Modifications by impregnation and grafting are commonly used for the preparation of amine-functionalized MCM-41. A comprehensive evaluation of the advantages and disadvantages of the two methods was performed in this work. MCM-41 was synthesized by the hydrothermal method, setting the amine-loading mass fraction at 40, 50, and 60 wt %. Three amine-modified adsorbents were prepared by impregnating polyethylenimine (PEI), and the three other adsorbents were prepared by grafting 3-aminopropyltriethoxysilane (APTS) onto MCM-41. The as-prepared adsorbents were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and N2 adsorption–desorption techniques. CO2 adsorption capacities were measured, and the experimental data were fitted with adsorption kinetic models. The cyclic stability of the adsorbents prepared by the two kinds of amine-modified methods was compared using the cyclic adsorption–desorption experiments. The characterization results showed that the target adsorbents were prepared successfully. The thermal stability of the adsorbents modified by grafting was better than the thermal stability of the adsorbents modified by the impregnation. Maximum CO2 adsorption capacities of 3.53 mmol g–1 (50% PEI–MCM-41) and 2.41 mmol g–1 (50% APTS–MCM-41) could be reached at 25 °C and 1 atm, which were 4.7 and 3.2 times greater than that of MCM-41. The Avrami model fitted the experimental data well, indicating a variety of interactions between the adsorbents and CO2. CO2 adsorption capacity after 5 adsorption–desorption cycles decreased by 14.22 and 5.19% for the adsorbents prepared by impregnation and grafting, respectively. It was concluded that MCM-41 modified by impregnation and grafting followed the same kinetic model. The absorbents modified by impregnation showed higher CO2 adsorption capacity and amine-loading efficiency, while those prepared by grafting had better thermal and cyclic stabilities.
Alcohol amine solutions have a high absorption capacity and rate for CO 2 capture, however, there are some shortcomings such as high energy-consumption and low stability. To enhance CO 2 capture performance of aqueous MEA, a functional ionic liquid ([NH 2 e-mim][BF 4 ]) was introduced based on the advantages for CO 2 capture. Absorbents were prepared with the molar concentration ratio of [NH 2 e-mim] [BF 4 ] to the 30 vol% aqueous MEA of 0 : 10, 1 : 9, 2 : 8, 3 : 7, 4 : 6 and 6 : 4. The density and the viscosity of the investigated absorbents were measured and the effects of the molar fraction of [NH 2 e-mim][BF 4 ] (n I ) and temperature on CO 2 absorption performance were investigated. CO 2 desorption performance of the solvent at different temperatures was discussed. The stability performance of the absorbent with n I of 2 : 8 (I/M 2:8 ) was examined by five consecutive cyclic tests. The results showed that for pure CO 2 , the I/M 2:8 displayed the highest absorption performance at 303 K under 1 bar: a comparable CO 2 absorption capacity of the 30 vol% aqueous MEA and a higher CO 2 absorption rate at the later absorption stage.Moreover, with the increase of temperature, CO 2 absorption capacity and rate decreased, while CO 2 desorption efficiency and rate increased. 393 K was chosen as the optimum desorption temperature with the desorption efficiency of 99.31%. The introducing of IL contributed to CO 2 desorption performance of the absorbents significantly. The properties (CO 2 absorption capacity, mass loss, density and viscosity) of the I/M 2:8 during the cycles suggested that the IL-MEA mixture had an excellent stability performance.
Although the use of ‘task‐specific’ amine‐functionalized imidazolium‐based ionic liquids (ILs) such as [NH2emim][BF4] and conventional imidazolium‐based ILs [bmim][BF4]), as absorbents for CO2 capture, possesses some unique advantages, they have a number of disadvantages when independently used for CO2 capture. This study examined a series of binary liquid mixtures of [NH2emim][BF4] and [bmim][BF4] for CO2 capture, exploiting the advantages and reducing the disadvantages of each of the components. The CO2 absorption performances of the mixtures were investigated as well as their physicochemical properties. Densities, viscosities, and surface tensions of the mixtures of varying molar fractions of [NH2e‐mim][BF4] (from 0.2–0.5 mol/mol) were experimentally measured over a temperature range of 298.0–343.0 K at a fixed pressure of 0.1 MPa. Thermal expansion coefficients, excess logarithmic viscosities, surface entropies, and surface enthalpies were calculated based on the experimental data. All the estimated physicochemical properties in a mixture with a mole fraction of [NH2e‐mim][BF4] of 0.4 had variation characteristics significantly different from those in mixtures with other mole fractions, which might be attributed to the large interaction between the two kinds of IL components and showed a positive effect on CO2 absorption and desorption. The above laws were consistent with those of the CO2 capture performances of the IL mixtures basically. An IL mixture containing 0.4 mol/mol [NH2e‐mim][BF4] and 0.6 mol/mol [bmim][BF4] would be an optimal CO2‐capturing absorbent. The findings in this study may enrich the database and provide a theoretical support for CO2 capture with IL mixtures. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.