Amine-functionalized poly(ionic liquid) brushes for carbon dioxide adsorption

Imidazolium-based poly(ionic liquid) brushes were attached to spherical silica nanoparticles bearing various functionalities by using a surface-initiated atom transfer radical polymerization ("grafting from" technique). A temperature-programmed desorption process was applied to evaluate and analyze the carbon dioxide adsorption performance of the synthesized polymer brushes. The confined structure of the surface-attached polymer chains facilitates gas transport and adsorption, leading to an enhanced adsorption capacity of carbon dioxide molecules compared with pure polymer powders. Temperature-programmed desorption profiles of the synthesized polymer brushes after carbon dioxide adsorption reveal that the substituent groups on the nitrogen atom at the 3-position of the imidazole ring, as well as the associated anions significantly affect the adsorption capacity of functionalized poly(ionic liquid) brushes. Of the tested samples, amine-functionalized poly(ionic liquid) brushes associated with hexafluorophosphate ions exhibit the highest carbon dioxide adsorption capacity of 2.56 mmol g-1 (112.64 mg g-1 ) at 25 °C under a carbon dioxide partial pressure of 0.2 bar.

The design and synthesis of solid sorbents for effective carbon dioxide adsorption are essential for practical applications regarding carbon emissions. Herein, we report the synthesis of composite materials consisting of amine-functionalized imidazolium-type poly(ionic liquid) (PIL) and metal organic frameworks (MOFs) through complexation of amino groups and metal ions. The carbon dioxide adsorption behavior of the synthesized composite materials was evaluated using the temperature-programmed desorption (TPD) technique. Benefiting from the large surface area of metal organic frameworks and high carbon dioxide diffusivity in ionic liquid moieties, the carbon dioxide adsorption capacity of the synthesized composite material reached 19.5 cm3·g−1, which is much higher than that of pristine metal organic frameworks (3.1 cm3·g−1) under carbon dioxide partial pressure of 0.2 bar at 25 °C. The results demonstrate that the combination of functionalized poly(ionic liquid) with metal organic frameworks can be a promising solid sorbent for carbon dioxide adsorption.

According to the present data, KA zeolite, which can adsorb only water vapor, helium, and hydrogen, has the greatest selectivity in drying. The feasibility of using this zeolite in devices for selective drying of gases used in gas-analysis systems was studied. The results of the experiments were approximated by the thermal equation of the theory of bulk filling of micropores. The limiting value of the adsorption depends on the temperature, and it can be calculated according to the density of the adsorbed phase and the adsorption volume. The critical diameters of the water and carbon dioxide molecules are close to the dimensions of the KA-zeolite pores, something that determines the activated nature of the adsorption of these substances. Experiments on coadsorption of water vapor and carbon dioxide by a fixed bed of KA-zeolite under dynamic conditions showed that the adsorption of these substances has a frontal nature. The time of the protective action of the layer of zeolite during adsorption af water vapor exceeded by more than an order the time of the protective action during adsorption of carbon dioxide. The results showed that this adsorbent can be used for selective drying of gas mixtures containing carbon dioxide in batch-operationmore » devices. Beforehand, the adsorbent should be regenerated with respect to moisture, and then it should be saturated with carbon dioxide by blowing the adsorbent with a gas mixture of the working composition until the equilibrium state is reached.« less

Effects of potential models on the adsorption of carbon dioxide on graphitized thermal carbon black: GCMC computer simulations

Amine-functionalized imidazolium-based poly(ionic liquid) brushes on mesoporous silica were synthesized via “grafting through” technique and were applied as model sorbents to understand physisorption and chemisorption of carbon dioxide molecules. The experimental results reveal that the total adsorption capacity of model sorbents derived from temperature programmed desorption (TPD) approach reaches 1.72 mmol·g−1 that is much higher than the sum of adsorption capacity of bare mesoporous silica and free polymers at 25 °C under carbon dioxide partial pressure of 0.2 bar. The proposed physical adsorption and chemical adsorption of carbon dioxide molecules in TPD response curves were validated by volumetric desorption measurement. It is also observed that physical adsorption is completely reversible and chemical adsorption is irreversible. The results demonstrate that the temperature programmed desorption technique is an effective approach to differentiate chemisorption and physisorption of gaseous species on solid sorbents, which is beneficial for understanding of adsorption mechanism and materials design.

Enhancement of desulfurization by hydroxyl ammonium ionic liquid supported on active carbon

A theoretical study on the selective adsorption behavior of dimethyl ether and carbon monoxide on H-FER zeolites

