertiary amines for CO2 capture: designing for mesoporous CO2 adsorbents

CO(2) emissions, from fossil-fuel-burning power plants, the breathing, etc., influence the global worming on large scale and the man's work efficiency on small scale. The reversible capture of CO(2) is a prominent feature of CO(2) organic-inorganic hybrid adsorbent to sequester CO(2). Herein, (3-aminopropyl) trimethoxysilane (APTMS), [3-(methylamino)propyl] trimethoxysilane (MAPTMS), and [3-(diethylamino) propyl] trimethoxysilane (DEAPTMS) are immobilized on highly ordered mesoporous silicas (SBA-15) to catch CO(2) as primary, secondary, and tertiary aminosilica adsorbents. X-ray photoelectron spectroscopy was used to analyze the immobilized APTMS, MAPTMS, and DEAPTMS on the SBA-15. We report an interesting discovery that the CO(2) adsorption and desorption on the adsorbent depend on the amine type of the aminosilica adsorbent. The adsorbed CO(2) was easily desorbed from the adsorbent with the low energy consumption in the order of tertiary, secondary, and primary amino-adsorbents while the adsorption amount and the bonding-affinity increased in the reverse order. The effectiveness of amino-functionalized (1(o), 2(o), and 3(o) amines) SBA-15s as a CO(2) capturing agent was investigated in terms of adsorption capacity, adsorption-desorption kinetics, and thermodynamics. This work demonstrates apt amine types to catch CO(2) and regenerate the adsorbent, which may open new avenues to designing "CO(2) basket".     

Facile assembly of mesoporous silica nanoparticles with hierarchical pore structure for CO2 capture

In the work, we propose an efficient one-pot approach for synthesis of a new type of mesoporous silica nanoparticles (MSNs). That can be successfully realized by using tetraethylorthosilicate (TEOS) and N-[3-(trimethoxysilyl)propyl]ethylenediamine (TSD) as the silica precursors and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent through a facile assembly process. The as-synthesized MSNs possess a spherical morphology with about 230 nm, a relatively high surface area of 133 m²/g, and a hierarchical pore size distribution. When applied as the sorbents, the amine-functioned MSNs demonstrate the enhanced adsorption capacity for CO₂ capture (at 1 bar, 15 vol% CO₂, up to 80.5 mg/g at 75 °C), high selectivity, and good cycling durability, benefiting from the suitable modification of polyethyleneimine.     

Fabrication of mesoporous polymer monolith: a template-free approach

Mesoporous polyacrylonitrile (PAN) monolith has been fabricated by a template-free approach using the unique affinity of PAN towards a water/dimethyl sulfoxide (DMSO) mixture. A newly developed Thermally Induced Phase Separation Technique (TIPS) has been used to obtain the polymer monoliths and their microstructures have been controlled by optimizing the concentration and cooling temperature.     

The polymeric ionic liquids/mesoporous alumina composites: Synthesis,characterization and CO2 capture performance test

The CO₂ capture materials and technology have received much attention in recent years due to the environmental deterioration caused by the greenhouse gas emissions. Several imidazolium polymeric ionic liquids (PILs) were synthesized and immobilized on mesoporous γ-Al₂O₃ (MA) using ultrasonic immersion method. The prepared adsorbents were characterized by FT-IR, ¹H NMR, EA, TGA, SEM, XRD, BET and TEM, indicating the successful synthesis of the desired PILs/MA. The CO₂ adsorption capacity was investigated under different loading ratios, temperatures, pressures and CO₂ flow rates, whose optimal adsorption conditions were 1/1, 313 K, 5 bar and 10 mL/min, respectively. Moreover, the adsorption curves for P[VCIm]Cl/MA were coincident with pseudo-second order model, and the CO₂ adsorption kinetics model was calculated and obtained. Compared with P[VRIm]Cl and P[VEIm]Cl, P[VCIm]Cl/MA demonstrated an outstanding adsorption amount of 0.562 mmol/g under the suitable conditions, and its regeneration efficiency could achieve 94.8% after 5 times cycle.     