With large scale production of gas from shale resources, large volumes of pore space have been vacated. Therefore, there is a large capacity for storage of carbon dioxide in these resources. Furthermore, due to the higher affinity of the organic matter to carbon dioxide compared to methane, injection of carbon dioxide can replace the adsorbed methane and therefore, enhances the recovery of natural gas. The objective for this work is to investigate the sorption (adsorption of carbon dioxide and desorption of methane) in carbon-based organic channels using Molecular Dynamics (MD) simulations. In this study, adsorption isotherms of methane and carbon dioxide are compared by performing grand canonical Monte Carlo (GCMC) simulations in identical setups of carbon channels. Excess and absolute adsorption isotherms of these gases are plotted and compared. Furthermore, the surface selectivity of carbon dioxide over methane is computed to determine the competitive adsorption of these two gases. To simulate the displacement process, MD simulations of displacement of methane molecules with carbon dioxide molecules in presence and absence of pressure gradients are performed. The results are compared for different values of gas pressures and pressure gradients. According to the results, adsorption capability of carbon dioxide is found to be higher than that of methane under the same pressure and temperature. The selectivity values of carbon dioxide over methane is found to be higher than the ones for pressure range of 100 to 200 atm, which shows that carbon dioxide molecules have higher affinity to the surface compared with methane. It is also found that carbon dioxide molecules replace adsorbed methane molecules due to their higher affinity to the surface. Concentration of methane sharply decreases as carbon dioxide molecules are introduced in the channel. The results show that the amount of carbon dioxide storage and methane production rate increases as injection pressure increases. The results in this study can impact on the research and development of new tools for both candidate selection (selection of the sites for carbon dioxide storage) and development of predictive models for estimating of the amount of carbon dioxide intake.

CO adsorption performance of rubber wood activated carbon

The present work provides the first study of ordered mesoporous materials SBA-15 coated with microporous zeolites ZSM-5 using molecular simulations. Several model structures with characteristics such as periodic arrangement of mesopores, randomly arranged micropores, surface hydroxyls and bulk deformations of SBA-15 were used. Cartesian coordinates of ZSM-5 unit lattice were obtained from the literature and the 100 face of H-ZSM-5 unit cell was then placed on the surface of SBA-15 and the entire structure was equilibrated to obtain final configuration. The resulting structure was characterized using simulated small angle and wide angle X-ray diffraction, Connolly surface area (to compare BET area), accessible pore volume for nitrogen molecules (to compare with t-plot volume of micro and mesopores) and methane adsorption at 303 K. The orientation of ZSM-5 on the SBA-15 had no effect on the surface area, pore volume or adsorption capacity. In order to find out if the addition of microporous ZSM-5 should increase the total methane adsorption capacity due to addition of micropores, we studied adsorption on bare and coated SBA-15. However, total adsorption capacity was found to decrease, while the number of methane molecules adsorbed per unit cell of the SBA-15 structure increased. An existing experimental method (J. Am. Chem. Soc., 2004, 126, 14324) of the synthesizing hybrid ZSM-5/SBA-15 structure was studied using accessible micropore volume (by t-plot). It was found that the procedure made all the micropores inaccessible. A modification of the method or use of other host materials is suggested to use the benefits of narrow micropore distribution in ZSM-5.

Porous hyper-cross-linked aromatic polymers are one ofthe emergingclasses of porous organic polymers with the potential for industrialapplication. Four different porous polymeric materials have been preparedusing different precursors (indole, pyrene, carbazole, and naphthalene),and the composition and textural properties were analyzed. The materialswere characterized in detail using different physicochemical techniqueslike scanning electron microscopy, transmission electron microscopy,nitrogen adsorption at 77 K, Fourier transform infrared spectroscopy,X-ray diffraction, etc. The effect of textural properties and nitrogenspecies on carbon dioxide and nitrogen adsorption capacities and selectivitywas studied and discussed. The carbon dioxide and nitrogen adsorptioncapacities were measured using a volumetric gas adsorption system.The adsorption data were fitted into different adsorption models,and the ideal absorbed solution theory was used to calculate adsorptionselectivity. Among the studied samples, POP-4 shows the highest carbondioxide and nitrogen adsorption capacities. While POP-1 shows maximumCO2/N2 selectivity of 78.0 at 298 K and 1 barpressure. It is observed that ultra-micropores, which are presentin the prepared materials but not measured during conventional surfacearea measurement via nitrogen adsorption at 77 K, play a very importantrole in carbon dioxide adsorption capacity and determining the carbondioxide selectivity over nitrogen. Surface nitrogen also increasesthe CO2 selectivity in the dual mode by increasing carbondioxide adsorption via the acid–base interaction as well asby decreasing nitrogen adsorption due to N–N repulsion.

Surface thermodynamics of hydrocarbon vapors and carbon dioxide adsorption on shales

Nitrogen-doped porous carbons with uniformed pore structure and large surface area are promising materials as sorbents for acidic gases and electrocatalysts for oxygen-related reactions. Herein, we report the synthesis of nitrogen-doped porous carbon (NPC) materials through carbonization of imidazole-functionalized polyhedral oligomeric silsesquioxane (POSS) at 900 °C followed by removal of POSS blocks. The imidazole moieties act as both nitrogen and carbon sources and the POSS blocks are nano-sized hard templates. The resulting NPC has a surface area of 980 m2g−1 with average pore size of 4.7 nm and the pyridinic nitrogen in the formed NPC contribute to about 33% of overall nitrogen species. The carbon dioxide adsorption property and the electrocatalytic performance toward oxygen reduction reaction of the formed NPC are further evaluated. The formed NPC materials exhibit a total carbon dioxide adsorption capacity of 0.30 mmolg−1 at 30 °C under the partial pressure of carbon dioxide of 0.2 bar. Although the formed NPC is less active than commercial Pt/C catalyst for oxygen reduction reaction, the half-wave potential shifts to the negative side by only about 10 mV after 10000 cycling tests, demonstrating the great stability of the formed NPC materials.

Selective adsorption of supercritical carbon dioxide and methane binary mixture in shale kerogen nanopores

Water and carbon dioxide adsorption at olivine surfaces