Synthesis of ordered mesoporous carbonaceous materials and their highly efficient capture of uranium from solutions

An extremely effortless method was applied for successful synthesis of mesoporous carbonaceous materials(MCMs) using well-ordered mesoporous silica as template. Various characterizations(scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), Raman, X-ray photoelectron spectroscopy(XPS), Brunner-Emmet-Teller(BET) and Zeta potential) confirmed that MCMs had large surface area, uniform pore size distribution, and abundant oxygen-containing functional groups. The batch techniques were employed to study U(VI) adsorption on MCMs under a wide range of experiment conditions. The adsorption kinetics of U(VI) onto MCMs were well-fitted by pseudo-second-order kinetic model, indicating a chemisorption process. The excellent adsorption capacity of MCMs calculated from the Langmuir model was 293.95 mg g~(-1) at pH 4.0. The FT-IR and XPS analyses further evidenced that the binding of U(VI) onto MCMs was ascribed to the plentiful adsorption sites(–OH and –COOH groups) in the internal mesoporous structure, which could efficiently trap guest U(VI) ions. The results presented herein revealed that MCMs were ideal adsorbents in the efficient elimination of uranium or other lanthanides/actinides from aqueous solutions, which would play an important role in environmental pollution management application.     

A novel and template-free method for the spontaneous formation of aluminosilicate macro-channels with mesoporous walls

A simple and template-free synthesis pathway was developed leading to hierarchical meso-macroporous aluminosilicates made of an assembly of macro-channels with openings between 0.5 and 2.0 microm and mesoporous walls.     

Synthesis of biomorphological mesoporous TiO2 templated by mimicking bamboo membrane in supercritical CO2

A new approach is presented for preparing biomorphological mesoporous TiO2 templated by mimicking bamboo inner shell membrane via supercritical CO2 (SCCO2) transportation through titanium tetrabutyloxide (TTBO). The analysis of wide-angle X-ray powder diffraction (XRD) showed the prepared TiO2 in phase of anatase, and the small-angle XRD revealed the presence of mesopores without periodicity. The product exhibited the shape of crinkled films and extended in two dimensions up to centimeters. The electron microscopic observation showed that the TiO2 films were around 200 nm in thickness, and across the films there were numerous round or ellipse-shaped mesopores, being 10-50 nm in diameter, which were formed by the close packing of TiO2 particles. High-resolution transmission electron microscope (HRTEM) displayed that the single TiO2 particle size was about 12.5 nm. The UV-vis absorption spectrum was transparent in the wavelength of 320-350 nm for suspensions of the prepared mesoporous TiO2 in ethanol at the concentration of 5.0 mg/l. The mesoporous TiO2 prepared with the aid of SCCO2 exhibited an obvious blue shift compared with the TiO2 prepared by sol-gel infiltration. The possible mechanism for the formation of the mesoporous TiO2 is summarized into a biomimetic mineralization pathway. First, TTBO was transported to the membrane surface via SCCO2, and then condensed. Hydrolysis reactions between the functional groups of organic membrane and TTBO took place to form the nuclear TiO2, and the TiO2 seeds grew around the organic membrane into TiO2 mesoporous materials. The approach provides a low-cost and efficient route for the production of ceramics nanomaterials with unique structural features, which may have potential application in designing UV-selective shielding devices [S. Zhao, X.H. Wang, S.B. Xin, Q. Jiang, X.P. Liang, Rare Metal Mater. Eng. 35 (2006) 508-510].     

High-performance CO<Subscript>2</Subscript> capture on amine-functionalized hierarchically porous silica nanoparticles prepared by a simple template-free method

The adsorption of CO₂ on polyethyleneimine (PEI)-functionalized hierarchically porous silica nanoparticles (PSNs), prepared by using rice husk as a silica source via a simple template-free method, was reported in this study. Compared with traditional alkaline fusion and surfactant-templating methods for preparing waste-derived porous silica materials as CO₂ adsorbents, this method holds specific important advantages in being an inexpensive, and energy-saving process with faster production rate. The results revealed that the (NH₄)₂SiF₆ salt formed during the synthetic process served as an effective porogen, which can be readily removed by washing with water. Additionally, the total pore volumes of PSNs materials were strongly correlated to the amount of (NH₄)₂SiF₆. When evaluated as a support of PEI for CO₂ adsorption, 55PEI/PSNs(12/14) could reach 159 mg/g at 75 °C under 15 % CO₂, which was remarkably superior to those using waste silicate precursors reported in the previous literature. It was demonstrated that both PEI loading, and total pore volume of the PEI/silica composite sorbents, played key roles on CO₂ adsorption. Besides, 55PEI/PSNs(12/14) also showed high stability during 20 cycles of adsorption–desorption operation, implying its high potential in post-combustion CO₂ capture.     

CO2 capture by polyethylenimine-modified fibrous adsorbent

This work focuses on developing a novel adsorbent for CO2 capture, by coating polyethylenimine (PEI) on glass fiber matrix and using epichlorohydrin (ECH) as cross-linking agent. The physicochemical properties of the fibrous adsorbent were characterized. The CO2 adsorption capacity was evaluated. Factors that affect the adsorption capacity of the fibrous adsorbent were studied. The experimental results show that this fibrous PEI adsorbent exhibits a much higher adsorption capacity for CO2 compared with another PEI fiber prepared in our previous work, which employed epoxy resin as the cross-linking agent. A CO2 adsorption capacity as high as 4.12 mmol CO2/g of adsorbent was obtained for this fibrous PEI adsorbent at 30 degrees C, equal to 13.56 mmol CO2/g of PEI, with a PEI/ECH ratio of 20:1. The adsorbent can be completely regenerated at 120 degrees C.     

CO2 capture by hydrocarbon surfactant liquids

Here we found that CO(2) has high solubility in low-cost hydrocarbon surfactant liquids.     

CO(2) capture by a task-specific ionic liquid

Reaction of 1-butyl imidazole with 3-bromopropylamine hydrobromide, followed by workup and anion exchange, yields a new room temperature ionic liquid incorporating a cation with an appended amine group. The new ionic liquid reacts reversibly with CO2, reversibly sequestering the gas as a carbamate salt. The new ionic liquid, which can be repeatedly recycled in this role, is comparable in efficiency for CO2 capture to commercial amine sequestering reagents, and yet is nonvolatile and does not require water to function.     

A novel template-free sol–gel synthesis of silica materials with mesoporous structures and zeolitic walls

Hierarchical porous materials with zeolite structures show great promise in catalysis due to combining the advantages of zeolites and mesoporous materials. Here a novel template-free sol–gel method is developed to synthesize hierarchical porous silica materials. This method involves solvothermal recrystallization of the xerogel converted from uniform silicalite-1 precursor sol via vacuum drying process. The zeolite sol and the solid samples were characterized by laser light scattering, XRD, N₂ adsorption/desorption isotherm, FTIR, SEM, TEM and thermal analysis technologies. The results show that we obtain two novel materials with different mesoporous structures and silicalite-1 walls by using different recrystallization media, one of which has irregular arrays of mesopores, the other possesses 3D wormhole mesoporous structure. We speculate that formation of different mesoporous structures results from different nucleation and growth process of materials     

Simple fabrication of a phosphorus-doped hierarchical porous carbon via soft-template method for efficient CO2capture

Hierarchical porous carbons are widely used as adsorbents, catalyst supports, electrode materials, and other applications because of their high specific surface area (SSA), varied pore structure, adjustable porosity, and excellent physicochemical stability. Introducing heteroatoms such as N, P, or S, with electronegativities different from that of carbon, into the carbon skeleton can change the chemical properties of the surface and the density of the electron cloud around the carbon matrix, thus altering interactions of CO₂molecules with the surface and improving CO₂adsorption capacity. Therefore, doping heteroatoms in carbon materials has attracted a great amount of attention. In this paper, the template method was used with F108 (polyethylene glycol–polypropylene glycolpolyethylene glycol) as the template, resorcinol and formaldehyde solutions as the carbon sources, phosphoric acid as the phosphorus source, and KOH as the activator to prepare phosphorus-doped hierarchical porous carbons. Through a series of characterization and CO₂adsorption experiments, the influence of the amount of KOH and template agent on the pore structure of carbon materials was studied. We conclude that these phosphorus-doped hierarchical porous carbon materials are promising CO₂adsorbents.     

Preparation and characterization of templated porous carbons from sucrose by one-pot method and application as a CO2 adsorbent

The templated porous carbons were prepared from sucrose by one-pot method. In this method in which the pre-synthesis of the hard template is eliminated, the porous carbons were produced by organic-inorganic self-assembly of sucrose, tetraethyl ortosilicate (TEOS), Pluronic P123 and n-butanol in an acidic medium, and subsequent carbonization. The synthesis parameters such as sucrose amount, TEOS molar ratio and carbonization temperature were evaluated for describing their effects on the pore structures of the synthesized carbons. The prepared porous carbons were characterized by N₂ adsorption, thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The carbon dioxide adsorption uptakes of the obtained porous carbons were determined at 1 bar and 273 K. The templated carbon obtained with the lowest TEOS molar ratio exhibited the highest BET surface area of 1289 m²/g and micropore volume of 0.467 cm³/g, and showed the highest CO₂ uptake of 2.28 mmol/g.